Coastal pollution declining, NOAA survey reports Chlordane, DDT, dieldrin, PCB decrease in Chesapeake Bay


Pollution levels have fallen at more than 100 sites along the nation's coastline, including Hog Point on the Chesapeake Bay, according to a federal program that closely monitors contaminant levels in mussels and oysters.

But coastal pollution is still a major problem in many areas of the United States, with numerous shores closed to swimming and shellfishing, and some undergoing expensive cleanup programs.

The study monitored 14 elements and compounds. The elements under study were arsenic, cadmium, copper, mercury, nickel, lead, selenium and zinc, all of which can be harmful to humans and sea life in high concentrations.

The organic compounds under study were DDT, chlordane, dieldrin (all pesticides), butyltin (a paint additive), PCB (an electrical industry chemical) and PAH (a widespread byproduct of industrial and oil pollution). In high concentrations, many of these compounds can cause cancer and genetic mutations or can interfere with reproduction.

154 sites monitored

Dr. Thomas P. O'Connor of the National Oceanic and Atmospheric Administration, the head of the study, said that many of the 14 chemicals had been outlawed or restricted in their use or discharge into waterways. In other cases, he said, the declines appeared to be caused by voluntary cutbacks or economic changes that reduced industrial reliance on the dangerous chemicals.

"There are lots of decreases and some increases," he said, adding that the declines were comforting but not wholly unexpected, given the increasing efforts in recent years to stem coastal pollution.

The study monitored mussels and oysters at 154 sites from coast to coast and found 217 decreases in chemicals and 41 increases. The main finding in the vast majority of cases, however, was no change of concentration, with 1,898 such readings out of a total of 2,156 samples.

The greatest number of decreases were for chlordane (43), PCB (26), DDT (24) and cadmium (20). The greatest increases were for mercury (7), lead (7), zinc (6) and arsenic (5).

zTC The study, "Trends in Chemical Concentrations in Mussels and Oysters Collected Along the U.S. Coasts from 1986 to 1993," was published last year in the journal Marine Environmental Research. The ocean agency also published a version of the report titled, "Recent Trends in Coastal Environmental Quality: Results from the Mussel Watch Project."

The effort began in 1986. A report in 1992 found that

concentration trends, where evident, tended downward over the program's first five years.

The current report shows that the downward trend is continuing and illustrates it with greater statistical strength.

Shellfish are used for the continuing study because they rapidly absorb environmental contaminants and are easy to collect and examine. Since no single species is common to all coasts, seven different kinds are being collected, including the blue mussel and the American oyster.

Mussels live either partly buried in the sea bottom or attached to rocky surfaces by means of threads. Adult oysters attach themselves to seabed objects with either cement or tough threads.

The shellfish were sampled from sites that average 12 miles apart in estuaries and bays, and 43 miles apart along open coastlines. Almost half the sites are near urban areas, which were selected on the assumption that chemical contamination is higher there and more likely to have undesirable biological effects.

Findings by area

The reported findings are broken down by sampling site. For instance, the waters around Brewster Island in Boston harbor showed declines in copper, chlordane and dieldrin. Hempstead harbor on Long Island Sound had drops in arsenic, cadmium, copper, nickel, lead, zinc, chlordane, DDT and PCB.

Hog Point in Chesapeake Bay showed declines in chlordane, DDT, dieldrin and PCB.

And Harbor Island in San Diego Bay had drops in cadmium, nickel, lead, zinc and butyltin.

Despite the general downward trend, the study noted that 21 sites had high and increasing concentrations of chemicals, and called for them to get special attention from cleanup experts.

The upward trends, the ocean agency report said, "should be interpreted as indicating that ongoing human activity is increasing chemical contamination."

The sites of concern included the Shark River in New Jersey, Naples Bay in Florida, Biloxi Bay in Mississippi, Lovers Point in Pacific Grove, Calif., and Keehi Lagoon in Honolulu Harbor.

Lead was the only chemical measured by the program whose concentration was repeatedly found to be above a public health guideline in many places.

The only other chemicals above a safe level were PCBs found one year in Buzzards Bay, Mass., and cadmium found one year in Lake Pontchartrain, La.

Pub Date: 2/23/97

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