Perspectives on Mercury Conference
By James Wiener and Teresa Naimo, forwarded by Joyce Brite
|ROBBIE - I received this on a bulletin board. It may be of interest to subscribers in light of the recent discussions on safety and mercury. Please edit as necessary. If this submission strays too far off the topic of automatic music machines and safety, please return it to me.|
Thanks for helping Jody with the monumental editing task!
[ Editor's Note:
[ Thanks for the words of support to Robbie. He lends a
[ fresh perspective to the editing and gives me a chance
[ to cope with other obligations (including the upcoming
[ MBSI convention, setting up a Web page, taking my 5 year
[ old son to organ concerts, etc...
[ I'm posting the remaining portion of your message
[ without further editing. I found it quite interesting.
---------- Forwarded message ----------
PERSPECTIVES ON THE FOURTH INTERNATIONAL CONFERENCE ON MERCURY AS A GLOBAL POLLUTANT, Hamburg, Germany, August 4-9, 1996
James Wiener and Teresa Naimo (Upper Mississippi Science Center, La Crosse, Wisconsin) recently attended the Fourth International Conference on Mercury as a Global Pollutant. This report summarizes their perspectives on the mercury conference and on the state-of-the-science in the ecotoxicology of mercury in the environment.
This excellent international conference was attended by a diverse disciplinary array of scientists studying the biogeochemistry, sources, environmental transport, bioaccumulation, and ecotoxicological effects of mercury in the environment. The conference attracted more than 400 scientists from 30 countries, and much of the information presented at the conference was directly relevant to research initiatives being jointly explored by the USGS and NBS.
Mercury Pollution in Historic Perspective:
Mercury (Hg) is a toxic metal with no known essential function in living organisms. The severe consequences of mercury contamination of aquatic food chains were first recognized in the 1950s and 1960s in Minamata and Niigata, Japan, where human consumers of methylmercury-contaminated fish were severely poisoned (many died). In the 1960s, humans and birds consuming seed grain treated with alkylmercury fungicides were also poisoned. These tragedies prompted widespread reductions in point-source discharges of mercury into surface waters and in the agricultural use of alkylmercury fungicides. Concentrations of methylmercury declined in fishes inhabiting mercury-polluted surface waters after point-source discharges of mercury were reduced, although concentrations in fish have remained unacceptably high in some waters.
In the past decade, high concentrations of mercury have been found in fish from low-alkalinity and humic lakes, newly flooded reservoirs, and wetland ecosystems. These findings have renewed public concern about environmental mercury in many developed countries. In the United States, many state health and fishery management agencies have responded to the current fish-mercury problem by issuing advice concerning consumption of sport fishes. Many developing countries are now experiencing problems with mercury pollution as the result of releases from gold-mining areas and certain industrial operations.
Methylmercury is neurotoxic, damaging the central nervous system. To date, societal concern about mercury in aquatic ecosystems has stemmed largely from the potential adverse health effects of consuming methylmercury-contaminated fish, because human exposure to methylmercury is almost wholly due to fish consumption.
Adverse Biotic Effects and Information Gaps:
Our understanding of the biogeochemistry of mercury remains far from complete. In the last decade, however, applications of new methods for contamination-free sampling and ultra-trace analysis of air, rain, and water have shown that seemingly small amounts or inputs of mercury can cause significant contamination of fishes in certain ecosystems. In fact, many of the freshwater ecosystems with recent fish-consumption advisories seem to be lightly contaminated environments in which inorganic divalent mercury is readily converted to methylmercury, the neurotoxic form accumulated in fish. This certainly seems to be the case in the South-Florida Everglades, an ecosystem being studied by state, private-sector, academic, and federal scientists, including a multi-disciplinary team led by David Krabbenhoft (USGS, Madison, Wisconsin) with funding from the USGS Ecosystem Program. It is also evident that some human activities, such as construction of new reservoirs, increase mercury levels in fish largely by creating environmental conditions that enhance the microbial production of methylmercury. The scientific challenge is to identify and understand the processes and interactions that enhance the production, bioaccumulation, and trophic transfer of methylmercury in such ecosystems.
Ongoing investigations by wildlife toxicologists--studies that were decidedly under-represented at this international conference--strongly suggest that methylmercury contamination of aquatic food webs in certain ecosystems is adversely affecting fish-eating wildlife, such as loons, wading birds, mink, and otters. Evidence suggesting a link between methylmercury exposure and adverse reproductive effects in fish-eating wildlife was recently examined at a workshop on mercury in wildlife, convened in April 1996 in Fairfax, Virginia. (The workshop was organized by Douglas Knauer and Mike Meyer of the Wisconsin Department of Natural Resources, and was co-sponsored by the Electric Power Research Institute and the Wisconsin Department of Natural Resources.) The embryos of vertebrate organisms are highly sensitive to methylmercury. In mammals, all prenatal effects of methylmercury poisoning seem to be irreversible, because they involve developing neural pathways. The effects of methylmercury on birds are much more severe in embryos and chicks than in adults, and low-level dietary exposures that cause no measurable effect in adult birds can significantly impair egg fertility, hatchling survival, and overall reproductive success. The dietary concentrations of methylmercury needed to significantly impair reproduction in birds are only one-fifth of those that produce overt toxicity in the adult.
Concerns about piscivorous (fish-eating) wildlife could greatly influence future actions and perspectives on the mercury issue. The National Biological Service (soon to be the USGS Biological Resources Division) could contribute greatly to improving scientific understanding of the ecotoxicological consequences of methylmercury contamination of aquatic food chains for upper trophic levels.
Prepared by James G. Wiener and Teresa J. Naimo; August 19, 1996
United States Department of the Interior
National Biological Service
Upper Mississippi Science Center
2630 Fanta Reed Road, P.O. Box 818
La Crosse, Wisconsin 54602-0818
phone 608-783-6451; fax 608-783-6066
(Message sent Mon 19 Aug 1996, 18:43:09 GMT, from time zone GMT-0500.)