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

CAS number: 62–73–7

NIOSH REL: 1 mg/m3 TWA [skin]

Current OSHA PEL: 1 mg/m3 TWA [skin]

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 0.90 mg/m3 (0.1 ppm) TWA [skin]

Description of Substance: Colorless to amber liquid with a mild, chemical odor.

LEL:. . Unknown

Original (SCP) IDLH: 200 mg/m3

Basis for original (SCP) IDLH: No useful data on acute inhalation toxicity are available on which to base the IDLH for dichlorvos. If the IDLH were estimated from the female rat oral LD50 of 55 mg/kg [Mattson et al. 1955 cited by Patty 1963], an IDLH of 400 mg/m3 would be chosen. On the basis of an analogy with parathion, however, which has an OSHA PEL of 0.1 mg/m3 and an IDLH of 20 mg/m3, an IDLH of 200 mg/m3 has been chosen for dichlorvos which has an OSHA PEL of 1 mg/m3.

Short-term exposure guidelines: None developed


Lethal concentration data:

Species Reference LC50 LCLo Time Adjusted 0.5-hrLC (CF) Derivedvalue
RatMouse Gig Sanit 1968Gig Sanit 1968 15 mg/m313 mg/m3 ———- 4 hr4 hr 30 mg/m3 (2.0)16 mg/m3 (2.0) 3.0 mg/m32.6 mg/m3


Lethal dose data:

Species Reference Route LD50(mg/kg) LDLo(mg/kg) Adjusted LD Derived value



Hartley and Kidd 1984Ikuzawa et al. 1966

Kokshareva et al. 1977

Technical News 1972










700 mg/m3427 mg/m3

70 mg/m3

119 mg/m3

70 mg/m343 mg/m3

7.0 mg/m3

12 mg/m3


Human data: Exposure to a concentration of 1 mg/m3 for 7.5 to 8.5 hours resulted in a plasma cholinesterase depression of 20 to 25% [Hunter 1964].

Revised IDLH: 100 mg/m3Basis for revised IDLH: The revised IDLH for dichlorvos is 100 mg/m3 based on an analogy to parathion. Since the toxicity of dichlorvos is about 10 times lower than parathion (based on acute oral toxicity data in animals), the revised IDLH for dichlorvos is 10 times the revised IDLH for parathion (10 mg/m3).



1. Gig Sanit [1968]; 33(10):35 (in Russian).

2. Hartley D, Kidd H, eds. [1984]. Agrochemical handbook. Nottingham, England: Royal Society of Chemistry, 1983-86, p. A141.

3. Hunter C [1964]. Communication to TLV Committee from Tunstall Laboratory, Sittingbourne, Kent, England. [From ACGIH [1991]. Dichlorvos. In: Documentation of the threshold limit values and biological exposure indices. 6th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, pp. 446-448.]

4. Ikuzawa M, Yonemoto S, Aoki H, Sumimoto S, Matsumoto K, Ohara K [1966]. Studies on the toxicity of various insecticides for mice (I) on the oral acute toxicity of single and mixed insecticides. J Osaka Cty Med Cntr 15:553-563.

5. Kokshareva NV, Kovtun SD, Kagan YS, Mizyukova IG, Medvedev BM [1977]. Action of diethixime, a new cholinesterase reactivator, on the central nervous system. Bulletin Exp Biol Med 83:32-35.

6. Mattson AM, Spillane JT, Pearce GW [1955]. Organophosphorus insecticides: dimethyl 2,2-dichlorovinyl phosphate (DDVP), an organic phosphorus compound highly toxic to insects. J Agri Food Chem 3(4):319-321.

7. Patty FA, ed. [1963]. Industrial hygiene and toxicology. 2nd rev. ed. Vol. II. Toxicology. New York, NY: Interscience Publishers, Inc., p. 1942.

8. Technical news: ortran. [1972]. Japan Pesticide Information No. 13, pp. 36-38.