May 19, 1995
Sri Lanka Bans Two Toxic Pesticides
On June 1, 1995, Sri Lanka will ban the broad-spectrum
organophosphate insecticides methamidiphos and monocrotophos
on grounds of potential hazards to users who do not abide by
the required precautions, according to the Sri Lankan
Registrar of Pesticides. In a March 1995 announcement, the
Director of the Seed Certification and Plant Protection
Centre declared the phaseout of these pesticides, and
recommended the insecticides chlorpyrifos and dimethoate as
"safer alternatives."
Monocrotophos and methamidophos are extremely toxic
chemicals. Both are classified as World Health Organization
(WHO) Ib* pesticides and exposure to small amounts of either
one is enough to cause acute pesticide poisoning. As with
other organophosphates, acute poisoning from these chemicals
can cause headaches, nausea, vomiting, diarrhea, neurological
disorders and death. Exposure to monocrotophos presents
additional threats, including possible genetic mutations, and
psychological disorders of depression and anxiety for people
who are repeatedly exposed.
Monocrotophos and methamidophos have been implicated in
numerous poisonings, chronic illnesses and fatalities
throughout the world. A 1987 study of pesticide dangers in
northeast Nicaragua, prompted by an epidemic of 584
poisonings, determined that methamidophos and carbofuran were
responsible for 77% of these poisonings. A separate study in
1988 found methamidophos among three most frequently cited
causes of acute pesticide poisoning for nontraditional export
farmers in the Guatelmalan highlands. Similarly,
monocrotophos was among the five agrochemicals most
frequently responsible for poisonings between 1984-1991 in
the state of Parana, Brazil. In Paraguay, an extensive
1990/91 study of paralysis of the limbs in children,
originally thought to have been brought on by polio,
suggested that monocrotophos drift from nearby cotton fields
was the most likely culprit.
Also of concern are potential problems resulting from
consumption of produce tainted with monocrotophos and
methamidophos residues. In 1987, an outbreak of 120 cases of
acute organophosphate poisoning in Hong Kong prompted an
investigation by the government Health Department; officials
blamed methamidophos residues on vegetables imported from
China for the outbreak. Since 1987, more than 600 poisonings
in Hong Kong have been attributed to the same cause. In Egypt
as well, there have been fatal pesticide poisonings linked to
the consumption of pesticide residues, including
monocrotophos and methamidophos, every year from 1986 to
1991.
Unfortunately, the alternatives to methamidophos and
monocrotophos that the Sri Lankan Registrar of Pesticides is
promoting, chlorpyrifos and dimethoate, pose many hazards of
their own. In California, chlorpyrifos was the chemical
second most responsible for pesticide poisonings between
1984-1990; though not as acutely toxic as methamidaphos or
monocrotophos, according to the Journal of Pesticide Reform,
as little as 1/5 ounce chlorpyrifos may be sufficient to kill
an "average-sized" (60kg) adult. Compounding this danger,
chlorpyrifos is transformed inside mammals to chlorpyrifos-
oxon, a chemical roughly 3000 times as toxic to the nervous
system as chlorpyrifos. Studies have indicated that repeated
exposure of laboratory animals to chlorpyrifos causes delayed
neuropathy, a condition in which nerve damage can lead to
cramps, weakness, numbing of the extremities and, in some
cases, paralysis of the lower limbs. Finally, while not
considered carcinogenic, chlorpyrifos is frequently sold in
formulations which use carcinogenic xylenes as solvents.
Dimethoate has its own host of problems. In one 1991
Malaysian study, every surveyed sprayer working regularly
with dimethoate reported suffering "often" from nausea, sore
eyes and headaches, all of which are symptoms of
organophosphate poisoning. Other studies have indicated that
this insecticide can cause personality changes such as
anxiety and depression in people who have been repeatedly
exposed. The US Environmental Protection Agency considers
dimethoate a "possible carcinogen," and has placed the
chemical under Special Review.
All four of these chemicals are broad spectrum insecticides
which kill beneficial insects as well as pests, persist to
varying extents in the soil or water and keep farmers on the
pesticide treadmill. The decision to ban monocrotophos and
methamidophos is a bold and necessary step, and one for which
the Sri Lankan government should be commended - according to
the "United Nations Consolidated List," no other nations have
banned these pesticides, and only China has severely
restricted their use. However, if Sri Lanka wishes to protect
farmers and consumers and create an agriculture that is
ecologically sustainable, the government needs to promote
non-pesticide alternatives, not just different chemicals.
*WHO defines Class Ib pesticides as "highly hazardous." WHO
classifies chlorpyrifos and dimethoate Class II, or
"moderately hazardous."
Sources: Seed Certification and Plant Protection Centre Press
Release, March 24, 1995; Journal of Pesticide Reform, Winter,
1994; D. Murray, 1994. Cultivating Crisis: The Human Cost of
Pesticides in Latin America. University of Texas Press:
Austin, TX; B. Dinham, 1994. The Pesticide Hazard. Zed Books:
London; New Jersey Hazardous Substance Fact Sheet,
Dimethoate, 60-51-5; New Jersey Hazardous Substance Fact
Sheet, Monocrotophos, 624-83-9.
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