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1ATOXNG"I' PIP - F.NDOSLLFnN tittp://ace.orst.edu/cgi-bin/mt's/01/pipsicndosull'.11iiii In rabbits, the beta -isomer is cleared from blood plasma more quickly than the alpha -isomer, with reported blood half-lives of approximately 6 hours and 10 days, respectively [2], which may account in part for the observed differences in toxicity. The metabolites are dependent on the mixture of isomers and the route of exposure [2]. Most of the endosulfan seems to leave the body within a few days to a few weeks. Ecological Effects: Effects on birds: Endosulfan is highly to moderately toxic to bird species, with reported oral LD50 values in mallards ranging from 31 to 243 mg/kg [9,53], and in pheasants ranging from 80 to greater than 320 mg/kg [53]. The reported 5 -day dietary LC50 is 2906 ppm in Japanese quail [54]. Male mallards from 3 to 4 months old exhibited wings crossed high over their back, tremors, falling, and other symptoms as soon as 10 minutes after an acute, oral dose. The symptoms persisted for up to a month in a few animals [53]. Effects on aquatic organisms: Endosulfan is very highly toxic to four fish species and both of the aquatic invertebrates studied; in fish species, the reported 96 -hour LC50 values were (in ug/L): rainbow trout, 1.5; fathead minnow, 1.4; channel catfish, 1.5; and bluegill sunfish, 1.2. In two aquatic invertebrates, scuds (G. lacustris) and stoneflies (Pteronarcys), the reported 96 -hour LC50 values were, respectively, 5.8 ug/L and 3.3 ug/L [55]. The bioaccumulation for the compound may be significant; in the mussel (Mytelus edulis) the compound accumulated to 600 times the ambient water concentration [17]. Effects on other organisms: It is moderately toxic to bees and is relatively nontoxic to beneficial insects such as parasitic wasps, lady bird beetles, and some mites [9,17]. Environmental Fate: Breakdown in soil and groundwater: Endosulfan is moderately persistent in the soil environment with a reported average field half-life of 50 days [14]. The two isomers have different degradation times in soil. The half-life for the alpha -somer is 35 days, and is 150 days for the beta -isomer under neutral conditions. These two isomers will persist longer under more acidic conditions. The compound is broken down in soil by fungi and bacteria [9]. Endosulfan does not easily dissolve in water, and has a very low solubility [9,14]. It has a moderate capacity to adhere or adsorb to soils [14]. Transport of this pesticide is most likely to occur if endosulfan is adsorbed to soil particles in surface runoff. It is not likely to be very mobile or to pose a threat to groundwater. It has, however, been detected in California well water [12]. Breakdown in water: In raw river water at room temperature and exposed to light, both isomers disappeared in 4 weeks [12]. A breakdown product first appeared within the first week. The breakdown in water is faster (5 weeks) under neutral conditions than at more acidic conditions or basic conditions (5 months) [12]. Under strongly alkaline conditions the half-life of the compound is 1 day. Large amounts of endosulfan can be found in surface water near areas of application [51 ]. It has also been found in surface water throughout the country at very low concentrations [12]. Breakdown in vegetation: In plants, endosulfan is rapidly broken down to the corresponding sulfate [9]. On most fruits and vegetables, 50% of the parent residue is lost within 3 to 7 days [9]. Endosulfan and its breakdown products have been detected in vegetables (0.0005-0.013 ppm), in tobacco, in various seafoods (0.2 ppt-1.7 ppb), and in milk [12]. Physical Properties: • Appearance: Pure endosulfan is a colorless crystal. Technical grade is a yellow-brown color [9]. 3 of 4 5/12/00 2:01 PM