Monday, August 05, 2013

Fish and mercury

Mercury in fish is in the news again. Here in California it is apparently not wise to eat fish from any inland waters. Apparently the fish have too much methyl mercury. The reason, they say, is that the waters are still polluted with mercury dating back to the gold-rush over 150 years ago. One article said that the inorganic mercury changes to methyl mercury in the water. This is not true.

 The only way inorganic mercury can change to organic mercury is by it being converted by small organisms in the water. The organisms can be plant or animal in nature. In order for inorganic mercury to become organic it has to be methylated, i.e., made water-soluble. Methylation can be done in a laboratory or in a living organism. It does not happen by itself.

Now to the toxicity of methyl mercury. It is very toxic. I have come across a case that involved fish. A friend told me about a couple who fished on San Francisco Bay every day. They ate the fish every day and the wife gained a lot of weight. She went to the doctor who gave her a diet that was supposed to help her lose weight. As she lost weight, she felt worse and worse. They did all the tests to explain all her symptoms, and they found a lot of mercury in the blood.

The mercury in the blood was explained by the fact that mercury from the fish was stored in the woman's fat, and when she lost weight the mercury went into the bloodstream to make her ill. In this woman's case they were unable to remove her mercury through chelation. The woman died from mercury poisoning.