Environmental Engineering Reference
In-Depth Information
that were affected by the use of tributyltin (TBT) in antifouling
paints applied to boats to prevent algae and barnacles from
attaching to the hull (see Chapter 5). Previously, copper had
been the main toxic ingredient in these paints, but TBT was
more effective and long-lasting. As discussed in the previ-
ous chapter, tin-based chemicals, even at extremely low lev-
els, caused female snails to develop male sexual organs and
to become sterile, and populations crashed. TBT is now pro-
hibited in marine paints in most countries, and snail popula-
tions are recovering. Most boats are again being painted with
copper-based paints that are far from benign but are much
less toxic than TBT, and research efforts are underway to find
nontoxic or less toxic methods to prevent fouling. One popular
formulation being used is adding a substance called irgarol
to copper-based paints to boost their effectiveness. Though
not an endocrine disruptor, irgarol is highly toxic to plants,
including phytoplankton, seaweeds, and seagrasses. It is fairly
stable in water and sediment, and has become a widespread
contaminant in the vicinity of marinas and poses a continual
risk to the environment.
Some other pesticides and industrial chemicals in very
low concentrations also may affect hormone functions, and it
is suspected that reported decreases in human sperm counts
and increases in sperm abnormalities may be a result of expo-
sure. Many reproductive abnormalities in different animals
have been reported in nature. Alligators from Lake Apopka in
Florida that were exposed to pesticides had reduced penis size
and sperm abnormalities. Intersex frogs appear in areas where
the herbicide atrazine is used. Mosquitofish near paper mills
have intersex conditions in which females grow an extended
anal in called a gonopodium, typically seen only in males.
The eggshell thinning noted in birds exposed to DDT was
probably also an example of endocrine disruption, although
that term had not yet been coined when the problem occurred.
Endocrine disrupting chemicals appear to be involved with
increased incidence of hermaphroditism in some fishes and
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