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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
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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
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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.
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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
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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)
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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
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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"
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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
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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
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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
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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
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Exposure assessment – from perception to reality
• Risk evaluation by an occupational hygiene professional
Intrinsic toxicity Route of exposure Preventive measures
x - = Risk
DurationFrequencyComparison with tolerance level
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Exposure assessment – from perception to reality
• 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.
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Proactive exposure assessment Example : Prevention of health risks from exposure to lead
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Proactive exposure assessment Example : Prevention of health risks from exposure to lead
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
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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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Reactive exposure assessment : Lead on surfaces
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Reactive exposure assessment : Lead on surfaces
Inside surface of spiral casing
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Reactive exposure assessment : Lead on surfaces
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)
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Reactive exposure assessment : Lead on surfaces
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
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Reactive exposure assessment : Lead on surfaces
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
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Reactive exposure assessment : Lead on surfaces
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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Reactive exposure assessment : Lead on surfaces
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
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Reactive exposure assessment : Lead on surfaces
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
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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
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Merci beaucoup !