More than Half of Watershed's Tidal Rivers Contaminated by Chemical Pollutants

February 2007 -- Fifty-three percent of the tidal tributaries in the Bay watershed are contaminated by chemical pollutants in fish tissue, according to newly compiled data by the Bay Program.

Levels of certain chemical contaminants found in fish from these tributaries are high enough that the tributary has been listed as an impaired water body under the Clean Water Act. The listings include:

• PCB concentrations in fish tissues in the Bush, Patapsco, Magothy and South rivers on the western shore of Maryland.
• PCB concentrations in fish tissues in the Chester, Corsica, Bohemia and Sassafras rivers on Maryland's Eastern Shore.
• PCB and/or mercury concentrations in fish tissues in the York, James, Elizabeth and Pamunkey rivers in Virginia.

A tidal tributary containing any impairment due to chemical contamination in fish is included in this figure, whether the impairment is on a small segment of a river or whether it covers an entire river. The Bay Program's long-term goal is to reduce chemical contaminants in 100 percent of the watershed's tidal tributaries to levels that will not have an impact on the Bay's living species or on human health.

PCBs and methylmercury—the organic form of mercury—are highly persistent in the environment. Rather than breaking down, these contaminants attach to sediment at the bottom of rivers and move through the food chain in a process called bio-accumulation.

• Small organisms that live in and near contaminated bottom sediments take up PCBs as they feed.
• Fish and other animals higher up in the food chain accumulate PCBs in their tissues when they eat these smaller, contaminated organisms.
• In turn, humans and fish-eating wildlife accumulate PCBs in their tissues when they consume contaminated fish.

Fish consumption advisories for PCBs and mercury are widespread across the nation. They are issued by each state for specific fish and shellfish species in certain water bodies within that state. Some fish consumption advisories are limited to sensitive populations, such as women who are pregnant or nursing, or certain parts of a body of water.