People who frequently eat deep sea fish over a long period of time had elevated mercury levels in their blood and hair, a study by clinical toxicologist Wu Ming-ling (吳明玲) at the Taipei Veterans General Hospital has found.
One three-year-old girl was found to have 40 times more mercury in her blood than recommended by the WHO.
Wu presented the findings of a study she conducted between 2007 and 2011 at a research seminar held by the hospital. She said that 31 patients with high levels of mercury in their blood and hair — including six children — had all been longtime consumers of sea fish and deep sea fish.
The six children exhibited symptoms of attention deficit hyperactivity disorder (ADHD), delayed development and allergic rhinitis, she said, adding that they had eaten fish five to seven times per week because their parents considered fish to be healthy food.
Although deep sea fish have health benefits because they contain omega-3 fatty acids that can help brain development in children and offers protection against heart disease in adults, large-sized fish and deep sea fish are upstream in the ocean food chain and thus might be contaminated with mercury and dioxins, she said.
A 41-year-old mother was found to have elevated levels of mercury in her hair during a health examination. Eight months later the levels of mercury in her blood and hair were several times higher than normal, Wu said.
Wu said the woman’s three-year-old and five-year-old children were found to have even higher levels of mercury, and were suffering from mercury poisoning.
The level of mercury in the three-year-old girl’s hair was as high as 52.28 parts per million (ppm) — the WHO’s recommended level is 1 ppm —and she had a blood mercury level of 205.7 parts per billion (ppb). The recommended level is 5 ppb to 10 ppb.
Her father displayed symptoms of allergic contact dermatitis, had blood in his urine, heart arrhythmia, coronary artery problems, hyperlipidemia and kidney disease, while the mother had a renal cyst and experienced chronic fatigue. The children had allergic rhinitis, with the five-year-old being diagnosed with ADHD and the three-year-old having delayed language development and unexplained abdominal pain.
Wu cautioned against consuming excessive amounts of deep sea fish, especially women who intend to get pregnant or who are breastfeeding and young children.
People should also avoid the skin, visceral fat and the heads of large-sized fish, Wu said.
The recommended amount of deep-sea fish consumption is 80g to 100g per month, she said.