Environmental Engineering Reference
In-Depth Information
case that only a broad indication of the level or nature of exposure may be deduced
from epidemiological studies.
Quantitative description of dose-response relationships may be hampered by
incomplete information on exposure (especially for biologically relevant time win-
dows), by exposure or dose misclassification, or by the use of surrogate markers of
exposure. Incorrect information about the exposure may bias the description of the
exposure-response relationship. If there are wide confidence intervals around the
results there can be substantially different policy endpoints depending on whether
the upper bound, the lower bound or the midpoint has been chosen for policy making
(Samet et al.
1998
).
Commonly too there are insufficient epidemiological data to discriminate
between alternative models that could describe the dose-response relationship.
This is particularly important at very low exposure levels and this is where both
epidemiological and toxicological data are often limited.
The reviewer or risk assessor should answer the basic question of whether the
epidemiologic data, in an individual study or cumulatively, are adequate for use
in dose-response evaluation. There is no formula or quantitative weighting scheme
prescribed for making this judgement.
If epidemiologic data adequate for dose-response evaluation are not available,
and a Risk Assessment is being developed for use in making an important regulatory
decision, and if it is feasible to develop new epidemiologic data, or to extract new
data from existing studies, an effort should be made to develop and provide good
epidemiologic dose-response data that can be used together with, or in preference
to, high-dose animal data.
12.4.6 Undertaking Health Studies
In some situations there will be a need to undertake health studies as part of a Risk
Assessment. The design of health studies should be underpinned by epidemiological
principles. A range of factors needs to be considered before embarking on a health
study (ATSDR (
1996
):
•
public health significance including the scientific value for the Risk Assessment
and generalisation to other situations;
•
community perspective and involvement;
•
ability to provide definitive results;
•
resource availability;
•
support from local, state and federal agencies
The first level of health studies explore or generate hypotheses about exposure-
outcome associations and address specific exposures, community health concerns,
or specific information needs. Examples are:
•
cross-sectional studies;
•
pilot;
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