Exposure Pathways : exp 

 

The Exposure Pathways component of the FRAMES system starts with pollutant concentration in a transport medium and estimates the average daily dose to exposed individuals from contact with the transport medium or a secondary medium contaminated by the transport medium.  Each exposure pathway analysis in FRAMES involves definition of a transport medium (or medium of measurement), and exposure route for transfer of pollutant from the transport medium to man, exposure conditions for the individual receiving the pollutant, and conversion of the average daily dose to a measure of health impact.  These steps are used for all transport and exposure pathways except exposure to measured direct radiation fields.  The direct radiation exposure pathway does not involve a specific pollutant, but rather is used to estimate health impacts from exposure to a measured radiation field.

The pollutant concentrationin the transport medium is the starting point for the exposure analysis. This concentration is generally represented as a 70-year averaged value. When the exposure duration is less than 70 years, the concentration represents the average for the exposure duration considered for a given exposure scenario. Such an average value can be provided by the user for the measured soil concentration and measured food concentration transport pathways. For other transport pathways, the calculated 70-year average value is used as an approximation for individual and population exposures.

The transport medium may or may not be the medium of exposure. For example, the groundwater transport pathway generates estimates of pollutant concentration at the well. In this case, the well water is also the medium of exposure, although some modifications to the concentration are possible during transfer through the treatment plant and distribution system to the individuals exposed during domestic water uses. When the well water is used for irrigation of agriculture crops, the exposure medium is not the well water, but the foods produced. For agricultural pathways, models are use to estimate the transfer of pollutants from the irrigation water to the food consumed by humans. For each transport and exposure pathway, the processes affecting the concentration and transfer to the exposure medium are defined in the following sections.

The models for the exposure pathway require definition of several parameters.

Six major transport pathways may be considered including special pathways for handling exposure to measured pollutant levels in soils and foods, and measurement of direct radiation fields. These transport pathways and their associated exposure pathways may indicate the transport medium, the exposure medium, and the intake or exposure route for each exposure pathway. The discussion for a given exposure pathway defines the transport pathways leading to the exposure pathway, the special transfers and processes considered in determining the pollutant concentration in the exposure medium, and the exposure model used to estimate the average daily dose or lifetime radiation dose.

TYPICALLY CONSUMES . . .

TYPICALLY PRODUCES . . .