Do California Lakes, Streams, or Ocean Locations Have Fish With Contaminants at Levels of Concern?

In the two-year statewide screening study, 3483 fish representing 46 species were collected from 68 locations on the California coast. PCBs also reached levels of moderate concern, and were the only other contaminant with problematic concentrations.  It is important to note that data from this study are insufficient for OEHHA to be able to develop new fish consumption recommendations.

Statewide Patterns in
Methylmercury: Coast
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Methylmercury can affect the developing nervous system in children and adolescents, potentially leading to learning disabilities.

Based on the most contaminated species at each location surveyed, the  following results for methylmercury were obtained:

• 37% of the 68 locations were in the "no consumption" range (>440 ppb)
  
  
• 54% exceeded the USEPA threshold used in 303(d) listing (300 ppb)
  
  
• 99% exceeded the Advisory Tissue Level for eating two servings per week (70 ppb)

Percentage of Locations
Above Thresholds

Overall, 63% of the locations had a most highly contaminated species below 0.44 ppm (these locations are shown in orange, yellow, and green on the map).  This represents an estimate of the percentage of locations where frequent consumption of all species, at a number of servings per week to be determined in the future by OEHHA when sufficient data are available for evaluation, is likely to be safe.

Many locations, 25 of the 68 sampled (37%), were in the high contamination category, with an average for the most contaminated species exceeding 0.44 ppm (shown in red on the map).  More than half of the locations (37 of 68, or 54%) had a most highly contaminated species with an average above the 0.30 ppm threshold used by the State Water Board to identify impaired water bodies (shown in orange on the map).

Multiple sources are likely to contribute to methylmercury contamination of California coastal waters, including global emissions to the atmosphere; upwelling from ocean sediments; historic mercury, gold, and silver mining; and urban and industrial wastewater and stormwater.

Statewide Patterns
in PCBs: Coast
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PCBs were the only other contaminant that reached concentrations in fish tissue that pose potential health concerns to consumers of fish caught from California coastal waters. PCBs may cause cancer, damage the liver, digestive tract, and nerves; and affect development, reproduction, and the immune system.

Based on the most contaminated species at each location surveyed, the following results for PCBs were obtained:

• 7% of the 68 locations were in the "no consumption" range (>440 ppb)
  
  
• 66% exceeded the Fish Contaminant Goal (3.6 ppb)

Percentage of Locations
Above Thresholds

Overall, 63 of 68 (93%) locations had a most highly contaminated species below 120 ppb – this represents an estimate of the percentage of locations where frequent consumption of all species, at a number of servings per week to be determined in the future by OEHHA when data are sufficient for evaluation, is likely to be safe.  Five of the 68 locations (7%) were in the high contamination category, with an average for the most contaminated species exceeding 120 ppb.  San Francisco Bay and San Diego Bay stood out as having elevated concentrations.

Other Contaminants

Other contaminants, including dieldrin, DDT, chlordanes, and selenium, were also analyzed, but were found at low levels.

Coast Study Report

A report, Contaminants in Fish from the California Coast, 2009-2010: Summary Report on a Two-Year Screening Survey, presents the data from this two year study. The study is providing information that will be valuable in prioritizing areas in need of further study to support development of consumption guidelines and cleanup plans, and that the public can use to be better informed about the degree of contamination of their favorite fishing spots.

• View documents related to the Coast Survey

Statewide Patterns in
Methylmrcury: Lakes
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Statewide Patterns
in PCBs: Lakes
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Methylmercury is the greatest concern. Mercury contamination is largely a legacy of California mining, but can also reach lakes through air deposition. It is a persistent problem throughout much of the state. Based on the highest species-average tissue concentration at each lake surveyed:

21% of the lakes surveyed had at least one fish species with an average methylmercury level high enough (> 440 ppb) that OEHHA would consider recommending no consumption of contaminated species for women between 18 and 45 years of age and children between 1 and 17 years of age. Those lakes are shown in Red on the map. It is important to note, however, that data from this study are insufficient for OEHHA to be able to develop new fish consumption recommendations.

In spite of the extensive mining activity in California, however, the degree of methylmercury contamination in the state’s lakes is not unusual and is comparable to the average condition observed across the U.S. in a recent national lakes survey.

In spite of the extensive mining activity in California, however, the degree of methylmercury contamination in the state’s lakes is not unusual and is comparable to the average condition observed across the U.S. in a recent national lakes survey.