Bringing epidemiology
and toxicology together
to better understand cause
and effect relationships requires attention
to several interconnected problems:
problems of
commitment,
complexity,
and of
communication.
The most
fundamental of these
is commitment as it is reflected
in the basic purpose of
environmental epidemiology. The
purpose of epidemiology
is not to prove cause/effect
relationships,
and not only because scientific proof is elusive.
The purpose of epidemiology
is to acquire knowledge
about the determinants
and distributions
of disease and to apply that
knowledge to improve public health.
A key problem,
therefore,
is how much and what kinds
of evidence are sufficient
to warrant public health
(typically preventive)
actions?
The assessment
of available evidence lays
the foundation for the problem of complexity:
relevant evidence arrives
from toxicologic
and epidemiological
investigations,
and reflects the acquisition
of knowledge
from many levels
of scientific understanding:
molecular,
cellular,
tissue,
organ systems,
complete organisms
(man and mouse),
relationships between individuals,
and on to social
and political processes
that may impact human health.
How to combine evidence
from several levels
of understanding
will require the effective
communication
of current methodological practices.
The practice
of causal inference
in contemporary environmental
epidemiology,
for example,
relies upon three largely qualitative methods:
systematic narrative reviews,
criteria-based
inference methods,
and (increasingly)
meta-analysis.
These methods are described
as they are currently used
in practice
and several key problems
in that practice
are highlighted including the relevance
to public health practice of toxicological evidence.
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