Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
pathways results in the possibility of integrating the concept of
product stewardship, which would include extraction, manufacturing,
consumer use and disposal. If society sets the performance goal of
exposure minimization both for humans and for the ecosystem, the
commercial and governmental institutions can devise more
cost-effective responses. For example, a company might receive credit
for reformulating a product that reduces exposures to VOCs in the
home. The cost to the company might be far less in terms of exposure
reduction per capita than equipping the manufacturing site with
emissions control equipment that reduces local concentrations.
Before exposure trading across media, across pollutants or
between employees and the general public can seriously be considered,
the science of exposure assessment must mature. A great deal more must
be learned about risk-producing behaviours and activities, about
variation in individual susceptibility, and about the chronic as well
as acute implications of mixtures of pollutants. Progress has been
made in these areas, and studies are continuing. Perhaps the
contribution of exposure assessment to environmental epidemiology best
exemplifies its advancements in recent years. As environmental
epidemiology is practised today, quantification of exposure measures
play a significant role vital to study design and to interpretation.
Linet et al.'s article (1997) on residential exposures to magnetic
fields and acute lymphoblastic leukemia in children is an excellent
case in point. They measured magnetic field strength in the current
and former housing in over 1200 cases and controls. No associations
were reported for direct measures of magnetic field strength exposures
in this study, although some previous studies had found association
between childhood leukemia and surrogate indicators of exposures to
magnetic fields (power line classification schemes).
Exposure information has influenced risk management and public
policy. A well-known example involves materials containing asbestos.
In the USA, as a result of US EPA's response to actions regarding the
handling of asbestos-containing material in schools as well as
numerous legal suits on behalf of asbestos industry workers, there was
a costly and widespread effort to remove all asbestos from buildings.
Eventually the review and public dissemination of studies showing
insignificant exposures to asbestos to building occupants in the vast
majority of situations resulted in a clarification of US EPA's policy
and an end to the indiscriminate removal of all asbestos-containing
material regardless of its condition (HEI, 1991; Camus et al., 1998).
We now see the concern for protecting the public from
environmental risk requiring more information about exposures.
Recently, the US Congress passed the Food Quality and Protection Act.
For the first time legislation has explicitly recognized the problem
of multiple source exposure. The Act requires that EPA and other
agencies account for aggregate or multiple sources of exposure when
setting maximum allowable levels (i.e., tolerances) for pesticides in
food. In this case, regulations are ahead of the science as current
knowledge on the numerous pathways of pesticide exposure is not
sufficient to establish a standardized methodology.
So in recent years, we have seen exposure analysis gain status.
In 1998 the International Society of Exposure Analysis (ISEA) held its
8th annual conference in conjunction with the International Society
for Environmental Epidemiology. ISEA has a journal with more than 500
subscribers worldwide. The European Commission in 1995 published
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