FONOFOS

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: 944-22-9; Chemical Formula: C₁₀H₁₅OPS₂

OSHA formerly had no limit for fonofos. The ACGIH has a limit of 0.1 mg/m³ TWA, with a skin notation, for this light-yellow liquid, which is similar to ethyl parathion and other cholinestase inhibitors. The proposed PEL was an 8-hour TWA of 0.1 mg/m³, with a skin notation; NIOSH (Ex. 8-47, Table N1) concurs with this limit. The final rule’s PEL for fonofos is an 8-hour TWA limit of 0.1 mg/m³, with a skin notation.

In male rats, the average acute oral LD(50) of technical fonofos has been reported to be 13.2 mg/kg (Stauffer Chemical Co. 1974, as cited in ACGIH 1986/Ex. 1-3, p. 275). For female rats, an average oral LD(50) of 3 mg/kg has been reported (NIOSH 1974d). The acute dermal LD(50)s reported for rats and guinea pigs are 147 and 278 mg/kg, respectively (Weir and Hazleton 1981/Ex. 1-1135). Weir and Hazleton reported that no localized eye irritation occurred when 0.1 ml of technical fonofos was instilled into rabbit eyes; however, death resulted in these animals within 24 hours after the instillation (1981/Ex. 1-1135). Dietary studies of rats lasting 105 weeks have shown 10 ppm (about 0.2 mg/kg) to be a no-effect level. Dogs fed fonofos for 14 weeks showed no-effect dietary levels of 8 ppm; no carcinogenic effects were observed. Rats showed reproductive effects at dietary levels of 10 ppm and 31.6 ppm (about 0.7 mg/kg)(Stauffer Chemical Co. 1974, as cited in ACGIH 1986/Ex. 1-3, p. 275).

There are no reports of human poisonings caused by fonofos, although it is known to be a cholinesterase inhibitor (ACGIH 1986/Ex. 1-3, p. 275). There were no comments, other than NIOSH’s, on fonofos.

In the final rule, OSHA is establishing an 8-hour PEL of 0.1 mg/m³ TWA for fonofos to protect exposed workers from the significant risk of cholinesterase inhibition that is characteristic of exposure to this and other organic phosphate pesticides. OSHA considers cholinesterase inhibition a material impairment of health.

A skin notation is also established, based on evidence in animals that fonofos can readily penetrate the skin and cause death. The Agency concludes that these limits will substantially reduce this significant risk.