Ann. occup. Hyg., Vol. 46, No. 5, pp. 435-437, 2002
© 2002 British Occupational Hygiene Society
Published by Oxford University Press
Editorial |
Occupational Exposure Limits—Britain Tries Again
Editor-in-Chief
BRITAIN’S EXPOSURE LIMITS
Since the Control of Substances Hazardous to Health (COSHH) Regulations came into force about 12 yr ago, Britain has had a legally enforceable system of exposure limits. This is now likely to have a major overhaul.
There are at present two types of limit, Occupational Exposure Standards (OESs), which broadly speaking are supposed to be set low enough to prevent any ill-health developing, and Maximum Exposure Limits (MELs), which are set for substances that have ‘serious health implications’ and for which it is not always practicable to achieve a level that will prevent disease. OESs can be exceeded under some circumstances, and exposure by inhalation does not have to be reduced any further than the OES. MELs define a maximum permissible exposure, but exposure must also be reduced as far as reasonably practicable. (This is a legally defined concept which means that exposures must be reduced to a level where further reduction would involve a cost grossly disproportionate to the benefit achieved.) Topping (2001) recently described the system in detail. The list of limits, and guidance aimed at employers, is published annually in EH40 (Health and Safety Executive, 2002).
This system has strengths, notably the frank recognition that for some substances a desirable limit to protect health is not practicable, and the involvement of experts nominated by employers’ and employees’ organizations and other interests in determining for which substances a MEL is applicable, and what the level should be. However, a market survey on behalf of the Health and Safety Executive (HSE) showed that the carefully negotiated and executed dual-limit system was an almost complete failure in terms of the all-important understanding and application by users of chemicals (Topping et al., 1998). There were other problems intrinsic to the system which have become more troublesome as time has gone by, and the need to run a system compatible with the European Union’s Chemical Agents Directive has increased the problems. The HSE has now issued a discussion document on a possible new scheme with a view eventually to changing the COSHH Regulations. The document can be downloaded from http://www.hse.gov.uk/condocs, and comments are invited by the end of July; but there will be a further consultation later on the more formal legislative proposals.
THE PROBLEMS
The discussion document is very honest about the problems with the present system. The most important is that it has failed to get through to the users of chemicals, as already mentioned. The HSE responded to this by introducing COSHH Essentials, a system of controls that employers would implement based on suppler information about hazard, and user observation of the form of use (Health and Safety Executive, 1999a,b). This has been widely acclaimed, and there has been much interest internationally (e.g. Rühl et al., 2002). COSHH Essentials is now freely available on-line at http://www.coshh-essentials.org.uk. But there were two other major problems with the OES–MEL system which would probably have required change anyway.
The first was with the assumption that limits could be established which provided good enough protection for no further reduction in exposure to be required. The problem was foreseen in what was probably the first published description of the system, by Rolt (1987). He said that for a limit like this, no further reduction would be required if a level with no adverse effect ‘could be established with certainty’. Of course, this condition is hardly ever fulfilled. In practice, as the discussion document readily acknowledges, most OESs have been lifted unchanged from the ACGIH TLV list, and the ACGIH emphasize that, although the values are believed to protect nearly all workers, they are not fine lines between safe and dangerous conditions, and good practice is to continue to reduce exposure. The practical outcome, therefore, is that OESs permit employers to expose their workforce to levels that may affect the health of some employees, and there is no legal requirement to reduce exposure further.
There have also been differences in the effective definition of OESs, as to whether or not they were intended to eliminate all risk of ill-health. Rolt (1987) spoke of the intended limits as ‘not without risk, but the risks appear to merge with, and are comparable to, the general risk to which all workers are routinely exposed’. The criteria for setting OESs, first published by Carter (1989), and reproduced in EH40, say that OESs are set at a level ‘at which there is no indication that the exposure is likely to be injurious’. When I chaired WATCH, the responsible tripartite committee, we took the line that some health effects were not injurious, and could be disregarded for limit-setting purposes. This philosophy was applied, for example, in setting the limit for kaolin. In this case, the OES was set at a level which corresponded to a clear decline in FEV1 over a working lifetime, which was undoubtedly a health effect, but which the subject would not have noticed and which was therefore considered to be not injurious (Standring et al., 1994). However, the current discussion document refers to the wide assumption that the OES is ‘a "safe" limit offering complete health protection for all individuals’ (para 55), ‘at which no ill-health will occur’. If this absolute approach is applied, it is clearly going to make the setting of OESs harder. Even if the intentions are clear, there are considerable problems over what health end-points should be considered, as illustrated by Heederik et al. (2002) in this issue.
The second intrinsic problem with the process is the criterion that a MEL can only be set for a substance which ‘has, or is liable to have, serious health implications for workers’. This may have been introduced originally to help those who saw MELs as introducing onerous legal duties for substances which were fairly trivial in their effects. The result, however, is that there are substances which do not meet the criteria for either OESs or MELs, and for which a limit cannot therefore be set under COSHH.
THE SOLUTION?
The discussion document presents the response of a working group of the Health and Safety Commission’s Advisory Committee on Toxic Substances (ACTS). It sets out seven key objectives for exposure limits in Britain, and proposes three options for a new approach. One of these is tinkering with the present system to remove the worst problems, the second is a system of exposure limits linked to good practice, and the third is a variant of this, with a dual-limit system. The discussion document recognizes that the first option does not solve the problems, so it can probably be disregarded.
At the moment the COSHH Regulations require an employer to prevent exposure or adequately control it. For substances with exposure limits, adequate control is defined in terms of compliance with the two types of exposure limit, as appropriate for their type. The Working Group proposes that the definition of adequate control in Regulation 7 of COSHH should now have two components which must both operate: to ‘apply the principles of good occupational hygiene practice; and comply with the limit value’. Compliance means keeping exposure below the limit, and ‘The good practice requirement would represent what a good employer does to ensure that exposure to a substance with an exposure limit is not exceeded.’ The principles of good occupational hygiene practice included in Regulation 7 would be amplified in guidance for particular substance–task combinations, but as a default the COSHH Essential approach would be specified, making use of the HSE’s work to relate exposures to different levels of COSHH Essentials control.
Although good practice would have to be followed, there would no longer be a requirement for exposure to be reduced as far as reasonably practicable for substances that currently have MELs. However, to meet the requirements of the EU Carcinogens Directive, this requirement or similar would need to be incorporated into regulations for category 1 and 2 carcinogens.
The discussion document gives examples of entries in EH40 under the new system. The entry would include not only the exposure limit, but a brief statement of the main health effect (replacing the present health R phrases) and the COSHH Essentials control approach appropriate at room temperature, and a reference to process or substance specific guidance. This guidance would be freely available on the Internet.
QUESTIONS
If the HSE and ACTS had all the answers, they would presumably not have issued a Discussion Document. It is always easier to see the problems with a system operating at present than with a possible substitute, but some questions about the proposal stand out. One is, ‘How will good practice be enforced?’ HSE guidance cannot be enforced as if it were regulation, and if the exposure is below the limit, then an inspector might have an uphill job persuading an employer to implement specific ‘good practice’ measures if they are only in guidance.
There are a couple of references to the guidance reflecting the nature of the hazard, so that ‘good practice advice for a mild nasal irritant would be different from that for a substance causing occupational asthma’. It is not obvious how this ties in with the concept that good practice is what is required to keep exposure below the limit. If the two substances instanced have the same exposure limit and the same propensity to become airborne, logically the same controls should keep them below the exposure limit whatever their hazard. Perhaps, however, we need to be surer that the higher hazard material will not exceed its limit—which raises the difficult question of what, statistically, ‘will not exceed’ means. The definition of compliance with US exposure limits has been hotly debated in this journal (e.g. Hewett, 1998; Rappaport et al., 1998), but the issue is technically and operationally difficult and there is no clear definition of compliance with British limits. In any case, control of inhalation exposure cannot be isolated from control of other routes of exposure.
For the professional outside the HSE, important questions must be ‘What is the place of the professional in all this?’ and, above all, ‘Will it work?’ Some will see an alternative interpretation of the evolution of COSHH exposure limits: the system took the ACGIH limits, which are explicitly designed to be applied by the professional, and slotted them into a system designed to be applied by the employer. The response to the failure of the system, demonstrated by the market research, was not to strengthen the hand of the professional, but to give the employer better guidance on control, through COSHH Essentials, despite the common experience that controls often need skilled implementation before they are effective. Now, this control guidance is to be simplified, so that the employer is not pressed so hard to think about scale of the process and volatility or dustiness of the substance before choosing a control option. This is all intended to be cheaper than requiring the employer to use an expert. However, a good consultant may save an employer expensive capital investment by suggesting a simpler solution. If COSHH Essentials and the new exposure limit system do work, they are of world-wide importance. But perhaps this has contributed to the collapse of full-time training of occupational hygiene professionals in Britain through lack of demand.
Maybe this is being over-critical. COSHH was a big step forward; perhaps it had faults because of the need to get agreement from a range of interests, but the HSE has done what it can to put things right. It is faced by a vast sea of chemical users who do not understand the present system, and needs to induce these users to use appropriate controls. The fundamental idea of the new proposals, of coupling exposure limit compliance and good practice, is clearly right, even though it is unclear how it will be implemented. However, before taking this further step we certainly need to know that COSHH Essentials is really effective at controlling exposure when used without professional help, not just that more people are using it than the old system. The HSE has shown admirable self-questioning in its use of market research to show up the faults of the old system. It is important to see a similar review of COSHH Essentials before the new proposals take us further in that direction.
REFERENCES
Carter JT. (1989) Indicative critieria for the new occupational exposure limits under COSHH. Ann Occup Hyg; 33: 651–2.
Health and Safety Executive. (1999a) COSHH Essentials: easy steps to control chemicals. London: HSE. ISBN 0 7176 2421 8.
Health and Safety Executive. (1999b) The technical basis for COSHH Essentials: easy steps to control chemicals. London: HSE. ISBN 0 7176 2434 X
Health and Safety Executive. (2002) EH40/2002 Occupational exposure limits 2002. London: HSE. ISBN 0 7176 2083 2.
Heederik D, Thorne PS, Doekes G. (2002) Health-based occupational exposure limits for high molecular weight sensitizers: how long is the road we must travel? Ann Occup Hyg; 46: 439–46.
Hewett P. (1998) A log-normal distribution-based exposure assessment method for unbalanced data. Ann Occup Hyg; 42: 413–7, 420–1.
Rappaport SM, Kupper LL, Lyles RH. (1998) A log-normal distribution-based exposure assessment method for unbalanced data. Ann Occup Hyg; 42: 417–20, 421–2.
Rolt DA. (1987) The aims of legislation. Ann Occup Hyg; 31: 73–80.
Rühl R, Lechtenberg-Auffarth E, Hamm G. (2002) The development of process-specific risk assessment and control in Germany. Ann Occup Hyg; 46: 119–25.
Standring P, Phillips AM, Darvill M, Ogden TL. (1994) Kaolin: criteria document for an occupational exposure limit, EH65/13. London: HSE. ISBN 0 7176 0762 3.
Topping M. (2001) Occupational exposure limits for chemicals. Occup Environ Med; 58: 138–44.
Topping MD, Williams CR, Devine JM. (1998) Industry’s perception and use of occupational exposure limits. Ann Occup Hyg; 42: 357–66.
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  M Topping and H Kromhout Design of measurement strategies for workplace exposures * Author's reply Occup. Environ. Med., November 1, 2002; 59(11): 788 - 789. [Full Text] [PDF]
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