Page 162 - Materials Chemistry, Second Edition

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relationship includes understanding the importance of the intensity of exposure, the
concentration vs. time relationship, whether a chemical has a threshold level, and
the shape of the dose–response curve. In the determination of a dose response and
exposure response, the following aspects need to be considered: the metabolism of
a chemical at different doses, its persistence over time, and an estimate of the
similarities in disposition of a chemical between humans and animals.
The dose–response and exposure–response functions are based on toxicological
dose-oriented and epidemiological exposure-oriented studies. Figure 4.3 proposes
to illustrate the difference between the toxicological and the epidemiological
approaches. Although the toxicological approach is based on bioassays or animal
tests that allow determining dose–response functions, the epidemiological approach
uses empirical studies in which correlations are established between exposure situ-
ations and observed human effects. In this way exposure–response functions, which
allow an estimation of human effects depending on the exposure concentration, are
calculated. Epidemiological studies focus more on macropollutants responsible for
respiratory effects such as SO , NO and particles because they usually act together
x
2
and it is quite difficult to conduct laboratory assays. The dose–response functions
permit the determination of risk due to the accumulation of pollutants in the human
organism. The risk is a way to foresee the probability of physical impacts. Bioassays
are the foundations to obtain toxicological information for micropollutants, i.e.,
heavy metals and the huge number of organic compounds like PCDD/Fs or PAH

Emission

Fate

Exposure
Correlation Empirical studies

Risk due to Prevision Physical
accumulation impact

Prevision
Dose - Potential cancer Exposure -
response function risk factor response function

Bioassays
animal tests

FIGURE 4.3 Comparison of the toxicological approach by bioassays and animal tests and
the epidemiological approach using empirical studies to determine damage factors for human
health impacts.

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