INDENE

OSHA comments from the January 19, 1989 Final Rule on Air Contaminants Project extracted from 54FR2332 et. seq. This rule was remanded by the U.S. Circuit Court of Appeals and the limits are not currently in force.

CAS: 95-13-6; Chemical Formula: C₉H₈

OSHA had no former limit for indene. The ACGIH has a TLV-TWA of 10 ppm for this colorless liquid. The proposed PEL was 10 ppm as an 8-hour TWA, a limit with which NIOSH (Ex. 8-47, Table N1) concurs. The final rule promulgates an 8-hour TWA PEL for indene of 10 ppm.

Early inhalation studies of indene reported injury to the spleen, liver, and kidneys of rats exposed to indene vapor concentrations of 800 to 900 ppm for six 7-hour periods (Cameron and Doniger 1939/Ex. 1-470). Some animals were found at necropsy to have severe necrosis of the liver with hemorrhage; kidney necrosis was also observed. No other organ damage was found and no deaths occurred as a result of these exposures (Cameron and Doniger 1939/Ex. 1-470). By analogy with the effects of exposure to other monoaromatic hydrocarbons, exposure to indene is likely to irritate the mucous membranes. In laboratory animals, chemical pneumonitis, pulmonary edema, and hemorrhage have resulted from the aspiration of indene liquid into the lung, and repeated skin contact has caused dermatitis as a result of the defatting properties of indene (Gerarde 1960b/Ex. 1-738b). In dermal studies of rats, one to eight applications of 0.1 ml to the shaved skin were reported to have no effect; three applications of 0.5 ml to guinea pig skin also produced no effect (Cameron and Doniger 1939/Ex. 1-470). The oral toxicity of indene appears to be moderate, with adult rabbits tolerating a single dose of 1 gram without signs of systemic toxicity (Gerarde 1960b/Ex. 1-738b). Subcutaneous injection of 1 gram, however, caused liver pathology and fatalities; high oral doses (2.5 ml of a 1:1 v/v mixture in olive oil) were uniformly fatal, with characteristic liver, lung, and gastrointestinal changes. Chronic administration of 3 mg/m³ indene for 105 days caused catalase inhibition and stimulation of blood cholinesterase in rats, but no effects were observed in rats exposed at 0.6 mg/m³ (Dyshinevich 1976/Ex. 1-631). No comments (other than those from NIOSH) were received on this substance.

The final rule establishes an 8-hour PEL of 10 ppm TWA for indene. OSHA concludes that this level will reduce the significant risks of irritation, pulmonary effects, and systemic toxicity which may constitute material impairments of health that are associated with exposure to levels above the new PEL.