What's the point of occupational exposure limits
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My keynote presentation at the Australian Institute of Occupational Hygienists conference in Canberra December 2017.
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What's the point of occupational exposure limits
- 1. What’s the point of occupational exposure limits? John Cherrie
- 2. 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
- 3. 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
- 4. Around 1,000 new cases of lead poisoning diagnosed in Britain in 1900
- 6. 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
- 9. 0.2mg/m3 The recommended limit for Pb in air in 1921
- 10. 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
- 11. 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.
- 12. 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
- 14. 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
- 15. 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.
- 16. 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
- 17. Does “compliance” protect health?
- 18. 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.
- 19. Kaizen = “change for the better” 改善 is the Japanese word for “continual improvement”
- 20. 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
- 21. 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.
- 23. 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
- 24. 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
- 25. 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
- 27. 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
Notes de l'éditeur
- Thank you. I am very pleased to be back in Australia to speak at your conference. I am also grateful to Safety Equipment Australia for their support to enable me to contribute. In Europe it seems as though we have great problems in brining forward new binding occupational exposure limits. For more than 10 years we have been discussing modernising the legislation, and only now is the process coming to an conclusion. In this time the world has not stopped, things have carried on. So what’s the point of occupational exposure limits?
- In my talk I will discuss how OELs became the essence of the occupational hygiene paradigm, and then were absorbed into legislation. I think we need to reappraise the concept because OELs are in crisis, we need to ask the question: do they really protect worker health? Against this backdrop we note that exposures generally decline over time and we could harness this in a new approach that builds on the ideas of continuous improvement.
- Lead is one of our ancient poisons. The Greeks and Romans added it to food and wine as a preservative or improver. There are many written examples of what are probably outbreaks of lead poisoning and certainly by the 2nd Century BC, Nicander was describing the acute effects of exposure in the form of paralysis and colic.
- In more recent times we also had problems with lead and around 1900 in Britain there were about 1000 new cases of lead poisoning diagnosed each year.
- Physicians of the time were well aware of the problem and in his 1902 treatise on “Dangerous Trades” Thomas Oliver of Newcastle upon Tyne devoted almost 100 pages to the problem. The picture shows a young woman carrying a bowl filled with white lead from a vat to a stove for drying. This was a particularly dusty job and Oliver wrote that “I have known young women die from plumbism within three months of entering a white lead factory and working in the stoves”. Note that the woman is wearing a facemask. Employment of women in this job was banned in 1898.
- Throughout the 20th Century we saw a remarkable decline in lead poisoning, which was mostly unaffected by wars or the passing of important health and safety legislation. The slight upturn in the 1960s is almost certainly due to a change to using blood lead determinations as part of the diagnostic criteria for lead poisoning. In 1980, when the problem was almost completely solved we introduced the Control of Lead at Work Regulations (CLAW).
- We didn’t have formal legal exposure limits for the majority of this time, although people understood that the exposure was the main determinant of poisoning.
- In a memorandum from the Factory Department of the British Home Office, there is a section that sets out a limit value. Somewhere about 2 milligrams (or 0.002 grams of lead) is the lowest daily dose which, inhaled as a fume or dust, may in the course of years set up chronic plumbism. They go on to talk about inhaling 10 cubic metres per work day. Which would give a OEL of…
- ACGIH compiled it’s first list of limit values in 1940s, although other less comprehensive lists were available earlier. Pb limit still 0.15 mg/m3 in Australia, although I understand it is under review.
- Exposure standards in Australia Exposure standards have been established in Australia for approximately 700 substances and mixtures. These are legal concentration limits that must not be exceeded.
- We really have to ask the question – does compliance with an OEL protect health?
- In a review of published evidence for temporal trends that we published in 2007 we identified 38 cases where there was informative data for aerosols. We analyzed the temporal trends on the log-scale assuming an exponential decline in exposure level over time. 58% of these involving aerosols there was a significant reduction in exposure, typically between 5% and 10% per year. Only one dataset (3%) showed a significant increase.