A report from the National Oceanic and Atmospheric Administration shows falling levels of contaminants and metals in the mid-Atlantic oyster population.

The report follows 20 years of studies of 140 trace metals and organic compounds in mussels and oysters in U.S. coastal waters, including the Chesapeake Bay.

The manager the agency's Mussel Watch Program, Gunnar Lauenstein, says mussels and oysters are good indicators of contamination levels because they filter the water.

The report found a drop in the pesticide DDT and the industrial PCBs in mussel and oyster tissues from 1986 to 2006.