A comparison of different methods for assessment of dermal exposure to non-agricultural pesticides in three sectors

This report describes work carried out by the Institute of Occupational Medicine (IOM) on behalf of the Health and Safety Executive (HSE), to investigate dermal occupational exposures in the non-agricultural pesticides application industries and compare the efficacy of two of the most commonly used methods of exposure assessment.The study involved field investigations of pesticide application techniques in three industry sectors, specifically pest control, timber treatment and erodible anti-fouling (EAF) paint application. Private and public sector organisations participated in the study. Efforts were made to ensure (within the scope of the study) that the selected organisations and application techniques were representative of the industry as a whole.The participating organisations in the pest control area were predominantly local authorities (three out of four studies). All five timber preservation companies and all three users of EAF paints (shipyards) were in the private sector.Operations surveyed in the pest control sector included spraying of water-based formulations of various active ingredients and powder application (primarily on wasps’ nests). Spraying of water-based formulations was the method of application used in all of the timber treatment surveys, both sprayers and pump attendants being included. EAF paint was applied by spray guns in all cases, and both sprayers and “”potmen”” (who assisted the sprayers) were included.The two methods of assessment of dermal exposure that were investigated were (i) “”whole body sampling”” wherein the operator wears an absorbent oversuit which is later sectioned, and extracted for analysis of material collected, and (ii) “”patch sampling”” where absorbent patches are attached to the outer clothing of the operator at various places, and similarly removed, extracted and analysed on completion of the task. Exposure information gathered by these methods was supplemented by visual observation of work practices by experienced occupational hygienists.In addition, operators were issued with a questionnaire to determine the levels of hazard awareness in the various industry sectors, and attitudes to wearing of personal protective equipment (PPE). The range of measured dermal exposures in the study as a whole (in terms of the total mass of pesticide deposited on the body) was large, covering some 5 orders of magnitude. The lowest levels were observed in the pest control sector followed by the timber and masonry preservation sector. Much higher levels were observed in the EAF paint sector. In general, dermal exposure for sprayers was greater than for their assistants (pump attendants and potmen).Much of this work has been aimed at determining the comparison between the patch method and the whole suit method for measurement of potential dermal exposure. This has been assessed (a) for the study population as a whole, (b) for the individual industry sectors, (c) for individual workers, and (d) for individual sections of the oversuits (upper arm etc.).For the study population as a whole, a generally linear relationship exists between the results obtained by the two methods.In terms of individual sectors, in the pest control and timber treatment sectors the patch method overestimated the total potential dermal exposure (as assessed by the whole suit method) by, on average, a factor of two. In the EAF paint sector the patch method underestimated the potential dermal exposure by an average of approxiametely 40%.For individual wearers, the ratios of the potential dermal exposure determined by the whole suit method to the patch method varied from less than to greater than one. As a general indication of variability, about 50% of the ratios were between 0.5 and 2, but several lay well outside this range.For the individual sections of the oversuit, the patch method both underestimated and overestimated the suit method. The level of agreement between the two methods varied greatly for different sections, the best agreement being for the lower legs, and the worst for the front torso.The overall indication is that the accuracy of the patch method as a means of assessing potential dermal exposure increases according to the number of patches included in the assessment. Its accuracy in assessing dermal exposure for a group of workers is better than for a single worker, and its accuracy in assessing whole body exposure is better than for assessment of regional exposure.In general, the patch method has been shown to be an acceptable method for determining the order of magnitude of potential dermal exposure and can be used with confidence to identify operators who are most likely to be dermally exposed to pesticides. However, the results also suggest that there is considerable room for improvement of the patch method, particularly in terms of its accuracy in assessing whole body and regional exposure for individuals. In particular, it is recommended that further work should be be carried out to determine the optimal number and distribution of patches over the body of the worker.Observation of work practices together with analysis of material collected on absorbent gloves indicated that potentially substantial dermal exposure can arise from contact with contaminated surfaces and from handling contaminated equipment in all industry sectors. “”