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Methomyl Page 4 of 7 Daphnia magna(a small,freshwater crustacean)is 28.7 ppb(29). ` Effects on Other Animals (Nontarget species) Methomyl is highly toxic to bees both by direct contact and through ingestion(s IL 30).Applications should be coordinated with periods of minimum bee activity so that methomyl is never applied while bees are actively visiting treatment areas(5). The LD50 for a 90%pure formulation of methomyl was 11.0 to 22.0 mg/kg in mule deer(20).Symptoms of acute poisoning in these animals included drowsiness,drooling,diarrhea,and tremors(2J0 . ENVIRONMENTAL FATE Breakdown of Chemical in Soil and Groundwater r Because of its high solubility m water 58,000 u ml and its soil half-life 33 days),methomyl may have potential for 8 tY � ( 8/ ) ( Y Y groundwater contamination Ql .It is very mobile in sandy loam and silty clay loam soils,but only slight leaching was observed in a silt loam and in a sandy soil.Adsorption of methomyl to soil particles is weak to moderate(26,30).In one national survey which did not detect methomyl m groundwater,methomyl was found m drinking water from groundwater sources.It was also found,in a survey of widely used pesticides in Palm Beach County,Florida(15,23).Methomyl has been detected at very low levels,9 ppb and 1.2 ppb respectively,in groundwater in New York and New Jersey(30 . Lifetime Health Advisory level of 200 ppb has been established for methomyl. Methomyl is rapidly degraded by soil microbes(14).The dissipation half-life for methomyl in soil is reportedly three to six weeks(23,24).However,one month after methomyl-treatment,test soil had traces of the insecticide and some of its V breakdown byproducts,or'metabolites'(14).Methomyl residues are not expected to be found in treated soil after the growing season in which it is applied(155). ` Under aerobic conditions,methomyl has a soil half-life of 30-45 days and degrades predominately to carbon dioxide.It is relatively stable to hydrolysis under neutral and acidic conditions.Under basic conditions,it degrades with a half-life of 30 days.Under anaerobic conditions,acetonitrile is the major metabolite in the early stages of degradation,but carbon dioxide is the end product,with total conversion within 8 days(30). v Breakdown of Chemical in Water •' Methomyl should be kept out of any body of water and should not be applied where runoff is likely to occur(5).Aqueous solutions of methomyl have been reported to decompose more rapidly on aeration,in sunlight or in alkaline media(33). One study indicated a half-life of six days for the insecticide in water(15).Its'hydrolysis half-life'in soil,or the time that ` it takes for half of it to be broken down in groundwater,is estimated at over 25 weeks(23).In one experiment the hydrolysis half lives of methomyl in solutions at pHs of 6.0,7.0 and 8.0 were 54,38,and 20 weeks respectively.In pure water,the hydrolysis half-life has been estimated to be 262 days.Methomyl is unlikely to bioconcentrate in aquatic systems r Breakdown of Chemical in Vegetation .. Following soil treatment,plants take up methomyl through their roots and move it throughout the plant by a process called 'translocation.'When methomyl is applied to plants,its residues are short-lived(13).After it is applied to leaves,it has a three-to-seven day half-life(8, 14).Less than 3%methomyl remained in cabbage plants one week after they were given r foliar treatment with the insecticide(19). PHYSICAL PROPERTIES AND GUIDELINES Breathing of dust,and skin contact with methomyl dust or solutions,should be avoided and prevented.Appropriate protective clothing,including respirator mask,goggles,and gloves,should be wom to prevent the possibility of skin ` contact with this toxic material(16).Like most organic powders or crystals,under extremely dusty conditions,methomyl may form explosive mixtures in air(7).A reentry interval of 24 hours may lessen the possibility of poisoning(9). Methomyl users should not contaminate water by cleaning of equipment or disposal of wastes associated with the insecticide(5).Discarded methomyl is considered a hazardous waste product under the Resource Conservation and i. http://pmep.cce.comell.edu/profiles/extoxnetfhaloxyfop-methylparathion/mediomyl-ext.htird 1/2/2004