摘要：
Perceived needs for extensive chemical-specific toxicological information
have impeded efforts to assess risks and evaluate likely public
health protection benefits of possible standards for hazardous air
pollutants (HAPs). This paper discusses opportunities to use effects
of HAPs on early effect biomarkers, such as birth weights, to predict
likely changes in rare quantal effects of concern that would be
relevant for the quantification of likely regulatory benefits from
exposure reductions. In the birth weight example, even modest exposures
to common air pollutants can be seen as producing a kind of tax
on the limited resources available to the fetus to grow and develop.
In contrast to teratogenic effects, dose response relationships
for fetal growth restriction in animals are often nearly linear,
suggesting that the developing fetus may not generally have untapped
“functional reserve capacity” that is expected to buffer
the effects of modest exposures to toxicants in the traditional
toxicological paradigm. Given this mechanistic perspective, supported
in part by parallel dose response relationships between reported
cigarette smoking and both birth weight and infant mortality, restriction
on fetal growth can be associated with changes in quantal end effects
of concern that are more difficult to assess directly in epidemiological
studies.
