TRIMETHYLBENZENE

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: 25551-13-7; Chemical Formula: (CH₃)₃C₆H₃

OSHA formerly had no exposure limit for trimethylbenzene. The ACGIH TLV for all isomers of trimethylbenzene is 25 ppm as an 8-hour TWA. The proposed PEL was 25 ppm as an 8-hour TWA; NIOSH (Ex. 8-47, Table N1) concurred with the 25-ppm TWA limit, and the final rule establishes this limit for this liquid.

A study by Battig, Grandjean, and Turrian (1957/Ex. 1-104) provides the basis for the final rule’s limit; this work reports symptoms among 27 workers exposed to a solvent containing 30 percent 1,3,5-trimethylbenzene and 50 percent 1,2,3-trimethylbenzene. A “significant number” of these workers were reported to have experienced symptoms of nervousness, tension and anxiety, and asthmatic bronchitis. The peripheral blood of these workers “showed a tendency to hypochromic anemia” and a somewhat abnormal clotting ability. This group of workers had been occupationally exposed to total hydrocarbon concentrations ranging from 10 to 60 ppm for several years. The authors of the study recommended maintaining employee exposures below 35 ppm (Battig, Grandjean, and Turrian 1957/Ex. 1-104). No comments other than that from NIOSH (Ex. 8-47) were received on this substance.

In the final rule, OSHA is establishing a 25-ppm 8-hour PEL to reduce the significant risks of bronchitis and blood effects reported to occur in exposed workers.