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Rotenone The
widely used botanical insecticide rotenone (Derris™, Prentox™, Chem
Fish™) is often used by home and commercial "organic"
gardeners as an alternative to commercial "chemical"
insecticides. Yet, farmers and gardeners should be aware of rotenone's
potential hazards and toxicity. Despite
widespread use and findings that residues are persistent, all agricultural
uses of rotenone were exempted from tolerances (the establishment of
maximum legal residue levels) in 1955 by the Food and Drug Administration
(FDA), and, therefore, most data requirements were waived. EPA, now
responsible for the establishment of tolerances, is reevaluating the 1955
exemption and has issued a special Data Call-in notice for residue data. Rotenone
and rotenone resins are found in the roots of 68 species of legume plants,
but most commercial supplies come from the South American cubé,
the Malaysian derris, and Brazilian tembo plants. The resins are not very
soluble in water, and are usually used either as a dust or in an oil or
kerosene solution, sometimes mixed with the quicker-acting pyrethrins
and the synergist piperonyl butoxide. Dust formulations have also long
been used on animals to control lice and ticks, and on humans for treatment
of chiggers and scabies. Noxfire™ has been used as a drench to control
fire ants on lawns, and one formulation is registered as a mosquito larvicide.
Rotenone
is non-phytotoxic and unstable to sunlight, air and water, so applications
lose their efficacy within a week. Toxicologically,
rotenone is a slow-acting nerve poison which acts by inhibiting
respiratory metabolism in cells, essentially paralyzing affected insects.
Specifically, rotenone interferes with the mitochondrial
electron-transport system. In animals, it is very poorly absorbed by the
gastro-intestinal tract, and is so irritating that it promptly induces
vomiting. However, in prolonged feeding tests in rodents, rotenone caused
growth depression. Test animals fed dust formulations of rotenone
developed muscle tremors, severe pulmonary and skin irritation from
exposure to dust, severe hypoglycemia (low blood sugar), clonic
convulsions, and respiratory depression resulting in death. EPA has no
record of human fatalities or clinical poisoning reports. EPA
conducted a Pre-Special Review investigation of rotenone in 1975. This was
triggered by data indicating that rotenone could arrest cell
multiplication and cause developmental abnormalities in frog eggs and
chick embryos. Also, a controversial Spanish carcinogenicity study
purported to find high incidences of mammary tumors in rats. In 1981, the
Agency concluded that the Spanish study had major deficiencies, and that
attempts by an EPA contractor and the National Toxicology program to
duplicate it in two species of rats and one mouse species had filed to
detect any increase in tumors over the control animals. In
1980, the U.S. Fish and Wildlife Service took on the burden of paying for
further toxicological studies (chemistry, environmental fate, teratology,
mutagenicity, metabolism, and residue studies in water and fish) in order
to maintain rotenone's registration when it became clear, according to
EPA, that 'no industrial sponsors (were) willing to conduct or fund the
research studies needed to obtain registrations by fishery managers and
fish culturists. At best, the gross sales of one of the major fishery
chemicals is less than $500,000 per year." Researchers
have found that rotenone dust residues persist on lettuce and tomatoes
nearly twice as long as do wettable powders, with half-lives between 3 and
5 days, and that both the parent and major metabolite are stable to
boiling in tomato homogenate. Still, despite outstanding questions of
ecological and health effects, the use of rotenone is widely accepted
under organic certification programs. References: DeWilde,
A.R., et al. 1986. "A case of fatal rotenone poisoning in a
child." J. Forensic Sci. 31:1492-98. Gosselin,
R.E. 1984. Clinical Toxicology of Commercial Products. Williams
& Wilkins, Baltimore, MD. Hayes,
W.H. 1982. Pesticide Studies in Man. Williams & Wilkins,
Baltimore, MD. Newsome,
W.H. & J.B. Sheilds. 1980. "Residues of rotenone and rotenolone
on lettuce and tomato fruit after treatment in the field with rotenone
formulations." J. Agric. Food Chem. Jul/Aug. p. 772. Thomson,
W.T. 1984. Agricultural Chemicals: Insecticides. Thomson
Publications, Fresno, CA. U.S.
Department of Health & Social Services. 1988. "Toxicology and
carcinogenesis studies of rotenone in F344/N rats and B6C3F1 mice."
National Toxicology Technical Report Series No. 320. National Institutes
of Health. Bethesda, MD. U.S.
EPA. 1988. Guidance for the reregistration of pesticide products
containing rotenone as the active ingredient. Office of Pesticide
Programs. Washington, DC. U.S.
EPA. 1983. Data call-in notification: Rotenone. Office of Pesticides and
Toxic Substances. Washington, DC. U.S.
EPA. 1981. Rotenone; Completion of Pre-RPAR Review. [46 FR 36745]. U.S.
EPA. 1980. Minutes of meeting between EPA & FWS regarding rotenone:
November 3, 1980. Office of Pesticide Programs. Washington, DC. U.S.
EPA. 1980. Rotenone: Pre-RPAR Review. Office of Pesticides & Toxic
Substances. Washington, DC. Reprinted from Pesticides and You, Volume 7, No. 3, August, 19807.
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BEYOND PESTICIDES |
