Myers G J, Davidson P W
Department of Neurology, University of Rochester School of Medicine and Dentistry, New York 14642, USA.
Environ Health Perspect. 1998 Jun;106 Suppl 3(Suppl 3):841-7. doi: 10.1289/ehp.98106841.
Mercury is present in the earth's crust and is methylated by bacteria in aquatic environments to methylmercury (MeHg). It is then concentrated by the food chain so predatory fish and sea mammals have the highest levels. Thus, consuming seafood leads to exposure. MeHg readily crosses the placenta and the blood-brain barrier and is neurotoxic. The developing fetal nervous system is especially sensitive to its effects. Prenatal poisoning with high dose MeHg causes mental retardation and cerebral palsy. Lower level exposures from maternal consumption of a fish diet have not been consistently associated with adverse neurodevelopmental outcomes. However, most studies have considerable uncertainty associated with their results. Two large controlled longitudinal studies of populations consuming seafood are underway that are likely to determine if any adverse effects can be identified. No adverse associations have been found in the Seychelles, where exposure is mainly from fish consumption. In the Faroe Islands where exposure is primarily from consumption of whale meat and not fish, adverse associations have been reported. The Seychelles population consumes large amounts of marine fish containing MeHg concentrations similar to commercial fish in the United States. Current evidence does not support the hypothesis that consumption of such fish during pregnancy places the fetus at increased neurodevelopmental risk.
汞存在于地壳中，在水生环境中会被细菌甲基化为甲基汞（MeHg）。然后，它会通过食物链富集，因此掠食性鱼类和海洋哺乳动物体内的含量最高。所以，食用海鲜会导致接触甲基汞。甲基汞很容易穿过胎盘和血脑屏障，具有神经毒性。发育中的胎儿神经系统对其影响尤为敏感。高剂量甲基汞的产前中毒会导致智力迟钝和脑瘫。母亲食用鱼类饮食导致的低水平接触与不良神经发育结果之间并未始终存在关联。然而，大多数研究的结果都存在相当大的不确定性。目前正在对食用海鲜的人群进行两项大型对照纵向研究，这可能会确定是否能识别出任何不良影响。在主要通过食用鱼类接触甲基汞的塞舌尔群岛，未发现不良关联。在主要通过食用鲸肉而非鱼类接触甲基汞的法罗群岛，已报告存在不良关联。塞舌尔群岛的居民食用大量含有甲基汞的海鱼，其甲基汞浓度与美国的商业鱼类相似。目前的证据并不支持孕期食用此类鱼类会使胎儿面临更高神经发育风险这一假设。
