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The U.S. Environmental Protection Agency (EPA)-Region III asked the Agency for Toxic Substances and Disease Registry (ATSDR) to review chemical contaminant levels detected in fish from the Anacostia and Potomac Rivers and to determine if eating the fish would pose a public health hazard.

In July 1989, the District of Columbia (DC) issued a fish consumption advisory for the Anacostia and Potomac Rivers. The advisory warned the public against eating channel catfish, carp, and eels caught in DC waters.

In 1991, staff from the District of Columbia Environmental Control Division provided 20 fish samples for chemical analysis. The samples were a composite of fillets from three to 27 fish. The species tested were largemouth bass, American eel, pumpkinseed, redbreast sunfish, brown bullhead, channel catfish, bluegill, longear sunfish, and common carp.

The samples were analyzed by ECO LOGIC, Inc. using EPA approved methods. The data from these analyses were provided to ATSDR. The quality assurance/quality control information indicated the data were of high quality.

The fish samples were analyzed for metals, volatile organic chemicals, polychlorinated biphenyls (PCBs), polychlorinated dibenzodioxins and polychlorinated dibenzofurans, semi-volatile organic chemicals, and organochlorine pesticides.

In general, the levels of organochlorine compounds were higher in eels and catfish than in largemouth bass and sunfish. This is expected because eels and catfish: (1) have a higher body fat content in which these compounds bioaccumulate, and (2) are bottom feeders so they would have more contact with contaminated sediments.

The maximum concentration of PCBs in a fish sample was 2.60 parts per million (ppm), which was detected in a composite of fillets from three eels. In channel catfish composites, the highest PCB concentration was 2.00 ppm, and in largemouth bass, 0.062 ppm.

The highest concentration of DDT (0.234 ppm) was also detected in an eel composite, and the highest concentrations of chlordane (0.234 ppm) was detected in a catfish composite. The maximum concentrations of 2,3,7,8-tetrachlorodibenzodioxin (TCDD) (2.3 ppt) and TCDD equivalents (6.3 ppt) were found in a catfish composite.


The Food and Drug Administration (FDA) has jurisdiction over the levels of contaminants in fish sold in interstate commerce. The FDA has set Action Levels for the following contaminants: PCBs (2 ppm), chlordane (0.3 ppm), DDT and metabolites (5 ppm), and mercury (1 ppm). Of the contaminants detected in fish from DC waters, only PCBs exceeded an FDA Action Level. However, it may not be appropriate to use FDA Action Levels to assess the consumption of fish from DC waters because: (1) The FDA Action Levels apply only to fish sold in interstate commerce. (2) The FDA Action Levels factor in economic considerations. (3) Fish consumption rates for sport fishermen could be higher than those assumed for the consumption of commercially bought fish.

The health risks associated with eating fish with chemical contamination depends on the contaminant levels as well as the amount, frequency, and length of fish consumption. In this consultation, ATSDR will conservatively assume that an active sport fisherman will eat one meal of fish (8 ounces or 227 grams) per week, every week, for 30 years. This equates to a fish ingestion rate of 32 grams per day. For lower fish consumption rates, the calculated risks would be proportionally less.

In DC fish, the contaminant found at the highest concentration and posing the greatest health hazard was PCBs. The maximum concentration of PCB residues detected in a fish sample was 2.60 ppm, which was detected in a eel composite sample; in a catfish composite, the highest concentration was 2.00 ppm. The following calculations will be based on catfish consumption, since this species is more widely eaten than eels. A sport fisherman who eats an average of 32 grams of catfish a day contaminated with PCBs (2.00 ppm) would receive a dose of:

(32 x 10-3 kg/day) x (2.0 mg/kg) = 9.14 x 10-4 mg/kg/day.
70 kg bodyweight

This dose exceeds EPA's chronic Reference Dose (RfD) for PCBs (Aroclor 1254) of 2 X 10-5 mg/kg/day for non-cancer health effects.

The EPA classifies PCBs as a Category B2 carcinogen, indicating that it is a probable human carcinogen. The EPA's National Center for Environmental Risk Assessment recommended that a cancer slope factor of 2 (mg/kg/day)-1 be used for PCBs in biota. Therefore, the cancer risk from eating catfish from DC waters under the assumed exposure scenario would be:

2.0 (mg/kg/day)-1 x (9.14 x 10-4 mg/kg/day) x 30 years/70 years = 7.83 x 10-4

This risk level exceeds what is typically acceptable for the general population.

Chlordane and DDT were detected at levels below the FDA Action Levels. Under the exposure assumptions stated above, the maximum concentrations of these chemicals would not be expected to pose a hazard for non-cancer health effects. The EPA classifies chlordane and DDT as Category B2 carcinogens. Consumption of fish containing the maximum concentrations of chlordane and DDT would pose a cancer risks in excess of 1 x 10-5 for each chemical. Therefore, these contaminants would further add to the risk of consuming fish from DC waters.

The FDA has not proposed an Action Level for dioxin (TCDD) in fish, but it has recommended that fish from the Great Lakes should not be eaten if they contain more than 50 ppt of TCDD. None of the fish from DC waters exceeded this level. However, using the above exposure assumptions, eating catfish containing 6.3 ppt of TCDD equivalents would pose an estimated cancer risk of 1.9 x 10-4. This risk would further increase the cancer risk from other organochlorine contaminants.

The highest concentration of mercury (0.46 ppm) was detected in a composite of bass fillets. Mercury accumulates through the food chain, so it is not surprising that the highest concentration was detected in a predator fish at the top of the food chain. Most mercury in fish is in an organic form. For an active sport fisherman, consumption of bass from two of the composites would result in a mercury dose in excess of the EPA's RfD for organic mercury (1 x 10-4 mg/kg/day). None of the other fish composites had mercury concentrations that would exceed a level of health concern for a sport fisherman.


  1. The reported concentrations of chemical residues in fish from the Anacostia and Potomac Rivers could pose a public health hazard for sport fishermen.


  1. Continue the fish consumption advisory for the affected waterways.

Kenneth G. Orloff, Ph.D., DABT

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