Threat by chemical substances: Legislation, production, use and waste - Environmental Deterioration and Contamination: Problems and their Management - page 63

- Eggshell thinning and altered sex organ development have been observed in birds

of prey exposed to the pesticide DDT, resulting in severe population declines. Birth
defects have been found in fish eating birds, which are directly related to exposure
to another dangerous persistent chemical, PCB;

- A presumed pesticide spill in Lake Apopka (Florida, USA) provides a well-

publicized example of potential endocrine disrupting chemical effects on the
decrease in alligator numbers. The alligators had a variety of sex organ and
other developmental abnormalities attributed to exposure to high levels of various
organochlorine contaminants that can affect the endocrine balance;

- Population declines in amphibians such as frogs are typical in both unpolluted and

polluted habitats world-wide. Scientists have found a correlation with the presence
of EDs;

- There is extensive evidence that chemicals found in the waste outflows from pulp

and paper mills and sewage treatment plants can affect reproduction and devel-
opment in fish. A variety of endocrine changes are involved, but it is not yet fully
clear which chemicals are responsible for the changes;

- The females of certain marine organisms such as snails, slugs, whelks and periwin-

kles develop male sex organs when exposed to tributyltin (TBT). TBT, a chemical
used in antifouling paints, provides the clearest example in invertebrates of an
endocrine effect caused by an environmental contaminant. This has resulted in
world-wide declines in the populations of the mentioned species.

We can state that none of the above mentioned cases are fully discovered, even
though several explanations have been proposed, the exact cause of the changes and
damage remains unknown. EDs may be present in food, drinking water, wastewa-
ter, surface waters. Their degradation in the environment may be restricted: many
of them are persistent or only 10-50% is degraded during the biological wastewater
treatment. Epidemiological and ecological assessments as well as experimental studies
have demonstrated reproductive alterations as a consequence of long-term exposure
to EDs such as hormones applied in medication, pesticides and POPs such as poly-
chlorinated and polybrominated biphenyls, dioxins, bisphenol A, dimethylsilbestrol
or methoxychlor.
Wildlife disturbances in sexual and reproductive functions and impaired offspring
survival have been observed in areas where chemical contamination is high. Current
scientific knowledge provides evidence that some abnormalities seen in wildlife are
caused by chemicals that function as EDs. However, in most cases, the evidence of a
causal link between the abnormalities and exposure to particular chemicals is weak.
How the findings in wildlife can be applied for humans is also a question.
Concrete concerns on human adverse health effects of EDs (IPCS, 2002) are
summarized here.

- Reproductive effects:

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Sperm quality : A number of studies report a decline (since the 1930s) in sperm
quality—i.e., sperm count, proportion of normal sperm, semen volume—in
several countries, which might be expected to affect fertility. Several surveys
refute this downward trend in human sperm quality. From testis develop-
ment and function variations within and between countries it is plausible that