I know a lot of you disregard my constant warnings against the consumption of tuna and other large predatory fish, so I figured I'd throw up an article or two on the joy of mercury poisoning...
Excessive mercury levels in quarter of Hong Kong babies
Organic mercury in fish causes severe concern all over the world. Only last week the UK Food Standards Agency advised pregnant women, and even women who intend to become pregnant, to cut swordfish, shark and marlin from their diet and to reduce their consumption of tuna to no more than two medium-sized tins or one tuna steak a week.
A quarter of infants in a Hong Kong study have been found to have excessive mercury in their blood, which can cause mental retardation, and doctors have warned expectant mothers against eating too much fish.
Mercury in fish is in the form of methylmercury which is readily absorbed into the blood after ingestion and distributed to all tissues of the body, in particular into the brain cells, in four days. In pregnant women, it readily crosses the placenta into the fetal circulation system and is deposited in the fetal brain.
In a study of 1,057 infants over a two-year period in Hong Kong, researchers found how much fish mothers consumed directly affected the amount of blood mercury found in their babies. As many as 25% of the infants in the study were found to have cord blood mercury concentrations of over 61 nmol/litre, the upper allowable limit. Three percent had blood mercury concentrations of over 100 nmol/L.
"Eating too much fish by the mother during pregnancy is the major factor in elevating the blood mercury level of the feotus," said Professor Fok Tai-fai at the Chinese University. Lam Wei-kei, a chemical pathology professor who also participated in the study, said: "The major source of human mercury intake is dietary methylmercury present primarily in fish and other seafood."
In adults, mercury poisoning causes personality changes, nervousness, irritability, fatigue, insomnia, headache, loss of memory, hearing and vision and even renal failure. In babies, it may lead to stillbirth, cerebral palsy, mental retardation, speech delay, poor control of chewing, salivation and swallowing. Curiously, however, fish commonly caught and heavily consumed in Hong Kong were not found to have excessive levels of mercury, the researchers said. "It isn't the case that our fish are particularly bad, it's because we are eating too much fish," Fok said in an interview wih reuters health.