journal osh

Journal of OccupationalSafety and Health

Editor-in-chiefIr. Hj. Abu Bakar Che’ ManExecutive Director, NIOSH

SecretariatAyop SallehSiham Ismail

Nurdiyana Mohd Jonis

The Journal

- Aims to serve as a forum for the sharing of research findings and information acrossbroad areas in occupational safety and health.

- Publishes original research reports, topical article reviews, book reviews, case reports,short communications, invited editorials and letters to editor.

- Welcomes articles in occupational safety and health related fields.

Associate Editors

Dr. Abu Hasan SamadExxonMobileProf. Dr. Krishna Gopal RampalMedical Faculty, UKMProf. Dr. Ismail BahariUniversiti Kebangsaan MalaysiaProf. Madya Dr. Mat Rebi Abd. RaniUniversiti Teknologi Malaysia

Editorial Board

Dr. Agus Salim M. BanonNIOSH, MalaysiaHajjah Maimunah KhalidNIOSH, MalaysiaAsiah JaffarNIOSH, MalaysiaZariman ZainuddinNIOSH, MalaysiaFadzil OsmanNIOSH, Malaysia

Journal of OccupationalSafety and Health

Jan 2004 Vol. 1 No.1

Contents

The Missing Elements of OSHMS and Safety Programmes 38-52- Calculating and Evaluating RiskJames F. Whitting

Hearing Loss in Walkman Users 12-18Sofia Jaffer, Mohd Shakil Razi

Neuropathy Due to Organic Solvent Exposure:Three Reported Cases From Pahang, Malaysia 19-22Agus Salim M.B., Malina, O, Hisanaga, N., Hirata M, Zainul Abidin

Emergency Response Programmein The Petrochimical Industry in Malaysia 32-37Jefferelli Shamsul Bahrin, Mohamad Husain Sajahan, Mohd. Nazri Hamad

Colour Vision of Workers in the Plastic Industry 6-11Sharanjeet Kaur, Mursyid A. and Ariffin A.E.

Introducing Journal of Occupational Safety and Health 1

Workplace safety is a priority. Much needs to be doneto encourage employees, employers and industries toput occupational safety and health at the top of theiragenda. The most important thing is our commit-ment in taking action; our commitment to make thenecessary changes to ensure that safety is at theforefront of everyone’s thinking.

The Journal of Occupational Safety and Health, (JOSH)the first to be published in Malaysia, aims to boostawareness on safety and health in the workplace.

It is no longer sufficient to simply identifying the hazardsand assessing the risks. We aim to increase understandingon the OSH management system. We aim to strengthencommitment to workplace safety and better workingconditions. We believe these aims can be achievedthrough participations and involvement from everyindustry.

Ir. Hj. Abu Bakar Che’ ManEditor-in-chief

We hope the contents of the journal will be read andreviewed by a wider audience hence it will have a broaderacademic base, and there should be an increasedcumulative experience to draw on for debate andcomment within the journal.

It is our hope that the journal will benefit all readers, asour purpose is to serve the interest of everybody fromall industries. Prime Focus will be on issues that are ofdirect relevance to our day-to-day practices.

I would personally like to take this opportunity towelcome all our readers and contributors to the firstissue of the journal. I look forward to receivecontributions from the OSH community in Malaysiaand elsewhere for our next issues.

From the Editor in Chief

Introducing the Journal ofOccupational Safety and Health

The National Institute of Occupational Safety andHealth (NIOSH) is delighted to announce thepublication of Journal of Occupational Safety andHealt.(JOSH). Beginning in January 2004, the newjournal will start with Volume 1, Issue 1.

JOSH is devoted to enhancing the knowledge andpractice of occupational safety and health by widelydisseminating research articles and applied studies ofhighest quality.

JOSH provides a solid base to bridge the issues andconcerns related to occupational safety and health. JOSHoffers scholarly, peer-reviewed articles, includingcorrespondence, regular papers, articles and short reports,announcements and etc.

It is intended that this journal should serve the OSHcommunity, practitioners, students and public whileproviding vital information for the promotion ofworkplace health and safety.

Apart from that JOSH aims:• To promote debate and discussion on practical andtheoretical aspects of OSH• To encourage authors to comment critically on currentOSH practices and discuss new concepts and emergingtheories in OSH• To inform OSH practitioners and students of currentissues

JOSH is poised to become an essential resource in ourefforts to promote and protect the safety and health ofworkers.

J Occu Safety Health 1 : 1, 2004

1

Abstract

Malaysia is blessed with oil and gas resources, which form raw materials for the petrochemical industry. Thepetrochemical industry creates added value to this resource and is an important contributor to the national economy.The petrochemical industry however also creates hazards of which fire or explosions and chemical release are of specialconcern. These hazards pose a risk not only to workers but also to the surrounding population and environment. Toensure industry is prepared to cope with emergencies, a comprehensive emergency response programme is necessary.This is inline with both the Malaysian Occupational Safety and Health (Control of Industrial Major Accident Hazards)Regulations 1996 and the Responsible Care initiative of the chemical industry. This paper describes elements to beconsidered in an emergency response programme for industry such as the concept of emergency management,organisation, duties and responsibilities, emergency system, training and mutual aid plans and agreements. We shallprovide related examples based on a multinational petrochemical company practice

Impact on industry: Educate industry of need and contents of a comprehensive emergency response plan.

Key words: Petrochemical, Emergency, Response

Emergency Response Programme in a PetrochemicalCompany in Malaysia

Jefferelli Shamsul Bahrin, Mohamad Husain Sajahan, Mohd. Nazri HamadBASF PETRONAS Chemicals Sdn. Bhd.

The Petrochemical Industry in Malaysia

Malaysia offers two great advantages tothe petrochemical industry. Firstly, the raw materialsfor the petrochemical industry - oil and gas arepresent naturally in abundance off the shores ofMalaysia. Secondly the Malaysian governmenthas invested in petrochemical related infrastructurein specially designated zones to support such anindustry. The three petrochemical industry zonesare Gebeng and Kertih on the east coast ofPeninsular Malaysia and Tanjung Langsat in thesouth of Peninsular Malaysia. Currently there are27 petrochemicals plants throughout the countryproducing 38 different types of petrochemicals.Petrochemicals are used to create value addedproducts in the agriculture, food, clothing, housingand transportation industry (MalaysianPetrochemicals Association, 2003). Although thepetrochemical industry stimulates economicgrowth, it also creates new hazards to the

environment it operates in. Fire, explosions andchemical release are of special concern. Thesehazards have potential to cause damage not onlyto workers and structures within the plant area butalso to the surrounding population andenvironment. An emergency response programmeis necessary to mitigate potential consequencesof such an event.

Creating an Emergency ResponseProgramme

An emergency is defined as a situation orstate characterised by a clear and marked reductionin ability of people to sustain their normal livingconditions with resulting damage risks to health,life and livelihoods (Wisner B, Adams.J, 2002).Another definition is an unexpected conditionrequiring specific action plans to normalise (i.e.fire, explosion, leak of products or gas, loss ofcontainment or threats) ( BASF-PETRONAS Site

Case Study J Occu Safety Health 1 : 3-8, 2004

3

The process of creating a programmebegins with a needs and resource assessment. Theneeds and resources available to differentindustries vary and thus the need to customizeprogrammes to suit a particular industry. InMalaysia, there are specific laws, regulations andguidelines published related to EmergencyResponse. Some plants are also required to adhereto their own corporate guidelines or publicationson emergency response programmes. There arealso many books commercially market on thissubjects which form a useful source of information.

Knowledge of the company operationsbackground as well as internal resources availablesuch finances, manpower and equipment are alsovital in developing a comprehensive emergencyresponse program. Information on externalresources such as distance to from nearest firebrigade and their incident management capabilityare important. Also important is to know thedistance from nearest medical service (Departmentof Occupational Safety and Health, 1996), specialtyservice offered and their ability to manage masscasualties (BASF Occupational Medicine andHealth Protection Department, 2003). In this paperwe shall share our experience in creating andexecuting our own emergency responseprogramme. We believe this paper will form a usefulguide to other industries in particular petrochemicalcompanies in developing their own emergencyresponse programme.

BASF PETRONAS Chemicals (BPC) Sdn.Bhd.

BASF-PETRONAS is a joint venturePetrochemical Company between BASFAktiengesellschaft of Germany and PetroliamNasional Berhad (PETRONAS) of Malaysia on a60: 40 basis, involving an initial investment of RM3.4 billion. The production complex consists of 12

plants, which are located in Gebeng, Pahang. Themain products are acrylic monomers, oxo productsand butanediol product. The total work force isaround 840 employees. The plant runs 24 hours aday, seven days a week and thus there are asignificant amount of workers who work on shift.There are a total of four different shift groupswhereby each shift period lasts for 12 hours. Ashift worker generally works 4 shifts per week. AManaging Director, who is assisted by 4 directorsfrom the Operations and Technical, Marketing andLogistics, Human Resource and Administration,and Corporate Functions division, manages thecompany (BASF-PETRONAS CorporateInformation, 2003).

Emergency Response Programme in a Petrochemical Company in Malaysia

HSE Manual, 2003). A programme is defined as anordered list of events to take place or proceduresto be followed. Important elements in a programmeare the overall plans and the resources required toexecute the plans. A comprehensive emergencyresponse programme would cover not only on-siteincidents but also off-site incidents, which mayoccur during the transportation of products.

4

Emergency Response Related Laws inMalaysia

The Malaysia government has recognisedthe need to regulate activities with potential tocause major hazards. The Occupational Safety andHealth (Control of Industrial major HazardsInstallation) Regulations 1996 states the need forsuch industries to create their own emergencyresponse programmes. The Fire Services Act 1988states the need for premises to obtain a firecertificate of which the details required to obtainthis certificate are listed in the Fire Services (FireCertificate) Regulations 2001. The elementsrequired to obtain a fire certificate are those relatedto personal safety facility, fire prevention, fireprotection, fire fighting facilities, special needs andfire fighting team on site.

Although there is no specific mention inthe Fire Services (Fire Certificate) Regulations 2001on the need of an emergency response programme,all the provisions mentioned are in fact elementswithin such a programme. The Uniform BuildingBy-Laws, 1984 state the need for fire alarms, firedetection, fire extinguishment and fire fightingaccess. These items are also elements of anemergency response system. The National SecurityCouncil Directive No 20 is another important pieceof legislation which clearly states that industrialaccidents such as explosions, fire, pollution andleaks of hazardous material from plants areincidents covered under the directive. Thisdirective also defines the levels of disaster andhow the disaster and aid should be managed.

Emergency Response Related Guidelines

In 2001, the Fire and Rescue Departmentcame up with guidelines ( Jabatan Bomba danPenyelamat Malaysia, 2001)on how to create anemergency response programme (ERP), whichincorporates the Incident Command System (ICS).The emergency response plan needs toincorporate the ICS and the Incident Action Plan(IAP) both on site and offsite. The ERP report mustcontain information on the managementorganisation for the building or industry, process/operation flow chart, risk assessment and hazardidentification for process and storage areas as well

as transport. Other areas covered in this guidelinesare procedures, strategy and tactics, training andexercise, mutual aid arrangements, creation ofpredesignated facilities, fire fighting, rescue andhazmat equipment, ERP demonstration and exercise,the need for preparation of ERP by trainedindividuals, the need to submit ERP/ICS to theMalaysia Fire and Rescue Department,responsibility to audit, implementation training andneed for ERP to be a living document.

Commercially available programmes such asChemWatch as well as Chemical Safety Data Sheetsobtained from companies producing chemicalsform a valuable source of information on suchmaterial. The document contains information onphysicochemical properties of the chemical andalso that on First Aid measures, antidotes ifavailable as well as toxic effect of chemicals to theenvironment. Some Multinationals produce theirown guidelines for handling chemical emergencies.

BASF is one such company. TheirOccupational Medicine and Health Departmentcreated a guideline on Medical Management (BASFOccupational Medicine and Health ProtectionDepartment, 2002) of exposure to 20 chemicals ofconcern produced by the BASF group. It containsadvice, which has been tailored for first responders,paramedics, doctors at site and doctors at hospitalas well as the patient in managing chemicalexposures. Since BASF-PETRONAS is partlyowned by BASF we have access to this usefulresource document.

Emergency Response Human Resourcein BPC

A Manager who heads the Health andSafety department, reports to the OperationsDirector. The Chief of the Fire Departmentresponsible for responding to fire and chemicalincidents reports to the Health, Safety andEnvironment Manager. The Fire Departmentconsists of 15 full time Fire professionals. The teamis led by a fire officer and assisted by 6 fire marshals.Two fire marshals work office hours whereas theother 4 work on shift. These 15 individuals areemployed full time at the fire department. For everyshift there are also 2 fire fighters on duty. Thecompany has created an emergency response team,

Case Study

5

J Occu Safety Health 1 : 3-8, 2004

Emergency Response Resources fromNeighbouring Industries

BASF PETRONAS Chemicals is located inthe Gebeng Industrial Zone. In 1999, BASFPETRONAS signed an agreement to be part of thearea mutual assistance program in cases ofemergency. This understanding is known asGebeng Emergency Mutual Aid (GEMA)agreement. It helps enlarge the pool of resourcesand is especially beneficial for the smaller industriesthat may be less well equipped to cope with majorincidents. To enhance emergency preparedness andcooperation, a yearly drill is conducted at one ofthe facilities during which emergency response teammembers from neighbouring plants will come andassist. Site visits are also conducted amongmembers to the different plans to get a better ideaof their operations and how to best respond in anemergency.

Emergency Response Plans in BPC

The BPC Emergency Response Plan isdocumented in it’s emergency response manual aswell as the site emergency medical serviceprocedure. This plan outlines the organisation,system and procedures to be followed in anemergency. The contents of the emergencyresponse manual include definitions, emergencymanagement concepts, organisation, duties and

Emergency Response Equipment andFacility Resource in BPC

Structurally, a building known as theResponse Centre was built to house emergencypersonnel and equipment. Within this building islocated the emergency treatment room as well asthe call center which is open 24 hours a day, 7 daysa week. The call centre shall respond to any offsiteor onsite incidents. All calls are recorded andrelayed through an integrated messaging system.The fire officer on duty shall activate the relevantpersonnel to respond and provide specialisedadvice to the caller on managing the incident. Theemergency response system includes heat, smoke,fire and gas detection devices and alarm systems,air horns, fire fighting systems and a messagingnetwork system. A dry chemical foam truck andHazmat foam truck are available to facilitate firefighting and containment of chemical leaks and


which consists of shift plant employees who aretrained to assist the fire department duringemergencies (BASF-PETRONAS Site HSEManual, 2003).

The Occupational Health Physician who isresponsible for the emergency medical servicereports to the Director of Human Resource. Theemergency medical service is led by theOccupational Health Physician and assisted by 5paramedics and 1 occupational health nurse. Thelead paramedic and occupational health nurse workoffice hours, whereas the other 4 paramedics workshifts (BASF-PETRONAS Site HSE Manual, 2003).The company has also created an advance firstaider team, which mainly consists of shift plantemployees who are trained to assist the paramedicsduring emergencies. There will always be at leastbetween 7-8 advanced first aiders on duty everyshift. The first aiders are trained in basic lifesupport, how to assist paramedics and some plantspecific concerns such as handling chemicalemergencies. These group of specially trained firstaiders are known as Advanced First Responders(AFR) ( Jefferelli SB, Husain MSJ, Nasrudin S,2003). Although reporting to different superiors,the fire and medical service work closely togetherin planning and executing the emergency responseprogramme in the plant.

spills (BASF-PETRONAS Site HSE Manual, 2003).Emergency showers are constructed near workareas to allow rapid decontamination. First aid boxesare also available at strategic locations. Medicalfacilities for emergencies available at the clinicinclude a fully equipped ambulance and emergencyroom and emergency shower facilities. Among theequipment available are assessment tools such asstethoscopes and vital signs monitor, respiratorymanagement equipment such as oxygen, intubationset, suction pumps and ventilators, circulatorymanagement equipment such as intravenous drips,defibrillator, immobilisers such as splints andcervical collars, transport equipment such asstretchers and scoop stretchers and bleedingarrestors such as suture sets and bandage ( JefferelliSB, Husain MSJ, Nasrudin S, 2003).

6

responsibilities, emergency systems, training andmutual aid plans. There are three types of teamsinvolved in execution, which are the emergencyresponse team (ERT), plant emergencymanagement team (PEMT) and site emergencymanagement team (SEMT). The emergencyresponse team is led by the fire marshal and advisedby the shift supervisor of the affected plant. Amongthe duties of the fire marshal is to lead theemergency response team, inform the PEMT ofdevelopments, determine level of emergency, seekplant specific advice and inform the local fireauthorities (BOMBA). The advisor (shiftsupervisor) shall provide plant specific advice, isresponsible for shutting down and securing plant,activating the PEMT and announcing theemergency on the PA system. Other ERT membersassist the fire department in specific activities suchas fire fighting and containing chemical release.The PEMT is activated in level two emergencieswhereby the incident can no longer be containedby internal resources. The complex GeneralManager leads this team. His duty is to develop astrategy for handling the emergency, obtainresources needed to handle emergency such asfood, manpower, service, equipment and logistics,recommends activation of SEMT and informs themof development. In level 3 emergencies the SEMTis activated. The Operations and Technical Directorwho is also known as the Kuantan Site Directorleads the team. He will inform the ManagingDirector of the situation, approve release ofinformation to the media, next of kin and othersand inform the relevant authorities such as thepolice department, district office and others. TheHealth Safety and Environment (HSE) Manageradvises the SEMT on HSE matters. The emergencyresponse manual also provides emergencyorganization structures and incident flowcharts.The manual also lists the available emergencysystems and information on training methods,training sessions and drills. An Incident ActionPlan, which prepares for every possible hazardscenario on site is also available. This plan shalldetermine the incident scenarios for the drills to becarried out (BASF-PETRONAS Site HSE Manual,2003).

The site emergency medical serviceprocedure ( (BASF-PETRONAS Site HSE Manual,

2003) defines the personnel involved and theirduties, specific work areas, victim tagging system,phases of medical emergencies and flow chart. Thepersonnel involved are divided into occupationalhealth physician (OHP), lead paramedic, paramedicon duty, paramedic on call, occupational healthnurse, GEMA members and AFRs. The first healthpersonnel to respond in an emergency will be theparamedic on duty. His duties are to respond tocall for assistance, anticipate number of victims,type of injury and need to call for support, establishMedical Command post and perform triage, providefirst aid and initial treatment, stabilize victim priorto transport to clinic, coordinate AFR on duty,updates OHP and lead paramedic on the situationand report writing and record keeping. Thedocument also details roles of other personnel.Areas where primary and secondary triage iscarried out namely the medical command post andclinic are defined. The tagging system used issimilar to international standards using tagscoloured green, yellow, red and white to indicatethe severity of injury and urgency of treatment.The level of emergencies is divided into 4 phases.In phase 1, the medical situation can be controlledinternally.

In phase 2, the medical situation can becontrolled and coordinated internally but externalassistance is required from GEMA members. Inphase 3, assistance is required from external bodiesother than GEMA members. In phase 4, the situationcan no longer be coordinated by the MedicalEmergency team but needs to be managed by thegovernment medical authorities. The flow chartfurther illustrates the chain of events andresponsibilities3.

The Importance of Drills

An emergency response plan itself does notassure preparedness and ability to respondsuccessfully to an incident. An important elementin an emergency response program is training. Thiswill help ensure all equipment is in order, personnelrespond accordingly and that the system used isunderstood and works. Among the weakness wehave identified from drills conducted include delayin arrival of rescue team at site, delay in donningfull protective gear, lack of air or gas monitoring,

Case Study

7


activation of wrong alarm, failure todecontaminate victim, poor communication,failure to setup medical command post, failure toestablish a safe zone and failure to request formedical backup. Similar weaknesses wereidentified during drills conducted in BASF,Germany (Andreas Zober, 2003). The lessonslearnt form every drill is conveyed to thestakeholders and remedial action is taken to avoidthe same mistakes repeating itself.

Conclusion

Petrochemical industries are a majorhazard. Steps can be taken to reduce the risk ofincidents occurring as well as reducing theimpact of such incident should it occur. Acomprehensive emergency response programmeis instrumental in the latter. The programme mustnot only look good on paper but must bepractical. The roles of every party must be clearand drills to identify weaknesses in the systemneed to be conducted regularly. A goodEmergency Response Programme is like goodinsurance. You want to be well covered but hopeyou will never have to use it.

Acknowledgments

We would like to express our gratitude toJohn Duncan Fastier, Dr Friederich Towae,Ghazali Hasan, Ismail Mohd Noh, Dr MatthiasSchoenfeld, Prof Andreas Zober, Dr RudolfGambihler, Dr Peter Tang, Dr Mohd. SharkawiJaya and Dr Abu Hasan Samad for their support.

References

Malaysian Petrochemicals Association. (2003). CountryReport From Malaysia, Asia PetrochemicalIndustry Conference, 2003.

Wisner B, Adams. J. (2002). Environmental health inEmergencies and Disasters, A practical Guide, WorldHealth Organisation

BASF-PETRONAS Site HSE Manual. (2003). Emer-gency Response ManualDepartment of Occupational Safety and Health. (1996).

Guidelines on First-Aid Facilities in the Workplace. BASF Occupational Medicine and Health Protection

Department. (2003).Occupational Medicine andHealth Protection Program in the BASF Group.

BASF-PETRONAS Corporate Information, 2003Occupational Safety and Health (Control of Indus-trial Major Hazards Installation) Regulations 1996

Fire Services Act 1988Fire Certificate (Fire Services) Regulations 2001Uniform Building By-Laws 1984.Jabatan Perdana Menteri. Majlis Keselamatan Negara,

Arahan No.20. Dasar dan Mekanisme Pengurusandan Bantuan Bencana Negara, Bahagian Kesela-matan Negara.

BASF Occupational Medicine and Health ProtectionDepartment. (2002). Chemical Emergency Manage-ment Guidelines.

BASF-PETRONAS Site HSE Manual. (2003). Emer-gency Medical Service Procedure.

Jefferelli SB, Husain MSJ, Nasrudin S. (2003). Emer-gency Medical Provisions at a Multinational

Chemical Company. Presentation at the National Confe-rence on Occupational Safety Health, SunwayPyramid 14-15 July, 2003.

Andreas Zober. (2003). Medical Management ofEmergencies and Disaster in the Chemical Industry,BASF Aktiengesellschaft.


8

9

The Missing Element of OHSMS and Safety Programmes- Calculating and Evaluating Risk

James F. Whitingrisk@workplace pty ltd

Abstract

How realistically and reliably can an OHSMS or safety programme be meaningfully constructed andinterpreted without an objective basis for risk calculation and evaluation? Does the descriptor ‘at risk’ have any usefulmeaning? Don’t we all know that all actions involve some risk ? All behaviours are ‘at risk’.

To be confident that employees at all levels need to understand and may possibly want to change their risk takingbehaviours at work, we need to be confident that they can understand & evaluate the risks adequately,AND to be confident that they can understand & evaluate the risks adequately,we need to be confident that they can perceive the risks adequately,AND to be confident that they can perceive the risks adequately,we need to be confident that they can assess the risks adequatelyAND to be confident that they can assess the risk adequately,we need to be confident that they can calculate the risks adequately.

Nearly all OHSMS and safety programmes don’t recognise the need, and don’t provide any adequate process, foradherence to all of the logic chain above. Breaking any single link of the chain breaks the logic of the chain itself andcontinues the frustration of current programmes the on-going confusion and lack of agreement of what is ‘at risk’. Thispaper describes how successful safety systems and programmes need to provide all stakeholders with at least onemethod calculating risk and hence provide an objective basis for understanding, prioritisation and assessment of workplacerisks. Currently, the term ‘at risk’ in “at-risk behaviour” has no more practical meaning than ‘unsafe’ , the old traditionalterm it replaced. There is still just as much argument, confusion and inconsistency with the term because it has noobjective basis and worse no objective criteria for evaluating and agreeing on risk tolerability. Unless all stakeholders aregiven both a method for calculating risk levels, and a framework of criteria for agreeing on tolerability, then the programmesdo not advance beyond the perennial confusion and lack of agreement of what is “unsafe”. Nothing is being achieved ingetting closer to removing the problems associated with the persistent and subjective assumption that we all innatelyagree on what is “safe” i.e. we all share the same risk tolerability levels (the myth of ‘safety is common sense’). Withouta basis for calculating risk levels, current programs lack an objective basis for selecting and prioritising, which behavioursare ‘at risk’. This paper describes the necessary risk management philosophy and components of a successful OHSMSor safety programme by providing the missing risk management links. The processes will be described in details andexplanations of the importance of integration of risk management philosophies and methods with safety programmes willbe provided.

The Role of Risk Management in SafetySystems and Programmes

Shifting the “zero risk-absolute safety” paradigm

Just as important as the methods of riskcalculation and evaluation, there is an essentialneed to shift the safety culture from the non-existent“zero risk-absolute safety” paradigm to that of “risk

tolerability” - whereby no injuries and illnesses areever “acceptable” and only risks fully managed toALARP are “tolerable”. (ALARP = As Low AsReasonably Practicable). (Fig 1)

For once and for all, employees areencouraged to recognise the difference betweenthe intellectually-dishonest concept of “a safetythreshold or zero risk threshold” and theworkable,realistic but more demanding concept of

Article Review J Occu Safety Health 1 : 9 -24, 2004

9

“a spectrum or range of risk with possible zeroinjuries and illnesses”, (Figure 2) Managers andEmployees see for the first time the real significantdifferences between ‘zero risk’ and ‘zero injuries’.

The former is the concept that has held thesafety profession back because it is seen and knownas unreal, while the latter involves the moredemanding recognition of the futile belief in a non-existent safety threshold which separatesabsolutely ‘safe’ from absolutely ‘unsafe’. No riskto ‘at risk’. Just substituting the words ‘at risk’ for‘unsafe’ is not incorporating the essential riskmanagement concepts that are needed in anyrealistic safety behaviour-based culture/programme.

Tolerable’ is a better term than‘Acceptable’

Implicit in the paradigm shift is the need torecognise that ‘acceptable’ is a passive, defeatistalmost fatalist term, whereas ‘tolerable’ is an active,dynamic, term that indicates that we have notaccepted nor given up but are still activelyinterested and working hard to control our workrisks better. A new safety culture based on risk man-agement always substitutes tolerable for accept-able, tolerate for accept, tolerability for acceptability.

The philosophy at the heart of this belief isfundamentally important. Many organizations canadopt a realistic and rewarding Safety Vision basedon this philosophic framework expressed in wayssimilar to :- “We will never accept any injuries/illnesses anywhere anytime AND we will What isan intolerable risk? Need not and should not be aqualitative subjective question. Tolerable can andmust be objectively quantified. Agreed quantitativetolerable risk levels (lines in the sand) need toreplace meaningless ‘unsafe’ or ‘at risk’ descriptors.The vertical axis in Figure 1 can be assignedquantitative values representing the 2 boundariesof ALARP. The author’s paper at ASSE 2001covered how “tolerability can be quantified” andhence minimise uncertainty and confusion on whatis tolerable?

Figure 1: Two lines in the sand- Deciding a risk above which is “intolerable”- another risk level below which is “broadly tolerable”even “negligible”- and the in-between risks are only tolerable if assuredthat they are being managed to as low as reasonablypracticable ALARP

Figure 2: There is no threshold that separates risk fromno-risk or “safe”- rather there is always a continuum orspectrum of risk

The Missing Element of OHSMS and Safety Programmes - Calculating and Evaluating Risk

10

The Absolute Link Between RiskPerception And Behaviour

We need to emphasise the importance offocussing on the absolute link between riskperception and behaviour. We need to recognisethat ‘managed risk’ is achievable while ‘zero-risk’ isnot. The term managed risk-taking behaviour is usedto refer to any behaviour that is required tominimise risk to health and safety. Examplesinclude following Agreed Standard WorkProcedures (ASWPs), e.g. wearing PPE, reportinghazards and incidents, using appropriate manualhandling techniques, and so on. There areobviously many factors that influence, initiate,activate and control human behaviour. All safetyprograms need to recognise the importance of riskperception in the Activator A component of theABC Model of explaining behaviour. (Figures 3A,3B, 3C and 3D)

The ABC model has combined the best ofthe 2 models - the Cognitive model and theBehaviourist model. Risk perception is seen as thepowerful if not ultimate prompt, cue, stimulus, oractivator A for behavioural choice at aconscious level and also as a powerful reinforcerof past experiences or consequences of pastbehaviours at an automated conditionedresponse form of behaviour B. It is alwaysimportant to remember that what risk level(chances of positive outcomes and chances and ofnegative outcomes) are perceived are real to theperson involved. Perception is reality! If we believe/perceive that a certain line of action has a higherchance of providing a good outcome for us thanthe chances of providing a negative outcome, thenwe take that line of action or behaviour.

By definition, rational behaviour is always taken‘for good reasons’

No one takes risks for the chance of harm orloss-rather they take them for the perceived or realchance of good outcomes, profit or gain forthemselves or their organisation. No one is stupidor careless or. If you dig deep enough, you usuallyfind well-motivated employees taking actions forvery good reasons. Saving time or taking short cutsis one of the best reasons anyone can find becauseit meets all the prominent business imperatives!!

It is important to note that a great deal moresubstandard practices (SSPs) and substandaradconditions (SSCs) occur than near misses (or nearhits) and incidents. Because they quite frequentlyoccur (and can be measured without requiringindividuals to report their occurrence), and becausethey are also directly related to the causation ofincidents, these SSPs and SSCs can therefore beused as a more reliable indicator of safetyperformance than incident statistics or reports ofnear misses. The technique for measuringsuccess with positive Standard Practices (SPs) (not negative SSPs and SSCs), and using thesemeasurements as indicators of safety performance,is called safety sampling or risk sampling.

Safety sampling or risk sampling is animportant behaviour based strategy by whichemployees (not managers alone) measure how oftenthey are succeeding with their own previously-agreed standard practices or risk-tolerablebehaviours. These measures provide a positiveindication of how well risks are being managed butmore importantly the results are “owned” by theemployees. Safety sampling or risk sampling is notabout managers conducting audits of unsafe acts(or practices), rather it is about employeesconducting audits of their own agreed or standardacts (or practices). As a result they obtain realtangible measures of the outcomes of their riskmanagement decisions.

A safety systems approach needs to bebased on a “coach” rather than a “cop” culture. Itdoes not expect our front line managers/supervisors/team leaders to be acting primarily aspolicemen. More importantly, there is directobjective evidence of the consequences of theirrisk perceptions. Of course, incident/injury/illness/claims statistics still need to be closely monitoredin order to see that a certain approach or techniqueis actually meeting its long term goal of decreasingincident rates. However, safety sampling or risksampling provides an excellent means of settingnecessary short term goals, and evaluatingprogress towards achieving these goals.

Use of SPs are excellent PerformanceMeasures because they are positive, prospective,leading, upstream, and process-oriented not as withso many traditional measures such as injurystatistics which are negative, retrospective, lagging,downstream and outcome indicators.


11

We should never criticise each other for findingshort cuts but we should do so if we take thembefore doing a comparative risk assessment withthe currently agreed way.

Factors Influencing Risk Perception

When and how do we agree when a Risk is not aRisk?

As an aside, it is worth remembering that noone wants to be completely risk averse. “Telling aninvestor there is no hope of beating the averagesis like telling a six-year-old there is no Santa Claus.It takes the zing out of life,” Malkielwrites. (Krause,1984).

People’s perceptions of the level of risk arenot determined solely by quantitative, numerical

Figure 3B: Examples of Activators - Note the prominence of “risk perception”

Figure 3D: Exercies to demonstrate the feedback loop from consequences to Activators and 3 qualities of re-inforcers of risk perception - positivity, immediacy, and certainty

Findings* He has never been injuredbefore* Others in the Team don’t useCSP* General ‘macho’ risk-takingculture

PreviousConsequence?

Yes / No?Yes / No?Yes / No?

SSP=Operator NOT using the

Typical Incident InvestigationFindings* Time is saved / Job donefaster* More comfortable withoutequipment* Someone is seriouslyinjured* Team Leader ignored whathe saw* Manager gives reprimand* Other team members liked

Value +/-

Figure 3A: The ABC Model of Human Behavior Figure 3C: Examples of Consequences - experiential re-inforcers of risk perception

data but are also strongly influenced by many othersubjective factors. The accurate perception of riskby all employees within an organization of whatthe organization regards as “tolerable” and“intolerable” is important for effective risk man-agement. “Common sense” cannot be assumed asautomatic without considerable effort in discussionand argument in achieving commonality andagreement on those risks which are “tolerable/acceptable” and those which are not. This is whythe phase of discussion/interpretation of safetysampling or risk sampling is important and valuable.A common position can be achieved but notassumed. Employees’ risk perceptions are subjec-tive risk estimates which usually differ from objec-tive risk data in a number of ways. (Table 1) It isimportant that organizations are aware of the biases


12

in employees’ subjective assessments of risk, sothey can develop mechanisms to reduce the impactof these biases. Biases in risk perception can affectthe accuracy of task risk assessment, including theidentification, assessment of the likelihood andconsequences, and the selection/implementationof the risk control measures.

Biases in employees’ risk perceptions

Employees tend to underestimate the riskfrom tasks that they perform frequently’. This biashas been called ‘risk habituation’, It appears to bedue to people becoming accustomed to beingexposed to the hazards, therefore underestimatingthe risk and becoming complacent about thehazards. This complacency may be due to the factthat they have performed the tasks very often andhave never experienced an accident - a case offamiliarity breedingapathy. As it is based on avigorous on-going discussion of safety or risksampling results, the “good” reasons for SSPsincluding biases in risk perception are more readilyexposed.

Employees can become more aware of theirbiases in risk perceptions. Work group discussionsneed to be very direct, relevant, and specific to thehazards that employees are exposed to mostfrequently, and use actual SSPs to highlight thepotential consequences.

A potentially exposed person’s views/perceptions ofto lerability of a risk are influenced by: Is the risk ...?

Perceived as ‘more tolerable’ Perceived as ‘less tolerable’

voluntary / internal / free choice externally imposedunder an individual’s control controlled othersclearly beneficial to exposed person little or no obvious benefitnatural components synthetic / artificialeffects apparently statistically certain Effects statistically uncertainnegative effects delayed negative effects immediatefamiliar characteristics unusual, exoticequitable, fairly distributed inequitable, unfairly distributedminor consequences catastrophic consequencesgenerated by a trusted source generated by an non-trusted sourcetargets adults targets childrenassociated with benign words associated with ‘dread’ words

Perceived as ‘more tolerable Perceived as ‘less tolerable’

Table 1: Risk Characteristics which influence Risk Perception and Tolerability Adapted from“Acceptable Risk” by Baruch Fischoff, et al NY: Cambridge University Press 1981

On the other hand there is evidence tosuggest that employees overestimate the risk fromtasks that are notoriously dangerous, operationsthat they perform infrequently or hazards thatproduce a feeling of ‘dread’ or that they perceiveas ‘unknown’. Employees appear to overestimatethe risk when they focus too much on the vivid, orgruesome consequences and not enough on thelikelihood of the event occurring. They focus onthe consequences and therefore overestimate therisk.

Overestimation of risk can be just asworrying as underestimation. If employees areconcerned about one risk factor or hazard in anoperation, they may not pay sufficient attention toother risk factors or hazards. This phenomenonreinforces the need for giving employees a methodfor objective estimation or calculation of risk levelsto reduce the effects of biases. In order to minimiseoverestimation bias, organisations need to developprocesses to ensure that employees consider allaspects of risks posed by all the kinds of exposuresassociated with an operation.


13

Aside: Always consider the 3 terms - hazard,exposure and risk together. Risk analysts can forgetthe value of the term exposure in clarifying thedifference between hazard and risk - eg. A hazardcan only be a risk if there is exposure!

Providing information on a risk assessmentproforma, to prompt employees to considercommon hazards such as tripping hazards - thatmight be omitted from the assessment, can reducethe impact of this bias. Examples of previousaccidents where an inaccurate risk judgement wasa causal factor will be useful. The more practicalknowledge an individual has about an activity, themore likely he is to be able to identify all the hazardsand have accurate perceptions about thecharacteristics of the exposure and hence the risk.So it is essential that those performing riskassessments have the relevant practical experienceof performing the tasks being assessed.

Supervisors can be more likely tounder-estimate risk than front-line employees. It canbe argued that supervisors tend to underestimaterisk because for them, the risk-benefit trade-off forthe risk taking activity is biased towardsproductivity and this can lead them tounderestimate the risk. Involving all team/workgroup members in the risk assessment process cancounter-balance the supervisors’ underestimationof risk and may reduce the impact of this bias.

Mechanisms to reduce the impact of riskperception biases.

Adapted from Anon (1999)1) Are risk assessments performed by anindividual or a team with the following skills :-

-Practical knowledge of the operation beingassessed?-Knowledge of risk assessment techniques?-Overview of other factors (such as operations)that may influence the risk?

2) Do risk assessment training courses provideskills training to reduce perception biases?

3) Are the employees who are going to performthe operation involved in the risk assessment?

4) Is the accuracy of risk assessments performedby frontline employees monitored?

5) Was the way employees think about riskconsidered when risk assessments processes,

procedures, and documents were beingdesigned?

6) Do risk assessment procedures ensure that task-specific risk assessment are performed earlyenough to ensure that sufficient time is availableto implement the control measures and are notpressured to allow work to proceed?

7) Are task risk assessments performed by peoplewho have the authority and resources requiredto implement additional risk control measuresthey feel are required?

8) Do risk communication campaigns addressbiases in risk perception in order to combatcomplacency about operations frequentlyperformed?

Sub Standard Practices, Conditions andErrors

The immediate causes of an incident aredivided into categories: substandard practices(SSPs), substandard conditions (SSCs), and errors.Often the traditional terms unsafe acts (or ‘at-risk’behaviours) and unsafe conditions are usedinstead. However, “substandard” is preferable asit implies measurement against an agreed standard(set by legislature, professional bodies, companiesor joint risk assessments with supervisors andemployees). The term “unsafe” requires a largedegree of arguable, subjective judgement. Safetyis relative not absolute. Safer means lower risk andare achievable. Safe means zero risk and is notachievable at all times in all places under allcircumstances.

Safety is NOT zero risk taking rather it istaking only necessary risks and only after they arefully assessed and managed. SSPs are thebehaviours that we are interested from the point ofview of understanding and changing intolerablerisk -taking behaviour. A SSP can be defined asany practice that deviates from an agreed tolerable(quantitative) standard (i.e. the Agreed Standardpractice, or ASP). Examples include using animproper tool or method, using hazardoussubstances without the prescribed precautions,lifting a small compact article from floor height withstraight knees, choosing not to use or defeatingthe protective safeguards provided on a machine.


14

Similarly, a SSC can be defined as acondition that deviates from an agreed tolerable{quantitative) standard. Examples include defectivetools, lack of machine guarding, objects placed inaccess lanes. The interactions bet ween SSPs andSSCs are important. SSPs can lead to SSCs, andvice versa. For example the SSP of placing orleaving an article in a passageway leads to a SSC.The SSC of insufficient lighting may lead to theSSP of not using safety glasses when doing aprecise job with a grinder or a VDU operator usingwrong screen settings. Consequently thedistinction between SSPs and SSCs is not absolute.Therefore, although it is primarily concerned withminimising the frequency of use of SSPs, theprocess also will help to minimise the occurrenceof SSCs as well as Errors.

Human Error

Errors should always be seen as ConsequencesNOT Causes!

The 2 main categories of human performancedifficulties ‘errors’ - (with no intent and due toergonomic mism atches between person, task andenvironment) and ‘sub-standard practices’ (SSPs)(intentional acts for ‘good reasons’ which replacethe old ‘unsafe acts’ or ‘at risk behaviours’). (Figure4)

The most common good reason in the caseoftaking SSPs is to take a per ceived short-cut tosave perceived time, money and effort. We shouldnever criticize people for finding shortcuts becausethat is the perennial smart, necessary business,commercial imperative i.e. to find smarter, better,more efficient, more productive ways of doingthings. To criticize finding short cuts is duplicitous.All our other spoken, written communications inour workplaces favour and encourage the findingof short cuts, BUT we must recognise thedifference between finding a short cut and using itonly after a risk assessment is performed to justifyit replacing the currently Agreed Standard WorkProcedure (ASWP). As with SSPs, there are alwaysvery good reasons for errors. (usually ergonomicmismatches).

“Human error” as part of HumanPerformance Difficulties is a term that has manydifferent definitions. Extending Rasmussen’s work,Reason (1988) proposed a definition that has gaineda great deal of acceptance: error embraces all thoseoccasions in which a planned series of mental orphysical ac tivities fail to achieve the intendedoutcome, and when these failures cannot beattributed to the intervention of some chanceagency. Behavioural scientists use very negativewords such as human failures and violations. Thepreferred neutral term is Human PerformanceDifficulties which can be “errors” or SSPs. It isimportant to note that error refers to unintentionaldifficulties only.

Many human “failures” - I prefer“performance difficulties” - are performed withsome degree of intention, i.e. very ‘good’ reasons.Errors are always associated with ergonomicmismatches between the human, the work and/orwork environment. Humans often have difficultydoing what they want or need to do because thereare incompatible work tasks or work environments.

To account for intentional ‘failures’, Reasonuses another term, “violation”, defined asdeviations from those practices deemed necessary(by designers, managers and regulatory agencies)to maintain the safe operation of a potentiallyhazardous system. As we can see, these“violations” can be regarded as the same as“substandard practice” SSPs. The term“substandard practice” is more appropriate

Figure 4: Categories of Behaviours

H uman Per for mance Difficulties

E r r or s

Slips M istakes R outinecorrupted habit becomes

new 'standard' way

E xceptional'one of short cut

without risk assessment

SSkill-basedB ehaviour

RR ule-basedB ehaviour

KK nowledge-based

B ehaviour

* B ehavioural Scientists use 'violations' but prefer Sub Standar d Pr actices SSPs- old term was 'unsafe acts' or new term 'at-risk behaviour'- always intent / choice but always for 'good' reasons A dapted fr om R eason

B ehavior s of C hoice *


15

however as it does not imply blame to the sameextent as the term “violation” can.

Errors are unintentional types of SSPs. Theyare not performed with intentional disregard of theAgreed Standard to be used. For example, pressingthe incorrect switch or button or key, not wearinghearing protection may be an honest or unknowingmistake. Errors can also lead to SSCs (eg. forgettingto replace a guard on a machine after doing amaintenance task will lead to a SSC). Errors canalso occur in management decisions andsupervisory performance as well as in employeeactions. Directly focusing on SSPs which involvesome degree of choice or intent, without assumingor implying that the person has any wilful intentof harm or damage, is not directly concernedwith Errors. The risks due to SSCs and Errorsneed to be addressed fully by other parts of yourHSE programs. There is no suggestion ofmisguided emphasis on human behaviour in ourchoice of SSPs. Rather the emphasis is on theprinciple that there are always “good” reasonsfor people choosing SSPs. The goal is forworkgroups in a program to identify and analysewhat are the “good” reasons which lead us to useSSPs.

It is also essential that we remember that allrational behaviour is risk taking for “good” positivereasons, i.e. expecting benefits and gains. Risktaking is always speculative, i.e. for the perceivedgain, but with recognition of thechance of loss or harm as well. No one takes a riskfor the chance of loss. The types of behaviours ofinterest to are SSPs which involve some degree ofchoice or intent.

Root causes

SSPs. SSCs and Errors can be regarded asimmediate “causes” of incidents - they are theevents that are most closely associated with theincident itself. However, these immediate causescan be regarded as symptoms of the root or morebasic causes. All incidents can be regarded asresults of breakdowns in one or more aspects ofthe management system of control.

Root causes include:management safety policy and decisions

(eg. inadequate policy and programs, inadequateprogram standards, failure to comply with AgreedStandards), supervisory performance (eg.inadequate instruction, non-enforcement of rules,safety not included in job instruction, schedulingissues, fatigue),

personal factors (eg. lack of knowledge,unsuitable physical or psychological conditions,tiredness, fatigue, lack of vigilance), and

job/ environmental factors (eg. inadequateand non-agreed work standards, inadequate designor maintenance of equipment, speed, ie ergonomicmismatches). It is easy to see how root causes canlead to SSPs and SSCs. Thus, it would seem thatwe should focus on these root causes in an effortto control health and safety risk rather than onSSPs and SSCs.

Although the focus is on specificbehaviours (and thus immediate causes), theimplementation will necessarily involve a detailedexamination of the root causes that result in SSPs,and the identification and development ofappropriate solutions to overcome these rootcauses.Focuses are on specific behavioursbecause of the effectiveness and many advantagesassociated with this approach.

The role of SSPs in incident causation

Some studies have reported statistics onthe relative roles of SSPs and SSCs in incidentcausation. Heinrich’s (1959) study of 75 000incidents is the most well known. For each accident,he isolated one major immediate cause or significantcontributory factor.

Aside: There is never 1 and only 1 “cause”of an incident. He found that 88% of the incidentshad a SSP as the major immediate cause, and 10%of the incidents had a SSC as the major immediatecause.

Other studies have usually allowed morethan one immediate cause or contributory factorto be used for each incident. These studies haveusually found a similar number of incidents haveSSPs and SSCs as immediate causes, with usually70- 90% of incidents involving SSPs and 70-90%


16

involving SSCs. The National Occupational Healthand Safety Commission NOHSC (WorksafeAustralia) researchers conducted a study of 1020work related fatalities that have occurred inAustralia (Feyer and Williamson, 1990). Theirresults were that 91% of the fatal incidents hadbehavioural factors involved in their causation. Thestatement that most incidents are caused by SSPsis wrong and inappropriate. Many factors combineto produce an incident. A SSP may be one of manyreasons why an incident occurred, but it is unlikelyto be one of the many underlying root causes.Similarly, the use of the term “cause” can implyblame to the individual responsible for the SSP .

There are always good reasons whybehaviours occur, and connotations of blameshould be avoided. Studies investigating the roleof SSPs in incident causation often do notdistinguish between the relative role of intentionalSSPs and unintentional (errors). Both are certainlyimportant.

The studies have also used differentmethods and classification systems. There is a needfor more effective management of the behaviouralside of incident causation. However, it is theconditions side of the incident causation modelthat appears to have received more attention inthe past. Critics of behaviour-based safetywrongly claim that SSCs and their physical riskcontrol solutions are ignored. Legal and logicalimperatives such as the risk control hierarchydictate that physical and engineering aspects ofincident causation and risk control must takeprecedence over behavioural aspects but cannotdo so exclusively. It is just as illogical to rely solelyon engineering and physical solutions as it wouldbe to do so with behavioural options. It is equallywrong to assume that physical and engineeringcontrols are the complete answers. The commonprinciple called KISS (Keep It Simple Stupid)reinforces this harmful and incorrect approach.

While having some value in ensuringcorrective actions or risk control options are keptas uncomplicated as possible, it assumes that awork environment can be engineered to be ‘idiotproof or ‘fool proof’ i.e. it assumes that we canmake work so safe that even an idiot couldn’t gethurt. This belief gives a dangerous and wrongcomfort zone, because as is proven in all incident

studies, there are always aspects of SSPs wherepeople (Infinitely clever, motivated and innovativehumans) choose to vary or defeat or circumventeven the best safeguards/controls for a perceivedgain or benefit. Often the perceived gain or benefitis corporate rather than personal. A well-motivatedhuman can defeat everything which an imaginativeengineer can invent!

Aside: Maybe we should recognise theneed to replace the KISS Principle, Keep It Simple

Stupid by the MISS Principle. Make It SaferSunshine.

Types of Positive Behaviours of Interestto Safety Systems and Programs

The aim of OHSMS and safety programs isultimately about creating a system designed toincrease the use of certain agreed SPs and hencedecrease the use of certain SSPs. Most discussionsregarding the management of risk-taking behaviouremphasise the need to decrease the use of SSPs.In contrast, we must emphasise the importance ofincreasing the use of SPs. Focusing on desiredpositive behaviour, and reinforcing suchbehaviour, is a very important principle of effectivebehaviour management. However, increasing theuse of SPs and decreasing the use of SSPs arecomplementary aims. We need to focus on SPs asthis positive approach is more effe ctive forchanging behaviour, but we need to focus on SSPsinitially in order to understand why they occur andhow to best increase the frequency of SPs.

SSPs can be divided into those that areroutine and those that are exceptional. Routine orhabitual SSPs appear to be shaped by two mainfactors: the natural human tendency to take thepath of least effort, and an environment that isrelatively indifferent or forgiving (Reason, 1988).We need to orient our safety programmes todecreasing the occurrence of both routine andexceptional SSPs. Table 3 lists many of the commonSSPs of concern in industry. The reader isencouraged to rewrite them as positive SPs. SPscan be divided into those that are formally defined(i.e. specified in ASWPs, safety rules or by othersimilar means), and those associated with initiative(eg. checking the suitability of another individual’smachine guarding if something does not appear tobe right).


17

Table 2: Brief List of Error Types

- too early / too late- too much / too little- too long / too short- in wrong direction- on wrong object- wrong action on right object- in wrong sequence

- omitted

- forming an incorrect diagnosis

- not supported by available information

- omitted- on wrong object- wrong check on right object- check mistimed

- not obtained- wrong information obtained

- incomplete / confusing- wrong / inaccurate- too late / not timely

- of controls, tools, equipment

Brief List of Error Types

Actions

DecisionMaking

Checking

Information

Communication

Misalignment

The Value of Employee-Owned & AgreeStandard Work Procedures (ASWPs)

The SPs required for a certain task oractivity need to be formally defined and agreed bythe interested parties by a formal process. Thisformal definition is required to ensure that theappropriate behaviour is known, agreed and willbe consistently used. If the required behaviour isnot formally defined, then we are relying on“common sense” or the initiative of the relevantindividuals to guess if their perceptions ofappropriate (tolerable risk) behaviour match theperceptions of others. As we all know, thisapproach does not work because “common sense”cannot be assumed and is not common untilcommonality is achieved by formal discussion andagreement. SPs can be defined in terms of safety

rules, applicable to a certain work area or severaltasks, and the ASWPs for specific tasks. Thesesafety rules and ASWPs need to be developed bythe involved employees, after they thoroughlyanalyse what behaviour is required and reasonableto expect of the individuals concerned.Consequently, a Job Safety Analysis (JSA), leadingto writing of the procedure used to set up a ASWP,is a very important and essential component ofany approach to managing risk - taking behaviour.

Such an integrated analysis needs to leadto 1 and only 1 Agreed Standard Work Procedure(ASWP); Not a safe way, not a quality way, not anenvironmental way, not the productivity way butsimply your organization’s or workgroup’s agreedstandard way of doing each and every job as wellas you need and can do! All risk discussions andconsultations need to be based on the 7 principles- adapted from Corvello :-• Accept and involve all personnel as necessary

consultative ‘partners’• Plan carefully what is to be said and/or written

and evaluate your efforts• Listen to all your employees’ individual and

specific concerns.• Be honest, frank, and open.• Coordinate and collaborate with other credible

sources.• Meet the needs of internal and external media.• Speak/write clearly and with empathy and

compassion.

Risk Perception and the Shift of SafetyCulture to a Risk Management Paradigm

The ultimate influence on, or Activator Aof, a person’s behaviour is the individual’sperception of the level of risk associated with agiven situation and the use of certain types ofbehaviour. This perception of risk is a function of:1. The extent to which the person believes he/she is personally exposed and susceptible to agiven outcome (i.e. injury or illness); (“It won’thappen to me”)2. The extent to which the person believes the

outcome is serious; and3. The extent to which the person believes that

preventative action would be effective.


18

Table 3: Typical Sub Standard Practices SSPs - This is obviously only a representative - not an exhaustivelist. The reader is encouraged to rewrite these as positive SPs - no ‘nots’, or ‘don’ts’

1. Not following specified Agreed Standard Work Procedures.

2. Using unsuitable manual handling techniques (eg. lifting with the load not as close to the body as possible;

moving heavy items with large degree of spinal twisting or sudden jerking movements).

3. Not storing or disposing of articles appropriately (ie. poor housekeeping) (eg. free-standing gas cylinders;

placing or leaving articles in passageways; not cleaning up liquid spills).

4. Not reporting hazards or incidents observed, or injuries sustained.

5. Unsuitable placement of body in relation to task (et. Standing too close to a machine, standing with back

to a main passageway).

6. Operating machines or tools with methods other than that recommended (eg. at faster speeds than

recommended, for different purposes than recommended).

7. Not using the protective guards of a machine, or by passing/defeating safety devices or procedures.

8. Not using designated access lanes/passageways when moving around a workplace.

9. Not using appropriate lockout/tag out procedures (eg. not turning equipment off before starting

maintenance).

10. Using unsuitable working postures (eg. sitting slouched for long periods, not varying osture regularly).

11. Not wearing (and maintaining) required PPE in appropriate ways.

12. Wearing inappropriate clothing or other items (eg. loose, long hair or loose clothing around revolving

machinery; gloves while grinding).

13. Distracting, teasing, abusing, starting behaviour.

14. Not reporting near hits

15. Not discussing appropriate work methods with fellow employees

16. Not completing agreed number of risk analyses

17. Not completing agreed number of hazard/risk audits

18. Not reviewing agreed number of Standard Work Procedures - Practices

Although risk perception is the ultimatedeterminant of behaviour, it is again a belief orattitude, and consequently it is difficult to observe,measure or change by directly focusing on theinternal state itself. Perception of risk is stronglyinfluenced by personal experience with thesituation or task and observation of others in thesame situation. Short of actually having an incident(or even simulating incidents), there is often littlethat can be done to directly influence thisperception of risk when there are other motives inthe situation (eg. benefits for working quickly ortaking short-cuts).

An individual’s or workgroup’s tolerabilityof risk is an extremely complex concept thatdepends on personal, individual, corporate and

social values. In the workplace OHS context, theultimate arbiter of what is tolerable is usually aregulator or judge who is often called upon todecide whether the risk I benefit tolerabilityequation was evaluated according to thecommunity’s prevailing legal and moral standards.

On a day-to-day basis, the risk takers andthe risk makers are the appropriate riskmanagers. However, this principle assumes thatthe risk takers and the risk makers know and fullyappreciate all positive and negative dimensions ofthe risk.


19

Risk Level Estimation by Risk ScoreCalculation

All employees and managers need to beactive, committed participants in safety systemsand programs. Hence they all need to given theknowledge and skills to calculate risk. Thisprocess need not be time-consuming nor complex.The author can teach an employee how to reliablyand consistently calculate risk in as little as 1 hour.The Risk Analysis phase of Risk Managementconsists of 3 alternative or sequential levels ofanalysis. (See AS/NZS 4360: Risk Management:1999*)(* becoming the defector ISO world standard forrisk management.)

The 3 levels of risk analysis are:- qualitative- semi-quantitative- quantitative ORA

Qualitative risk analysis is the fastestassessment involving simple judgement of whetherthe risk is capable of being classified by verbaldescriptors such as “high/low” OR “high/moderate/low”.

Semi-quantitative risk analysis involves thenumerical assessment of the components of riskseparately then compounding them into an overallestimation of the risk level by a numerical score.

There are 2 common alternative forms ofsemi-quantitative risk analysis:-

The Matrix Method - 2 components of Risk(R) - Consequence (C) and Likelihood (L)(Figure 5) and,

The Tie-Line Method - 3 components ofRisk (R) - Consequences (C) Exposure(E)Probability (P) (Figure 6)

If a scale of 1 to 6 is chosen for each ofthe sizes of the components (See Tables 4 and 5),then the compounded risk score level ranges from2 to 12.

Notes:1) For convenience only, the term likelihood is

reserved for the Matrix or LC method and theterm probability is used in the Tie-Line/CEPmethod.

2) The 2 semi-Q methods are consistent and theTie-Line or CEP Method is essentially the sameas the Matrix method except that (L) likelihoodof the whole risk scenario has been broken into2 components - (E) exposure (duration/frequency of the critical breakdown event) and(P) the probability of the whole risk scenarioproceeding in its entirety as specified.

3) The Matrix/LC method is usually chosenbecause it can be faster than the Tie -Line/CEPmethod but its results can be less reliable andinconsistent.

4) Risk Scores provide the (often missing)objective basis for prioritising target beha-viours and compiling the traditional Criticalbehaviour lists, or similar, used for safety orrisk sampling.

5) The objective Risk Score settle the debatesabout tolerability:

11-12 Intolerable5 -10 ALARP1 -4 Broadly Tolerable / Negligible

Quantitative Risk Analysis QRA involvesdetailed specification of the risk scenario with agiven Consequence and all the risk factors/frequencies/probabilities for each of the events ina combination of logic trees such as Event andFault Trees. The ORA method yields a riskevaluation with an expression similar to:“the risk of the ..scenario VVV.. leading to aconsequence of ZZZ is 1 chance in 10000 perannum” OR“ the probability of ...VVV ...with consequence ZZZoccurring is 0.0001 per annum”.

With QRA, the Consequence andProbability are not compounded as in semi-0analysis methods. Safety systems and programoften can choose the “middle-of-road” semi-Qmethod as a reasonable workable compromise of:


20

- Ease of learning- time-to-perform, and- accuracy/reliability/consistency of risk scoring results.

The semi-Q method of risk scoring can beassisted by the use of Z -CARD TM pocket cardswhich replicate the Matrix or Tie-Lines of Figures5 and 6 as well as Tables 4 and 5. Their pocketportability maximises accessibility at the workplace.

Conclusion

Everyone involved in safety systems andprograms need the knowledge and skills associatedwith Risk Management otherwise there willcontinue to be confusion and argument about whatis an “at risk” behaviour and what is not. “Theterm “at risk” is no more helpful than the old term“unsafe act”. The pocket cards constitute adecision support system which can reduce theimpact of biases in risk perception by providingfront-line employees with a formal method to makeprobability and consequence/severity estimates.The results of generic risk analyses can supportemployees performing task-specific assessments.The development of programs/processes thatheighten employees’ awareness of the importanceof low consequence but high likelihood hazardswhen performing a risk assessment will also beworthwhile.

But the over-riding success of safetysystems and programs depends vitally on theavailability and understanding of tools to makeselection of target behaviours and meaningfuldiscussion of the results of safety or risk sampling.Stakeholders not having the knowledge or skill todo risk calculation is the “missing link” in mostsafety programmes and processes.

Philosophy Platform for Improved SafetyPerformance: “When all employees are fullyinvolved and participating in:- identifying their risks,- assessing them,- choosing risk control options, and- self-samplingtheir own agreed standard practices, then they will“own” and tolerate those standard practices ascoping with the residual risk that always remainsafter physical, engineering, risk control measureshave been implemented”


21


22

Reference

Anon. (1999). Extract from The Chemical Engineer.14-16.

Anon. (1993). System Safety Programme Requirements.AMSC Number F6861.

Anon. (1998). Risk Analysis of Technological Systems- Application Guide. AS 3931.

ACSNI. (1999). Human Factors Study Group ThirdReport: Organising for Safety. (London: HMSO AS/ NZS 4360).

Corvello, VT etal. (1988). Seven Cardinal Rules of RiskCommunication. U.S. EPA Washington, DC, April1988, OPA-87-020. Dwyer, J. (1998). Don’t gambleon risks. Works Management. 17-21.

Feyer, A., & Williamson, A. (1990) The involvement ofbehaviour in incident causation. (Paper presentedat Futuresafe 90 Congress, May 1990, Gold Coast.)

Fischoff B. , etal. ( 1978). How safe is safe enough? Apsychometric study of attitudes towards techno-logical risks and benefits. Policy Sciences, 9, 127-152.

Fischoff, Baruch etal. (1981). Acceptable Risk NY:Cambridge University Press. 1981.

Heinrich, H.W. (1931). Industrial Accident Prevention:A Scientific Approach. McGraw Hill Book Co.

IEC 61508-5: Functional safety of elect or programmableelectronic safety-related systems - Part 5

Krause, T.R., etal. (1984). Behavioural science appliedto incident prevention. Professional Safety, VoI29(7),Pp 21-27.

Malkiel Reason, Random Walk J (1988). Residentpathogens and risk management. (Paper presentedat World Bank Workshop of Safety Control andRisk Management, Washington.)

Royal Society. (1992). Risk Analysis, Perception,Management. The Royal Society.

Whiting, J.F. (1995). Proof Positive - Positive Perfor-mance Measures. Australian Safety News October1995

Whiting, J.F. (1996). Absolutely Safety Conscious.Corporate Risk Annual. p13

Whiting, J.F. (1997). Safety is Minimal TolerableRisk to People and Profit. (APOSHO 13 SafetyConference HONG KONG: 20 - 22 April 1997)

Whiting, J.F. (2000). Risk Tolerability. (ProceedingsVisions 2000 Conference Gold Coast).

Whiting, J.F. (2001). Risk Tolerability Framework -Developing and Implementing a Practical,Workable Framework for Your Workplace. (ASSEConf. 2001 Anaheim Session 704)

Whiting, J.F. (2001). Diligence and Governance need aRisk Tolerability Framework. (ARIMA Confe-rence, Canberra, Nov 2001)

Zimolong, B. (1985). Hazard perception and riskestimation in accident causation. In R E Eberts &CG Ederts (Eds.), Trends in Ergonomics/HumanFactors II. Amsterdam: Elsevier Science Publishers(pp 463-470).


23

Abstract

A study was undertaken to determine the effect of polyethylene and polystyrene used in the manufacture ofplastic items on colour perception. Colour vision was assessed using the Ishihara plates, panel 015 test and the FarnsworthMunsell 100-Hue test. Two factories were chosen at random. One factory (referred here as factory A) used virgin resinin pellet form (polyethylene) in the manufacturing of plastic containers to store consumer edible oil. The other factory(referred as factory B) used polystyrene to make plastic bags. A total of 39 healthy employees from factory A (mean age26.4 :t 8.2 years) and 40 healthy employees from factory B (mean age 26.8 :t 9.6 years) were recruited in this study. Acontrol group of 27 normal healthy subjects (mean age 27.4 :t 4.3 years) who were employees of UKM with nooccupational involvement with petroleum derivatives were also recruited in this study and they performed the samecolour vision tests. All subjects passed the Ishihara plates test showing that none of the subjects (employees of factoryA and B, and control subjects) had a congenital red-green defect. All control subjects passed all of the colour vision testswhilst some employees of factories A and B failed the 015 and FM100 Hue tests. For employees from factory A resultsfrom the 015 test showed that 7 (17.9%) had a tritan (blue-yellow) type of defect and 1 (2.6%) had a complex type ofdefect. The FM 100 Hue results of factory A employees showed that 51.3% (n=20) had a complex type of defect. Totalerror scores (TES) calculated from the FM 100 Hue test revealed that employees from factory A had a statisticallysignificant higher mean TES of 65.13:!: 48.31 compared to that of control subjects with a mean TES of 31.26:!: 14.93. Foremployees in factory B, 10 employees (25.0%) had a tritan (blue-yellow) type of defect and 2 (5.0%) had a complex typeof defect. Results of the FM 100 Hue test showed that 4 employees (1.0%) had a tritan type of defect whereas 22(55.0%) had a complex type of defect. Mean total error scores (TES) calculated from the FM 100 Hue test revealed thatemployees from factory B had a statistically significant higher mean TES of 71.54 :t 54.63 compared with that of controlsubjects with a mean TES of 31.26 :t. 14.93

The above results show that employees of the plastic factories studies are associated with a higher risk ofacquiring colour vision defects as compared to normal subjects who are not engaged in the plastic manufacturing industry.This may have an implication towards the future retinal health of employees in petrod1emical-based industries.

Key words: polyethylene, polystyrene, colour vision

Colour Vision of Workers in the Plastics Industry

Sharanjeet-Kaur, Mursyid A. and Ariffin A.E.Faculty of Allied Health Sciences, Universiti Kebangsaan Malaysia

Introduction

Interest in the colour perception of workersexposed to neurotoxic chemicals is relativelyrecent with very little research having addressedthe topic. However, during the 1999 InternationalSymposium on Neurobehavioral Methods andEffects in Occupational and Environmental Health,it was revealed that the number of chemicalsaffecting visual function was progressivelyincreasing (Gobba 2000).

It has been shown that chemical-relatedcolour vision impairment is an early effect that cangenerally be detected at low exposure levels if the

method used to test colour vision is sensitiveenough, provided that the results are evaluated byadequate methods, and that an appropriatelyselected control group is compared with (Gobba2000).

The petrochemical industry is a largeindustry producing basic plastic materials. Plasticsand resins make up about 60% of thepetrochemical end-product. The petrochemicalindustry produces basic raw materials such asethylene, propylene and vinyl chloride. Furtherderivates include basic plastics, such as

Original Articles J Occu Safety Health 1 : 25-30, 2004

25

26

polyethylene, polypropylene and polyvinyl chlo-ride. Three quarters of the total consumption ofplastics are targeted at basic plastics where West-ern Europe, USA and Japan use 64% of the totalpolyethylene produced (http:www.itcilo.itlenglish/actrav/telearn/ash/kemi/ctm9.htm). It is the largestvolume petrochemical product in the world.

One of the most widely studied plastics isstyrene. It is part of the family of polymers and isproduced from ethylene gas. Studies (Campagnaet al. 1995, 1996; Chia et al. 1994; Eguchi et al. 1995;Fallas et al. 1992; Gobba 2000; Gobba & Cavalleri1993a; Gobba & Cavalleri 2000; Gobba et al. 1991;Kishi et al. 2001) have shown that styrene can af-fect colour vision, even at lower exposure levelsthan the current Threshold Limit Value (TLV) pro-posed by the American Conference of Governmen-tal Industrial Hygienists (ACGIH) (ACGIH 1997).

However, other plastics like polyethylenehave not been much studied. One study (Gos et al.1999) showed that lacrimation disorders couldresult as a consequence of present workplace,number of hours of work per day, number of daysworked per week, previous workplace and type ofwork involved, duration of work at previousworkplace, history of colour vision problemspresently or in the past, history of colour visionproblems in other family members, medicalproblems such as diabetes, hypertension, heartdisease, etc, consumption of drugs, medications,traditional foods or medications, alcohol, historyof cigarette or tobacco smoking (if yes, thennumber of cigarettes or cigars smoked per day) andexposure to it. Another study (Zdzieszyska& Gos 1995) showed that exposure topetroleum derivatives in the petrochemicalindustry could result in colour vision defects.Theobjective of the present study was to evaluate thestatus of colour vision of workers employed in themaking of plastic products from polyethylene andpolystyrene using standard clinical colour visiontests.

Material and Methods

A cross sectional study was carried out onseventy-nine healthy individuals aged between21 years and 35 years who worked in a plastic

product manufacturing environment.

Place of studyTwo factories were randomly chosen. One

factory (referred to here as factory A) used virginresin in pellet form (i.e. polyethylene) to make plas-tic containers to store consumer edible oil. The otherfactory (referred as factory B) used polystyrene tomake plastic bags. All tests for the factoryemployees were conducted in a room provided bythe management at the factory site.

SubjectsA total of 39 healthy employees (mean age

26.4 :t 8.2 years) from factory A and 40 healthyemployees (mean age 26.8 :t 9.6 years) fromfactory B were recruited in this study. A controlgroup of 27 normal healthy subjects (mean age 27.4:t 4.3 years) who were employees of UKM with nooccupational involvement with petroleumderivatives were also recruited in this study andthey performed the same colour vision tests as thefactory employees. The control subjects were testedat the Optometry Clinic in UKM.

Tests conducteda. Questionnaire

Employees who volunteered to participatein this study first filled in a questionnaire. Thequestionnaire consisted of demographic data of thesubjects: duration of work at present workplace,number of hours of work per day, number of daysworked per week, previous workplace and type ofwork involved, duration of work at previousworkplace, medical problems such as diabetes,hypertension, etc.

b. Preliminary testsVisual acuity was measured for distance

using the Snellen chart and at near using a readingchart. Only subjects with best corrected distancevisual acuity of 6/6 or better and best correctednear acuity of N6 at 40 cm or better were included inthe study. Subjects with any systemic, ocular andneurological disease were excluded from the study.Direct ophthalmoscopy was also done to screenfor any ocular pathology.


27

c. Colour vision testsColour vision was assessed using the

Ishihara plates, panel 015 test and the FarnsworthMunsel1100-Hue (FM 100-Hue) test. The Ishiharaplates were used as a screening test for red-greencongenital defects. The 015 test FM100 Hue testswere mainly used as clinical tests for determing thepresence of acquired colour vision defects. Test-ing was done under daylight conditions. Subjectwore their best correction whilst doing both testsat a distance of 35 to 40 cm. The testing conditionswere similar for all three groups.

Results

a. Demographic dataThe demographic data of the subjects is

shown in table 1. The study group (employees fromfactories A and B) comprised predominantly ofmales. Most of the workers were foreigners, that isBangladeshis. They had been working at theirrespective factories for periods between 2 to 3 years.They worked almost 12 hours per day, and 7 daysper week. They reported of no medical or ocularproblems. There were also some employees whoconsumed alcohol and who smoked cigarettes. Themean age of the employees in factory A was 26.4 :8.2 years, in factory B it was 26.8 :t 9.6 years andthat of the controls was 27.4 :t 4.3 years. Therewere no statistically significant differences in themean ages of the three groups [ANOVA p > 0.05].As a whole one or two persons, all women, wereeither taking a traditional herbal remedy called Jamuor multivitamins.

b. Preliminary testsAll subjects had a distance visual acuity (V

A) of 616 or better when tested with the Snellanchart and a near acuity of N6 or better when testedwith a reading chart. Ophthalmoscopy did not showany fundus abnormality in any of the subjects.

c. Colour vision tests.Table 2 shows the number and percentage

of subjects having errors and therefore havingcolour vision defects on testing with the Ishiharaplates, panel 015 test and the FM100 Hue test. Itcan be seen that all subjects passed the Ishihara

plates test. However, the factory workers werefound to have colour vision defects when testedwith the 015 and FM100 Hue tests. Eight (20.5%)and 20 (51.3%) employees from factory A had colourvision defects with the 015 and FM100 Hue testsrespectively. Twelve (30.0%) and 26 (65.0%)employees from factory B had colour visiondefects with the 015 and FM100 Hue testsrespectively. All control subjects showed no de-fects when tested with the Ishihara plates, panel015 and FM100 Hue test.

Study Group / Ishihara Panel FM100Colour Vision TestPlates D15 Hue Test

Factory A 0 8 (20.5%) 20 (51.3%)Factory B 0 12 (30.0%) 26 (65.0%)Controls 0 0 0

Table 1: Demographic data of all subjects.

Data Factory A Factory B Factory C

Number of Subjects 39 40 27

Gender: Males 31 (79.5%) 29 (72.5%) 7 (25.9%) Females 8 (20.5%) 11 (27.5%) 20 (74.1%)

Race: Malays 8 (20.5%) 10 (25.0%) 21 (77.8%) Chinese 3 (7.7%) 2 (5.0%) 5 (18.5%) Indians 8 (20.5%) 10 (25.0%) 1 (3.7%) Others 20 (51.3%) 18 (45.0%)

Duration of Work (Years) 2.1 + 2.8 2.8 + 3.1 8.4 + 5.4

Duration of 11.28 + 1.50 11.36 + 1.50 8.11 + 1.20Work Per Day (Hours)

Duration of 6.6 + 0.5 6.7 + 0.5 Not Work Per Week (Days) relevant

General & Ocular Health Good Good Good

Traditional 1 person 1 person 5 persons Remedies taking taking taking Taken Jamu Jamu (2.5%) multi- (2.6%) 1 person vitamins taking (18.5%) multivitamins (2.5%)

Alcohol Consumed 3 (7.7%) 4 (10.0%) 0

Cigarettes Smoked 9 (23.1%) 12 (30.0%) 1 (3.7%)

Mean Age 26.4 + 8.2 26.8 + 9.6 27.4 + 4.3

Table 2: Number (%) of subjects showing colour visiondefects


28

The type of colour vision defect obtainedwas also analysed using the method devised byVingrys & King-Smith (1988). It can be seen fromtable 3 that colour vision testing with panel 015 testshowed that 7 (17.9%) employees fromfactory A and 10 (25.0%) employees from factory Bhad a tritan or blue-yellow type of colour visiondefect. A further 1 (2.6%) employee from factory Ashowed a complex or non-polar type of colour de-fect. On the other hand, testing with the FM100Hue test showed that 20 (51.3%) employees fromfactory A had a complex or non-polar type ofdefect whereas 4 (1%) employees from factory Bshowed a tritan or blue-yellow type of colourvision defect whilst a complex or non-polar type ofdefect was demonstrated by 22 (55.0%).

Table 3: Types of colour defects found.

Total Error scores (TES) were alsocalculated from the FM100 Hue test results. Themean TES for the three groups are shown in table 4.There was a statistically significant difference inmean TES between the two study groups and thecontrols (ANOVA, p<0.05). There was however nodifference in mean TES between the two studygroups.

Table 4: Mean TES of all subjects calculated from theFM100 Hue test.

Discussion and Conclusion

The factory workers in the present studywere found to have colour vision defects whentested with both the 015 and FM100 Hue tests.20.5% (n=8) and 51.3% (n=20) of employees fromfactory A had colour vision defects with the 015and FM100 Hue tests respectively. And 30.0%(n=12) and 65.0% (n=26) of employees fromfactory B had colour vision defects with the 015and FM100 Hue tests respectively. The higherpercentage of colour defectives detected with theFM 100 Hue test is testimony of the establishedfact that it is a more sensitive test for detectingacquired colour vision defects (Fletcher & Voke1985). All control subjects showed no defects whentested with the Ishihara plates. 015 and FM100 Huetests.

As for the type of acquired colour visiondefect, the 015 test showed that 17.9% (n=7) ofemployees from factory A and 25% (n=10) ofemployees from factory B had a tritan or blue-yellow type of defect. Another 2.6% (n=1) ofemployees from factory A showed a complex or non-polar type of defect, while 5% of employees fromfactory B had a complex defect. On the other hand,colour vision testing with the FM100 Hue testshowed most employees to have the complex typeof defect as opposed to a tritan defect per se. 51.3%(n=20) of employees from factory A had a complexdefect and 55.0% (n=22) of factory Bemployees showed a complex or non-polar type ofarrangement of defect, signifying appreciablereclassification of the nature of colour visiondefect within the employees as a whole. By thesame token the percentages of tritan defects re-vealed with the FM100 Hue test was expectedlyreduced dramatically in both groups, i.e. from 17.9%to none for factory A employees and from 25% to1% for factory B employees.

Whatever the exact nature of the type ofdefect present, these results show that working inan environment involved with the manufacturingof plastic products is associated with the presenceof an acquired type of colour vision defects.

Groups TES SD

Factory A 65.1 48.3

Factory B 71.5 54.6

Controls 31.3 14.9

Factory D15 Test FM100 Hue Test

A RG defect: 0 RG defect: 0BY defect: 7 (17.9%) BY defect: 0Complete: 1 (2.6%) Complete: 20 (51.3%)

B RG defect: 0 RG defect: 0BY defect: 10 (25%) BY defect: 4 (1%)Complete: 2 (5%) Complete: 22 (55%)


29

The nature of colour vision testing allowssome flexibility in the diagnosis of type becausedifferent clinical tests probe into different aspectsof colour perception (Aspinall 1974).Notwithstanding, taking the FM100 Hue test on itsown, the fact that more subjects had a defect withnon-polar arrangement could be interpreted as adeterioration of whatever tritan defects that wasoriginally present. Bresnick et al. (1987) has shownin his diabetic series that tritan defects couldbecome complex and show non-polar arrangementdue to progressive deteriorations from the outerretinal layers towards the optic nerve. Thus, theobservation of non-polar defect could reflect asimilar trend of progression in the severity of theacquired colour vision defect, taking into accountof the 015 test results that there was in thebeginning a tritandefect present. Total ErrorScores (TES) calculated from the FM100 Hue testshowed that there was a statistically significant dif-ference in mean TES between the control and fac-tory employee groups (ANOVA, p<0.05). There washowever no significant difference in mean TES be-tween the two factory employee groups. The em-ployees from factory A had a mean TES of 65.1 :t48.3, employees from factory B had a mean TES of71.5 :t 54.6 whereas the controls had a mean TES of31.3 :t 14.9. This corroborates the earlier results pre-sented. No correlation between TES andduration of work at the factories could be found.As the number of subjects studied in the two studygroups was small and the duration of work wasaround 2 to 3 years only, no significant correlationcould be established.

The mean age of the employees in factory Awas 26.4 :t 8.2 years, in factory B was 26.8 :t 9.6years and that of the controls was 27.4 :t 4.3 years.There was no statistically significant difference inthe mean ages of the three groups (ANOVA p >0.05). This meant that any colour vision defect seenin the employees of the plastic productmanufacturing factory were most probably due totheir smoking activity. Ophthalmoscopy also didnot show any fundus abnormality in any of thesubjects in both groups. The crystalline lens of allsubjects did not show any significant sclerosis ei-ther to account for the defects found. This indi-cates that the acquired colour vision defects seeninthe factory employees are most likely due to prob-

lems within the visual pathway, presumably partsassociated with the central or peripheral nervoussystems. None of the subjects had a congenitalcolour vision defect as shown by passes on theIshihara test by all subjects.

As a whole, it can be seen that 51% to 65%employees working in an environment whereplastic products are manufactured show anabnormal colour perception, with 1% having a blue-yellow or tritan type of defect and 51% to 55% hav-ing a complex non-polar colour vision defect. Itappears that being in the environment whereplastics products are being manufactured posts arisk to having an effect on colour vision.

One may speculate how the chemicals couldhave entered the body, with the respiratory tractbeing high on the list. As neurotoxins have beenshown to affect colour vision (Baelum et al. 1990;Campagna et al. 1995, 1996; Cavalleri et al. 1994;Chia et al. 1994; Eguchi et al. 1995; Fallas et al. 1992;Gobba 2000; Gobba & Cavalleri 1993a; Gobba &Cavalleri 2000; Gobba et al. 1991, 1993b, 1998, 1999b;Gonzales et al. 1998; Kishi et al. 2001; Muttray et al.1999; Nakatsuka et al. 1992; Raitta et al. 1978, 1981;Vanhoorne et al. 1996), it is not impossible that plas-tics manufacturing chemicals could do likewise inas far as affecting the nervous system.

The very fact that this could be shown,presumably, at a very early stage by deteriorationof the colour vision function is a significantindicator indeed for any corrective orprecautionary measures to be initiated. Subclinicalit may well be, but acquired colour vision defectshave unfailingly been shown before to signifyserious underlying central and peripheral nervoussystem disorders (Foster 1991 ); the results of thepresent study suggest that polyethylene andpolystyrene are capable of similar insults.

References

ACGIH. (1997). Threshold Limit Values for chemicalsubstances and physical agents and biological expo-sure indices for 1997. ACGIH (American Confer-ence of Governmental Industrial Hygienists), Cin-cinnati.

Aspinall PA. (1974). Inter-eye comparison and the 100hue. test. Acta Ophthalmologica. 307-316.

Baelum J, Lundqvist GR, Molhave L, Andersen NT.(1990). Human response to varying concentrationsof toluene. Int Arch Occup Health. 65-71.


30

Birch J. (1993). Diagnosis of defective colourvision. Oxford: Oxford University Press.

Campagna D, Gobba F, Mergler D, Moreau T, GalassiC, Cavalleri A, Huel G. (1996). Color vision lossamong styrene-exposed workers neurotoxicologicalthreshold assessment. Neurotoxicology.1Z: 367-374.

Cavalleri A, Gobba F, Paltrinieri M, Fantuzzi G, Righi E,Aggazzotti G. (1994). Perchloroethylene exposurecan induce colour vision loss. Neurosci Lett ill 162-166.

Chia SE, Jeyaratnam J, Ong CN, Ng TP, Lee HS. (1994).Impairment of color vision among workers exposedto low concentrations of styrene. Am J Ind Med.481-488.

Eguchi T, Kishi R, Harabuchi I, Yuasa J, Arata Y, KatakuraY, Miyake H. (1995). Impaired colour discrimina-tion among workers exposed to styrene: relevance ofurinary metabolite. Occup Environ Med. 534-538.

Fallas C, Fallas J, Maslard P, Dally S. (1992). Sub-clinical impairment of colour vision among workersexposed to styrene. Br J Ind Med. 679-682.

Foster OH (ed) (1991). Inherited and acquired colourvision deficiencies. MacMillan: London.

Gobba F. (2000). Color vision effect of neurotoxins.Neurotoxicology. ~(5): 857-862.

Gobba F, Cavalleri A. (2000). Evolution of color visionloss induced by occupational exposure to chemicals.Neurotoxicology. ~(5): 777-781.

Gobba F, Cavalleri A. (1993a). Kinetics of urinaryexcretion and effects on colour vision after exposureto styrene. In: Butadiene and Styrene: Assessmentof Health Hazards, Sorsa M, Peltonen K, Vainio H,Hemminki K, eds., Lyon, IARC Scientific Publica-tions, p 79-88.

Gobba F, Galassi C, Imbriani M, Ghittori S, Candela S,Cavalleri A. (1991). Acquired dyschromatopsiaamong styrene-exposed workers. J Occup Med. 33:761-765.

Gobba F, Fantuzzi G, paltrinieri M, Righi E, Cavalleri A.(1993b). Colour vision impairment intetrachloroethylene exposed workers. (Proceedingsof the 24th International Congress on OccupationalHealth. ICOH, Book of Abstracts, Nice, France),September - October 1993. 239.

Gobba F, Righi E, Fantuzzi G, Pedrieri G, Cavazzuti L,Aggazzotti G. (1998). Two-year evolution of perchloroethylene-induced color vision loss. ArchEnviron Health. 196-198.

Gobba F, Ghittori S, Imbriani M, Roccatto L, CavalleriA. (1999b). Colour discrimination loss in workersexposed to solvent mixtures. (International Symposium on Neurobehavioral Methods and Effects inOccupational and Environmental Health. NationalInstitute for Working Life, Program and Abstracts,Sweden), June 1999. 136.

Gonzales M, Velten M, Cantineau A. (1998). Increasedacquired dyschromatopsia among solvent-exposedworkers: an epidemiology study on 249 employeesof an aluminium-foil printing factory. Int Arch OccupEnviron Health. Z1: 317-324.

Gos R, Jarmak A, Korzycka, Nowicz B, ZdzieszyskaM, Goralczyk M, Sztarba T, Jurowski P,Gruntmeyer M, Kapica A. (1999). Lacrimation disorders in workers chronically exposed to petroleumderivatives. Med Pr. 25- 29.

Johnson. (1992a). The Ishihara test: on the preventionof job discrimination. J Am Optom Assoc. ~(5): 352-360.

Kishi R, Eguchi T, Yuasa J, Katakura Y, Arata Y, HarabuchiI, Kawai T, Masuchi A. (2001). Effects of low-Ieveloccupational exposure to styrene on colour vision:dose relation with urinary metabolite. Environmental Res. (1): 25-30.

Littlewood R, Hyde F. (1993). Screening for congenitalcolour vision defects. A comparison between Ohkumaand Ishihara test. Aust & NZ J Ophthalmol. ~(1): 31-35.

Muttray A, Wolters V, Jung, Konietzko J. (1999).Effects of high doses of toluene on color vision.Neurotoxicol Teratol. 41-45.

Nakatsuka H, Watanabe T, Takeuchi Y, Hisanaga N,Shibata E, Suzuki H, Huang MY, Chen Z, au as,Ikeda M. (1992). Absence of blue-yellow color vi-sion loss among workers exposed to toluene ortetracholoroethylene, mostly at levels below occupational exposure limits. Int Arch Occup Environ-Health. 4: 113-117.

Raitta C, Seppalainen AM, Huuskonen MS. (1978). N-haxane maculopathy in industrial workers. (Albrechtv Graephes Arch klin exp Ophthal). 66-110.

Raitta C, Teir H, Tolonen M, Nurminen M, HelpioE,Malmstrom S. (1981). Impaired color discrimina-tion among viscose rayon workers exposed tocarbondisulphide. J Occup Med. 189-192.


31


Hearing Loss in Walkman Users

Sofia Jaffer, Mohd Shakil RaziDepartment of Audiology and Speech Sciences, Universiti Kebangsaan Malaysia

Abstract

This retrospective study was conducted at the audiology clinic of UKM in the year 2000. It was intended todetect the effect of walkman on the hearing system of its users and to investigate whether distortion product otoacousticemission test can provide an early and reliable sign of cochlear damage or not. Distortion product otoacoustic emissiontest helps to determine the function of outer hair cell. Outer hair cells get damaged with exposure to loud sound, drugsand aging. Thirty subjects (20 in the study group and 10 in the control group), between the ages of 19-25 years, whofulfilled all the criteria of selection, were investigated. There were two sets of criteria (general and specific). Anyone,in the control or study group, failing in any of these criteria was excluded from the study. According to the generalcriteria, it was essential for all the subjects to have clean ear canals, normal hearing at all the frequencies (250Hz-8000Hz), normal middle ear function (Type A tympanogram), no middle ear problem, not used/using any ototoxicmedicine, no family history of hearing loss, no history of ear surgery, not exposed to any form of loud noise like disco,concert, F1 racing or gun shooting. According to the special criteria it was essential for the subjects in the control groupto have never used a walkman and those in the study group must have been using a walkman for at least 6 months.

Comparison of distortion product emission levels between control and study groups revealed that emissionswere significantly lower in the study group, across all the frequencies, suggesting outer hair cell damage in the walkmanusers. These differences reached level of statistical significance (p<0.05) at 2, 4, 6 and 8kHz. Using walkman at anintensity unsafe for hearing and a duration longer than recommended is suspected for the outer hair cell damage in ourstudy group. Those using walkman for longer duration and higher intensity manifested much lower emission levels.Our study supports the literature that distortion product emission test is a much sensitive test than pure-toneaudiometry, as it can detect cochlear damage long before it appears in an audiogram. It is recommended that people whoare exposed to loud noise regularly should be monitored with distortion product emission test. It is suggested that theuse of walkman

Introduction

Our hearing system is facing the assaultand bearing the consequence of the sound aroundus at all times (Table-1). It tends to manifest theeffect of noise in the form of tinnitus with a bangand hearing loss, insidiously. The damaging effectof noise on our hearing (noise induced hearingloss) is not apparent during the early stages ofexposure. Initially, the noise induced hearing lossmay be temporary, with hearing being recoveredsome time after the noise exposure has stopped.But with repeated exposure to loud noise, hearingloss eventually becomes permanent. The hearingloss tends to start in the higher frequencies andspreads gradually with further exposure (Taylor etal., 1965).

Some of the noise we are exposed to (roadtraffic noise, noise at the construction sites,blasting horn of a car or noise of a bike withoutsilencer), are unavoidable. There are many others(walkman, rock concerts, F1 racing, orchestra, discomusic, and gun shooting etc.), we deliberatelyexpose ourselves to without even thinking orrealizing about their effect on our hearing system.The level of noise we are exposed to (Table 1) andNIOSH’s recommended exposure limit(Table 2) provides a clue about the damagingeffects of noise on our hearing system.

Walkman is a popular gadget used bypeople during leisure time, exercise, reading,while at work, walking on the road or waitingfor bus, taxi or a train. It is used by people ofvarious age and of different background. It is

Original Articles

32

relatively more common amongst the teenagers andyoung adults for recreational and educationalpurposes. Regular walkman users use it to enjoymusic, to block off background noise while studying or performing work or to drown outbackground noise.

Noise Levels Around Us dBA

Children’s toy weapons 153Jet engine (near) 140Shortgun, Jet take off (100-200 ft) 130Firecrackers 125-156Discotheque 120Symphonic music peak 120-137Rock music band 110-150Power saw 110Pneumatic drill 110Garbage truck 100Subway, Motorcycle, Lawnmover 90Walkman, Portable cassette player 85-100Telephone tone 85Electric shaver 85Industries / Factories 85Flute 85-111Violin 85-103Average city traffic noise 85Vacuum cleaner, Hair dryer, Inside car 70Normal piano practice 70Normal Conversation 60

Noise Level (dBA) Recommended Exposure Limit(REL)

85 40 hours per week*8 8 20 hours per week9 1 10 hours per week9 4 05 hours per week97 21/2 hours per week

100 11/4 hours per week

* week of 5 working daysIn other words, exposure to 85 dBA for 40 hours/week is the same asbeing exposed to,

88 dBA for 20 hours per week9 1 10 hours per week9 4 05 hours per week97 21/2 hours per week100 11/4 hours per week


Table 1: Noise Levels Around Us

Table 2: NIOSH’s Recommended Exposure Limit (REL)

Ever since its introduction, people havedebated whether or not walkman has any damagingeffect on hearing or not? To some it is a primesuspect because it can deliver music at loudnesslevels hazardous to our hearing (Airo et al, 1996;Bradley et al, 1987; Rice et al, 1987). Others,Turunen et al, (1991, a,b); Hellstrom, (1991);Hellstrom and Axelsson, (1988) believe that it notthe case as the length of time that a person listensto a walkman is shorter than the length of timeworkers are exposed to industrial noise, so therisk of acquiring a permanent hearing loss fromwalkman use is comparatively small. This argumentmay be true if people are using it at a levelconsidered safe for hearing. Airo et al, (1996)believes that its prolonged use at higher soundlevels is harmful to hearing because, the louderthe sound the lesser time it takes for the damagesto occur (OSHA, 1995).

In view of the controversy, it was felt thatthere is a need to further investigate the effect ofwalkman on the hearing of its users.

Methods

This study was carried out in the year 2000at the Audiology clinic of UKM, Jalan Temerloh,Kuala Lumpur. Students between the ages of 19and 25 years volunteered to participate in thisstudy. Information about them was collectedthrough an interview and a short questionnaire.Only those who passed all the criteria of selectionwere selected for this study.

There were two sets of criteria. Anyone, inthe control or study group, failing in any of thesecriteria was excluded from the study. According tothe general criteria, it was essential for all thesubjects to have clean ear canals, normal hearingat all the frequencies (250Hz-8000Hz), normalmiddle ear function (Type A tympanogram), nomiddle ear problem, not used/using any ototoxicmedicine, no family history of hearing loss, nohistory of ear surgery, not exposed to any form ofloud noise like disco, concert, F1 racing or gunshooting. According to the special criteria it wasessential for the subjects in the control group tohave never used a walkman and those in the studygroup must have been using a walkman for at least6 months. None of the subjects were smokers.

33

Medical history and history of noiseexposure was obtained through a questionnaireand personal interview. Otoscopic examination wascarried out to check the ear canal for wax, discharge,infection and tympanic membrane. Pure toneaudiometry was carried out using Madsendiagnostic pure-tone audiometer and TDH-39headphone. Tympanometry was carried out usingGSI middle ear analyzer.

For distortion product otoacoustic emissiontest, following Bio-Logic equipments were used.Scout distortion product otoacoustic emissionsoftware, AuDX Scout Sport machine, connectedto the software through a computer was used todeliver the stimuli and record the responses. Bio-Logic probe ear tips (Adult foam tips). Technicaldetails: distortion product otoacoustic emissiontesting was carried out using the 750Hz-8000Hzdiagnostic protocol. Analysis was made at 750Hz,1kHz, 1.5kHz, 2kHz, 3kHz, 4kHz, 6kHz, and 8kHz.Pure-tone stimuli were presented at frequency f1and f2. Intensity of stimulus, L1 and L2 was keptconstant at 65 and 55dBSPL respectively. The f2/f1 ratio was 1.2-1.3. Iso-f2/f1 Paradigm was used inthis research. In this paradigm, f2/f1 ratio is keptconstant (at 1.2) and f1 and f2 frequencies are variedin such a way as to produce well-spacedlogarithmic frequency scale equal to the geometricmean of f1 and f2. The response collected fromthis paradigm is called “DP-Gram or DPEaudiogram”. Response pattern of emission areexpected to mirror the frequency configuration ofthe hearing seen in the pure-tone audiogram.

To determine the effect of intensity ofsound on distortion product oto-acoustic emission,intensity level at which our walkman users wouldhave been using their walkman was calculated onthe basis of the reported findings on the followingelements. Good speech to noise (S/N) ratio, noisereduction rating (NRR) of walkman headsets,intensity at different volumes, noise levels of soundaround us, purpose of using walkman by thestudents, exchange rate and NIOSH’srecommended exposure limit (REL). Consideringall the factors mentioned above, the possibleintensity level at which our subjects were usingtheir walkman was at least between 90-100 dB.

Based on NIOSH’s recommended exposurelimit (REL), the safe exposure duration for walkmanfor those using it at 90 dB level would be around

10 hours per week or 90 minutes per day and forthose using it at 100 dB would be 1º hours perweek or 11 minutes per day. Most of the subjectsinvolved in our study were using walkman for timelonger than REL. These timings would change ifwe take 85 dB as the safe limit or alter the tradingrelationship from 5 dB to 3 dB or vice versa.

If the sound level of the walkman isconstant over the entire period it is used, the dailynoise dose D can be calculated by D = 100 C/Twhere C is the total length of time (in hours)walkman is being used in a day, and T is thepermissible duration of exposure for thecorresponding sound level (OSHA guidelines). Assingle-number compound descriptor “daily noisedose” incorporate a time-weighted average,therefore, it was used. In the case of daily noisedose, the time weighting is according to the 5 dBtime/intensity trade dictated by OSHA regulation.

As a composite sound exposure descriptor,Leq (equivalent level) can also be used. Leq is a time-weighted energy average experienced over a givenperiod of time as if the sound was unvarying.Calculation of Leq values is based on an equationderived from an integral calculus equation. Leq = Li+ 10 log xi. Where, Li is the level experienced for aperiod of time and xi is the proportion of time Lioccurs with respect to total time. Unlike, daily noisedose, Leq uses 3 dB trading relationship.

To check the reliability of our test results,subjects were tested again after two weeks. Resultwas analyzed using independent t-test and Wilcox-Signed Ranked tests.

Result

The result is based on 30 subjects whofulfilled all the selection criteria. Twenty of themqualified for the study group and ten for controlgroup. Sample consisted of 26 boys and 4 girls.The mean age of subjects in the control group was22 years (SD = 1.7), and in the study group it was21.5 years (SD = 1.8). The t-test showed nosignificant difference. All the cases had normalhearing (Figure 1) and type A tympanogramsuggesting normal middle ear function. Use ofwalkman varied from 1-5 hours a day (between 6-30 hours a week). The daily noise dose was thereforebetween 12.5% (if walkman was used for one hour

J Occu Safety Health 1 : 31-37, 2004Original Articles

34

a day at 90 dB) and 300% if walkman was used for 6hour a day at 100 dB). This means, increase in theintensity level and duration of walkman use exposesits users to more sound than is permissible. Thistherefore increases the risk of auditory damage.

Distortion product otoacoustic emissionamplitude levels were measured as a function offrequency. Mean distortion product otoacousticemission levels of control group were compared withwalkman users to analyze the difference. DP-gram ofthe control group was used as reference data. Themean distortion product otoacoustic emission valuesobtained from the control and study group along withthose using walkman for different length of time(Table 3).

Figure 2 shows that the DPOAE amplitude in thecontrol group is much robust than in the walkmanusers, at all the frequencies. They reached the levelof statistical significance at and above 2kHz, (p<0.05).This finding suggests that the walkman noise hasaffected the cochlear hair cells of its users. Thisdamage is however not manifested in pure toneaudiogram, yet.

Figure 2: Comparison of DPOAE Levels in BothGroups

In Figure 3, comparison of the distortionproduct otoacoustic emission levels of controlgroup and those using walkman for different lengthof time is presented together. It is clear that, nomatter what the duration of use of walkman is, theDPOAE level in its users is low at all thefrequencies.

Figure 4, displays the finding between thecontrol group and those using walkman forapproximately 6 hours. It is evident that distortionproduct otoacoustic emission is stronger in thecontrol group than those using walkman forapproximately 6 hours. These differences werestatistically significant at 3kHz.

Figure 5, compares the finding between thecontrol group and those using walkman for ª12hours/week. Distortion product otoacousticemission is stronger in the control group than inthe walkman users. The differences in emissionlevels are statistically significant at 4, 6 & 8kHz.

Figure 6. Those using walkman >12 hours/week manifest widespread cochlear damage(manifested by greater reduction in cochlearemission level). These differences in emissionlevels reached the level of statistical significanceat 2, 4, 6 and 8kHz.

Frequency Mean DPOAE Mean DPOAE Amplitudei n Amplitude in in Walkman UsersH z Control Study ~ 6 hrs 6-12 hrs >12 hrs

Group Group

750 11.0 3.5 9.0 7.2 3.01000 12.0 4.2 8.0 6.0 3.01500 9.0 3.1 6.0 5.2 -1.02000 7.0 -1.0 7.0 5.0 -2.03000 6.0 -0.9 1.0 0.8 -6.54000 8.0 -1.4 4.0 -4.0 -8.06000 5.0 -7.2 3.3 -5.0 -11.08000 3.0 -9.5 1.6 -10.0 -14.0


35

Discussion

Most of us do not realize that our dailyactivities, whether occupational or recreational, canbe potentially hazardous to hearing. Exposure toloud noise can damage the hearing mechanisms inour ears. With a short-term exposure to noise suchas an occasional rock concert, hearing will mostlikely to recover within a day. However, if it is aregular feature then there is a high likelihood thatover time some permanent hearing loss will develop.Other recreational activities that can be potentiallydamaging to hearing include snowmobiles,motorcycles, firearms (i.e. target shooting orhunting) etc. Listening to stereos or Walkman-typeradios at loud levels is also suspected to causehearing problem.

In our study, we have tried to establish theeffect of walkman use on the outer hair cells ofcochlea. We noted that the amplitude of distortionproduct oto-acoustic emission of walkman userswas worse than those who were not using it. Thisfinding is in line with that of West and Evans (1990),that loss of or damage to the outer hair cells reducesor abolishes the oto-acoustic emission level. Weconsider our finding very important because innone of our cases this cochlear damage wasmanifested in their audiogram. As a matter of fact,all the subjects included in this study (bothgroups) had absolutely normal hearing. It isinteresting to note that hearing threshold ofsubjects in the study group was worse than theircounterparts. It is true that not all the frequencieshave shown the same level of damaging effect.This must not come as a blessing because theoverall picture is quite consistent. Similarly, itshould not be a matter of consolation that thedamaging level in cochlea did not reach the levelof statistical significance. On the basis of ourfinding, we believe that the notion “all is well if theaudiogram is normal” is misleading. Whatappeared to be the hallmark of noise inducedhearing loss (acoustic notch at 4kHz) should nowbe considered to be an outdated parameter in thediagnosis of noise induced hearing loss. In thelight of what we have observed, it is appropriate tosuggest that if distortion product oto-acousticemission results indicate cochlear damage inpeople exposed to noise, there is no justificationto wait for the appearance of the acoustic notch.

Figure 3: Effect of Duration of Use on DPOAE

Figure 4: DPOAE: Control vs Walkman Users (~6hrs)

Figure 5: DPOAE: Control vs Walkman Users (6-12 hrs)

Figure 6: DPOAE: Control vs Walkman Users (>12 hrs)


36

Our finding is important in the sense that it canhelp the audiologists and hearing conservationiststo take action to prevent the occurrence of hearingloss long before it starts showing up in audiogram.As far as the walkman users in our study areconcerned, manifestation of hearing loss in theiraudiogram is a matter of time if they do not takepreventive measures. Our distortion product oto-acoustic emission finding should in fact serve as awarning to them.

To substantiate that the cochlear damagewe noted was in fact due to walkman use. Welooked at two important elements “intensity andduration of use of walkman”. Both these are directlyrelated to the damage to our hearing (Table 2).

First, we calculated the expected intensitylevel of walkman, hypothetically. This calculationwas based on the sound level necessary tomaintain S/N ratio of +15, NRR of walkmanheadsets, intensity provided by walkman and noiselevels of sounds around us. We did not take intoaccount the type of walkman used because volumecontrol and loudness level produced by differenttypes of walkman is different.

In the calculation of the intensity level, theobjective of use of walkman (enjoying music, blockoff background noise while studying or performingwork and to drown out background noise of rushhour traffic noise etc.) was also taken into account.Research has shown that the traffic noise (noise atbus stands, train stations and other places) isusually between 80-85 dBA. The walkman usersneed a loudness level of 90-100 dB to drown outthe background noise and enable them to enjoymusic. This, to the walkman user, may appear to a“comfortable loudness level” but it is beyond therecommended safe level of 85 dB. This means thatthe hearing system of our subjects is at risk.

Secondly, we looked at the effect of theduration of exposure to 90-100 dB sound. UsingNIOSH’s recommended exposure limit (Table 2) andthe exchange rate mechanism (which states thatfor every 3 dB increase in noise exposure thedamage doubles, Table 2), the safe exposureduration for our subjects was calculated. It wasconcluded that the safe exposure duration forthose using walkman at 90 dB level would be 90minutes per day and for those using it at 100 dBlevel it would be 11 minutes per day. Our subjects

are using walkman for much longer time. This meansthat they are causing an unseen damage to theouter hair cells of cochlea.

Finally, calculation of the daily noise dosesupports the above findings. Use of walkmanvaried from 1-5 hours a day (between 6-30 hours aweek). The daily noise dose was therefore between12.5% (if walkman was used for one hour a day at90 dB) and 300% (if walkman was used for 6 hour aday at 100 dB). This means, increase in the durationof walkman use by a subject exposes him/her tomore sound than is permissible. This thereforeincreases the risk of auditory damage.

On the basis of what has been explainedabove, we believe that the weak emission noted inwalkman users is the reflection of cochlear damageoccurring due to unsafe loudness level and longerduration of walkman use.

We noted that the cochlear hair cell damageis directly proportional to the duration of the useof walkman, i.e., greater the use greater the haircell damage. It is also noticed that there is a specificpattern of cochlear hair cell damage, “cone shapedspread”, i.e., less damage for short duration ofexposure and more for the longer duration and moredamage at higher frequencies.

Conclusion

Walkman can cause hair cell damage incochlea, which if continued unabated (if intensitylevel and duration of use is not reduced) mayeventually give rise to hearing impairment in itsusers. Distortion product otoacoustic emission testcan detect cochlear damage well before it appearsin a pure tone audiogram. Test-retest resultindicates that DPOAE test can be used in clinicalpractice with high degree of reliability.

Caution

Even though the findings of our study arerevealing and extremely useful. It is important tomention that because of small sample size, cautionmust be exercised in interpreting our findings.Considering the importance of this study, it isessential that a large-scale study is conducted tosubstantiate our findings.


37

It is suggested that, distortion productotoacoustic emission finding should not be ignoredjust because pure tone audiometry results arenormal. Normal audiogram with abnormal distortionproduct otoacoustic emission suggests that theouter hair cells are damaged. Steps must be takento protect hearing before damaged hair cells startto die due to continuous exposure to high level ofnoise and audiogram starts showing hearing loss.

Rule of Thumb

If a person sitting or standing nearby canhear the sound emitting from your walkman: thesound is too loud. Should this happen, the volumemust be lowered.

Suggestion

People exposed to loud sound should havetheir hearing checked regularly with distortionproduct otoacoustic emission test. Distortionproduct otoacoustic emission test is less timeconsuming and more efficient in detecting cochleardamage. It is recommended that the intensity ofsound and duration of use of walkman must bereduced to the level safe for hearing system.

References

Airo E, Pekkarinen J, Olkinoura P. (1996). Listening tomusic with earphones: an assessment of noiseexposure. Acoustica, 82 (6): 885-894.

Bradley R, Fortnum H, and Coles R. (1987). Patternsof exposure of school children to amplified music.Br J Audiol, 21: 119-125.

Hellstrom PA. (1991). The effect of hearing fromportable cassette players: A follow up study. J SoundVibr. 151 (3): 461-469.

Hellstrom PA and Axxelsson A. (1988). Sound levels,hearing habits and hazards of using portable cassetteplayers. J Sound Vibr. 127: 521-528.

OSHA Regulations. (1995). Standards - 29 CFR, 1910-1995.

Rice CG, Rossi G, and Roper RG. (1987). Sound levelfrom personal cassette stereo players. Br J Audiol,21: 273-288.

Turunen-Riseet I, Flottorp G, and Tvette O. (1991-a).Personal cassette stereo players (walkman), do theycause noise induced hearing loss. Scand Audiol, 20:239-244.

Turunen-Riseet I, Flottorp G, and Tvette O. (1991-b).A study of the possibility of acquiring noise inducedhearing loss by the use of personal cassette stereoplayers (walkman). Scand Audiol Suppl, 34: 133-134.

West PDB and Evans EF, (1990). Early detection ofhearing damage in the young listeners resulting fromthe exposure to amplified music. Br J Audiol, 24:89-103.


39

Introduction

Adverse effects from chronic exposure toorganic solvent have been documented in manydeveloped countries. Based on the epidemiologicalstudies, it has clearly shown that there is arelationship between organic solvent exposureand clinical complications such as peripheralneuropathy fatigability, irritability and memoryimpairment (Costa and Manzo, 1998). In Malaysia,however there is no scientific evidence reportedso far.

This report documents clinical evidencesuggestive of chronic organic solvent exposureand its effect on the nervous system.

Neuropathy due to Organic Solvent Exposure: ThreeCases Reported From Pahang, Malaysia

Agus Salim M.B.a

, Malina, Ob

, Hisanaga, N.c

, Hirata M , Zainul Abidind

a

Occupational Health Division, National Institute of Occupational Safety and Healthb

Medical Faculty, Universiti Putra Malaysiac

National Institute of Industrial Health, Japand

Department of Occupational Safety and Health

Abstract

Exposure to organic solvent during work activities has been known to be associated with significant clinicalconditions such as peripheral neuropathy and neurobehavioral changes. Three reported cases of peripheral neuropathymost likely due to exposure to chronic organic solvent were reported recently in Bentong Malaysia. These casesshowed a compatible clinical history, occupational history, examination and neurological study that link with peripheralneuropathy due to organic solvent poisoning. Proper education and training with review of engineering control measuresare among preventive and corrective measures recommended. More comprehensive study in order to establish significantcausal-effect relationship as documented evidence is recommended.

Keywords: Organic solvent, occupational exposure, neurological studies, neuropathy

Methods

Malaysia’s Department of OccupationalSafety and Health (DOSH) as a regulatory body isresponsible to conduct inspection and enforcementactivities under the Occupational Safety and HealthAct 1994 (OSHA 1994). A few cases of neurologicalimpairment in a company located in Pahang werereported to the department. DOSH and NationalInstitute of Occupational Safety and Health(NIOSH), Malaysia in collaboration with JICA(Japan International Co-operation Agency) projectteam, initiated a detail investigation. Theinvestigation included walk through survey,workers interview, clinical assessment on thesuspected cases. Based on the initialinvestigations, there were three cases thatpresented with neurological problems.

Short Communication J Occu Safety Health 1 : 39-42, 2004

40

All the three cases were further examinedclinically and sent to NIOSH for neurologicalstudies. The tests included the following:

Test Instruments used

Grip test Tracker C.H.E(Unit = kg) (J Tech Medical Industries, US)

Pinch Test Tracker C.H.E(Unit = kg) (J Tech Medical Industries, US)

Balance test Balance Master(Neuro Com System, US)

Nerve Conduction Neuropack SigmaVelocity (Nihon Kohden Japan)

Brainstem auditory Neuropack Sigmapotential (Nihon Kohden Japan)

The tests were carried out under strictprocedures and expert supervision (Colin et al.,1996)

Background of the company

The company, situated in Pahang Malaysiawas established in 1989 and currently one of theworld’s largest PVC floor manufacturer. Organicsolvents used in the work process include MEK,MIBK and Toluene, which are mainly used in theprinting section.

Results

Case 1:A 33 year old Malay man, who had been

working with the company since 1990 complainedthat he had numbness and weakness of both handsfor 6 months. The problem actually began in 1999when he started having lethargy and reduced efforttolerance after being posted to coating sectionwhere he had to dip his hand into Methyl EthylKetone (MEK) solution without using properpersonal protective equipment. Later on, he wasposted to printing section (July 2001) which usedhigh quantity of MEK, Methyl Isobutyl Ketone(MIBK), cyclohexanone and toluene. Since then,he started feeling numbness and weakness of theextremities.

Apart from the above complaints he alsosuffered heavy headedness, headache, dizzinesson standing up, difficulty in concentrating,fatigability, abnormal thirst and palpitation. Thesymptoms were worst during the working hours.He perceived that the severity of the symptomswere associated with the intensity of exposure toorganic solvent or duration of working hours. Thesymptoms were reduced after he left printing workin December 2001.

Subjective symptoms reported during thework process when exposed to organic solventsinclude smell of solvents, eye irritation,nasopharyngeal irritation, headache, drunkenfeeling, sleepiness and edematous face

Clinical examination revealed a non distinctpattern of sensory loss over the upper extremities.Main muscles bulk, power and tone were found tobe normal. Reflexes were also normal.

Nerve conduction velocity test revealed aslow velocity of the sural nerve i.e 45 m/sec (49 -65m/sec) and brainstem evoke potential test showeda lengthened right cochlear nucleus response.

Case 2:A 23 year old Malay man, had been working

for the company since 1995. He was posted toprinting section since 1997 where he had exposureto main organic solvents used namely MEK, MIBK,cyclohexanone and toluene. He complained ofhaving weakness of the right hand. The symptomwas also associated lethargic and insomnia.

He admitted that he had been having healthproblems since 1997 which is 2 years after hestarted the job in printing section. At that time hecomplained of having numbness over theextremities (glove and stocking distribution). Itbecame more severe during work-days andimproved after he left the printing section in 1999.Other symptoms that he experienced washeadache, feel dizzy on standing up, difficulty toconcentrate, anxiety, occasional fainting spell andpalpitation.

Previously, he was also involved in manualhandling activity of lifting heavy object i.e 40 - 50kg , 20 times a day ( 4 days a week).

Subjective symptoms during work whenexposed to the organic solvent were smell of

Neuropathy due to Organic Solvent Exposure: Reported Cases From Pahang, Malaysia

41

solvents, eye irritation, nasopharyngeal irritation,face blushing, headache, dizziness, drunken feelingand sleepy.

Clinical examination revealed a reducedgripping power of all digits in the right hands. Nosensory loss was noted and other examinationrevealed normal.

Neurological tests revealed abnormalfindings on pinch test (right palmar), slowconductivity of median (sensory) and sural(sensory) nerves while brainstem evoke potentialtest showed altered latencies in certain standardwaves for both left and right sides.

Summary of the case

All the three cases showed the followingcharacterisitics:1. Common symptoms namely heavy headedness,

headache, dizziness, paraesthesia in extremities,numbness in extremities, reduced muscularstrength, feel dizzy on standing up and palpita-tion.

2. Occupational history indicating that they wereinvolved heavily with organic solvents namelyMEK, MIBK, cylohexanone and toluene.

3. Subjective symptoms suggestive to theimpairment function of central and peripheralnervous systems.

4. Clinical findings of peripheral neuropathy.5. Lab neurological tests of abnormal nerve

conduction velocity and brain evoked potentialtests.

6. The symptoms were prominent during workingdays and less during holidays. The changes insymptoms were consistent with the degree ofexposure to organic solvents.

7. No history of alcohol or any other drugs abuse.

Discussion

Based on the results of interview, clinicalexamination and neurological studies, the casesshown evidencesuggestive of organic solventpoisoning due to occupational activities. Withextensive reviews from clinical and occupationalpoints of view, there is a possibility thatneuropathies reported in these cases areoccupational in origin. Effects of otheroccupational hazards other than organic solventswere excluded during interviews. Past medicalhistory, hereditary factors, personal habits suchas smoking, alcohol or any drug effects were alsoruled out. The temporal relationship between the

Case 3:A 34 year old Malay man, had been working

with company for 12 years. He noticed havingnumbness of extremities associated with frequentattack of dizziness and headaches since he joinedthe printing section in 1993 (heavy involvementwith MEK, MIBK, cyclohexanone and toluene).The symptoms were prominent during the workinghours and the severity would change consistentlywith the changes of organic solvent exposure. Thenumbness of the hand improved where it was onlyconfined to the tip of fingers after he left the printingsection in 1997. Other associated symptomsincluded heavy headedness, headache, difficultyto concentrate, blurred vision occasionally,tinnitus, reduced muscle strength, gait disturbanceduring headache, finger tremor, fatigability,dizziness on standing up, palpitation andpsychological craving towards organic solvent(addiction).

At present he is working in calendaringsection and is partly involved in varnishing sectionwhere he is exposed to diethylene glycolmonomethyl ether. He has also had a back painproblem as he was involved in heavy liftingactivities.

Subjective symptoms during work withexposure to organic solvent include smelling ofsolvents, eye irritation, nasopharynegeal irritation,headache, dizziness and sleepiness.

Physical examination revealed sensory lossover the finger tips of both hands. Muscles bulk,power and tone and all reflexes are normal.

Neurological tests revealed slowconductivity for median, peroneal and sural nerves(both motor and sensory) and shortened latenciesin standard waves frequency of brain evokepotential tests.

Short Communication J Occu Safety Health 1 : 39-42, 2004

42

Proper education and training with reviewof engineering control measures are amongpreventive and corrective measures suggested.More comprehensive study in order to establishsignificant causal-effect relationship asdocumented evidence is recommended.

References

Costa G.L. & Manzo L. (1998). Occupationalneurotoxicology. CRS Press: Florida.

Colin, D.M., Ray, C., Clare, J.F., Francois, M., & Pamela,E.P. (1996). Clinical neurophysiology EMG, nerveconduction and evoked potentials. ButterwothHeinemann: Oxford

symptoms and organic solvents exposure i.e theonset starts after the exposure and the severity ofthe symptom change with the intensity ofexposure supports the diagnosis.

Clinical and laboratory findings supportthe evidence and though it is not definite, it issuggestive thatorganic solvents would be the maincause in all the three cases reported withsubjective symptoms of both central andperipheral nervous system.

Neuropathy due to Organic Solvent Exposure: Reported Cases From Pahang, Malaysia

1

Guidelines for Contributors

The Journal of Occupational safety and Health is concerned with areas of current information in occupationalsafety and health issues in Malaysia and throughout the world.

General Guidelines

· Manuscripts should be sent in triplicate to the Secretariat, Journal of Occupational Safety andHealth, Information Services Unit, NIOSH, Lot 1 Jalan 15/1, Section 15, 43650 Bandar Baru Bangi,Selangor. (fax 03-8926 5900, tel 03 -892 96731). Please do not fax or e-mail original submissions.

· Prepare manuscripts in accordance with the Publication Manual of the American PsychologicalAssociation (APA), Fifth Edition.

· Submit a cover sheet including: article title, author(s) name(s), affiliation(s), and complete mailingaddress, phone, fax, and e-mail address of the corresponding author. If at any time during thereview or publication process this contact information changes, please contact the secretariat withthe updated information.

· We will send you an acknowledgment when we receive your submission.

· Manuscripts must be typed double spaced on standard-sized paper using 11- or 12-point type (useTimes Roman or similar font). Include page numbers.

· Organisation of material for empirical investigations should follow standard reporting format -“Problem,” “Method,” “Results,” “Discussion,” and “Summary.” We also ask that each authorincludes a section at the end of the manuscript that explains the topic’s “Impact on Industry.”

· For theoretical discussions or commentaries and literature reviews, appropriate headings shouldbe inserted to provide a general outline of the material.

· Clarity of language and presentation are essential, and care should be taken to avoid unnecessarytechnical terminology.

· An abstract, l00 to 150 words, should accompany the manuscript. This should summarise the studyand include the subheadings “Problem,” “Method,” “Results,” “Discussion,” and “Summary.” Itmay not be necessary for all subheadings to be included, based on the nature of the manuscript.However, we do ask that all authors include a sentence or two on the “Impact on Industry,” whichwill be included in the abstract.

· Authors must include five keywords or phrases for indexing.

· A short biographical sketch of each author should also be submitted noting educational background,present and past employment, and research interests.

· Define all abbreviations.

· Keep a copy of the manuscript for reference.

· The editorial office retains the customary right to style.

· All material submitted for publication is assumed to be submitted exclusively to the journal unlessotherwise stated.

· Once your manuscript is accepted for publication, it may be reproduced with, stored in the retrievalsystem or transmitted in any form or by any means, electronic, mechanical and photocopying withthe consent and permission by the publisher. Application for permission should be addressed to :ISU, NIOSH, Lot 1, Jalan 15/1 Section 15, 43650 Bandar Baru Bangi, Selangor Darul Ehsan.E-mail: [email protected]

1

· Permission to reproduce previously published material must be obtained in writing from the copyrightholder and acknowledged in the manuscript.

References:

All references must be formatted in accordance with the Publication Manual of the American PsychologicalAssociation (APA), Fifth Edition.

For example:

Journal Articles:

Smith, A.B., Adams, K.D., & Jones, L.J. (1992). The hazards of living in a volcano. Journal of Safety Research,23(1),81-94.

Book:

Perez, A.K., Little, T.H., & Brown, Y.J. (1999). Safety in numbers. Itasca, IL: National Safety Council. See theAPA manual for more detailed instructions.

Tables and Figures:

Tables and figures should be on separate sheets from the text, in accordance with APA style, numberedconsecutively and given a short but explicit title. Figures must be supplied as glossy photographs orprofessionally or electronically drawn artwork using heavy white paper and black ink. A notation should bemade in the text showing approximately where each table or figure should appear (e.g., Insert Table 3 here).When referring to a particular table or figure in the text always use its number. All tables will be re-set in theproduction process. All figures will be scanned from the original.

Computer Disks:

If you send a computer disk with your submission, please label it with the author(s) name(s) and manuscripttitle. Disks will not be returned. Only Microsoft Word format is accepted.

Offprints:

Authors will receive 10 complimentary offprints of their article. Larger quantities will be made available inmultiples of 100, the cost to be determined by the amount ordered and the length of the article.

Subscription InformationJournal of Occupational Safety and Health (ISSN 1675-5456) is published bi-annually by Information

Services Unit, NIOSH, Malaysia. Subscription prices are available upon request from the publisher or fromwww.niosh.com.my. Issues are sent by standard mail. For orders, claims, product enquiries and advertising

information, contact Diyana / Siham 03-8929 6747 or [email protected]

Advertising RatesEnquiries to be directed to the secretariat.

Secretariat AddressNational Institute of Occupational Safety and Health

Lot1, Jln 15/1 Section 15, 46350 Bandar Baru Bangi SelangorTel: 603-8929 6747 Fax: 603-8926 2900

E-mail: [email protected] Website: www.niosh.com.myKdn No.: PP13199/8/2004

journal osh

Documents