Human Exposure To Halogenated Aromatic Compounds

从1978年到1982年，我们登记并跟踪了大约900名北卡罗来纳州的儿童。我们测量了她们母亲母乳中的多氯联苯和DDE，并跟踪了她们的哺乳过程。我们发现，DDE水平较高但多氯联苯水平不高的女性断奶时间较早，我们推测DDE、S雌激素活性可能产生了这种影响。后来，我们在墨西哥复制了早期断奶和DDE的发现。2001年，撒哈拉以南非洲的十几个国家要求免除世界范围的滴滴涕禁令，以便将其用于预防疟疾。利用我们关于断奶的数据，以及NIEHS/NICHD关于滴滴涕与早产关系的数据，我们估计，喷洒滴滴涕导致的婴儿死亡率增加与有效控制疟疾造成的婴儿死亡率下降是同一数量级，并建议应使用滴滴涕记录所有婴儿死亡以及断奶时间。我们还估计了母乳喂养对美国等发达国家死亡率的影响，发现即使在美国，母乳喂养的儿童在出生后第一年的死亡率也大大降低。 多氯联苯(PCB)是最普遍和最持久的环境污染物之一，在世界各地的大多数人类中都能检测到。多氯联苯本身是有毒的、致畸的，会导致实验动物的学习障碍和行为异常。在儿童中，即使在低背景水平下，经胎盘暴露也可能产生轻微的精神运动、认知和记忆障碍。此外，热降解多氯联苯的复杂混合物有两种质量中毒。已经发生了两次这样的曝光，一次是在1968年的日本(玉树)，另一次是在台湾(玉城)。与我们在台湾的同事一起，我们一直在跟踪雨城母亲所生的118名儿童，并在2002年报告称，他们在16岁时仍有认知障碍和行为障碍，即使他们是在母亲接触辐射后6年才出生的。我们现在有接触辐射后13年内出生的儿童的数据，并希望确定母亲何时开始生下未受影响的孩子。滴滴涕于1972年在美国被禁止，并于2001年在斯德哥尔摩公约上被提议在全球范围内禁用。然而，撒哈拉以南非洲的国家要求豁免，理由是疟疾死灰复燃，以及它们需要使用滴滴涕控制疟疾。尽管他们的推理假定DDT没有毒性，但我们已经表明，接触DDE较多的女性断奶更早，我们的NIEHS/NICHD同事也表明，接触DDT会增加早产。由于这两种影响都可能增加婴儿死亡率，我们进行了风险分析，以估计因接触滴滴涕而增加的婴儿死亡人数和因滴滴涕病媒控制而减少的婴儿死亡人数。由于多氯联苯和滴滴涕是致癌物质，它们在母乳中的存在造成了监管困境，因为当局不希望建议不要母乳喂养，也不想倡导食用受污染的食物。我们以前曾在含有致癌物的情况下进行母乳喂养的风险-风险分析，但在发达国家，几乎没有发现有关母乳喂养对死亡率的保护的数据。今年，我们找到了一个合适的数据集，用来评估母乳喂养对美国新生儿后死亡率的影响。 在撒哈拉以南非洲，由于使用滴滴涕而导致的婴儿早期断奶和早产死亡率的增加，与极其有效的疟疾控制所造成的下降幅度相同。在美国，母乳喂养与新生儿死亡风险的大幅降低有关，如果所有儿童都母乳喂养，大约1200人的死亡可以被预防或推迟。

From 1978 to 1982, we enrolled and followed about 900 North Carolina children. We measured, among other things, PCBs and DDE in their mothers' breast milk, and followed the course of lactation. We found that women with higher DDE, but not PCB, levels weaned earlier, and we speculated that DDE?s estrogen activity might produce the effect. We later replicated the early weaning and DDE finding in Mexico. In 2001, more than a dozen countries in sub-Saharan Africa requested exemption from the world-wide ban on DDT in order to use it for malaria prevention. Using our data on weaning, as well as NIEHS/NICHD data on the relation between DDE and preterm birth, we estimated that the increase in infant mortality from spraying DDT was of the same order as the decrease from effective malaria control, and suggested that all infant deaths as well as time at weaning should be documented of DDT were to be used. We have also estimated the effect of breastfeeding on mortality in developed countries like the US, and find that even in the US breastfeed children have a substantially reduced mortality rate in the first year of life. Polychlorinated biphenyls (PCBs are among the most ubiquitous and persistent of environmental contaminants, and are detectable in most human beings worldwide. PCBs per se are toxic, teratogenic, and can cause impaired learning and behavioral abnormalities in laboratory animals. In children, transplacental exposure even at low, background levels may produce subtle psychomotor, cognitive, and memory impairment. In addition there have two mass poisonings by complex mixtures of heat-degraded PCBs. Two such exposures have occurred, one in Japan (Yusho) in 1968 and the other in Taiwan (Yucheng). With our colleagues in Taiwan, we have been following the 118 children born to Yucheng mothers, and reported in 2002 that they still had cognitive impairment and disordered behavior as 16 year olds, even if they had been born as long as 6 years after their mothers' exposure took place.We now have data on children born up to 13 years after the exposure, and hope to determine when, if ever, the mothers began to have unaffected children. DDT was banned in the US in 1972, and was proposed for a worldwide ban at the Stockholm Convention in 2001. However, countries in sub-Saharan Africa asked for exemptions, based on the resurgence in malaria and their need to use DDT for malaria control. Although their reasoning assumed no toxicity from DDT, we have shown that women with greater DDE exposure wean earlier, and our NIEHS/NICHD colleagues have shown that DDT exposure increases preterm births. Since both of these effects could increase infant mortality, we did a risk analysis to estimate the increase in infant deaths attributable to DDT exposure and the decrease attributable to DDT vector control.Because PCBs and DDT are carcinogens, their presence in breast milk creates a regulatory dilemma, in that authorities do not wish to recommend against breastfeeding but do not want to advocate the consumption of a contaminated food. We had previously done risk-risk analysis of breastfeeding in the presence of carcinogens, but found few data on the protection against mortality from breastfeeding in developed countries. This year we found a suitable data set with which to estimate the effect of breastfeeding on post-neonatal mortality in the US. The increase in infant mortality from early weaning and pre-term birth that would occur in sub-Saharan Africa from the use of DDT is of the same order of magnitude as the decrease resulting from extremely effective malaria control. In the US, breastfeeding is associated with a substantial reduction in the risk for post-neonatal mortality, and about 1200 deaths could be prevented or delayed if all children breastfed.