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Chemical Contaminants

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chemicalcontaminants2010 (57.5 KB)       
chemicalcontaminants2010 (96 KB)       

Importance

Chemical contaminants such as metals and polychlorinated biphenyls (PCBs) can be found in the Chesapeake Bay’s fish and bottom sediments. Toxic chemicals can harm the Bay ecosystem and human health. Toxins tend to accumulate in predatory species at the top of the food web. These contaminants have the potential to affect humans who eat contaminated fish.

By analyzing the tissues of specific types of fish, scientists can estimate the overall presence of contaminants in the Bay ecosystem.

Goal

The Bay Program’s goal is for 100 percent of analyzed segments in the Bay and its tidal tributaries to contain no impairments due to toxic chemicals.

Trends

Long-term trend

N/A – can only compare the 2006, 2008 and 2010 303(d) assessments by Maryland, Virginia and the District of Columbia.

Short-term trend (10-year trend)

N/A – can only compare the 2006, 2008 and 2010 303(d) assessments by Maryland, Virginia and the District of Columbia.

• In 2008, 28.1 percent of tidal tributaries were unimpaired, down from 33.7 percent in 2006.
• In 2010, the amount of unimpaired tidal segments decreased to 27.8 percent.

303(d) lists are updated every other year. The next update will be in 2012.

Change from previous year

Based on the 2010 303(d) assessments by Maryland, Virginia and the District of Columbia, 27.8 percent of the goal was achieved. This is compared to 28.1 percent in 2008.

There may be little positive change in the short term because a majority of impaired waterways have persistent problems with PCBs in fish tissues.

Additional Information

Chemical contamination in the Chesapeake Bay is often characterized as a localized problem in “hot spots” or the “Regions of Concern” (Baltimore Harbor, Anacostia River and Elizabeth River). This indicator shows that chemical contaminants are a concern in segments beyond these localized areas.

• More than two-thirds of monitored tidal segments in the Bay contain partial or full impairments related to chemical contaminants.
• Metals, PCBs, and priority organics exceed the impairment threshold in parts or entire tributaries that deliver water to the mainstem of the Chesapeake Bay.
• PCB listings are present in 100 percent of impaired or partially impaired segments.

Because many of these substances bioaccumulate, contaminant concentrations in fish tissues will not decrease quickly, even if fewer toxic chemicals are delivered to waterways.

Chemical Contaminants Indicator Data

The data used in this indicator are the same data used by Maryland, Virginia and the District of Columbia to determine impairments for the 2010, 2008 and 2006 impairment listing years.  Some of the 2006 listings were first determined during previous listing cycles, which used data beginning in 1996. Therefore, a 10-year period is reflected in the data.

It is valuable to use state data to feed the indicator because the states use this data to develop 303(d) lists and eventually TMDLs.

Virginia and Maryland use different contaminant concentration thresholds and different fish species to determine whether a body of water passes the “fishable” designation of use. For this reason, there is some variation between adjacent waters. For example, the Middle Chesapeake Bay segment covers portions of both Maryland and Virginia, but it is counted as a single segment. Virginia has assigned this segment an impairment due to PCBs, but Maryland has not. Therefore, the segment is considered partially impaired following the method used for all other waters under consideration. The segment is included in the overall count of PCB listings within major tidal waters.

Contact

Greg Allen
U.S. Environmental Protection Agency
(410) 267-5746

Source of Data

Chesapeake Bay Program Office