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EXTOXNET PIP-NICOSULFURON �*./ A *.w Page 3 of an acute dietary LC50>1000 ppm. It is considered practically non-toxic to honey bees (50, *). ENVIRONMENTAL FATE • Breakdown of Chemical in Soil and Groundwater: Biodegradation is an important degradation mechanism for nicosulfuron. The half-life of nicosulfitron in a silt clay soil is 26 days. However, anaerobic conditions slow down the degradation process. The half-life of nicosulfuron in silt clay soil/water is 63 days. The main degradates are pyridine sulfonamide and pyrimidine amine(47, 38, 50). Nicosulfuron is very mobile in sandy loam and silt loam soils. The pyridine sulfonamide degradate is more mobile than the parent compound. The pyrimidine amine degradate is the least mobile(50). The formulated product Accent has a photolysis half-life at 25 degrees C of 60- 67 days in soil with a pH of 6.2. Field dissipation half-life of the same material was 3 weeks at pH 6.5, 7 weeks at pH 7.4, and 2 weeks at pH 8 (47). Accent poses minimal risk of leaching to groundwater according to calculations using EPA's Pesticide Root Zone model (PRZM). The soil-binding characteristics and values place the herbicide in EPAOs classification of low to intermediate soil mobility (46). • Breakdown of Chemical in Surface Water: The formulated product Accent has a photolysis half-life at 25 degrees C of 14-19 days in water with a pH of 5, 200-250 days at a pH of 7, and 180-200 days at a pH of 9. The hydrolysis half-life of the same material is 15 days at a pH of 5 (47). • Breakdown of Chemical in Vegetation: Foliar absorption is the primary means of nicosulfuron uptake by plants (50). PHYSICAL PROPER-TIESPROPER-TIES AND GUIDELINES It may form flammable or explosive dust-air mixtures. It is stable under normal temperatures and pressures. Thermal decomposition products may include toxic oxides of carbon, nitrogen, and sulfur(48). No corrosion or physical change was observed for the end use product after being stored at room temperature for 10 months for either solid granules or container material of construction(high-density polyethylene) (50). Physical Properties: • Appearance: Technical nicosulfuron can be recognized as white powder or colorless crystals(37). • Chemical Name: 2-[[(4,6-dimethoxypyrimidin-2-yl)aminocarbonyl]aminosulfonyl]-N,N-dimethyl-3- pyridinecarboxamide (46) • CAS Number:111991-09-4 (37) • Molecular Weight: 410.4 • Water Solubility: @ 25 degrees C: 0.04 g/100g pH=5.0; 1.2 g/IOOg pH=7.0; 3.9 g/100g pH=9.0(5 1) • Solubility in Other Solvents: @ 25 degrees C: 0.04 g/100g pH=5.0; 1.2 g/100g pH=7.0; 3.9 g/100g pH=9.0 (51) • Melting Point: 141-144 degrees C (46, 50) • Vapor Pressure: 1.2 x 10 to the minus 16 torr at 25 degrees C (46, 50) • Partition Coefficient: at 25 degrees C: 0.44 (pH 5); 0.017 (pH 7); 0.01 (pH 9) (47, 50) • Adsorption Coefficient: at 25 degrees C: 15.4 (pH 4.3),Keyport Silt Loam; 78.8 (pH 5.4),Flanagan Silt Loam; 28.8 (pH 6.5), Cecil Sandy Loam; 38.4 (pH 6.6), Woodstown Sandy Loam (47) Exposure Guidelines: • ADI: 1.25 mg/kg/body weight/day (49) • MCL: Not Available • RfD: Not Available • PEL: Not Available • HA: Not Available • TLV: Not Available http://extoxnet.orst.edu/pips/nicosulfhtm 7/1/2006