what's the point of occupational exposure limits
TRANSCRIPT
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What’s the point of
occupational exposure limits? John Cherrie
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Summary…
• OELs, the essence of occupational hygiene
• Legislative tools - compliance
• OELs in crisis – do they really work to protect the health of
workers?
• Things just keep getting better
• A new paradigm – Kaizen
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Lead poisoning
Nicander of Colophon (130 BC)
described the effects of several
poisons, including the effects of
lead
Waldron, H A. 1973. “Lead Poisoning in the Ancient World..” Medical History 17 (4): 391–99.
Public Domain Theriaca 002.jpg Created: 10th century
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Around 1,000 new cases of lead poisoning diagnosed in Britain in 1900
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Lead poisoning data.png
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Lead poisoning data.png
McElvenny et al. 2015. “Mortality of a Cohort of Workers in Great Britain with Blood Lead Measurements..”
Occupational and Environmental Medicine 72 (9): 625–32.
WWI
WWII
HSW Act
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Occupational exposure limit
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0.2mg/m3
The recommended limit for Pb in air in 1921
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Threshold Limit Values…• The first systematic list of “modern” OELs was published in
1946 by ACGIH
• 144 Maximal Allowable Concentrations
• Not until 1956, was the term Threshold Limit Value (TLV) used
• In the 1940s the MAC for Pb was 0.15 mg/m3
• 1953 it was made clear these were average concentrations over an 8-hour working day
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TLVs become widely accepted…
• By the 1970s many countries or groups had adopted
TLVs or produced their own limits
• In 1948 William Yant, first president of the AIHA
warned, mandatory limits were usually minimum
requirements, “representative of the worst
permissible conditions”
Ziem, G E, and B I Castleman. 1989. “Threshold Limit Values: Historical Perspectives and Current
Practice..” Journal of Occupational Medicine. 31 (11): 910–18.
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The essence of occupational hygiene
• Hygienists assess (measure) exposure
• We assume risk is associated with
exposure
– There is an exposure-response
curve
• If exposure exceeds an agreed
threshold then conditions are
unacceptable
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Legislation and compliance…
EU Chemical Agents Directive (1998)
“where an occupational exposure limit value effectively established on the
territory of a Member State has been exceeded, the employer shall
immediately take steps, taking into account the nature of that limit, to
remedy the situation by carrying out preventive and protective measures.”
Carcinogens and Mutagens Directive
“Exposure shall not exceed the limit value of a carcinogen as set out in
Annex III.”
http://treball.gencat.cat/web/.content/09_-_seguretat_i_salut_laboral/documents/05_-_promocio_i_campanyes/Jornades/Arxius/EN_689/01.Raymond_Vincent_EN689_Barcelona_Nov_2016.pdf
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Do users understand OELs?
…most employers rely heavily on information from suppliers and
personal experience and rather less on “official” information
“The very low understanding and use of OELs reported in this
survey calls for a reappraisal of the OEL system and its
contribution to securing the aims of good occupational hygiene
practice.”
Topping MD, Williams CR, Devine JM. Industry's perception and use of occupational exposure limits.
Ann Occup Hyg 1998 Aug 1;42(6):357–66.
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Some problems with OELs…
• Compliance focusses attention on worst situations
• Setting limits may get mired in legal argument
• There may be insufficient human or animal toxicology
data to set a limit
• Employers don’t measure exposure levels
• Exposures are much higher than a health-based limit
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Does “compliance” protect health?
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Something is working…
Creely KS et al. (2007) Trends in inhalation exposure--a review of the data in the published scientific literature. Ann Occup Hyg.; 51(8): 665-678.
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Kaizen = “change for the better”
改善 is the Japanese word for “continual improvement”
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OELs become (almost) pointless…
• Put emphasis on continually reducing exposure for the
whole working population
• Success is now measured by the annual percent
reduction in exposure for an industry sector
• Provide targets with a backstop to deal with the
criminals
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nepSi.eu
• European Network for Silica, formed by
employee and employer associations
• Agreed appropriate measures to improve
working conditions through good practice,
with training for workers
• Monitoring exposure and provision of health
surveillance
Tuomi T, Linnainmaa M, Väänänen V, Reijula K. Application of good practices as described by the NEPSI agreement coincides with a
strong decline in the exposure to respiratory crystalline silica in Finnish workplaces. Ann Occup Hyg; 2014 Aug;58(7):806–17.
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nepSi.eu in Finland
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Acceptable and
tolerable risks…
• Risk-based concept for
carcinogenic substances at
work in Germany
• Risks for a working lifetime
– 8 hours per day over a working
life of 40 years.
http://www.baua.de/en/Topics-from-A-to-Z/Hazardous-Substances/TRGS/TRGS-910.html
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Tolerable
Concentration of a substance with a risk of 4:1,000
Corresponds roughly to the lung cancer risk for non-smoker
Exposure must be below this limit
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Acceptable
Concentration of a substance with a risk of 4:10,000
From 2018 reduced to 4:100,000
Corresponds to cancer risk from environmental risk
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Conclusions…
• OELs are necessary but not sufficient to protect worker health
• Exposures generally decrease over time
• Continuous improvement is an alternative to compliance
• Exposure monitoring to assess progress
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