Evaluating Mercury Concentrations in Midwest Fish in Relationship to Mercury Emission Sources

Abstract

Mercury serves as one of the most visible forms of inorganic pollution in the public eye and is most commonly associated with contaminated fish. For many years pregnant women and women of child-bearing age have been instructed by both the Food and Drug Administration and the Environmental Protection Agency to limit their intake of fish due to concerns with mercury. Atmospheric deposition of mercury is the primary route of uptake in fish. In recent years there has been significant discussion regarding the influence of local and global sources of mercury concentrations in fish. Few studies exist that attempt to sufficiently evaluate the relationship between mercury concentrations in fish and their proximity to mercury sources (most notably coal-fired power plants). To remedy this, mercury concentrations in fish tissue collected from over 250 locations throughout four states in the Midwest were spatially analyzed using Geographic Information Systems (GIS) technology to determine whether there appeared a relationship between the locations of mercury emission sources and concentrations of mercury in fish. It proved difficult to portray the relationship based on a simple linear analysis of distance between the location of a sample and the concentration. However, when sources were buffered based on an approximation of watersheds within the commonly accepted area of localized deposition, there appeared a clear relationship for large mouth bass, the most prominent predatory species in the Midwest (the relationship did not hold true for bottom-feeders as expected since they do not bioaccumulate mercury at the same rate as predators).