occupational exposure assessment · 2013. 11. 15. · 1 occupational exposure assessment: why you...

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Occupational exposure assessment:Why you need an industrial hygienist

Jan-Erik Deadman, PhDCorporate health and safety advisor

OEMAC ConferenceMontreal, September 29, 2013

2 Vice-présidence – Ressources humaines, Hydro-Québec

Learning objectives

• Recognize the importance of assessing the right route of exposure

• Recognize the importance of correctly understanding the reference standard

• Be more critical of exposure assessments

• Recognize the central role of the industrial hygienist in the management of occupational health risks


Plan

• Exposure assessment : – Central to occupational health– The process in detail– Interactions with the occupational health team, managers

and workers– From perception to reality– Proactive exposure assessment– Reactive exposure assessment

• Conclusions

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Exposure assessment

"How important is this exposure?" "Does it represent a risk to health?""Does it need to be reduced, and if

so, how should it be done?"

• The answers to these questions are found in one of the most important functions performed by the industrial hygienist : exposure assessment.


Exposure assessment : What is it?

• The process of estimating the magnitude of exposure to an agent and describing its sources, pathways and the uncertainties of the estimate

• Includes comparison with a reference value• Two fundamental goals

– identify determinants of exposure (factors that modify exposures) – identify risk to the health of exposed individuals

• Relies on observation, documentation and tools to evaluate a situation in the workplace

– Observation• vision, hearing, olfaction & 6th sense

– Documents• Ex., reference values, engineering plans / process flow charts• material safety data sheets, published reports

– Tools • Ex., equipment to measure concentration or level of exposure• video camera, air velocity meter, smoke generator


Exposure assessment : Central to occupational health

Risk control

Exposure / risk assessment

Risk management

Identify exposure to hazardsIdentify undesirable effects

Identify tolerance levels (standards : legal, health, comfort, best practices)

Evaluate exposure and risk

Identify appropriate control measures

Implement control measures

Evaluate effectiveness

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Exposure assessment : Central to occupational health

Exposure assessment

Riskcommunication

Education &training

Epidemiologicalsurveillance

Medicalsurveillance

Compliancemonitoring

ControlsEngineering

AdministrativeWork practice

Personalprotectiveequipment

Situation acceptable?- Legal standards

- Health-based standards- Comfort standards No

(Positive exposuredetermination)

Yes(Negative exposure

determination)


Exposure assessment : The process

• What is the hygienist looking for?– Opportunities for exposure– Interactions between workers, raw

materials, equipment and control measures that result in exposure to an agent at an undesirable level

• How does the hygienist do this?– Understanding :

• Operations and tasks that constitute the processes

• Physical, chemical and mechanical principles at work

• Worker's habits• Effectiveness of control

measures• Reference values (tolerance

limits)– Attentive observation of the work

situation :• People, equipment,

organisation of activities


Exposure assessment : The process

• Break down of activities into their basic steps

• Identification of raw materials, intermediates, final products, equipment, machinery and control measures used at each step:

– form, quantity, composition of materials

– intrinsic toxicity– propensity to be

released into the air– relative importance

of the quantity released

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Exposure assessment : Understanding the reference value

• Once exposure is adequately assessed, with what do we compare it ?

• Is there a relevant reference value?• For what (and whom) was it developed ? :

– which health effects?– chronic, acute, or sub-chronic?– which reference population?– which route(s) of exposure?

• What are the uncertainties?– "nearly all workers"


Interactions : It's teamwork !

• The industrial hygienist acts as the interface between the different occupational health experts :

• Safety officer / engineer• Industrial hygiene technician• Occupational physician / occupational health nurse• Ergonomist• Occupational psychologist

• … between the different workplace experts :• Worker (expert in work actually performed)• Engineer / process designer (expert in work as designed)• Manager (in between the above two…)

• … and with external agencies :• Analytical laboratory• Consultants• Regulatory agencies• Media


Exposure assessment : Interactions with OH professionals

• The occupational hygienist's strong suit : identify, quantify, and propose solutions for exposures that present chronic risks

• Adequate exposure assessment allows better focussing of :

– medical surveillance– epidemiological surveillance

Epidemiologicalsurveillance

Medicalsurveillance

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Exposure assessment : Interactions with workers / management

• Adequate exposure assessment also allows risk communication and training to be geared to actual (and not hypothetical) exposure levels


Exposure assessment : Interactions with management, engineering and workers

• Adequate exposure assessment also allows :– Better tracking of exposure trends – Better focussing of engineering, administrative or

work practice controls– Appropriate selection and use of PPE


Exposure assessment : proactive and reactive

Proactive (cause → consequence) : • Does a particular occupational situation present a risk to

health ?

Reactive (consequence → cause) : • Can the observed or alleged health effects be related to

an exposure in the workplace ?

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Exposure assessment – from perception to reality

http://www.pgbeautyscience.com/assets/images/safety/risk-hazard-exposure.jpg

… risk perceived by the process designer

… risk perceived by the worker



• Risk evaluation by an occupational hygiene professional

Intrinsic toxicity Route of exposure Preventive measures

x - = Risk

DurationFrequencyComparison with tolerance level



• Does this mean that we should disregard perception?

– Absolutely not !• The goal is to align

perceptions with objective risk assessment

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Proactive exposure assessment Example : Prevention of health risks from exposure to lead

• Hydro-Québec's objective : establish best practices to manage lead exposure and prevent health risks

• Guide for preventing risks to health from lead exposure

1. Identify activity and the expected risk category

2. Identify corresponding preventive measures

3. Inform workers about the effects of lead on health and preventive measures

4. Implement preventive measures, including a respiratory protection program

5. Monitor the implementation of preventive measures in the field

6. If necessary, monitor concentration of lead in air and surface contamination

7. Institute biological monitoring if indicated.





Low risk (< 50 ug/m3)

High risk (500 - 2500 ug/m3)

Moderate risk (50 - 500 ug/m3)

Very high risk (> 2500 ug/m3)

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Reactive exposure assessment : Lead on surfaces



• Hydroelectric generating station built in 1942 - 1945

• 48 MW • 4 Francis turbines• 15 employees • Overhaul of generating

units• Anticorrosive lead-

based paint used on many surfaces



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Inside surface of spiral casing



Lead identified on multiple surfaces by contractor• Lead present in paint (0,2 % to 8,7 %)• Hydro-Québec's objective : prevent health risks from lead exposure• Contractor's objective : establish level of contamination before

renovation work– Wipe sampling conducted by contractor to determine presence and

extent of any surface contamination– Reference value used by contractor and industrial hygiene consultant

• 11 µg / 100 cm2

– Results for surfaces (values expressed in µg / 100 cm2)• 23 wipe samples• < 11 µg / 100 cm2: 7 samples• > 11 µg / 100 cm2: 16 samples (up to 3,030 µg / 100 cm2)



Misinterpretation of the surface sampling results• Contractor concludes that exceedance of 11 µg / 100 cm2

reference value represents a risk to workers' health• Contractor informs our employees• Workers' health and safety board (CSST) asked to inspect• CSST inspector also equates the surface contamination

with risk, citing the 11 µg / 100 cm2 reference value • All renovation work is stopped until surfaces are cleaned

down to the reference value

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Reactive exposure assessment : Lead on surfacesRisk to health

Our position– Risk to health is assessed by evaluation of job tasks

(airborne exposure monitoring, combined with blood lead testing if indicated)

– Surface wipe sampling • is an indicator of the the presence (or absence) of lead,

solely useful for evaluating the presence of lead and effectiveness of cleaning measures,

• cannot be used to predict health risk



For what and for whom was the reference value developed?• (2001) US : HUD / EPA value for decontamination of floors in

residential environments– Prevention of lead-related health effects in children 1 to 2 y old

• Assumes that lead paint is eaten or that contaminated objects are put into the mouth

• Assumes complete absorption of lead in the body• Designed to limit blood lead in young children to < 10 µg/dL

• (2003) Canada : Department of National Defence (DND) adopts HUD / EPA guidelines for decontamination of shooting ranges

• (2006) Quebec : CSST recommends the DND values as a guideline for lead decontamination

• What does the literature say?– No correlation between surface contamination and exposure, or

risk to health



Is there a relevant surface contamination standard for adults?• Lange (2001)

– 108 µg /100cm2

– Highly conservative modeling of lead uptake in adults that assumes :

• 10 cm2 of contact surface on hands • 100% transfer from contacted surfaces to hands• 100% transfer from hands to GI tract• 35% absorption from the GI

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Hydro-Québec's actions• Cleaning / sealing of surfaces• Heightened preventive measures (PPE, hygiene)• Evaluation of exposure (airborne measurements & ingestion potential)

– Concentrations of lead in air• Reference value (TLV) : 0,05 mg/m3 (breathing zone)• Results

– Fixed station monitoring : < 0.002 mg/m3– Personal measurements : 0.01 to 0.02 mg/m3

– Concentrations of lead in blood• Reference value (TLV) : 0,5 µmol/L• Results

– 9 workers : < 0.01 µmol/L– 4 workers : 0.1 µmol/L



Consequences of misinterpreting the results• Worker anxiety, mistrust• Management anxiety• Unnecessary stoppage of work activities : costs• Imposition of unnecessary protective measures : costs,

inefficiencies• Presumption of "contamination" in other generating stations• Unnecessary legal, administrative procedures : costs• Personal exposure monitoring, measurement of lead in

blood : invasive


Conclusions

What does this case illustrate?• Despite our best efforts at identifying, evaluating, controlling and

communicating risk…unforeseen events will trigger crises• How "preventive" do we have to be ?

– Perceptions matter hugely ; tracking them is key• Root of the problem

– Inappropriate exposure assessment • Solution to the problem

– Appropriate exposure assessment (industrial hygienist)• Negative exposure determination as important as positive

determination in correcting perceptions– Effective communication (industrial hygienist)

• Aligning worker and management perceptions with reality• Aligning regulatory agency approach with reality

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Conclusions : The industrial hygienist

• A professional at the interface between people and their workplaces• Plays a central role in minimising risk to health in the workplace

– Global view • trained in anticipation, identification, evaluation, control and

communication of risks• interacts with other OHS professionals, management, workers,

analytical laboratories, regulatory agencies, and more – Objectivity

• diagnostic approach based on science and engineering• Indirect benefits

– increased employee implication in OHS – improvements in process design and efficiencies

• Future proofing– workplaces will continue to expose workers to health hazards, and the

risks will always need to be properly understood and managed


Merci beaucoup !