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Methomyl Page 3 of 7 in. the 8th to 16th day of gestation(9).In rats,no embryonic or teratogenic effects were observed at the highest dietary dose administered(400 ppm)(27,28 M0). 6. Mutagenic Effects In all of several assays(including Ames test,a reverse mutation assay,a recessive lethal assay,three DNA damage studies, an unscheduled DNA synthesis assay,and in vivo and in vitro cytogenetic assays),methomyl was not mutagenic (9 27 18).Methomyl showed no transforming activity in a host mediated hamster cell culture(26).There is no evidence that methomyl is a mutagen(30). (r Carcinogenic Effects �., There was no evidence of carcinogenicity in either rats or dogs that were involved in two-year feeding studies(11). Methomyl was not carcinogenic in 22 and 24 month studies with rats fed doses of up to 20 mg/kg,nor in a two year study with mice fed dietary doses of up to 93.4 mg/kg of body wgt/day(26. In a two year feeding study with mice fed 0,2.5,3.75 or 10 mg/kg no compound related tumors formed at any level.In another two year feeding study with dogs fed 0, 1.25,2.5, 10 or 25 mg/kg the NOEL was 2.5 mg/kg based on the occurrence of hemolytic anemia and non-neoplastic changes in the kidney and spleen at higher doses.No tumors were observed at any dose(27,28).Methomyl does not cause tumors in rats or mice(30). Acetamide,a suspected oncogen,is a minor metabolite of methomyl.No valid study of the metabolism of methomyl in the r human body is available.Tests for acetamide levels are needed and have been called for by the EPA(30). Organ Toxicity Lungs,skin,eyes,gastrointestinal tract,kidneys,and spleen have been affected in various experiments,depending on route of entry,duration of exposure,and dosage(16).Chronic feeding studies in rats and dogs showed dose related changes in tissues of the kidney and spleen.The NOEL in both rat and dog was 100 ppm or 2.5 mg/kg/day(30). The autopsies of methomyl-induced suicide victims revealed congested and fluid-filled tissue in many locations,including the stomach and lungs.This condition apparently results from decreased or inadequate circulation(19). Fate in Humans and Animals r Carbamates,the class of active ingredients in which methomyl is included,are quickly absorbed from the skin,lungs and gastrointestinal tract and are broken down and transformed in the liver.Although they do not appear to accumulate in any particular body tissue,they do alter many other enzyme systems besides the cholinesterases(1 7,9 11 19). v ECOLOGICAL EFFECTS r Methomyl is toxic to fish,birds and other wildlife(5). Effects on Birds r Methomyl is highly toxic to birds.The acute oral LD50 for bobwhite quail is 24.2 mg/kg(30).The oral LD50 of methomyl was 28 mg/kg in hens.All deaths occurred within ten minutes of dosing.The clinical signs of toxicity included ` tearing of the eyes,salivation,occasional convulsions,and respiratory disorders.In Japanese quail,the LD50 was 34 mg/kg(11).The LD50 of a 90%pure fomrulation was 15.9 mg/kg in eight-month old mallards,and 15.4 mg/kg in three- to-four month old male pheasants(20).The LD50 for starlings was 42 mg/kg and for redwinged blackbirds was 10 mg/kg L (2-9)- Effects on Aquatic Organisms Methomyl is moderately to highly toxic to fish and highly toxic to aquatic invertebrates(1_1 30).The 96-hour LC50 in rainbow trout for a liquid formulation of methomyl is 3.4 milligrams per liter(mg/1);for bluegill sunfish,it is 0.8 mg/I(8). A 28-day fish residue study indicated that methomyl did not accumulate in fish tissue(11_).The 48-hour LC50 for 4 http://pmep.cce.comell.edu/profiles/extoxnet/haloxyfop-methylpazathion/methomyl-ext.html 1/2/2004