EU Guidance Document for Exposure Assessment

The EU Technical Guidance Document (TGD) for risk assessment of new and existing substances and biocides (EC 2003) contains guidance on exposure assessment (Chapter 2). The core principles of human exposure assessments according to the TGD are humans may be exposed to substances in the workplace (occupational exposure), from use of consumer products (consumer exposure), 

Toxicological Risk Assessments of Chemicals A Practical Guide 

In a first screening step of the exposure assessment, the likelihood of an exposure of the three populations (workers, consumers, and man indirectly via the environment) to the substance under consideration has to be evaluated. If in the screening step it is indicated that exposure to one or more of the human populations does not occur or when the expected exposure is so low that it can be neglected further in the risk characterization phase, no further assessment is needed and the conclusion can be mentioned in the risk assessment report. 

If actual or potential exposure has been identified, a quantitative exposure assessment is necessary. Exposure levels/concentrations for each potentially exposed population need to be derived from the available measured data and/or from modeling. A range of exposure values to characterize different subpopulations and scenarios may result. These results are taken forward to the risk characterization where they are combined with the results of the effects assessment in order to decide whether or not there is concern for the human population exposed to the substance. In some cases all three types of exposure estimates may contribute to an overall exposure value (combined exposure), which should be considered in the risk characterization. 

It may often be useful to initially conduct an exposure assessment based on worst-case assumptions, and to use default values when model calculations are applied. Such an approach can also be used in the absence of sufficiently detailed data. If the outcome of the risk characterization based on worst-case exposure assumptions is that the substance is not of concern, the risk assessment for that substance can be stopped with regard to the effect/population considered. If, in contrast, the outcome is that a substance is of concern, the assessment must, if possible, be refined using a more realistic exposure prediction in order to come to a definitive conclusion. 

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