Our Stolen Futurea book by Theo Colborn, Dianne Dumanoski, and John Peterson Myers


  Semenza, JC, PE Tolbert, CH Rubin, LJ Guillette, Jr, and RJ Jackson. 1997. Reproductive Toxins and Alligator Abnormalities at Lake Apopka, Florida. Environmental Health Perspectives 105(10):1030-1032.

DDT, its metabolites, and other persistent bioaccumulated pesticides are prime suspects in the the alligator population decline that occurred in the early 1980s at Lake Apopka, Florida. Semenza et al. discuss the fact that two less persistent nematocides, dibromochloropropane (DBCP) and ethylene dibromide (EDB), known to be reproductive toxicants in humans, were also present in the complex mixture of chemicals that contaminated Lake Apopka. Some of the reproductive abnormalities resemble, at least superficially, known impacts of DBCP and EDB on people. Reviewing the available data, Semenza et al. conclude that DBCP and EDB may have been involved in producing the alligator population declines but that data are insufficient to establish (or reject) that with scientific certainty.



Semenza et al. describe the origins of contamination of the lake:

From 1957 to 1981, the facility (Tower Chemical Co.) manufactured and stored both chlorinated and organophosphate insecticides as well as a copper-salt-based fungicide at a site 1.5 miles from Lake Apopka. Wastewater from the manufacturing process was discharged into an unlined pond, and chemicals were burned or buried on site. During a heavy rain in 1980, the percolation pond overflowed and acidic wastewater discharged into a marsh that drains into Lake Apopka. DDT and other chemicals contaminated the lake during this extensive spill. The area surrounding the chemical company's plant was declared an EPA Superfund site in 1983. DDT and other pesticides have also entered the lake as a result of extensive agricultural activity surrounding the lake, primarily activity in orange groves and vegetable muck farms.

Semenza et al.'s review of historical records establishes that DBCP and EDB were both present at elevated levels in this chemical mix. These two chemicals damage sperm and reduce fertility in people. DBCP was banned in 1985 from use on all US crops. It was widely replaced by EDB, which had been used as a fumigant for grain, fruit and vegetables since 1945.


  While there are some similarities between established effects of DBCP and EDB on people and the observed abnormalities in alligators, there are also several substantial differences, which Semenza et al. acknowledge. The observed human effects were reversible: adult men exposed to DBCP in the workplace were subsequently unable to produce sperm. When the exposure was eliminated, however, they recovered. In contrast, the described effects on alligators have focused upon "organizational" impacts: reproduction impaired by errors during development that led to modified gonadal structures incapable of normal function. There may have been "organizational" impacts on DBCP-affected people, for example on the male children of women exposed occupationally, but these were not examined. Similarly, there may have been temporary but severe effects on alligators analogous to the DBCP effects on people. These were not studied, either.  




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