Myers G J, Davidson P W, Shamlaye C F, Axtell C D, Cernichiari E, Choisy O, Choi A, Cox C, Clarkson T W
University of Rochester School of Medicine and Dentistry, NY 14642, USA.
Neurotoxicology. 1997;18(3):819-29.
Mercury is widespread in the environment and exists in several physical and chemical forms. Prenatal exposure to methylmercury disrupts brain development. The most common mode of prenatal methylmercury exposure is maternal fish consumption. Studies of human prenatal exposure in Iraq following maternal ingestion of methylmercury treated grain suggested that maternal hair mercury concentrations above 10 ppm may be related to delayed developmental milestones and neurological abnormalities. This level of exposure can be achieved by frequent consumption of fish. The Seychelles Child Development Study analyzed developmental milestones similar to those determined in Iraq in a large controlled, prospective study of children exposed prenatally to methylmercury when their mothers ate fish. As part of this ongoing study, cohort children were evaluated at 6.5, 19, 29, and 66 months of age. At 19 months care-givers were asked at what age the child walked (n=720 out of 738) and talked (n=680). Prenatal mercury exposure was determined by atomic absorption analysis of maternal hair segments corresponding to hair growth during the pregnancy. The median mercury level in maternal hair was 5.8 ppm with a range of 0.5-26.7 ppm. The mean age (in months) at walking was 10.7 (SD = 1.9) for females and 10.6 (SD = 2.0) for males. The mean age at talking (in months) was 10.5 (SD = 2.6) for females, and 11.0 (SD = 2.9) for males. After adjusting for covariates and statistical outliers, no association was found between the age at which Seychellois children walked or talked and prenatal exposure to mercury. Normal ages at achievement of the developmental milestones walking and talking were found in Seychellois toddlers following prenatal exposure to methylmercury from a maternal fish diet. These results do not support the lowest effect levels in young children following prenatal methylmercury exposure predicted by the dose response analysis of the Iraq data. More detailed studies in older children are needed to determine if there are adverse effects in fish eating populations.
汞在环境中广泛存在，并以多种物理和化学形式存在。产前接触甲基汞会干扰大脑发育。产前接触甲基汞最常见的方式是母亲食用鱼类。伊拉克在母亲摄入用甲基汞处理过的谷物后对人类产前接触情况进行的研究表明，母亲头发中的汞浓度超过10 ppm可能与发育里程碑延迟和神经异常有关。经常食用鱼类就可能达到这种接触水平。塞舌尔儿童发展研究在一项大型对照前瞻性研究中分析了与伊拉克所确定的类似的发育里程碑，该研究针对母亲食用鱼类时产前接触甲基汞的儿童。作为这项正在进行的研究的一部分，对队列中的儿童在6.5、19、29和66月龄时进行了评估。在19月龄时，询问了照料者孩子开始走路（738名中有720名）和说话（680名）的年龄。通过对与孕期头发生长相对应的母亲头发段进行原子吸收分析来确定产前汞接触情况。母亲头发中的汞含量中位数为5.8 ppm，范围为0.5 - 26.7 ppm。女性开始走路的平均年龄（月龄）为10.7（标准差 = 1.9），男性为10.6（标准差 = 2.0）。女性开始说话的平均年龄（月龄）为10.5（标准差 = 2.6），男性为11.0（标准差 = 2.9）。在对协变量和统计异常值进行调整后，未发现塞舌尔儿童开始走路或说话的年龄与产前汞接触之间存在关联。塞舌尔幼儿在通过母亲鱼类饮食产前接触甲基汞后，在达到走路和说话这些发育里程碑方面的年龄正常。这些结果不支持根据伊拉克数据的剂量反应分析所预测的产前甲基汞接触对幼儿的最低影响水平。需要对年龄较大的儿童进行更详细的研究，以确定食用鱼类人群中是否存在不良影响。
