'Malathion' is an
organophosphate parasympathomimetic which binds irreversibly to
cholinesterase. Malathion is an
insecticide of relatively low human
toxicity.
In the former
USSR it was known as 'carbophos', in
New Zealand and
Australia as 'maldison' and in
South Africa as 'mercaptothion'.
[1]
However, malathion breaks down into
malaoxon, which is 60 times more toxic than malathion. For this reason, if malathion is used or somehow enters an indoor environment, as it breaks down into malaoxon, it can seriously and chronically poison the occupants living or working in this environment. Malathion present in untreated water is converted to malaoxon during the chlorination phase of water treatment, so malathion should not be used in waters that may be used as a source for drinking water, or any upstream waters.
In
1976, numerous
malaria workers in
Pakistan were poisoned by
isomalathion, a common impurity in malathion, which is capable of inhibiting
carboxyesterase enzymes in those exposed to it; the original toxicity evaluation for malathion had not anticipated isomalathion coexposure.
Clinical uses
Malathion is used as a treatment for
head lice,
body lice and
scabies. It effectively kills both the eggs and the adult lice.
Instances of use
Malathion was used in the 1980s in
California to combat the
Mediterranean Fruit Fly. This was accomplished on a wide scale by the near weekly
aerial spraying of suburban communities for a period of several months. Formations of three or four
agricultural helicopters would overfly suburban portions of
San Bernardino county releasing a mixture of malathion and
corn syrup, the corn syrup being a bait for the fruit flies.
Malathion was sprayed in many cities to combat
West Nile virus. In the Fall of 1999 and the Spring of 2000,
Long Island and the five boroughs of
New York City were sprayed with malathion. Use of the insecticide has been blamed for large
lobster die-off in
Long Island Sound.
[2]
Manitoba,
Province of Canada, ordered the city of
Winnipeg, Manitoba to be sprayed in
July 2005 as part of the
West Nile virus campaign. Prior to this, Malathion was used over the last couple of decades on regular basis during summer months to kill nuisance mosquitos, but homeowners were allowed to exempt their properties if they chose. Today,
Winnipeg is the only major city in
Canada with an ongoing Malathion nuisance adult mosquito control program.
Malathion is also used in conjunction with
diesel to fog an area where there are plenty of
mosquitoes. By diluting the mixture, it becomes much weaker. It is possible to dilute the mixture to the point where mosquitoes are not killed, but become more resistant to the mixture, making it less effective in subsequent foggings.
See also
★
Pesticide toxicity to bees
Sources
★ Brenner, G. M. (2000). ''Pharmacology.'' Philadelphia, PA: W.B. Saunders Company. ISBN 0-7216-7757-6
★ Klaassen, C. D. (2001). ''Casarett & Doull's Toxicology'' McGraw-Hill Medical. ISBN 0-07-134721-6
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