Article Text

Download PDFPDF

Design of measurement strategies for workplace exposures
  1. M Topping
  1. 1Health Directorate, Health and Safety Executive, Rose Court, 2 Southwark Bridge, London SE1 9HS, UK; michael.topping{at}
    1. H Kromhout
    1. 2Environmental and Occupational Health Division, Institute for Risk Assessment Sciences, Utrecht University, PO Box 80176, 3508 TD Utrecht, Netherlands; h.kromhout{at}

      Statistics from

      Request Permissions

      If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.

      I write in response to the article by Hans Kromhout,1 which sets out the case for exposure monitoring and proposes robust strategies for collecting data. He acknowledges that exposure monitoring may be expensive, but justifies it on the grounds that it is needed to ensure worker protection and data can be used for multiple purposes (hazard evaluation, control, and epidemiology). All this ignores the variety of competences and numbers of firms who use chemicals in the workplace.

      We agree that good quality exposure data are extremely valuable for assessing the effectiveness of control measures, studies on health effects related to use of specific substances, and for long term epidemiological studies. Now that workers do not normally remain in one job all their working life and may be exposed to many chemicals in different industries, the lack of well validated exposure measurements is a concern. It will limit our ability in the future to carry out meaningful epidemiological studies.

      In the UK we estimate that over 1.3 million firms are using chemicals. It is not realistic to suggest that all these firms should be carrying out the type of sampling regimes the article suggests. The costs would be astronomical and there is no capacity to collect, analyse, and interpret all the samples that would be generated. Recognising this and that small firms needed help to apply the risk assessment requirements of the Control of Substances Hazardous to Health (COSHH) Regulations, led HSE, in collaboration with industry and trade unions, to develop the COSHH Essentials.

      COSHH Essentials is not intended to replace the collection of well validated exposure data, where that is justified; rather it is intended to help firms, particularly small and medium sized firms, to properly control the chemicals they are using. Inevitably a generic system like COSHH Essentials which groups chemicals, has to err on the side of caution, but the controls recommended by COSHH Essentials were peer reviewed by an expert group established by the British Occupational Hygiene Society and have the support of the industry and trade unions. COSHH Essentials has been used now for over three years by many firms. We have not had complaints that the controls are over precautionary. Thus we reject the implication in the article about COSHH Essentials that “ill advised control measures will arguably be even more costly in the long run, a classic case of being ‘penny wise but pound foolish’”.

      The article misrepresents the purpose of the expert system, Estimation and Assessment of Substances Exposure (EASE). This was developed to help meet the requirement under the Dangerous Substances Directive for a risk assessment on new substances. As workplace exposure data cannot be collected on new substances prior to release to the marketplace, EASE was developed to provide an exposure estimate for use in risk assessment. It is entirely appropriate that this should be precautionary. It is not a weakness as the article implies. EASE is not intended as a tool to help employers control exposures in the workplace.

      The aim of chemical control is the protection of employees’ health. This is best achieved with a range of tools. EASE has a valuable contribution to make before substances are released into the marketplace; COSHH Essentials is proving to be a valuable and welcome tool for many small and medium sized firms, helping them to establish suitable controls. The recently launched electronic version will be of even greater help to many small firms. In other circumstances structured data collection is needed. These tools all have a valuable role to play. They should be viewed as complementary, not as alternatives as the article suggests.


      Author’s reply

      I would like to reply to the comments made by Dr Michael Topping with regard to my article on measurement strategies for workplace exposures.1 His response is focused on my introductory words on the development and promises of tools like COSHH Essentials and EASE.

      His main point is that I would ignore the variety of competences and number of firms who use chemicals in the workplace and that proper evaluation (with actual measurements of workplace exposures) would come with astronomical costs and would not be possible due to lack of expertise. Together with the editor of the Annals of Occupational Hygiene, I question whether the introduction of tools like COSHH Essentials has contributed to the collapse of full time training of occupational hygiene professionals in Britain through lack of demand for expertise.2 As I pointed out in my paper, measurement strategies that involve workers in the sampling procedure can be very cost efficient and have been shown to be working.3 The claim that nobody has been complaining about controls being over precautionary after using COSHH Essentials is no justification. For instance, what if a company, after applying COSHH Essentials is advised to take expensive control measures, while actual measurements show that exposure levels are well under the occupational exposure limits? With COSHH Essentials erring on the safe side, this will likely often be the case.

      The comment that I would misrepresent the purpose of the EASE expert system is false. Dr Topping forgets to mention that EASE was developed not only for new substances but also for existing substances.4 In addition I am aware of training courses that have been given in my own country where EASE was propagated as a tool to evaluate substance exposure in workplaces. If this expert system is only to be used for risk assessment purposes, HSE should start labelling it with the phrase “not intended to be used as a tool to help employers control exposures in the workplace”. However, in the documentation that came with my version of EASE we can read “Modelled data may be derived from the general purpose predictive model for exposure assessment in the workplace described in this paper and called EASE”.4

      The real problem with tools like EASE and COSHH Essentials is that they are not properly evaluated before they are launched into the occupational health arena. Peer review by an expert group established by the BOHS and support of industry and trade unions cannot replace the necessary scientific rigour of testing reproducibility and validity and having these studies peer reviewed in scientific journals. Testing validity long after introduction of a tool, as happened with EASE,5,6 would not have been tolerated when EASE would have been, for instance, a medical diagnostic tool, or even closer to home an analytical method to measure styrene. HSE is apparently not too happy with the accuracy of EASE either, since I am informed that a project is underway to create a more valid expert assessment tool.

      Even though Dr Topping justifiably suggests that the tools should be seen as complementary, the place of “structured data collection” remains unclear in his letter. One can deduce from the described use of EASE and COSHH Essentials that proper assessment of exposure by measurements would only have to take place at larger firms. Unfortunately, as we all know, that is not where the majority of workers perform their jobs. In my view, tools like EASE and COSHH Essentials should be used in the initial judgement step, and proper evaluation should always follow to prevent unnecessary investments or ill advised control measures. Given the enormous variability we have to take into account when evaluating chemical risks, we should never exclusively rely on generic tools that lack precision, and even worse, accuracy.

      Finally, I would like to suggest renaming COSHH Essentials into “Where there is no expert”. While staying in less developed countries, I cherished my copy of Where there is no doctor.7 Nowadays, I frequent my GP who has access to more precise and accurate diagnostic tools. To me it is unthinkable that poor man’s tools are being used to evaluate chemical hazards in a well developed country such as the UK.