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mirex, and chiordecone have been banned or severely restricted in North
America. However, some, like DDT, continue to be a concern because of local
contamination (Fleming et al. 1983) and because of the high residue levels in
birds that migrate to the near tropics (DeWeese et al. 1986). These birds in turn
pass the residues along the food chain and continue to hamper the full
recovery of some species such as the Peregrine Falcon (Falco péregrinus) in
North America.
Organochiorine insecticides are inexpensive to manufacture and, as long as
pest resistance has not resulted, relatively efficacious. They have been credited
with numerous successes in reducing the extent of some notable vector-borne
diseases, at least in the short term. Also, the human-health effects, at least the
short-term effects, of some of these products may be less severe than those of
the more toxic alternatives, especially under conditions in which pesticides
are used in developing countries. For these reasons, some members of the
international aid community advocate the continued use of these products in
the developing world. As our collective memory of the ecological ravages of
organochiorines fades, some would have us believe (Coulston 1985) that
thoroughly documented effects, such as the eggshell thinning induced by DDE
[1,1-dichloro-2,2-bis (4-dichiorophenyl) ethylenel - a metabolite of DDT -
did not take place and that the developed world overreacted by banning
organochiorine insecticides. Unfortunately, such revisionist rhetoric, however
ill-informed, is likely to be popular with debt-burdened developing countries
faced with an impending pest crisis.
Persistent organochiorines may need to be used in small quantities under
conditions that minimize release to the environment, e.g., underground injections
for termite control, until safer alternatives can be made available or at
least until aid budgets are increased to allow for the purchase of alternative
products that are more expensive but cause less ecological damage. Given the
evidence on the environmental effects of persistent organochlorines, anyone
advocating widespread use of these products, such as is now being proposed
for malaria control in Brazil, clearly does not have the long-term ecological
interests of that country or of the rest of the biosphere in mind.
Arguments of species diversity or ecological integrity may be insufficient to
convince governments to limit the use of persistent organochiorine pesticides.
However, there are other reasons to avoid these hazardous products. The use
of organochiorines has fostered secondary pest outbreaks after the selective
removal of insect and bird predators. Some of nature's most efficient rodent
control agents (predatory birds) are ultimately the hardest hit by the use of
persistent organochlorines.
Organochiorines that are still widely used in North America (Table 2) continue
to be assessed. For example, dicofol has recently been shown to cause egg-shell
thinning, similar to DDE (Schwarzbach et al. 1988), and its future use is,
therefore, uncertain.
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