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Abstract:
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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 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.
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