From Fate to Exposure and Risk Modeling with GIS
17.1 Exposure and Risk for Human Health
The spatial distribution of chemicals is one important step towards the characterization of their impact. However, the spatial variability of concentrations is as important as the spatial variability of the density of potential receptors: the combination of the two yields exposure. Once exposure is assessed, the associated risk can be evaluated. In this chapter, we introduce the basic elements of models necessary for the assessment of exposure and risk, which can be easily implemented in GIS on top of chemical fate and transport models, based on appropriate data about receptors, and assuming that maps of concentrations of chemicals in the different phases of environmental media (air, soil, water, vegetation) are known. We distinguish between exposure to contaminants of humans and ecosystems. In the first case, we speak about human health risk assessment, while in the second of ecological risk assessment. The main difference in approach between the two modes of risk assessment is that, for humans, the target of assessment is the individual, while in ecological risk assessment the target is the community of organisms and the whole ecosystem.
Concerning human health, we may observe that a chemical can interact with the human body through two fundamental processes: intake and contact. Intake occurs through inhalation and diet (eating and drinking) ...