Do California lakes, streams, or ocean locations have fish with contaminants at levels of concern?
National Monitoring - Mercury in Fish from National Parks
[Image source: USGS/NPS Report]Mercury (Hg) is a toxic, global contaminant that threatens ecosystem and human health. Human activities have increased atmospheric concentrations 3-5 fold during the past 150 years. Airborne Hg enters environmental cycles in complex ways, resulting in the contamination of even remote places. The National Park Service (NPS) protects some of the most pristine and sensitive wilderness in North America. There is concern that atmospherically deposited Hg could threaten the ecological integrity of aquatic communities in the parks and the wildlife that depend on them. In this study, the NPS and U.S. Geological Survey (USGS) examined Hg concentrations in more than 1,400 freshwater fish from 86 sites across 21 national parks in the western U.S., extending over a 4,000 km distance.
The USGS/NPS report of mercury in fish from 21 national parks is now available.
This publication is available at: http://pubs.usgs.gov/of/2014/1051/
California Statewide Monitoring
Statewide monitoring indicates that concentrations of methylmercury and other contaminants in indicator species are above human health thresholds in
some areas of the state.
The maps on this page present results from statewide surveys conducted by the Bioaccumulation Oversight Group of the State Water Resources Control Board's Surface Water Ambient Monitoring Program (SWAMP). These surveys are the first components of a new program that is tracking sport fish contamination in California lakes, coastal waters, and rivers and streams.
Fish tissue concentrations were compared with thresholds developed by the CalEPA Office of Environmental Health Hazard Assessment (OEHHA) and the U.S. Environmental Protection Agency (U.S.EPA).
- Results for California Rivers and Streams
- Results for the California Coast
- Results for California Lakes and Reservoirs
Sport Fish in Rivers and Streams
In this one-year survey conducted in 2011, 568 fish representing 16 species were collected from 63 river and stream locations throughout California. Contaminant concentrations were found to be low at the majority of locations sampled. However, the results indicate that methylmercury accumulation is of high concern in the Sacramento-San Joaquin Delta region. Methylmercury is generally a low concern in high elevation locations where trout species predominate. Concentrations of the other contaminants measured rarely exceeded OEHHA thresholds that would indicate a potential need for reduced consumption.
Statewide Patterns in Methylmercury:
Rivers and Streams
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Methylmercury
Methylmercury is the contaminant that poses the greatest concern for consumers of fish caught in California rivers and streams. 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:
- 13% of the 63 locations were in the "no consumption" range (>440 ppb)
- 24% exceeded the OEHHA Fish Contaminant Goal (220 ppb)
- 49% exceeded the Advisory Tissue Level for eating two servings per week (70 ppb)
Above Thresholds
Overall, 51% of the locations had a most highly contaminated species below 0.07 ppm (these locations are green on the map). This represents an estimate of the percentage of locations where frequent consumption of fish is likely to be safe with regard to methylmercury. Specific consumption frequencies will be determined by OEHHA when sufficient data are available for this type of evaluation.
A few locations, 8 of the 63 sampled (13%), were in the high contamination category, with an average for the most contaminated species exceeding 0.44 ppm (shown in red on the map). Almost a quarter of the locations (15 of 63, or 24%) had a most highly contaminated species with an average above the 0.22 ppm Fish Contaminant Goal (shown in orange on the map).
Multiple sources are likely to contribute to methylmercury contamination of California rivers and streams, including historic mercury, gold, and silver mining; global emissions to the atmosphere; and urban and industrial wastewater and stormwater.
Other Contaminants
Other contaminants, including PCBs, selenium, and the legacy pesticides dieldrin, DDT, and chlordanes, were also analyzed, but were found at low levels.
Rivers and Streams Study Report
A report, Contaminants in Fish from California Rivers and Streams, 2011, presents the data from this study. The study has provided 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.
Sport Fish in Coastal Waters
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
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
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PCBs (Polychlorinated Biphenyls)
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)
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.
Sport Fish in Lakes and Reservoirs
Statewide Patterns in
Methylmercury: Lakes
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Methylmercury
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: CHART TO RIGHT
- 21% were in the "no consumption" range (>440 ppb)
- 35% exceeded the USEPA threshold used in 303(d) listing (300 ppb)
- 43% exceeded the Fish Contaminant Goal (220 ppb)
- 56% exceeded the Advisory Tissue Level for eating 2 servings per week (150 ppb)
- 69% exceeded the Advisory Tissue Level for eating 3 servings per week (70 ppb)
Statewide Patterns
in PCBs: Lakes
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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.
PCBs were second to methylmercury as a potential health concern to consumers of fish caught from California lakes. Approximately 36% of the lakes had a fish species that exceeded OEHHA's Fish Contamination Goal. However, only 1% of the lakes sampled had a species with an average concentration level that exceeds OEHHA's threshold for considering a recommendation of no consumption. PCBs are persistent chemicals that were historically widely used in electrical, industrial and other applications. Other pollutants were also detected, but generally at low levels.
The report, Contaminants in Fish from California Lakes and Reservoirs, 2007-2008, presents the largest study on contaminants in fish ever conducted in California, and presents data on 272 of California’s more than 9,000 lakes and reservoirs. The study provides information that will be valuable in prioritizing lakes 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.
The Lakes Survey was the first component of a new program that is tracking sport fish contamination in California lakes, coastal waters, and rivers and streams. Results from the first year of a two-year survey of contaminants in sport fish from California coastal waters will be available in May 2011.