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: 16219-75-3; Chemical Formula: C9H12

OSHA had no previous limit for ethylidene norbornene. The Agency proposed a ceiling limit of 5 ppm, based on the ACGIH recommendation, and is establishing this limit in the final rule. NIOSH (Ex. 8-47, Table N1) agreed with the selection of this limit. Ethylidene norbornene is a colorless liquid which reacts with oxygen.

In a range-finding study, five of six rats died following a 4-hour exposure to 4000 ppm 5-ethylidene-2-norbornene (Smyth, Carpenter, Weil et al. 1969/Ex. 1-442). Other studies of longer duration have reported that exposures to 237 ppm for seven hours per day, five days per week, for 88 days resulted in death for 21 of 24 rats. No deaths resulted from repeated exposures at 90 ppm, but renal lesions and enlarged livers were observed; liver lesions, testicular atrophy, and hydrothorax occurred only at the 237-ppm level (Kinkead, Pozzani, Geary, and Carpenter 1971/Ex. 1-606). Beagle dogs similarly exposed to 93 ppm for 89 days survived but exhibited such effects as testicular atrophy, hepatic lesions, and slight blood changes. Less pronounced effects were seen after exposures to 61 ppm, and no effects were seen at 22 ppm (Kinkead, Pozzani, Geary, and Carpenter 1971/Ex. 1-606).

Human volunteers exposed for 30 minutes to ethylidene norbornene concentrations of 11 ppm experienced eye and nose irritation; at 6 ppm, transient eye irritation occurred (ACGIH 1986/Ex. 1-3, p. 261). Other than the comments submitted by NIOSH, OSHA received no comments on its proposal to establish a ceiling limit of 5 ppm for ethylidene norbornene.

In the final rule, OSHA is establishing a 5-ppm ceiling for this substance. The Agency finds that this limit is necessary to minimize the risk of irritation that has been documented to occur in occupational exposures to concentrations as low as 6 ppm for 30-minute periods. OSHA has determined that the eye and nasal irritation associated with exposure to ethylidene norbornene constitute material impairments of health. The Agency concludes that this limit will reduce this risk substantially.

Page last reviewed: September 28, 2011