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Arsenic (inorganic compounds, as As)

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

CAS number 7440-38-2 (Metal)

NIOSH REL 0.002 mg As/m3 15-minute CEILING; NIOSH considers inorganic arsenic compounds to be potential occupational carcinogens as defined by the OSHA carcinogen policy [29 CFR 1990].

Current OSHA PEL: 0.010 mg As/m3 TWA

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 0.01 mg As/m3 TWA, A1

Description of substance: Varies

Original (SCP) IDLH: 100 mg As/m3

Basis for original (SCP) IDLH: The chosen IDLH is based on the cat 1-hour LCLO of 100 mg/m3 for arsenic trichloride [Flury 1921 cited by NIOSH 1976].

Short-term exposure guidelines: None developed


Lethal concentration data:

Species Reference LC50 LCLo 0.5-hr Time Adjusted LC (CF) Derived Value
Cat Flury 1921 —– 100 mg/m3 1 hr 52 mg As/m3 (1.25) 5.2 mg As/m3
Cat Spector 1955 —– 200 mg/m3 20 min 79 mg As/m3 (0.96) 7.9 mg As/m3
Mouse Spector 1955 —– 338 ppm 10 min 726 mg As/m3 (0.69) 73 mg As/m3

Lethal dose data:

Species Reference Route LD50(mg/kg) LDLo(mg/kg) Adjusted LD Derived Value
Rat Davydova et al. 1987 oral 763 —– 5,341 mg As/m3 534 mg As/m3
Mouse Davydova et al. 1987 oral 145 —– 1,015 mg As/m3 102 mg As/m3
Rat Lehman 1951 oral 20 —– 53 mg As/m3 5.3 mg As/m3
Mouse MacEwen and Vernot 1972 oral 794 —– 2,090 mg As/m3 209 mg As/m3
Rabbit Muehlberger 1930 oral 50 —– 132 mg As/m3 13 mg As/m3
Dog Perkow 1971/1976 oral 38 —– 100 mg As/m3 10 mg As/m3
Rabbit Muehlberger 1930 oral 75 —– 88 mg As/m3 8.8 mg As/m3

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

Revised IDLH: 5 mg As/m3

Basis for revised IDLH: The revised IDLH for inorganic arsenic compounds is 5 mg As/m3 based on acute inhalation toxicity data in animals [Flury 1921; Spector 1955]. This may be a conservative value due to the lack of relevant acute toxicity data for workers. [Note: NIOSH recommends as part of its carcinogen policy that the “most protective” respirators be worn for inorganic arsenic compounds at concentrations above 0.002 mg As/m3. OSHA currently requires in 29 CFR 1919.1018 that workers be provided with and required to wear and use the “most protective” respirators in concentrations exceeding 20 mg As/m3 (i.e., 2,000 x the PEL).]


  1. Davydova VE, Neizuestnova EM, et al. [1987]. Toxicity of metallic arsenic. Gig Tr Prof Zabol 31(12):58 (in Russian).
  2. Flury F [1921]. Arsentrichlorid. In: Uber kampfgasvergiftungen. IX. Lokal reizende arsenverbindungen. Zeit Ges Exp Med 13:527-528 (in German).
  3. Lehman AJ [1951]. Chemicals in foods: a report to the Association of Food and Drug Officials on current developments. Part II. Pesticides. Q Bulletin Assoc Food Drug Off U.S. 15(4):122-125.
  4. MacEwen JD, Vernot EH [1972]. Toxic Hazards Research Unit annual technical report: 1972. Wright-Patterson Air Force Base, OH: Aerospace Medical Research Laboratory, Report AMRL-TR-72-62.
  5. Muehlberger CW [1930]. Toxicity studies of fluorine insecticides. J Pharmacol Exp Ther 39:246-248.
  6. NIOSH [1976]. CG17500. Arsenic chloride. In: Registry of toxic effects of chemical substances (RTECS) 1976 ed. Cincinnati, OH: U.S. Department of Health, Education, and Welfare, Public Health Service, Center for Disease Control, National Institute for Occupational Safety and Health, DHEW (NIOSH) Publication No. 76-191, p. 126.
  7. Perkow W [1971/1976]. Wirksubstanzen der Pflanzenschytz and Schadlingsbekampfungsmittel. Berlin, Germany: Verlag Paul Parey (in German).
  8. Spector WS, ed. [1955]. Handbook of toxicology. Vol. 1. Acute toxicities of solids, liquids and gases to laboratory animals. Philadelphia, PA: W.B. Saunders Co., pp. 324-325.