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Methomyl Page 2 of 7
<br /> In addition to cholinesterase-inhibition symptoms which maybe observed within 15 minutes to four hours of methomyl
<br /> ingestion,gastrointestinal disturbances may occur,such as lack of appetite,.nausea,vomiting,abdominal cramps and
<br /> 6. diarrhea(16).Liquid concentrate may be fatal if swallowed(2).Three men died after accidentally eating approximately
<br /> 12 to 15 mg of methomyl for each kg of body weight when it was mistaken for leavening and baked into their bread(6 9).
<br /> Methomyl is poisonous if inhaled,and may be absorbed through the mucous membranes of the respiratory tract,resulting
<br /> in systemic intoxication and cholinesterase inhibition.Inhalation of dust or aerosol may cause irritation,lung and eye
<br /> problems,with symptoms of chest tightness,blurred vision,tearing,wheezing and headaches appearing upon exposure.
<br /> ` Other systemic symptoms of cholinesterase inhibition may appear within a few minutes or several hours of exposure(2 3,
<br /> 16,3Q 32).
<br /> Methomyl is not readily absorbed by the skin and is therefore only slightly toxic via dermal exposure(26,32).However,
<br /> if sufficient amounts are absorbed through the skin,symptoms similar to those induced by ingestion or inhalation will
<br /> develop(32).Within fifteen minutes to four hours of exposure,the immediate area of contact may have localized sweating
<br /> and uncoordinated muscular contractions.Other symptoms associated with excess dermal exposure may include vomiting,
<br /> ` nausea,diarrhea,abdominal cramping,dizziness,and headaches(or any of the other symptoms previously mentioned)
<br /> (M)-
<br /> Application of the dry material or a 10%solution caused mild inflammation,but no injury to the cornea in the eyes of
<br /> rabbits(32).Pain,short-sightedness,blurring of distant vision,tearing,and other eye disturbances,as well as previously
<br /> mentioned symptoms of cholinesterase-inhibition,may occur within a few minutes of eye contact with methomyl(16,32).
<br /> Absorption through the eyes may be fatal.
<br /> The amount of methomyl that is deadly to one-half(50%)of experimental animals is called its acute oral lethal dose fifty
<br /> or LD50.The LD50 for methomyl in rats is 12-48 mg/kg,in mice it is 10 mg/kg,and in guinea pigs it is 15 mplkg(2, 19,
<br /> I` 2) dermal.When applied to the skin of rabbits,the deal LD50 was 5,880 mg/kg(2,32).The lethal concentration fifty,or
<br /> LC50,is that concentration of a chemical in air or water that kills half of the experimental animals exposed to it for a set
<br /> time period.The inhalation LC50 for male rats is 0.3 mg/liter(30).
<br /> CHRONIC TOXICITY
<br /> Prolonged or repeated exposure to methomyl may cause symptoms similar to the pesticide's acute effects(32).Repeated
<br /> exposure to small amounts of methomyl may cause an unsuspected inhibition of cholinesterase,resulting in flu-like
<br /> symptoms,such as weakness,lack of appetite,and muscle aches.Cholinesterase-inhibition may persist for two to six
<br /> weeks.This condition is reversible if exposure is discontinued.Since cholinesterase is increasingly inhibited with each
<br /> exposure,severe cholinesterase-inhibition symptoms may be produced in a person who has had previous methomyl
<br /> exposure,while a person without previous exposure may not experience any symptoms at all(t0).
<br /> In a 24 month study with rats fed doses of 0,2.5,5 or 20 mg/kg,the NOEL was 20 mg/kg.At 20 mg/kg,red blood cell
<br /> counts and hemoglobin levels were significantly reduced in female rats(3O).
<br /> Based on a 5 mg/kg NOEL in a two-year feeding study with dogs,and utilizing a 100 fold safety margin,the EPA has
<br /> established an ADI(Acceptable Daily Intake)for methomyl of 0.025 mg/kg of body weight/day 27 28 30).
<br /> EPA has established a lifetime Health Advisory level of 200 ppb for methomyl.Water containing methomyl at or below
<br /> this level is acceptable for drinking everyday over the course of one's lifetime and does not pose any health risk.
<br /> Reproductive Effects
<br /> Methomyl fed to rats at dietary doses of 2.5 or 5 mg/kg for three generations caused no adverse effect on reproduction,
<br /> nor was there any evidence of congenital abnormalities.The NOEL in this study was 5 mg/kg(9,3J0 .
<br /> r
<br /> A two-generation study at 3,780 and 60 mg/kg in the diet showed no adverse effects on the fertility of rats(27 28).
<br /> L Teratogenic Effects
<br /> No teratogenic effects were found in the fetuses of female rabbits that were fed 50 to 100 parts per million,(ppm)during
<br /> http://prep.cce.comell.edu/profiles/extmmet/haloxyfop-methylpazathion/methomyl-ext.html 1/2/2004
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