Office of Environmental Health Hazard Assessment


Chemicals in Fish

  • Harmful chemicals enter the environment through emissions, spills, and other sources.  Chemicals on land and in air can wash into waterways—lakes, rivers, streams, bays, and the ocean.
  • Fish can take in these chemicals from the food they eat.  People can take in these chemicals when they eat contaminated fish.

The levels of chemicals in fish vary from low to high depending on the type of fish and where it lives.  States, tribes, and local governments have issued advisories for eating fish that may be contaminated across the U.S.

  • The most common chemicals in fish in California are mercury, PCBs, DDTs, and dieldrin.

Mercury is a natural element in some rock and soil.  Methylmercury, a more toxic form of mercury, is found in many fish around the globe.

For more detailed information on mercury:

Methylmercury in Sport Fish: Information for Fish Consumers (Also available as a pdf file)

PCBs, a group of man-made chemicals banned in 1979, last a long time in the environment and build up in fish.

The long-banned pesticides DDTs and dieldrin are found at levels of concern in fish from only a few places in California.

Other Chemicals Now Being Tested in Fish

PBDEs” (polybrominated diphenyl ethers) are a type of flame retardant.  Since the 1970s, they have been used in many consumer goods such as couches, mattresses, carpet padding, clothing, televisions, computers, cell phones, car seats, stereos, and dashboards.  During the last 10 years, scientists realized that PBDEs were increasing in the environment—and in people.  The use of most PBDEs has since been banned or is being voluntarily stopped in many areas, including California.  Testing fish in California for PBDEs is fairly new but, so far, no fish have been found with levels of concern.


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