IRAC 1B; organophosphate
Common name chlorpyrifos (BSI, E-ISO, ANSI, ESA, BAN); chlorpyriphos ((m) F-ISO, JMAF); chlorpyriphos-éthyl ((m) France)
IUPAC name O,O-diethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate
Chemical Abstracts name O,O-diethyl O-(3,5,6-trichloro-2-pyridinyl) phosphorothioate
CAS RN [2921-88-2] EEC no. 220-864-4
Mol. wt. 350.6 M.f. C9H11Cl3NO3PS Form Colourless crystals, with a mild mercaptan odour. M.p. 42-43.5 ºC V.p. 2.7 mPa (25 ºC) KOW logP = 4.7 Henry 6.76×10-1 Pa m3 mol-1 (calc.) S.g./density 1.44 (20 °C) Solubility In water c. 1.4 mg/l (25 ºC). In benzene 7900, acetone 6500, chloroform 6300, carbon disulfide 5900, diethyl ether 5100, xylene 5000, iso-octanol 790, methanol 450 (all in g/kg, 25 ºC). Stability Rate of hydrolysis increases with pH, and in the presence of copper and possibly of other metals that can form chelates; DT50 1.5 d (water, pH 8, 25 ºC) to 100 d (phosphate buffer, pH 7, 15 ºC).
Biochemistry Cholinesterase inhibitor. Mode of action Non-systemic insecticide with contact, stomach, and respiratory action. Uses Control of Coleoptera, Diptera, Homoptera and Lepidoptera in soil or on foliage in over 100 crops, including pome fruit, stone fruit, citrus fruit, nut crops, strawberries, figs, bananas, vines, vegetables, potatoes, beet, tobacco, soya beans, sunflowers, sweet potatoes, peanuts, rice, cotton, alfalfa, cereals, maize, sorghum, asparagus, glasshouse and outdoor ornamentals, turf, and in forestry. Also used for control of household pests (Blattellidae, Muscidae, Isoptera), mosquitoes (larvae and adults) and in animal houses. Phytotoxicity Non-phytotoxic to most plant species when used as recommended. Poinsettias, azaleas, camellias, and roses may be injured. Formulation types DP; EC; GR; UL; WG; WP; Microcapsule. Compatibility Incompatible with alkaline materials.
Product analysis by rplc (CIPAC Handbook, 1985, 1C, 2028; AOAC Methods, 17th Ed., 981.03). Residues determined by glc (A. Ambrus et al., J. Assoc. Off. Anal. Chem., 1981, 64, 733; AOAC Methods, 17th Ed., 985.22; Man. Pestic. Residue Anal., 1987, I, 6, S8, S9, S13, S19; Anal. Methods Residues Pestic., 1988, Part I, M2, M5, M12). Details available from Dow AgroSciences.
Reviews K. D. Racke, Rev. Environ. Contam. Toxicol., 131, 1-151 (1993); M. G. Barron & K. B. Woodburn, ibid. 144, 1-93 (1995); D. J. Clegg & M. van Gemert, J. Toxicol. Environ. Health, B2, 211-255 (1999); FAO/WHO 86, 88 (see part 2 of the Bibliography). Oral Acute oral LD50 for rats 135-163, guinea pigs 504, rabbits 1000-2000 mg/kg. Skin and eye Acute percutaneous LD50 for rabbits >5000 mg/kg; (tech.) for rats >2000 mg/kg. Inhalation LC50 (4-6 h) for rats >0.2 mg/l (14 ppb). NOEL (2 y) for rats 1 mg/kg b.w. daily; (18 mo) for mice 0.7 mg/kg b.w. daily; (2 y) for dogs 1 mg/kg b.w. daily. ADI (JMPR) 0.01 mg/kg b.w. . Other Non-teratogenic. Toxicity class WHO (a.i.) II; EPA (formulation) II EC classification T; R24/25| N; R50, R53
Birds Acute oral LD50 for mallard ducks 490, house sparrows (Passer domesticus) 122, chickens 32-102 mg/kg. Dietary LC50 (8 d) for bobwhite quail 423 ppm. Fish LC50 (96 h) for bluegill sunfish 0.002-0.010, rainbow trout 0.007-0.051, roach 0.25, fathead minnow 0.12-0.54 mg/l. Daphnia LC50 (48 h) 1.7 μg/l. Algae NOEC for Selenastrum capricornutum >0.4 mg/l. Other aquatic spp. LC50 for Korean shrimp (Palaemon macrodactylus) 0.05 μg/l. Bees Toxic to bees. LD50 (oral) 360 ng/bee; (contact) 70 ng/bee. Worms LC50 (14 d) for Eisenia foetida 210 mg/kg soil. Other beneficial spp. Toxic to Collembola (J. A. Wiles & G. K. Frampton, Pestic. Sci., 47, 273 (1996)).
EHC 63 (WHO, 1986; a general review of organophosphorus insecticides). Animals In rats, dogs, and other mammals, following oral administration, rapid metabolism occurs, the principal metabolite being 3,5,6-trichloropyridin-2-ol. Excretion is principally in the urine. Plants Non-systemic in plants, not absorbed from soil via the roots. Residues taken up by plant tissues are metabolised to 3,5,6-trichloropyridin-2-ol which is conjugated and sequestered. Soil/Environment In soil, chlorpyrifos is degraded at a moderate rate; DT50 (lab.) 10-120 d (25 °C); field DT50 for soil-incorporated applications 33-56 d, for soil-surface applications 7-15 d. Primary route of degradation is transformation to 3,5,6-trichloropyridin-2-ol, which is subsequently degraded to organochlorine compounds and CO2. Koc 1250-12 600.