Note that the data published in the 2002 State of the Nation’s Ecosystems Report as well as the 2003 and 2005 Web-Only Updates have been superseded by the 2008 Report and thus should be used with caution. For the most recent data, purchase the 2008 Report from Island Press.

View Data for Estuary Areas

What Is This Indicator, and Why Is It Important? This indicator reports the percentage of sediments that exceed federal guidelines for concentrations of four major classes of contaminants––pesticides, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and heavy metals. The indicator reports on estuaries and ocean waters within 25 miles of the coast that have bottom sediments with varying degrees of contamination, the lowest indicating "possible adverse effects" on fish and other aquatic organisms from 1 to 4 contaminants and the highest indicating "probable adverse effects" from at least one contaminant.

Polluted sediments are a starting point for contamination throughout the food chain, potentially damaging marine life and affecting human health (see Selected Contaminants in Fish and Shellfish). Pollutants from industrial discharges, burning of fossil fuels, and runoff from farms and urban and suburban areas are carried to coastal waters by rivers, rainfall, and wind, where they accumulate on the bottom. Small organisms incorporate these contaminants into their bodies, and when they are eaten by other organisms, the contaminants may move up the food chain (bioaccumulation). Areas with contaminated sediments may also be unsafe for swimming and other recreation.

Why Can't This Entire Indicator Be Reported at This Time? No program exists to provide nationally consistent data on sediment contamination in ocean waters along the coast. Data for estuaries in in Alaska and Hawaii are not available.

What Do the Data Show? During 1999-2000, 42% of estuary sediments tested had contaminants above levels designed to predict "possible adverse effects" on aquatic life for one or more contaminants, and about 7% exceeded the level designed to predict "probable adverse effects." Data for the period from 1990-1997 are not comparable because they did not include the North Atlantic and Pacific Coast estuaries. In addition, the pesticide Dieldrin is no longer included in the suite of contaminants used to predict "possible adverse effects" or "probable adverse effects" (see technical note). For these reason, it is not possible directly to compare the data from the earlier time period to the 1999-2000 time period. (Note that all sites with contaminants exceeding the "probable adverse effects" guidelines also had 5 or more compounds exceeding the "possible adverse effects" level.)

Discussion The NOAA guidelines used here were developed as informal interpretive tools and are not intended as the basis for regulatory decisions. The "possible adverse effects" guidelines identify concentrations below which negative effects rarely occur, and thus levels above which such effects may occur. The "probable adverse effects" guidelines indicate levels above which negative effects are likely.