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Hydromethylnon Hydramethylnon
(AmdroTM, MaxforceTM, SiegeTM) is a
trifluoromethyl aminohydrazone, a metabolic inhibitor, used mainly in
granular baits or ready-to-use gelatin baits to control ants, cockroaches,
crickets and termites (U.S. EPA 1998).
The chemical is listed in toxicity category III by EPA (on a scale
of I to IV, I being the highest toxicity rating), requiring any products
to have the signal word CAUTION printed on the label due to eye irritation
(EXTOXNET 1996). Mode of Action
Hydramethylnon
works as a metabolic inhibitor by blocking the biological process in the
insect that makes Adenosine Triphosphate (ATP). ATP is a compound required
by most biological processes to provide energy for life. Without ATP, the
target pest becomes lethargic and stops eating. Death usually occurs
within 24 to 72 hours, although the speed of the product depends on
temperature and target insect activity. Toxicity
LD50
(lethal dose for 50% of the test population) values have shown
hydramethylnon to be slightly toxic through ingestion (1100 to 1300 mg/kg)
in rats and through skin exposure (5000 mg/kg) in rabbits. Acute exposure
can cause irritation to the eyes and mucous membranes lining the
respiratory tract (EXTOXNET 1996). EPA
has classified hydramethylnon as a ‘Group C’ carcinogen, or possible
human carcinogen. Studies in both rats and dogs have shown decreased food
consumption, while a 2-year rat study showed increased liver weights and
increased liver to body ratios (U.S. EPA 1995). Chronic studies done on
hydramethylnon have shown the testis to be a target organ of the
pesticide. Mice fed doses of approximately 3.8 mg/kg/day for 18 months
developed testicular lesions, while studies in both rats and dogs have
resulted in testicular atrophy. In a study of potential birth defects in
rabbits, doses of 10 mg/kg/day resulted in reduced fetal weights. Ecological Effects
Hydramethylnon
is highly toxic to fish in laboratory settings. The 96 hour LC50
(lethal concentration to 50% of the test population) is 0.16 mg/L in
rainbow trout, 0.10 mg/L in channel catfish and 1.70 mg/L in the bluegill
sunfish (Kidd 1991). Low to moderate capacity to accumulate in biological
tissue was demonstrated when hydramethylnon accumulated in bluegill
sunfish at 1300 times its concentration in surrounding waters (ETN 1996). Environmental Fate
Soil
half-life for hydramethylnon is estimated at around ten days. Breakdown
seems to be enhanced by light and soil organisms. Its low solubility in
water and strong absorption by soil organic matter give it low mobility
through the soil. This also decreases its likelihood to contaminate
groundwater. The reported half-life for hydramethylnon in water is 10 to
11 days over a pH range of 7 to 8.9 and 24 to 33 days at a pH of 4.9 (ETN
1996). References: Extension
Toxicology Network (ETN). Pesticide Information Profiles: Hydramethylnon.
<http://ace.orst.edu/cgi-bin/mfs/01/pips/hydramet.htm>. Kidd,
H. et al. 1991. The Agrochemicals Handbook. Third Edition. Royal
Society of Chemistry Information Services. Cambridge UK. pps.10-12. U.S.
EPA. 1998. Reregistration Eligibility Document: Hydramehtylnon.
Office of Pesticide Programs. Washington D.C. U.S. EPA. 1995. “Integrated Risk Information System Database.” Washington, D.C. pps. 10-14.
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