BENOMYL

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: 17804-35-2; Chemical Formula: C₁₄H₁₈N₄O₃

OSHA formerly regulated benomyl under its generic total particulate limit of 15 mg/m³. The ACGIH has established a total dust TLV-TWA of 10 mg/m³ for this substance. OSHA proposed a PEL of 10 mg/m³ as total particulate for benomyl, and the final rule establishes this limit and retains the Agency’s existing 5-mg/m³ respirable fraction limit. Benomyl is a white crystalline solid; exposures to this substance occur in its particulate form.

Studies of rats and rabbits indicate that the oral and skin absorption LD(50)s are greater than 10,000 mg/kg, and studies of guinea pigs show a very low risk of skin irritation. Application to the shaved intact skin of ten male guinea pigs (as aqueous suspensions containing 5, 12.5, and 25 percent benomyl) resulted in slight irritation; one of ten guinea pigs had mild erythema two days after application of the high concentration (E.I. du Pont de Nemours and Co., Inc. 1974, as cited in ACGIH 1986/Ex. 1-3, p. 49). In another study, instillation of 10 mg of dry 50-percent powder or of 0.1 ml of 10-percent suspension in mineral oil caused only temporary mild conjunctival irritation (E. I. du Pont de Nemours and Co., Inc., unpublished data, as cited in ACGIH 1986/Ex. 1-3, p. 49). NIOSH notes that benomyl exposure may cause adverse reproductive effects (Ex. 8-47, p. 12); no other comments on this substance were submitted.

In the final rule OSHA is establishing 10 mg/m³, total particulate, and 5 mg/m³, respirable particulate, for this substance as 8-hour TWA limits. The Agency concludes that these limits will protect workers from the significant risks of benomyl’s effects, which include irritation and erythema, and the possibility that exposure to benomyl may cause reproductive effects. OSHA finds that these health effects constitute material impairments of health. OSHA will also continue in the future to monitor the scientific evidence on the health effects associated with exposure to benomyl to determine whether a further reduction in the PEL is warranted.