Retrospective study of mercury in raccoons (Procyon lotor) in south Florida.

Museum and recent collections of raccoon hair were used to assess whether temporal or spatial trends existed in MMHg distributions in south Florida. The hypothesis that MMHg in raccoon hair had remained the same since 1947 could not be rejected. Some sampling regions showed increases while others did not. However, large differences existed between sites, amounting to a factor of 20 for raccoons collected during 2000 and during the period prior to 1960 (museum samples). Raccoon feeding behavior and the production of MMHg most probably accounted for the spatial differences. Large differences in MMHg concentrations existed in different tissues ranging in order of hair, liver, kidney, muscle, heart, brain, and blood in their respective ratios to blood: 96:10:6:5:4:2.5:1. Liver Hg is 7% MMHg, while hair Hg is 99% MMHg. These associations appear largely regulated by metabolic processes. Speciation of Hg is very important for gaining an understanding of ecosystem and organism Hg dynamics. Further work is needed to establish whether Se plays a role in Hg sequestration and whether hair Hg is a good surrogate for estimating Hg concentrations in other tissues in south Florida raccoon populations.

Developing consensus: mercury science and policy in the NAFTA countries (Canada, the United States and Mexico).

The international science community has recognized methylmercury in the aquatic food chain, as a potential environmental and human health risk. As a result, countries around the world have implemented a number of mercury management initiatives. The United States, Mexico and Canada in consultation with stakeholders are developing a trilateral North American Regional Action Plan (NARAP) on mercury. Through public involvement in the decision making process, the NARAP has offered opportunities for more transparency in transactions between governments, industry and stakeholders. In spite of the available scientific information, there are still important uncertainties associated with the mercury issue. These knowledge gaps include: the most appropriate methylmercury reference dose for sensitive groups; the percentage of the North American population that is at risk from methylmercury exposure; spatial and temporal mercury deposition patterns in each country; the link between mercury emissions, atmospheric deposition and methylmercury concentrations in fish; and the relative magnitude of contributions from natural and anthropogenic sources.

Selection of test methods to assess ecological effects of mixed aerosols.

Components of the mixed aerosols generated during military training are known to be of toxicological and/or ecological significance. There are few studies, however, quantifying mixed aerosol effects on ecosystems. Prompted by our finding that one or more of the compounds in the mixed aerosols commonly encountered in military training areas showed mutagenic effects in several species, a multiyear effort is evaluating the use of ecotoxicity testing methods to assess mixed aerosol ecological impacts. Selection of test methods for ecoepidemiology begins with the identification of the data required to meet defined environmental quality objectives. The data requirements are then matched with appropriate test methods, and testing results are related to important ecological effects resulting from aerosol exposure. The critical element of test system selection is to ensure that toxicity testing results relate to important ecological effects. The procedures developed for identifying test methods to assess mixed aerosols are also applicable to a range of environmental contaminants regulated by air, water, and solid waste regulations.