Risk Evaluation of Mercury Pollution - Mercury in the Environment - page 260

effects must be measured for each measurement end point.
These can then be compared and ranked.
The task of integrating the risk from mercury with other
stressors provides a great and continuing challenge. This
is an area requiring considerable development of methods.

effects of mercury is increasing daily, and will continue to do
so, providing insights into interindividual, intraspecifi c, and
interspecifi c differences that can help manage the risks from
mercury. The evaluation of the risks from mercury involves
multiple media, species, exposure routes, and effects.
Armed with information on fate and effects of mercury
in humans and other receptors, society still faces a number
of issues that require scientifi c and social inputs and that
require political and public policy decisions. These include
determining the risk to populations, communities, and
ecosystems; how to balance human and ecologic risk from
mercury; how to balance the risks from mercury against the
benefi ts of exposure (through fi sh consumption, industrial
production, mining); how to evaluate intermittent high
exposures; how to incorporate multiple stressors into risk
assessment; and what is acceptable risk for humans, other
receptors, and ecosystems.

Future Research Needs

Mercury risk evaluations change frequently with respect to
methods, information available, technologic advances, and
the questions the public, health professionals, ecologists,
and governments ask. It is increasingly clear, however, that
the risks from mercury can be controlled only by determin-
ing sources of mercury in the environment, the pathways of
exposure, and the concentrations of mercury in its different
forms, in environmental media and the food chain. The con-
centrations in biota then must be calibrated to effects, rang-
ing from sublethal effects to mortality; dose-response curves
need to be developed not only for mortality (the percent of
organisms that die at each exposure), but to several levels
of sublethal effects. Compiling dose-response curves for a
range of effects from mercury in different species (includ-
ing humans) will provide information on interspecifi c
(among species) variability. A major shortcoming of modern
risk evaluation is the assumption that doses are distributed
equally day by day, while recurrent exposures and intermit-
tent or pulsed doses are simply averaged. This is no more
logical than a person taking seven pills once a week rather
than one pill a day and assuming that effi cacy and toxic-
ity would be the same. The interaction among toxicants,
particularly mercury and PCBs (polychlorinated biphenyls),
requires continued attention, as does the interaction of mer-
cury and selenium. Far more studies of mercury levels and
effects in a wide range of biota are required to illuminate
a pattern in which interspecifi c extrapolation is reasonable.
Intraspecifi c (within a species) variability is also critical,
especially as a function of life stage (i.e. fetus, young, and
adult) and other vulnerabilities. The body of data on fate and

Acknowledgments

We have had stimulating discussions about both human and
ecological risk assessment, and on mercury, with many col-
leagues, and we thank them now: C. Chess, K. Cooper, M.
Gallo, B.D. Goldstein, D. Kosson, M. Peterson, C. W. Powers,
M. Lemire, D. Mergler, N. Ralston, E. Silbergeld, A. Stern, and
D. Wartenberg. We thank C. Jeitner and T. Pittfi eld for help
with the graphics. Over the years our research has been funded
by the NIMH, EPA, NIEHS (P30ES005022), the Department
of the Interior, the Department of Energy (through the Con-
sortium for Risk Evaluation with Stakeholder Participation,
AI # DE-FG 26-00NT 40938 and DE-FC01-06EW07053), the
New Jersey Department of Environmental Protection (Offi ce
of Science, and Endangered and Nongame Species Program),
Trust for Public Lands, New Jersey Audubon, the Jersey Coast
Angler's Association, and EOHSI. The conclusions and inter-
pretations reported herein are the sole responsibility of the
author, and should not be interpreted as representing the
views of the funding agencies.

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