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

CAS number: 74–97–5

NIOSH REL: 200 ppm (1,050 mg/m3) TWA

Current OSHA PEL: 200 ppm (1,050 mg/m3) TWA

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 200 ppm (1,060 mg/m3) TWA

Description of Substance: Colorless to pale-yellow liquid with a chloroform-like odor.

LEL: . . Noncombustible Liquid

Original (SCP) IDLH: 5,000 ppm

Basis for original (SCP) IDLH: Patty [1963] reported that light narcosis could be produced in animals at 3,000 ppm, and pulmonary edema and deaths during exposure at 27,000 ppm; delayed deaths occurred after exposure to 20,000 ppm [Comstock et al. 1953]. Patty [1963] also reported that guinea pigs survived 1-hour exposures but 1 of 3 guinea pigs died after 2-hour exposures to 8,000 to 10,000 ppm [Matson and Dufour 1948]. NIOSH [1974] cited 1,550 ppm as the mouse LCLO [Svirbely et al. 1947]. Scheel (member of the Standards Completion Program Respirator Committee), in an evaluation of the work of Van Stee [1974], determined a cardiac toxicity concentration for chlorobromomethane of 7,000 ppm. Based on an evaluation of the toxicological data cited above, an IDLH of 5,000 ppm was chosen.

Short-term exposure guidelines: None developed


Lethal concentration data:

Species Reference LC50(ppm) LCLo(ppm) Time Adjusted 0.5-hrLC (CF*) Derivedvalue


G. pig

G. pig


Comstock et al. 1952Comstock and Oberst 1953

Comstock and Oberst 1953

Matson and Dufour 1948

Matson and Dufour 1948

Svirbely et al. 1947



LC67: 27,000

LC67: 27,000







15 min15 min

15 min

2 hr

2 hr

7 hr

18,720 ppm (0.65)18,850 ppm (0.65)

17,550 ppm (0.65)

47,600 ppm (2.38)

19,040 ppm (2.38)

15,600 ppm (5.2)

1,872 ppm1,885 ppm

1,755 ppm

4,760 ppm

1,904 ppm

1,560 ppm


*Note: Conversion factor (CF) was determined with “n” = 1.6 [ten Berge et al. 1986].

Lethal dose data:

Species Reference Route LD50(mg/kg) LDLo(mg/kg) Adjusted LD Derived value
RatMouse Deichmann and Gerarde 1969Svirbely et al. 1947 oraloral 5,0004,300 ———- 6,506 ppm5,595 ppm 651 ppm560 ppm


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

Revised IDLH: 2,000 ppmBasis for revised IDLH: The revised IDLH for chlorobromomethane is 2,000 ppm based on acute inhalation toxicity data in animals [Comstock et al. 1952; Comstock and Oberst 1953; Matson and Dufour 1948]. This may be a conservative value due to the lack of relevant acute toxicity data for workers.



1. Comstock C, Fogleman RW, Oberst FW [1953]. Acute narcotic effects of monochloro-monobromomethane vapor in rats. AMA Arch Ind Hyg Occup Med 7:526-528.

2. Comstock CC, MacNamee JK, Ozburn EE, Fogelman RW, Oberst FW [1952]. Monochloro-monobromomethane: inhalation toxicity, pathology, and symptomatology in rats and mice. Army Chemical Center, MD: Chemical Corps Medical Laboratories, Research Report #113.

3. Comstock CC, Oberst FW [1953]. Comparative inhalation toxicities of four halogenated hydrocarbons to rats and mice in the presence of gasoline fires. AMA Arch Ind Hyg Occup Med 7:157-167.

4. Deichmann WB, Gerarde HW [1969]. Methylene chlorobromide (bromochloromethane). In: Toxicology of drugs and chemicals. New York, NY: Academic Press, Inc., pp. 390-391.

5. Matson AF, Dufour RE [1948]. The life hazards and nature of the products formed when chlorobromomethane extinguisher liquid is applied to fires. Chicago, Il: Underwriter’s Laboratories Inc., Bulletin of Research No. 42, p. 19.

6. NIOSH [1974]. PA52500. Bromochloromethane. In: The toxic substances list, 1974 ed. Rockville, MD: 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. 74-134, p. 476.

7. Patty FA, ed. [1963]. Industrial hygiene and toxicology. 2nd rev. ed. Vol. II. Toxicology. New York, NY: Interscience Publishers, Inc., pp. 1271-1272.

8. Svirbely JL, Highman B, Alford WC, von Oettingen WF [1947]. The toxicity and narcotic action of mono-chloro-mono-bromo-methane with special reference to inorganic and volatile bromide in blood, urine and brain. J Ind Hyg Toxicol 29:382-389.

9. ten Berge WF, Zwart A, Appelman LM [1986]. Concentration-time mortality response relationship of irritant and systematically acting vapours and gases. J Haz Mat 13:301-309.

10. Van Stee EW [1974]. A review of the toxicology of halogenated fire extinguishing agents. Wright-Patterson Air Force Base, Ohio: Aerospace Medical Division, Aerospace Medical Research Laboratory, Air Force Systems Command, AMRL-TR-74-143.