U.S. Long-term coastal contaminant temporal trends determined from mollusk monitoring programs, 1965–1993

Data from four large-scale programs that monitored chemical concentrations in marine mollusks were assembled to determine long-term trends in U.S. coastal waters. The programs were the 1965–1972 national Environmental Protection Agency (EPA) monitoring project, the EPA ‘Mussel Watch’ Program of 1976–1978, the ongoing National Oceanic and Atmospheric Administrationʹs Mussel Watch Project that began in 1986, and the ongoing State of Californiaʹs Mussel Watch Program that began in 1977. When concentrations from the four projects were evaluated together at common sites, decreasing national trends were found for PCBs, DDT and its metabolites, and dieldrin. When data from three of the four large-scale monitoring projects were evaluated for trace elements, decreasing trends were found for lead, cadmium, and silver. For copper, decreasing and increasing trends were approximately equal except for California where at five sites increasing trends were indicated. No trends were found for PAHs, nickel or zinc concentrations.