Abstract:
Multimedia fate and multipathway human exposure models are widely
adopted in assessments of toxicological risks of chemical emissions at
the regional scale. This paper addresses the question of how much
spatial detail is necessary in such models when estimating the intake
by the entire population in large, heterogeneous regions such as
Europe. The paper presents a spatially resolved multimedia fate and
multipathway exposure model for Western Europe, available as IMPACT
2002. This model accounts for relationships between the location of
food production and drinking water extraction as well as where
population cohorts live relative to where chemical emissions occur. The
model facilitates estimation of environmental concentration
distributions, related levels of contaminants in foods, and the
fraction of a chemical release that will be taken in by the entire
human population (the intake fraction) at the regional scale. To
evaluate the necessary spatial resolution, the paper compares estimates
of environmental concentrations and the intake fraction from the
spatially resolved model with the results of a consistent clone without
spatial resolution. An evaluation for disperse emissions of PeCDF
(2,3,4,7,8-pentachlorodibenzofuran, CAS# 51207-31-4) suggests
reasonable agreement with monitoring data for most impact pathways with
both versions of the model, but that the generic vegetation models for
estimating contaminant concentrations in agricultural produce require
improvement. A broader comparison for a range of organic chemicals
demonstrates that the nonspatial models are likely to be appropriate in
general for assessing dispersed sources of emissions. However, it is
necessary to include generic compartments in such nonspatial models to
account separately for emissions that enter lakes with long residence
times versus rivers that feed directly into seas. For assessing an
emission source in a specific location, using models that are not
spatially resolved can result in underestimation, or overestimation, of
the population's intake by at least 3 orders of magnitude for some
chemicals.
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