NOAA Finds Continuing Decrease In Toxic Organic Chemicals In Mollusks

The National Oceanic & Atmospheric Administration's (NOAA) National Centers for Coastal Ocean Science reported that researchers have found a continuing decrease in toxic organic chemicals in mollusks, specifically mussels and oysters, collected at more than 250 sites nationwide. The findings, linked to bans and restrictions on the use of polychlorinated biphenyl (PCB), chlorinated hydrocarbons, tributyltin and cadmium, was announced in Vol. 62, no. 4 of Marine Environmental Research, a scientific journal, according to an Oct. 2 statement.

Produced by the National Status & Trends Program's Mussel Watch Project, the report updates findings published in 1996. The results, based on data through 2003, show continued decreases in national median concentrations of the chemicals and no increases nationally. The Mussel Watch Project is the longest continuous contaminant monitoring program of U.S. coastal waters. It analyzes chemical and biological contaminant trends in sediment and the tissues of bivalves such as mollusks.

In reviewing data on 17 chemicals at 246 different sites, the NOAA scientists reported 108 increased concentrations and 830 decreased concentrations with a 95 percent level of confidence. Most of the decreases are among organic chemicals, with very few organic chemical increases. According to the report, the relatively few trends for concentrations of metals were evenly split between increases and decreases.

"The overall tendency for chemical contamination to be decreasing is good news for the United States," said John H. Dunnigan, assistant administrator of the NOAA Ocean Service. "These results exemplify the benefits of incorporating long-term chemical monitoring into the Integrated Ocean Observing System."

Each of the chlorinated hydrocarbons studied as part of the biennial update is banned or heavily restricted for use in the United States. Researchers noted it was not unexpected that concentrations of these chemicals have declined since the 1996 report. Researchers also stated the only unanticipated result after 10 additional years was that all decreasing trends remained statistically significant.

NOAA National Centers for Coastal Ocean Science:

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