Toxic Chemical Testing of California Sport Fish Offers Mixed Results

Sacramento–Results from a major study of toxic chemical concentrations in sport fish in California show that contamination from some toxics has declined, while that of others remains a problem.

The Surface Water Ambient Monitoring Program (SWAMP) has just released its Final Report: Bioaccumulation of Pollutants in California Waters: A Review of Historic Data and Assessment of Impacts on Fishing and Aquatic Life, which was completed for SWAMP by the San Francisco Estuary Institute (SFEI).

The report evaluated trends of toxic chemical concentrations in sport fish in California, comparing three decades of monitoring data on bioaccumulation collected by major state monitoring programs and smaller studies. Bioaccumulation refers to the build-up of chemicals in the tissue of a fish.

The results show major decreases in bioaccumulation for some contaminants, but little change in mercury contamination over time. Although still present in fish, the bioaccumulation of PCBs and DDT (which posed a serious problem in the 1970s) has steadily declined.

Nevertheless, bioaccumulation of toxics remains a problem in many of the states’ water bodies. Of the 390 sites sampled recently, 68 percent have bioaccumulation concentrations above levels of concern. Mercury is the chemical of primary concern; mercury concentrations generally show no decline over the last 30 years. Because of the use of mercury in gold panning and mining and quicksilver mines dating back to the Gold Rush, California is dealing with legacy, historic pollution in multiple bodies of water.

The report recommends additional monitoring and assessment and makes specific recommendations for a cost-effective bioaccumulation monitoring program in California.

SWAMP data is used by CalEPAa??s Office of Environmental Health Hazard Assessment (OEHHA) to develop sportfish consumption advisories for individual water bodies.

One key issue is that consumption advisories exist for only a fraction of the water bodies likely to need them. Many water bodies with elevated contaminant levels in fish are near population centers and are popular for fishing.

To begin to address this need, a program focused on lakes and administered by SWAMP began monitoring last year. The first year included sampling of 50 random lakes and 80 lakes popular for fishing. The remaining 120 popular lakes will be sampled this year. The information collected will help: Create a statewide assessment of bioaccumulation impacts on California lakes. Assess which individual lakes are so contaminated that clean-up actions are needed.

The report, by J.A. Davis, Ph.D., and others, is available at and on the SWAMP website.