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

CAS number: 76–44–8

NIOSH REL: 0.5 mg/m3 TWA [skin]; NIOSH considers heptachlor to be a potential occupational carcinogen as defined by the OSHA carcinogen policy [29 CFR 1990].

Current OSHA PEL: 0.5 mg/m3 TWA [skin]

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 0.5 mg/m3 TWA [skin]

Description of Substance: White to light-tan crystals with a camphor-like odor.

LEL:. . Noncombustible Solid

Original (SCP) IDLH: 700 mg/m3

Basis for original (SCP) IDLH: No data on acute inhalation toxicity are available on which to base the IDLH for heptachlor. The chosen IDLH, therefore, has been estimated from the male rat oral LD50 of 100 mg/kg [Gaines 1960 cited by ACGIH 1971].

Short-term exposure guidelines: None developed


Lethal concentration data:

Species Reference LC50(ppm) LCLo(ppm) Time Adjusted 0.5-hrLC (CF) Derivedvalue
CatMammal Izmerov et al. 1982Osetrov 1958 ———- 150 mg/m3200 mg/m3 4 hr4 hr 300 mg/m3 (2.0)400 mg/m3 (2.0) 30 mg/m340 mg/m3


Lethal dose data:

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





AAPCO 1966Edson 1960

Gaines 1960

Kenaga and Morgan 1978

Osetrov 1958

Truhaut et al. 1974
















812 mg/m3280 mg/m3

700 mg/m3

476 mg/m3

350 mg/m3

700 mg/m3

81 mg/m328 mg/m3

70 mg/m3

48 mg/m3

35 mg/m3

70 mg/m3


Human data: None relevant for use in determining the revised IDLH.

Revised IDLH: 35 mg/m3Basis for revised IDLH: The revised IDLH for heptachlor is 35 mg/m3 based on acute inhalation toxicity data in animals [Izmerov et al. 1982; Osetrov 1958]. [Note: NIOSH recommends as part of its carcinogen policy that the “most protective” respirators be worn for heptachlor at concentrations above 0.5 mg/m3.]



1. AAPCO [1966]. Pesticide chemicals official compendium. Topeka, KS: Association of the American Pesticide Control Officials, Inc. p. 576.

2. ACGIH [1971]. Heptachlor. In: Documentation of the threshold limit values for substances in workroom air. 3rd ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, pp. 123-124.

3. Edson EF [1960]. Applied toxicology of pesticides. Pharmaceut J 185:361-367.

4. Gaines TB [1960]. The acute toxicity of pesticides to rats. Toxicol Appl Pharmacol 2:88-99.

5. Izmerov NF, Sanotsky IV, Sidorov KK [1982]. Toxicometric parameters of industrial toxic chemicals under single exposure. Moscow, Russia: Centre of International Projects, GKNT, p. 71.

6. Kenaga EE, Morgan RW [1978]. Commercial and experimental organic insecticides. Entomological Society of America Special Publication 78-1:12.

7. Osetrov VE [1958]. Experimental data on toxicology of the insecticide heptachlor. Gig Tr Prof Zabol 2(5):15 (in Russian).

8. Truhaut R, Gak JC, Graillot C [1974]. Recherches sur les modalités et les mécanismes d’action toxique des insecticides organochlorés. I. Étude comparative des effets de toxicité aiguë chez le hamster et chez le rat. J Eur Toxicol 7(3):159-166 (in French).