Environmental Engineering Reference
In-Depth Information
was worse than when only MeHg or only Se was adminis-
tered (Heinz and Hoffman, 1998). Thus, toxicity to the devel-
oping embryo, at least in birds, may be additive in response
to a combination of elevated dietary MeHg plus Se, in spite of
a protective effect of Se in adults. More research with various
combinations of MeHg and Se are warranted.
It is recommended that future toxicologic studies focus
on a number of key issues:
.
Linking biomarkers of MeHg exposure and oxida-
tive stress to effects on reproduction and population
change in wild fish populations.
.
Linking environmentally realistic levels of MeHg
exposure or Hg accumulation in amphibian and
reptile species with toxic effects on reproduction,
neurochemistry, or other important physiologic
processes.
.
Determining the genetic (or other) basis for the species
differences in sensitivity to MeHg toxicity observed
in comparative egg-injection and other studies,
including the role of MeHg demethylation and Hg-Se
interactions.
.
Linking changes at the level of the transcriptome
or proteome with reproductive dysfunction,
neurotoxicity, or other toxic effects of MeHg in at-risk
fish and wildlife species.
.
Linking toxic effects of MeHg exposure in individual
animals to population-level changes in at-risk species.
conclusions
The uptake, metabolism, and effects of Hg in fish and wild-
life have been studied for more than 50 years, and much
has been learned regarding the dynamics of Hg in the envi-
ronment, its food-chain transfer, and its toxic effects. Some
research has documented subtle, yet potentially important
effects of Hg on behavior, neurochemistry, and endocrine
function in fish and wildlife at currently realistic levels of
environmental exposure. given that substantial anthropo-
genic Hg emissions on a global scale will almost certainly
continue well into the 21st century, the need for new
research on the ecotoxicology of Hg, and continued moni-
toring of Hg in fish and wildlife in various natural environ-
ments, will undoubtedly continue as well.
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