The presence of methylmercury and polychlorinated biphenyls (PCBs) in Californian sport fish is widespread and a concern for human health, the State Water Resources Control Board has announced. They specifically refer to sport fish caught in urban coaster waters. 19% of the coastline was found to have fish with levels of mercury much higher than the recommended limits for women of childbearing age and children.

SWAMP (State Water Resources Control Board's Surface Water Ambient Monitoring Program) has just released its findings on what it describes as the largest statewide survey of contaminants in sports fish in coastal waters ever made. They said that levels of PCBs and methylmercury in fish is of great concern.

This report, part of a two-year survey, has details on the first year, 2009, and includes information for 42 locations, focusing on Los Angeles and San Francisco.

California's greatest problem is the accumulation of methymercury. Of the 42 locations studied, 8 had at least one specimen with methylmercury levels well above the OEHHA (Office of Environmental Health Hazard Assessment) limit for women of childbearing age and children. Sharks were the main fish to have excessive levels of mercury.

32 of the locations were found to have moderate levels of methylmercury contamination.

Methylmercury has been linked to the nervous system developmental problems in children and teenagers, the authors explained. Children with high levels of mercury have a much higher risk of having learning disabilities. This contamination in California probably comes from regional and global emissions to the atmosphere, historic mining of gold, silver and mercury, and industrial and urban wastewater and stormwater.

The PCB recommended threshold level for human consumption is zero. High PCB levels were found in at least one specimen in 6 of the 42 locations. The worst areas for PCB contamination were San Diego Bay and San Francisco Bay.

31 of the 42 locations had moderate PCB contamination levels. Only five areas were deemed as safe.

PCBs can damage the nerves, digestive tract and liver. They also raise the risk of developing certain cancers. PCBs used to be used in industrial, electrical and some other application - they are now banned.

Low levels of other contaminants were also found, including selenium, chlordanes, DDT and dieldrin.

"SWAMP - Surface Water Ambient Monitoring Program - Coastal Study - Bioaccumulation in Sport Fish"
State Water Resources Control Board (California)

Written by Christian Nordqvist