Immediately Dangerous to Life or Health Concentrations (IDLH)
CAS number: 67–66–3
NIOSH REL: 2 ppm (9.78 mg/m3) 60-minute STEL; NIOSH considers chloroform to be a potential occupational carcinogen as defined by the OSHA carcinogen policy [29 CFR 1990].
Current OSHA PEL: 50 ppm (240 mg/m3) CEILING
1989 OSHA PEL: 2 ppm (9.78 mg/m3) TWA
1993-1994 ACGIH TLV: 10 ppm (49 mg/m3) TWA, A2
Description of Substance: Colorless liquid with a pleasant odor.
LEL: . . Noncombustible Liquid
Original (SCP) IDLH: 1,000 ppm
Basis for original (SCP) IDLH: The chosen IDLH is based on the statement by Patty  that 1,024 ppm produced dizziness, intracranial pressure, and nausea after 7 minutes with definite after-effects [Lehmann and Flury 1943]. Also, Lehmann et al.  reported that a 2-minute exposure to 1,107 ppm caused dizziness and vertigo. Because a person may become disoriented at concentrations greater than 1,000 ppm and be unable to escape, 1,000 ppm is chosen as the IDLH.
Existing short-term exposure guidelines: National Research Council [NRC 1984] Emergency Exposure Guidance Levels (EEGLs):
1-hour EEGL: 100 ppm
24-hour EEGL: 30 ppm
ACUTE TOXICITY DATA
Lethal concentration data:
|Species||Reference||LC50(ppm)||LCLo(ppm)||Time||Adjusted 0.5-hrLC (CF)||Derivedvalue|
|Clayton 1967Lehmann and Flury 1943
Lehmann et al. 1936
Tab Biol Per 1933
|2 hr4 hr
|32,000 ppm (1.6)19,235 ppm (2.0)
14,113 ppm (2.0)
13,750 ppm (0.55)
|3,200 ppm1,924 ppm
Other animal data: It has been reported that inhalation of 10,000 ppm has produced clinical anesthesia [NIOSH 1974] and that exposure for 2 minutes to 1,107 ppm has caused dizziness and vertigo [Lehmann et al. 1936]. Workers exposed 4 hours/day to concentrations of 57 to 71 ppm complained of lassitude, loss of appetite, and nausea [Challen et al. 1958]. Exposures to 390 ppm were tolerated for 30 minutes without complaint, whereas 1,030 ppm resulted in dizziness, intracranial pressure, and nausea in 7 minutes, with headache for several hours [Lehmann and Flury 1943].
|Revised IDLH: 500 ppmBasis for revised IDLH: The revised IDLH for chloroform is 500 ppm based on acute inhalation toxicity data in humans [Lehmann and Flury 1943]. [Note: NIOSH recommends as part of its carcinogen policy that the “most protective” respirators be worn for chloroform at concentrations above 2 ppm.]|
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