alpha-Methyl styrene

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

CAS number: 98–83–9

NIOSH REL: 50 ppm (240 mg/m3) TWA, 100 ppm (485 mg/m3) STEL

Current OSHA PEL: 1:00 ppm (480 mg/m3) CEILING

1989 OSHA PEL: 50 ppm (240 mg/m3) TWA, 100 ppm (485 mg/m3) STEL

1993-1994 ACGIH TLV: 50 ppm (242 mg/m3) TWA, 100 ppm (483 mg/m3) STEL

Description of substance: Colorless liquid with a characteristic odor.

LEL:. . . 1.9% (10% LEL, 1,900 ppm)

Original (SCP) IDLH: 5,000 ppm

Basis for original (SCP) IDLH: Because no data on acute inhalation toxicity are available on which to base the IDLH for a-methyl styrene, the chosen IDLH is based on an analogy with styrene which has an IDLH of 5,000 ppm.

Short-term exposure guidelines: None developed


Lethal dose data:

Species Reference Route LD50 (mg/kg) LDLo (mg/kg) Adjusted LD Derived value
Rat Wolf et al. 1956 oral 4,900 ----- 6,982 ppm 698 ppm

Other animal data: A considerable number of rats and guinea pigs exposed to 3,000 ppm for 7 to 8 hours/day, 5 days/week for up to 6 months died [Gerarde 1960; Wolf et al. 1956]. Rats and guinea pigs had slight changes in liver and kidney weights and some reduction in body weight following exposure to 800 ppm for 7 hours/day, 5 days/week for 27 days [Wolf et al. 1956]. No adverse effects were noted in rats, rabbits, mice, monkeys, and guinea pigs exposed 7 hours/day, 5 days/week for 5 months to 200 ppm [Wolf et al. 1956].

Human data: Four volunteers reported a definite unpleasant odor and slight eye irritation after about 2 minutes of exposure to 200 ppm [Wolf et al. 1956]. Strong eye and nasal irritation has been noted at concentrations above 600 ppm [Gerarde 1960; Wolf et al. 1956].

Revised IDLH: 700 ppm

Basis for revised IDLH: The revised IDLH for a-methyl styrene is 700 ppm based on acute toxicity data in humans [Wolf et al. 1956] and animals [Gerarde 1960; Wolf et al. 1956] and an analogy to styrene which has a revised IDLH of 700 ppm.


1. Gerarde HW [1960]. Toxicology and biochemistry of aromatic hydrocarbons. Princeton, NJ: Elsevier Publishing Company, pp. 131-133.

2. Wolf MA, Rowe VK, McCollister DD, et al. [1956]. Toxicological studies of certain alkylated benzenes and benzene. AMA Arch Ind Health 14:387-398.

Page last reviewed: December 4, 2014