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Sulfur dioxide

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

CAS number: 7446–09–5

NIOSH REL: 2 ppm (5 mg/m3) TWA, 5 ppm (13 mg/m3) STEL

Current OSHA PEL: 5 ppm (13 mg/m3) TWA

1989 OSHA PEL: 2 ppm (5 mg/m3) TWA, 5 ppm (13 mg/m3) STEL

1993-1994 ACGIH TLV: 2 ppm (5.2 mg/m3) TWA, 5 ppm (13 mg/m3) STEL

Description of substance: Colorless gas with a characteristic, irritating, pungent odor.

LEL: . . . Nonflammable Gas

Original (SCP) IDLH: 100 ppm

Basis for original (SCP) IDLH: The chosen IDLH is based on the statement by AIHA [1955] that 50 to 100 ppm is considered the maximum concentration for exposures of 0.5 to 1 hour [Henderson and Haggard 1943]. With regard to the atmospheric concentration immediately hazardous to life, AIHA [1955] reported that 400 to 500 ppm is considered dangerous for even short periods of exposure [Henderson and Haggard 1943] and that exposure to unendurable concentrations is not necessarily hazardous if escape is made within a few minutes.

Existing short-term exposure guidelines: National Research Council [NRC 1984] Emergency Exposure Guidance Levels (EEGLs):

10-minute EEGL: 30 ppm

30-minute EEGL: 20 ppm

60-minute EEGL: 10 ppm

24-hour EEGL: 5 ppm


Lethal concentration data:

Species Reference LC50




Time Adjusted 0.5-hr


Derived value
Rat Flury & Zernik 1935 ----- 993 20 min 864 ppm (0.87) 86 ppm
Rat Flury &Zernik 1935 ----- 611 5 hr 1,314 ppm (2.15) 131 ppm
Mouse Flury &Zernik 1935 ----- 764 20 min 665 ppm (0.87) 67 ppm
Mouse Hilado &Machado 1977 3,000 ----- 30 min 3,000 ppm (1.0) 300 ppm
Rat Kinkead & Einhaus 1984 2,520 ----- 1 hr 3,150 ppm (1.25) 315 ppm
Human Shupe et al. 1972 ----- 1,000 10 min 690 ppm (0.69) 69 ppm
Human Tab Biol Per 1933 ----- 3,000 5 min 1,500 ppm (0.5) 150 ppm

Other animal data: RD50 (mouse), 117 ppm [Alarie 1981].

Other human data: The maximum concentration for exposures of 0.5 to 1 hour is considered to be 50 to 100 ppm [Henderson and Haggard 1943]. It has been reported that 400 to 500 ppm is considered dangerous for even short periods of exposure [Henderson and Haggard 1943].

Revised IDLH: 100 ppm [Unchanged]

Basis for revised IDLH: Based on acute inhalation toxicity data in humans [Henderson and Haggard 1943; Shupe et al. 1972; Tab Biol Per 1933], the original IDLH for sulfur dioxide (100 ppm) is not being revised at this time.


1. AIHA [1955]. Sulfur dioxide. In: Hygienic guide series. Am Ind Hyg Assoc Q 16:332-333.

2. Alarie Y [1981]. Dose-response analysis in animal studies: prediction of human responses. Environ Health Perspect 42:9-13.

3. Flury F, Zernik F [1935]. Zusammenstellung der toxischen und letalen dosen für die gebräuchlichsten gifte und versuchstiere. Abder Hand Biol Arbeitsmethod 4:1289-1422 (in German). [From Back KC, Thomas AA, MacEwen JD [1972]. Reclassification of materials listed as transportation health hazards. Wright-Patterson Air Force Base, OH: 6570th Aerospace Medical Research Laboratory, Report No. TSA-20-72-3, pp. A250 to A251.]

4. Henderson Y, Haggard HW [1943]. Noxious gases. 2nd ed. New York, NY: Reinhold Publishing Corporation, p. 131.

5. Hilado CJ, Machado AM [1977]. Effect of sulfur dioxide on Swiss albino mice. J Combustion Toxicol 4:236-244.

6. Kinkead ER, Einhaus RL [1984]. Acute toxicity of thionyl chloride vapor for rats. Wright-Patterson Air Force Base, OH: Air Force Systems Command, Air Force Aerospace Medical Division, Aerospace Medical Research Laboratory, Technical Report AFAMRL-TR-84-069.

7. NRC [1984]. Emergency and continuous exposure limits for selected airborne contaminants. Vol. 2. Washington, DC: National Academy Press, Committee on Toxicology, Board on Toxicology and Environmental Health Hazards, Commission on Life Sciences, National Research Council, pp. 95-102.

8. Shupe JL, Olson AE, Sharma RP [1972]. Fluoride toxicity in domestic and wild animals. Clin Toxicol 5:195-213.

9. Tab Biol Per [1933]; 3:231 (in German).