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By Miriam Raftery

August 19,2016 (San Diego’s East County) – State and local water agency representatives have offered more information for the public following a recent report revealing that 150 reservoirs statewide are “mercury impaired,” including10 in San Diego County, as ECM reported

A key clarification is that the term “mercury impaired reservoirs” referred to testing of fish in those waters,  not testing of water for drinking.  Drinking water can test with no detectable mercury levels, yet still have high, unsafe concentrations of mercury in fish, particularly larger fish that have consumed smaller fish.  This problem raises a new issue: the need for new testing methods to detect low levels of mercury that while not unsafe in drinking water,  can result in unsafe levels in fish living in those waters.

“We monitor mercury concentrations in our lake water,but the levels are below detection,” says Mark Umphries from the Helix Water District. While drinking water is safe according to the district’s tests ,he adds,”We do not monitor fish tissue mercury” relying on tests by thestate. Buthe adds,”Farm raised trout and catfish that we stockinthe lakes have low levels.”

“To protect fish for consumption, the mercury levels need to be roughly 100 to 1,000 times lower than the drinking water threshold,” Amanda Palumbo, ‎Envirnmental Scientist at the State Water Resources Control Board, told ECM.  She said older testing methods for drinking don’t detect low levels of mercury in reservoir water that can accumulate in fish up the food chain.  Newer methods for detecting low mercury levels are what’s  needed, she added.

Umphries notes that a big part of the problem for water agencies is that much of the mercury contamination is caused by air pollution from coal-fired power plants deposited into lakes, streams and oceans. Pilot studies are underway to assess if there are any ways to reduce mercury in fish. Meanwhile, the state’s fishing guidelines for safe consumption are available at Lake Jennings bait and tackle shop.

Similarly, Sean Sterchi , district engineer with the state Water Quality Control Board in San Diego has affirmed that the County, too, relies on state testing.

While frequently eating fish caught in local reservoirs could exposure you to high mercury levels, fortunately the water is currently safe for drinking in all San Diego area reservoirs tested,  says Carrie M. Austin, P.E., environmental engineer and technical lead for the statewide mercury control program for reservoirs with the California  Environmental Protection Agency and the San Francisco Bay Water Board.

"The available data for California reservoirs indicate that the only issue is with methylmercury bioaccumulation in fish. Reservoir water is safe for drinking because no samples exceed the mercury drinking water threshold (MCL of 2 ug/L). This is true for all reservoirs in California for which we have data including San Diego reservoirs for which we have data.," Austin says.

If you fish at local lakes, rivers or in the ocean, the State of California has issued some guidelines for how to minimize your risk of unsafe mercury levels:

General Health Advice for People Catching and Eating Sport Fish in California

Tips to Protect Your Health

  • Fish that contain chemicals that may be toxic are found in different parts of California. The Office of Environmental Health Hazard Assessment (OEHHA)'s Good Catch California program provides information and advice to help people make healthy choices when eating fish.
  • The amounts of chemicals found in sport fish in California are not known to cause immediate sickness. But chemicals can collect in the body over time, and may eventually affect your health or that of your children.
  • This general advisory gives some tips on catching, preparing, and eating fish. It is not intended to discourage you from eating fish, but should be used as a guide to make your sport fish eating safer.

General Tips

Fish in a variety of locations rather than in one location.

Chemical levels can vary from place to place.

Eat different types of fish.

Some species of fish have more chemicals than others due to different feeding behavior.

If possible, eat smaller amounts of several different types of fish rather than a large amount of one type that may have high levels of chemicals.

What types of fish have higher levels of chemicals?

Fish that eat other fish (predatory fish) generally accumulate more mercury.

In lakes and rivers, bass species (striped bass, largemouth bass, smallmouth bass, and spotted bass) are often the top predators. In the ocean, sharks are the top predators. 

What types of fish have lower levels of contaminants?

Rainbow trout and various small sunfish (such as bluegill and redear sunfish) are often the least contaminated fish in water bodies.

Eat smaller fish.

Some chemicals can build up in fish as they get older.

The larger the fish, the higher the levels of chemicals they may contain, within the same species. For example, large striped bass usually contain more mercury than small striped bass.

It is always fun to catch large fish, but it is safer to eat smaller ones. If you keep large fish, freeze some of the fish and eat smaller meals spaced out over time.

Cooking and Preparing Fish

Eat only the fillet.

The fillet portions of fish are the safest parts to eat. Chemicals tend to be much higher in the guts, liver, and skin of fish. Do not eat these parts and do not use them to make sauces, stock or chowder. Also, avoid frequent consumption of any reproductive parts such as eggs or roe.

Eat only the meat of crabs—not their internal organs—because, in general, chemicals such as pesticides and PCBs are more likely to accumulate in the organs. Do not eat the soft “green stuff” (called “crab butter,” mustard, tomalley, liver, or hepatopancreas) that is found in the body section of crabs.

Cook fish or shellfish that you catch and observe quarantines.

Certain fish may carry parasites (worms), and shellfish that you gather may have viruses or bacteria that can make you sick. Cook fish thoroughly to destroy harmful parasites and germs.

Some shellfish, particularly mussels, may contain natural toxins that cause paralytic shellfish poisoning (PSP) or other serious illness, and even death. Cooking will not destroy these toxins, so it is important to observe shellfish quarantines.

Mussels are quarantined from May 1 through October 30 in California, and local quarantines may be posted for other bivalves. Call the 24-hour PSP information line for recorded information about quarantines in California at (800) 553-4133.

For more information on natural contaminants in fish and shellfish, contact the regional marine advisor for your area by calling the Cooperative Extension Office under the county government listings in your phone book.

The annual mussel quarantine does not apply to companies licensed by the State as certified shellfish harvesters. The California Department of Public Health tests and certifies the shellfish from these companies to be safe.

Get the Benefits of Eating Fish

Eating fish that are low in mercury and other chemicals can benefit your health and that of your family.

Fish contain heart-healthy fats called “omega-3s” that also benefit the brain and eyes. Fish species such as trout, salmon, bass, sardines, and anchovies generally contain higher levels of omega-3s than other species.

It is important for women to eat fish while they are pregnant because omega-3s help the baby’s brain develop.

Special advice for women ages 18-45, including pregnant women, and children 1-17 years

When OEHHA's advisories are to protect against mercury, OEHHA recommends lower eating amounts for women ages 18 – 45 and children 1 – 17 years.

Some chemicals may be passed on to the unborn child through the placenta. Babies and children are more affected by mercury because their brains are still developing. Following the advisories is therefore especially important for this special risk group.


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