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May 1994

Documentation for Immediately Dangerous To Life or Health Concentrations (IDLHs)


CAS number: 108–87–2

NIOSH REL: 400 ppm (1,600 mg/m3) TWA

Current OSHA PEL: 500 ppm (2,000 mg/m3) TWA

1989 OSHA PEL: 400 ppm (1,600 mg/m3) TWA

1993-1994 ACGIH TLV: 400 ppm (1,610 mg/m3) TWA

Description of substance: Colorless liquid with a faint, benzene-like odor.

LEL:. . 1.2% (10% LEL, 1,200 ppm)

Original (SCP) IDLH: 10,000 ppm

Basis for original (SCP) IDLH: With no reported human toxicological data, the chosen IDLH is based on the statement by Browning [1965] that Treon et al. [1943] were able to produce light narcosis in mice at 10,054 ppm. Browning [1965] also reported that Lazarew [1929] found the narcotic dose for mice to be 7,500 to 10,000 ppm. ACGIH [1971] noted that this narcotic dose (7,500 to 10,000 ppm) was for a 2-hour exposure [Lazarew 1929; Treon et al. 1943].

Short-term exposure guidelines: None developed


Lethal concentration data:


SpeciesReferenceLC50 (ppm)LCLo (ppm)TimeAdjusted 0.5-hr


Derived value
MouseIzmerov et al. 1982 10,172----- 2 hr16,275 ppm (1.6)1,268 ppm
MouseLazarew 192910,000-12,500 -----2 hr16,000-20,000 ppm (1.6) 1,600-2,000 ppm
RabbitTreon et al. 1943 15,227----- 1 hr19,034 ppm (1.25)1,903 ppm

Lethal dose data:


SpeciesReferenceRouteLD50 (mg/kg)LDLo (mg/kg)Adjusted LDDerived value
MouseIzmerov et al. 1982 oral2,250-----3,860 ppm386 ppm

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


Revised IDLH: 1,200 ppm [LEL]

Basis for revised IDLH: Based on health considerations and acute inhalation toxicity data in animals [Izmerov et al. 1982; Lazarew 1929; Treon et al. 1943], a value of about 1,600 ppm would have been appropriate for methylcyclohexane. However, the revised IDLH for methylcyclohexane is 1,200 ppm based strictly on safety considerations (i.e., being 10% of the lower explosive limit of 1.2%).


1. ACGIH [1971]. Methylcyclohexane. In: Documentation of the threshold limit values for substances in workroom air. 3rd ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, pp. 162-163.

2. Browning E [1965]. Toxicity and metabolism of industrial solvents. New York, NY: Elsevier Publishing Company, pp. 136-137.

3. Izmerov NF, Sanotsky IV, Sidorov KK [1982]. Toxicometric parameters of industrial toxic chemicals under single exposure. Moscow, Russia: Centre of International Projects, GKNT, p. 82.

4. Lazarew NW [1929]. Uber die giftigkeit verschiedener kohlenwasserstoffdampfe. Arch Exp Pathol Pharmakol 143:223-233 (in German).

5. Lazarew NW [1929]. Zur toxikologie des benzins (The toxicology of gasoline). Arch Hyg, pp. 228-239 (translated).

6. Treon JF, Crutchfield WE, Kitzmiller KV [1943]. The physiological response of animals to cyclohexane, methyl cyclohexane, and certain derivatives of these compounds. II. Inhalation. J Ind Hyg Toxicol 25(8):323-347.

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