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May 1994
Immediately Dangerous to Life or Health Concentrations (IDLH)

CAS number: 86-50-0

NIOSH REL: 0.2 mg/m3 TWA [skin]

Current OSHA PEL: 0.2 mg/m3 TWA [skin]

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 0.2 mg/m3 TWA [skin]

Description of substance: Colorless crystals or a brown, waxy solid.

LEL: Noncombustible Solid

Original (SCP) IDLH: 20 mg/m3

Basis for original (SCP) IDLH: Because no useful data on acute inhalation toxicity are available concerning the toxic effects produced by azinphos-methyl, the chosen IDLH has been based on an analogy with parathion, which has an IDLH of 20 mg/m3.

Short-term exposure guidelines: None developed


Lethal concentration data:

Species Reference LC50 LCLo Time Adjusted 0.5-hr LC (CF) Derived Value
Rat Newell and Dilley 1978 69 mg/m3 ----- 1 hr 86 mg/m3 (1.25) 8.6 mg/m3
Rat Sanderson 1961 79 mg/m3 ----- 1 hr 99 mg/m3 (1.25) 9.9 mg/m3

Lethal dose data:

Species Reference Route LD50(mg/kg) LDLo(mg/kg) Adjusted LD Derived Value
Rat Dubois et al. 1957 oral 16 ----- 115 mg/m3 12 mg/m3
G. pig Dubois et al. 1957 oral 80 ----- 560 mg/m3 56 mg/m3
Rat Gaines 1960 oral 11 ----- 77 mg/m3 7.7 mg/m3
Rat Gaines 1960 oral 13 ----- 91 mg/m3 9.1 mg/m3
Mouse Murphy et al. 1976 oral 8.6 ----- 60 mg/m3 6.0 mg/m3
Rat Sanderson 1961 oral 7 ----- 49 mg/m3 4.9 mg/m3
Mouse Sato 1959 oral 8 ----- 56 mg/m3 5.6 mg/m3
Dog Worthing 1991 oral 10 ----- 70 mg/m3 7.0 mg/m3v

Human data: Eight workers exposed to concentrations as high as 9.6 mg/m3 (no time period given) showed no signs or symptoms of illness [Jegler 1964].

Revised IDLH: 10 mg/m3

Basis for revised IDLH: The revised IDLH for azinphos-methyl is 10 mg/m3 based on acute inhalation toxicity data in humans [Jegler 1964] and animals [Newell and Dilley 1978; Sanderson 1961]. This may be a conservative value due to the lack of acute toxicity data for workers exposed to concentrations above 10 mg/m3.


  1. DuBois KP, Thursh DR, Murphy SD [1957]. Studies on the toxicity and pharmacologic actions of the dimethoxyl ester of benzotriazine dithiophosphoric acid. J Pharmacol Exp Ther 119:208-218.
  2. Gaines TB [1960]. Acute toxicity of pesticides in rats. Toxicol Appl Pharmacol 2:88-99.
  3. Jegler Z [1964]. Exposure to guthion during spraying and formulating. Arch Environ Health 8:565-569.
  4. Murphy SD, Cheever KL, Chow AYK, Brewster M [1976]. Organophosphate insecticide potentiation by carboxylesterase inhibitors. Proc Eur Soc Toxicol 17:292-300.
  5. Newell GW, Dilley JV [1978]. Teratology and acute toxicology of selected chemical pesticides administered by inhalation. Menlo Park, CA: Stanford Research Institute, p. 18. Prepared for Health Effects Research Laboratory, U.S. EPA, EPA-60011-78-003.
  6. Sanderson DM [1961]. Treatment of poisoning by anticholinesterase insecticides in the rat. J Pharm Pharmacol 13:435-442.
  7. Sato I [1959]. Studies on organic phosphorus gusathion and phosdrin. I. The toxicity of gusathion and phosdrin. Kuma Med J 12(1):312-317.
  8. Worthing CR, ed. [1991]. Azinphos-methyl. In: The pesticide manual: a world compendium. 9th ed. Old Woking, Surrey, England: Unwin Brothers Limited, p. 46.