A review of dioxins/furans and methyl mercury in fish from the Penobscot river, located near Lincoln, Maine

Abstract

The Agency for Toxic Substances and Disease Registry (ATSDR) was requested to review the analytical results of tissue samples from fish caught in the Penobscot river in Maine, calculate fish consumption limits and provide a public health opinion regarding the health implications associated with eating the contaminated fish. Fish consumption limits were calculated to provide guidance on the amount of fish that a person may eat monthly that would probably not pose a public health threat. Earlier, in 1987, the Maine Bureau of Health (BOH) issued a fish consumption advisory for portions of the Penobscot river to protect the public from exposures to dioxins/furans and methyl mercury-contaminated fish. From 1988 to 2003 the state of Maine conducted fish surveys at four locations along the Penobscot river to monitor the levels of dioxins/furans and methyl mercury contamination. In 2005, ATSDR reviewed the sampling results for two fish species (i.e., bottom feeders and predators) collected from the Penobscot river that revealed various levels of dioxins/furans and methyl mercury. The United States Environmental Protection Agency's (US EPA) guidance for evaluating potential health threats associated with contaminated fish recommends that a minimum of two target species be sampled including one predatory and one bottom feeding species. Target species are chosen to meet the following criteria: (1) known to accumulate high concentrations of target contaminants in their tissues; (2) normally populate the freshwater system being studied; (3) are routinely caught and consumed by anglers; (4) nonmigratory; (5) pollutant-tolerant; (6) easily identified; (7) abundant and easy to collect and (8) of sufficient size to provide adequate tissue samples for analyses of contaminants (US EPA, 2000). The analytical results of these fish tissue samples appear to indicate that toxic equivalency quotients concentrations of dioxins/furans have slightly decreased since 1988. In contrast, fish tissue levels of methyl mercury appear to have increased slightly since 1988. Dioxins/furans and methyl mercury levels detected in fish tissue samples caught in the Penobscot river located near Lincoln, Maine, may continue to pose a public health hazard to persons who consume the fish daily, depending on the amount consumed. The ATSDR concurred with Maine BOH's fish advisory for dioxins/furans and methyl mercury, that is, currently in place for portions of the Penobscot river near Lincoln.