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]"XI OXNGIT PIP-PARAQUAT / htt //ace.orsi.educ i- in/mfs/0I/ i P�P• P Q s! ara ual.htnl P' / �� b 8-day dietary LC50 value for the compound is 4048 ppm in mallards [58]. ,' • Effects on aquatic organisms: Paraquat is slightly to moderately toxic to many species of aquatic life, including rainbow trout, biuegill, and channel catfish [58,8]. The reported 96-hour LC50 for paraquat is 32 mg/L in rainbow trout, and 13 mg/L in brown trout [58]. The LC50 for the aquatic Invertebrate Daphnia pulex is 1.2 to 4.0 mg/L [8]. In rainbow trout exposed for 7 days to paraquat, the chemical was detected in the gut and liver, but not in the meat of the fish. Aquatic weeds may bioaccumulate the compound. In one study, 4 days after paraquat was applied as an aquatic herbicide, weeds sampled showed significant residue levels 87 . At high levels . [ ] g , paraquat inhibits the photosynthesis of some algae in stream waters [87]. • Effects on other organisms: Paraquat is nontoxic to honey bees [112). Environmental Fate: • Breakdown in soil and groundwater: Paraquatghly persistent in-the soil-environment. with reported feld alh 1f=Tives_of greathan 1000�days [11,58]. The reported half-life for paraquat in one study ranged from 16 months (aerobic laboratory conditions) to 13 years (field study) [113]. - UItravioIet light, sunlight, and soil microorganisms can degrade paraquat to products which are less toxic than the parent compound. The strong affinity for adsorption by soil particles and organic i _ matter may limit the bioavailability of paraquat to plants, earthworms, and microorganisms [11,58]. j: The bound residues may persist indefinitely and can be transported in runoff with the sediment. Paraquat is not significantly mobile in most soils [8]. That which does not become associated with soil particles can be decomposed to a nontoxic end product by soil bacteria [32]. Thus, paraquat does not present a high risk of groundwater contamination. Of 721 groundwater samples analyzed, only one contained paraquat, at a concentration of 20 mg/L [111]. I • Breakdown in water: Paraquat will be bound to suspended or precipitated sediment in the aquatic { environment, and may be even more highly persistent than on land due to limited availability of i oxygen. It had a half-life in a laboratory stream water column of 13.1 hours [114]. In another stud k Y� � paraquat dichloride was stable for up to 30 days [111]. In a third study of low levels in water, paraquat had a half-life of 23 weeks [111]. • Breakdown in vegetation: Paraquat dichloride droplets decompose when exposed to light after being applied to maize, tomato, and broad-bean plants. Small amounts of residues were found in I potatoes treated with paraquat as a desiccant, and boiling the potatoes did not reduce the residue [8]. I k Physical Properties: 1 • Appearance: Paraquat salts are colorless, white, or pale yellow crystalline solids, which are hygroscopic and odorless [1]. • Chemical Name: 1,I'-dimethyl-4,4'-bipyridinium [1] • CAS Number: 1910-42-5 ] • Molecular Weight: 257.20 1 • Water Solubility: 700,000 mg/L @ 20 C [1] • Solubility in Other Solvents: Dichloride salt is sparingly soluble in lower alcohols [1] • Melting Point: Decomposes @ 300 C [1] • Vapor Pressure: Negligible @ room temperature (paraquat dichloride) [1] • Partition Coefficient: 4.4683 [58] • AdsorptionCoefficient: 1,000,000 (estimated) [I I ] I { Exposure Guidelines: i i Zvi 1 1/26/408:17AM