Thursday, August 5, 2010

Mercury in our favorite Hawaiian fish

When we moved to Hawaii, we researched the health issues of mercury in local fish and found several reports stating that Hawaii had very low amounts of mercury compared to fish caught elsewhere in the world. Our favorite fish are ahi, mahimahi, ono, and salmon and we eat it a couple of times a week or more. 

Recently, we watched “The Cove”, a documentary about dolphin killing in Japan. The killing of the dolphins was disturbing, as was finding out that it is being supported by marine parks around the world.  But, the information about rapidly increasing mercury levels in the North Pacific Ocean was frightening since fish is one of our primary sources of protein.  Dolphins and fish cannot rid their bodies of mercury like humans can. And since our favorite large fish live on smaller fish, the mercury becomes concentrated in their flesh. The bigger and older fish have a greater concentration of mercury than smaller fish.

Mercury is devastating to the brain development of small children and developing fetuses.  But, even in adults, mercury in the brain will destroy neurons used for sensory perception, memory and motor skills.  Fortunately, humans can eliminate mercury, but it can take a long time and damage to the brain continues as long as the mercury contamination remains in the body.

Recent USGS studies have shown that mercury levels in the North Pacific Ocean have increased about 30% over the last 20 years and are continuing to rise, mostly due to the daily addition of coal burning power plants in China.  The mercury is released into the air and accumulates in streams which empty into the oceans. Mercury in water is converted to methylmercury which is absorbed by plankton and consumed by fish. Consumption of ocean fish and shellfish account for over 90 percent of human methylmercury exposure in the United States

The USGS research that concerns us was published in 2008. The graphs in the report show the latitude and longitude of China, with highly toxic areas along their coastlines.  The National Fisheries Institute disputes that there have been any cases of methylmercury toxicity in the US from consumption of commercial fish. Their evidence is based on a National Health and Nutrition Examination survey taken in 2002. We searched for recent reports on the health effects of the increasing amounts of mercury in the oceans from other US government organizations like the CDC, ATSDR, EPA or FDA and found nothing.  But organizations like are publishing their findings of alarming levels of mercury they are finding in fish bought from grocery stores in California and in sushi restaurants around the US.  Their site’s mercury calculator showed that our 6 oz meal of Ahi last week was 196% of the EPA limit.

Until we see research convincing us otherwise, we are cutting back on eating  ahi, mahimahi and ono, and replacing it with more Big Island raised, low fat, grass-fed, beef.

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