The exposure assessment attempts to quantify the contaminant intake rate for a given pathway. The intake of a contaminant via individual pathways can then be summed to estimate the total daily intake (Health Canada 2004).
Exposure via individual exposure pathways can be calculated by considering contaminant concentrations in environmental samples, human behavior information from exposure surveys and standard exposure parameters.
Alternatively, total exposure (for POPs) can be estimated by collecting human tissue samples for direct chemical analysis (i.e., blood and breast milk samples).
Health Canada’s Preliminary Quantitative Risk Assessment (PQRA) guidance, provides an Excel spreadsheet-based model which calculates the total daily intake (Health Canada 2004). A simpler model has been incorporated into the POPs Toolkit (view the Problem Formulation Tool). The equations used to calculate exposure are provided and discussed later in this module.