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.
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.
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
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
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.