From emissions to human exposure estimates: the importance of the expertise of the occupational hygienist
AbstractIn everyday activities, people are constantly exposed to many potentially harmful agents. The exposure assessment is essential in the evaluation of their impact on public health and is also a crucial step in the estimate of the dose-response relationship between a given environmental exposure and outcome. When an organism is exposed to a chemical can have an effect only if the substance is absorbed and reaches the target organ. The interaction between a chemical and a subject depends on: the environmental concentration of the chemical; the duration of exposure; the penetration pathway; the penetration speed. Therefore, it is firstly essential to define the best possible estimate of the concentration available for absorption, which is also called â€œexposure levelâ€. A comprehensive exposure assessment requires a in-depth analysis of both â€œoutdoorâ€ and â€œindoorâ€ air pollution to obtain an accurate and biologically relevant exposure estimate in the most effective and economic way. The choice of the measurement method is very important but it is very difficult to measure the real personal concentrations when the exposure assessment concerns the general population; it is then necessary to use surrogates of exposure. The two main exposure assessment approaches are classified into direct methods and indirect methods. In the latter category fall dispersion and simulation models that estimate environmental concentrations starting from fixed monitoring data. The use of environmental models allowed studies of large populations with low costs but also revealed many gaps. In fact, some of these models give unaccurate predictions on concentrations of pollutants measured in indoor environments. Some other models use both personal exposure data and environmental concentration data, allowing better estimates of the actual exposure and the prediction of theoretical exposures through the development of different possible scenarios. On the contrary, direct methods consist of determining the exposure of each study subject by the measurement of individual concentrations (external or internal dose). These techniques provide the best information for assessing exposure but are often very time and resource demanding. For this reason these metodologies were only used in studies of small groups of subjects. In addition, the determination of personal or individual exposures raises many critical issues, both methodologically and technologically. In addition, some environmental variables may increase the spatio-temporal variability of some pollutant concentrations. For all these reasons, the expertise of the â€œoccupational hygienistâ€ is pivotal in the exposure assessment process.
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