Annals of Occupational Hygiene Advance Access originally published online on July 14, 2006
Annals of Occupational Hygiene 2006 50(6):643-644; doi:10.1093/annhyg/mel046
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LETTERS TO THE EDITOR |
Reply
An ideal validation study of the complete COSHH Essentials package would use quantitative exposure assessment and tracking of employee health outcomes to assess the ability of small business proprietors to control exposures and, thereby, prevent ill-health. However, until such a study can be mounted, it is reasonable to evaluate the efficacy of COSHH Essentials' primary components—estimating potential exposure intensity and assigning appropriate controls. The sum may be better than the parts, but each part should function independently. We certainly hope that COSHH Essentials succeeds in reducing workplace morbidity by being an accessible and accurate tool for small business proprietors and their employees, but at this time we remain skeptical.Contrary to the statement of Evans and Garrod, COSHH Essentials is fundamentally an exposure prediction tool. The outcome of COSHH Essentials is a recommended control approach, but the basis for the recommendation is an exposure prediction model combined with assumptions about the magnitude by which different control approaches reduce exposure. Both our study (Jones and Nicas, 2006) and that of Tischer and colleagues (2003) used data from federal government field studies (and a federal risk assessment programme in the latter study) to explore the ability of the control approaches to limit exposures to the exposure prediction ranges defined by Maidment (1998).
Our study was limited to two common industrial processes (vapor-degreasing, bag-filling) for which monitoring data were available at multiple work sites. We used historical data, which means of course that COSHH Essentials had not been employed for selecting control approaches. However, we had sufficient details to apply COSHH Essentials to the reported operating conditions and to compare the class of the installed control approach with that recommended by COSHH Essentials. Although the control approach guidance documents illustrate the ‘best practices’ for controlling exposures in particular processes, COSHH Essentials recommends fundamentally one of four control approaches—general dilution ventilation, local exhaust ventilation, containment and special. Therefore, we judge that our comparisons were reasonable, even though the installed control approach was not necessarily the ‘best practice’ or was not described thoroughly.
We note that COSHH Essentials control approach guidance documents provide illustrations of best practices and capture velocities, but they are not engineering drawings specifying dimensions and CFM rates. As a result, small business proprietors could make a good faith effort to implement the guidance as illustrated but still not achieve the capture efficiency assumed by the control approach, perhaps owing to a failure to appreciate critical design parameters or owing to instability in control performance. This circumstance will increase the variability in capture efficiency observed for a control approach class applied to a particular process; such real-world variability may have been captured in our analysis.
School of Public Health, University of California Berkeley, CA 94720-7360, USA
*E-mail: mnicas{at}berkeley.edu
Received May 26, 2006;
REFERENCES
Jones RM and Nicas M. (2006) Evaluation of COSHH Essentials for vapour degreasing and bag filling. Ann Occup Hyg 50:137–47.
Madiment SC. (1998) Occupational hygiene considerations in the development of a structured approach to select chemical control strategies. Ann Occup Hyg 42:391–400.
Tischer M, Bredendiek-Kamper S, Poppek U. (2003) Evaluation of the HSE COSHH Essentials exposure predictive model on the basis of BAuA field studies and existing substances exposure data. Ann Occup Hyg 47:557–69.
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