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EXTOXNET PIP - DDT Page 5 of 6 volatilization,photolysis and biodegradation(aerobic and anaerobic) (73). These processes generally occur only very slowly. Breakdown products in the soil environment are DDE and DDD, which are also highly persistent and have similar chemical and physical properties (82, 84). Due to its extremely low solubility in water, DDT will be retained to a greater degree by soils and soil fractions with higher proportions of soil organic matter(82). It may accumulate in the top soil layer in situations where heavy applications are (or were) made annually; e.g., for apples (72). Generally DDT is tightly sorbed by soil organic matter, but it(along with its metabolites)has been detected in many locations in soil and groundwater where it may be available to organisms (82, 83). This is probably due to its high persistence; although it is immobile or only very slightly mobile, over very long periods of time it may be able to eventually leach into groundwater, especially in soils with little soil organic matter. Residues at the surface of the soil are much more likely to be broken down or otherwise dissipated than those below several inches (3). Studies in Arizona have shown that volatilization losses may be significant and rapid in soils with very low organic matter content(desert soils) and high irradiance of sunlight, with volatilization losses reported as high as 50% in 5 months (85). In other soils (Hood River and Medford)this rate may be as low as 17- 18% over 5 years (85). Volatilization loss will vary with the amount of DDT applied, proportion of soil organic matter, proximity to soil-air interface and the amount of sunlight(82). • Breakdown of Chemical in Surface Water: DDT may reach surface waters primarily by runoff, atmospheric transport, drift, or by direct application (e.g. to control mosquito-borne malaria) (73). The reported half-life for DDT in the water environment is 56 days in lake water and approximately 28 days in river water(83). The main pathways for loss are volatilization, photodegradation, adsorption to water-borne particulates and sedimentation (73)Aquatic organisms, as noted above, also readily take up and store DDT and its metabolites. Field and laboratory studies in the United Kingdom demonstrated that very little breakdown of DDT occurred in estuary sediments over the course of 46 days (82). DDT has been widely detected in ambient surface water sampling in the United States at a median level of 1 ng/L (part per trillion) (73, 76). • Breakdown of Chemical in Vegetation: DDT does not appear to be taken up or stored by plants to a great extent. It was not translocated into alfalfa or soybean plants, and only trace amounts of DDT or its metabolites were observed in carrots, radishes and turnips all grown in DDT-treated soils (82). Some accumulation was reported in grain, maize and riceplants, but little translocation occured and residues were located primarily in the roots (73). PHYSICAL PROPERTIES AND GUIDELINES Physical Properties: • Appearance: The physical appearance of technical product p,pO-DDT is a waxy solid, although in its pure form it consists of colorless crystals (79) • Chemical Name: 1,1'-(2,2,2-trichloroethylidene)bis[4-chlorobenzene]; 1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane (79) • CAS Number: 50-29-3 (79) • Molecular Weight: 354.51 (79) • Water Solubility: < 1 mg/L @ 20 degrees C (79) • Solubility in Other Solvents: cyclohexanone v.s., dioxane v.s., benzene v.s.,xylene v.s., trichloroethylene v.s., dichloromethane v.s., acetone v.s., chloroform v.s., diethyl ether v.s., ethanol s. and methanol s. (79). • Melting Point: 108.5-109 degrees C (79) • Vapor Pressure: 0.025 mPa @ 25 degrees C (79) • Partition Coefficient: Not available • Adsorption Coefficient: 100,000 (84) Exposure Guidelines: • ADI: 0.02 mg/kg/d(73) • MCL:Not Available • RfD: 0.0005 mg/kg/day (73) • PEL: 1 mg/meters cubed (8-hour) (73)