METHYL FORMATE

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: 107-31-3; Chemical Formula: HCOOCH₃

OSHA had a limit of 100 ppm TWA for methyl formate. The ACGIH also has an 8-hour time-weighted average of 100 ppm, with a TLV-STEL of 150 ppm. OSHA proposed to retain the 8-hour TWA of 100 ppm for methyl formate and to add a STEL of 150 ppm; NIOSH (Ex. 8-47, Table N1) concurs that these limits are appropriate. The final rule retains the 8-hour TWA of 100 ppm and adds a 15-minute STEL of 150 ppm. Methyl formate is a flammable, colorless liquid with an agreeable odor.

Methyl formate causes nose and eye irritation, vomiting, incoordination, narcosis, and death in guinea pigs exposed at high concentrations (Schrenk, Yant, Chornyak, and Patty 1936/Ex. 1-756). A 5-percent concentration was fatal in 20 to 30 minutes, a 1.5- to 2.5-percent concentration was dangerous in 30 to 60 minutes, and a 0.5-percent concentration (5000 ppm) was considered the maximum concentration tolerable for a 60-minute period without serious consequences. Lehmann and Flury (1943b/Ex. 1-963) observed that inhalation of 1.02 percent methyl formate for two to three hours caused pulmonary edema and death in cats; a concentration of 1600 ppm resulted in lung inflammation after one hour. Guinea pigs died when exposed by inhalation to 2.5 percent methyl formate (Lehmann and Flury 1943b/Ex. 1-963).

In studies of methyl formate exposure in humans, von Oettingen (1959/Ex. 1-499) reported that exposed workers showed temporary blindness, narcosis, mucous membrane irritation, and dyspnea. Fairhall (1957c/Ex. 1-1107) has reported that methyl formate is more irritating than either methyl or ethyl acetate. Only NIOSH commented on this substance.

In the final rule, OSHA is retaining the 8-hour PEL of 100 ppm TWA and adding a STEL of 150 ppm to prevent the significant risks of irritation, narcotic effects, and pulmonary damage, which constitute material health impairments that are associated with exposure to concentrations of methyl formate even for short periods (one hour or more). The basis for this limit is analogy to the toxicity of methyl acetate. The Agency concludes that these limits will substantially reduce these significant risks.