Hand exposure measurement, risk assessment

Exposure assessment is done under the strong assumptions that (1) an adequate model for exposure calculation is on hand and (2) sufficient data about all influential exposure factors are available. The calculation is a prognosis about the expected level of exposure or the burden. Direct methods of exposure assessment, such as personal sampling (air, radiation), duplicate studies (nutrition) and human biomonitoring, provide information on a measurement level. The exposure assessors and the risk managers should balance the reasons for using prognostic techniques instead of direct exposure measurement methods. Both should anticipate critical questions about the validity of the exposure assessment technique in the course of public risk communication. Questions heard by the authors from concerned persons include, for example ... 

Exposure assessments may be conducted for one of four purposes hazard evaluation leading to appropriate control efforts, monitoring to ensure compliance with workplace standards, dose-response characterization within the context of epidemiological studies, and estimation of dose or uptake for risk assessments. Assessment strategies and measurement techniques will differ depending on the purpose at hand. 

Unfortunately the Ideal situation does not exist and there are many difficulties which must be overcome before accurate risk assessments can be conducted. For pesticide applicators, the dermal route has been shown to be the most Important one. However, the methods used to measure the amount of pesticide landing on the skin are not very reliable and many studies conducted In the past did not try to estimate hand exposure. This omission Is a serious one because it has been shown that a very large percentage of the total dermal exposure Is to the hands. New methods using fluorescent tracer techniques are promising and will undoubtedly lead to more quantitative estimates of contact exposure. 

Acknowledgment that mixtures may cause risks that are not fully covered by single compound evaluations does not automatically imply that mixture assessments should be performed for all potential mixture exposures. This depends on the problem at hand, the specific exposure situation, and the available information. If a regulator must make a decision about the remediation of 1 contaminated soil plot, and it is already known that one of the mixture components exceeds the remediation threshold, and this fact results in a need for remedial action itself, then a mixture assessment is redundant. Mixture assessment for contaminated soils (and other compartments and exposure routes) is useful if the known individual components do not exceed their respective thresholds, but if it is suspected that the overall mixture may still cause unacceptable adverse effects, and in case risk managers have a limited budget for a large number of contaminated sites, that is, when they have to prioritize the most hazardous sites to be remediated first, while other sites should possibly be subject to simple risk reduction measures. The situation is different for mixture emissions. Here, potential mixture effects should always be addressed because the aim was and is to establish an emission level that is lower than a certain (acceptable) effect level. 

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