Chemical Studies on the Fate of Pesticides and Heavy Metals in the Tropical Environment

在热带环境中持续和大规模使用持久性和危险化学品，由于其全球污染和生态毒理学影响，引起了极大的关注。为了阐明这些化学品，如有机氯杀虫剂和重金属的行为和归宿，目前的研究计划已在印度南部的水稻种植区，具有代表性的热带气候。1987-1989年的研究结果表明：（1）六六六（BHC）、滴滴涕（DDT）等持久性有机氯杀虫剂在所有的环境介质和生物区系中都有较高的检出浓度。在空气和水样本中，这些有机氯的含量在8月至1月期间较高，反映出杀虫剂主要在水稻开花季节使用。目前的数据可能有助于解释“点源”地区在全球有机氯污染中的作用，因为印度是全球有机氯污染的主要来源之一。 关于我们 2）对热带地区（印度）和温带地区（日本）空气、水和稻田土壤中有机氯杀虫剂的残留水平进行比较后得出结论，在热带地区，由于高温和暴雨，大量的应用化学品迅速逃逸到大气和水圈中，因此持续使用3）热带地区持久性有机氯的具体模式不仅见于大气层和水圈，而且也见于其他区域。对母乳的分析表明，严格素食者的HCH和DDT含量最高。相比之下，非素食者和渔民社区的浓度较低。这些结果表明，在印度，与发达国家不同，蔬菜是膳食接触有机氯杀虫剂的主要途径。将印度母乳中的有机氯含量与其他国家母乳中的有机氯含量进行比较后发现，印度和中国的六氯环己烷含量极高，这表明它们目前是六氯环己烷污染的主要点源国家。我们还首次在印度母乳中检测到PCB残留物，但水平与其他发展中国家一样低。少

The continuous and large scale use of persistent and hazardous chemicals in the tropical environment are of great concern due to their global contamination and ecotoxicological impacts. In order to elucidate the behavior and fate of these chemicals such as organochlorine insecticides and heavy metals, the present research program has been undertaken in the paddy growing area of South India which has a representative tropical climate. The summary of our findings during the three year program (1987-1989) is as follows:1) Persistent organochlorine insecticides such as HCH (BHC) and DDT were detected in all the environmental media and biota with quite high concentrations. In air and water samples, these organochlorines showed higher levels from August to January, reflecting the application of insecticides largely during the flowering season of rice. The present data may aid in interpreting the role of a "Point Source" area in the global contamination of organochlorines since India is one o … More f the countries still using the persistent insecticides in large quantities.2) When the residue levels of organochlorine insecticides in air, water and paddy soil from tropical (India) and temperate (Japan) regions were compared, it was concluded that in the tropics, much larger quantities of applied chemicals were escaped rapidly into atmosphere and hydrosphere due to the high temperature and heavy rainfall and hence the continuing usage of chemicals in the tropical environment might be alarming in the context of their global contamination.3) The specific pattern of persistent orgaochlorines in tropical regions is seen not only in atmosphere and hydrosphere but also in other regimes. Analyses of human breast milk indicated the highest level of HCH and DDT in strict vegetarian group. In contrast, non-vegetarian and fishermen community showed lower concentrations. These results suggest that in India, unlike developed countries, vegetables are the principal routes of dietary exposure to organochlorine insecticides. Comparison of organochlorine levels of Indian breast milk with those of other countries revealed that HCH levels were extremely high in India and China, suggesting that they are the major point source countries of HCH pollution as of now. We also detected PCB residues for the first time in Indian breast milk, however levels were low as in other developing countries. Less