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 Aquatic EcosystemsToxic Chemicals: Page 2 Although persistent pesticides of the DDT family have been banned in the United States, they are still manufactured here and exported for control of malaria to many tropical countries. DDT is still present in a 17 square mile dumping area in the coastal waters off California. Montrose Chemical Corporation and two other companies dumped some 100 tons of DDT between 1947 and 1971, when it was banned. These ocean residues continue to enter the food chain through fish and other organisms. This has affected birds who feed on these fish, including brown pelicans and bald eagles on the California coast, who still laid thin-shelled eggs as a result of DDT contamination of their food supply 30 years after the ban. Highly toxic pesticides banned in the United States are still being used around the world, killing large numbers of birds and other wildlife. Diazinon, a pesticide commonly used on golf courses in the United States, and highly toxic to geese and other birds, was recently banned in the United States, along with Dursban, a commonly used lawn chemical. Pesticides and related chemicals that kill and cause mutations in wildlife are indeed still being broadcast in the United States as well as in other parts of the world. Only with more oversight and strong legislation to limit use and export of these chemicals can wildlife and aquatic ecosystems be protected.
DDT and other pesticides contaminate entire ecosystems in tropical countries, and some North American birds winter in areas where these chemicals are still used. Between 1992 and 1994 alone, the United States exported at least 247 million pounds of banned or restricted pesticides to the rest of the world. DDT, for example, is widely used for malaria control in Africa and Asia. Virtually no laws restrict this trade, which has the potential of causing major wildlife declines and extinctions.
In agricultural areas in northern Florida, American alligators (Alligator mississipiensis) have been found with abnormalities and poor reproductive success thought to have been caused by pesticides in their food supply (Colborn et al. 1996). Many synthetic chemicals react on animals in a manner similar to hormones. Dicofol, a pesticide related to DDT, was widely used in the vicinity of Lake Apopka, finding its way into the waters and causing abnormalities in alligators. Males developed unusually small penises and defective testicles, and females had abnormal eggs and sex organs (Colborn et al. 1996). The male alligators in this lake had elevated levels of female hormones, equal to those in normal female alligators, and one-fourth the normal level of testosterone; females had estrogen levels double the norm (Colburn et al. 1996). The reproduction of alligators in the area has nearly ceased altogether, with almost no eggs hatching (Colburn et al. 1996). Red-eared turtles of Lake Apopka, considered unlikely to be affected by this pesticide since they are plant-eaters, surprised researchers by exhibiting reproductive difficulties as well. Many turtles discovered had not developed normally as either male or female (Colborn et al. 1996).
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