Common name: Chlorpyrifos

Other name: chlorpyrifos (BSI, E-ISO, ANSI, ESA, BAN); chlorpyriphos ((m) F-ISO, JMAF); chlorpyriphos-&thyl ((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

Type: Insecticide for Agriculture

CAS RN: [2921-88-2]

M.F.: C₉H₁₁CI₃NO₃PS

Mol Wt: 350.6

 

Form (appearance): Colourless crystals, with a mild mercaptan odour

M.P.: 42-43.5℃

V.P.: mPa (25℃)

S.G.: 1.44 (20℃)

Solubility.: In water c. 1.4 mg/l (25℃). 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℃)

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℃) to q00 d (phosphate buffer, pH 7, 15℃)

Henry: 6.76×10-1 Pa m3 mol^-1 (calc.)

K_owlogP: 4.7

 

Formulation types: DP; EC; GR; UL; WG; WP; Microcapsule

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 q00 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

Compatibility: Incompatible with alkaline materials

 

Reviews: K. D. Racke, Rev. Environ. Contain. 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 38, 39 (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. [1982, 1999].
Other Non-teratogenic.

Toxicity: WHO (a.i.) II; EPA (formulation) II

EC hazard: 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.

Worms: LC₅₀ (14 d) for Eisenia foetida 210 mg/kg soil.
Bees: Toxic to bees. LD₅₀ (oral) 360 ng/bee; (contact) 70 ng/bee.
Other beneficial spp. Toxic to Collembola (J. A. Wiles & G. K. Frampton, Pestic. Sci., 47, 273 (1996)).

 

Plant: EHC 63 (WHO, 1986; a general review of organophosphorus insecticides).
on-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.

Animals: In rats, dogs, and other mammals, following oral administration, rapid metabolism occurs, the principal metabolite being 3,5,6-trichloro-2-pyridinol. Excretion is principally in the urine.

Soil/Environment: In soil, chlorpyrifos is degraded at a moderate rate; DT₅₀ (lab.) 10-120 d (25 ℃); 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. K_oc 1250-12600.