Long-term trends in DDT, polychlorinated biphenyls, and chlordane in California mussels

The California State Mussel Watch program is a long-term monitoring program conducted by the State Water Resources Control Board and the Department of Fish and Game. In a fifteen year time span, from 1977-1992, mussels were collected at 378 stations. From these stations, 47 were chosen to conduct statistical analysis based on the criteria that they had been sampled at least 6 times for total DDTs, total polychlorinated biphenyls (PCBs), and total chlordanes. Declines of total DDTs and chlordanes were noted at approximately half of the stations. Declines of total PCBs were noted at approximately one-quarter of the stations. Declines of PCBs but not DDTs in mussels near Los Angeles County's sewer discharge corresponded to declines of these contaminants in treated effluent.