OSHA formerly had no permissible exposure limit for ethion. The ACGIH has a limit of 0.4 mg/m3 TWA, with a skin notation. The proposed PEL was 0.4 mg/m3 as an 8-hour TWA, with a skin notation; NIOSH (Ex. 8-47, Table N1) concurs that these limits are appropriate, and the final rule establishes them. Pure ethion is an odorless and colorless liquid; however, technical-grade ethion has a very disagreeable odor.
Ethion is an insecticide that is used in a variety of forms, including 25-percent wettable powder, 2-, 3-, and 4-percent dust, 5-percent granules, and in several oil solutions and combinations with other chemicals. As a result, the acute toxicity values reported vary considerably.
NIOSH (1974d, as cited in ACGIH 1986/Ex. 1-3, p. 236) reports an oral LD(50) in rats of 13 mg/kg. Other reported values for oral LD(50)s in rats include 65 mg/kg, 96 mg/kg, and 208 mg/kg (Farm Chemicals Handbook 1974/Ex. 1-1147a; Association of American Pesticide Control Officials, Inc. 1969, as cited in ACGIH 1986/Ex. 1-3, p. 236; Hayes 1963/Ex. 1-982). Studies with 95 percent technical ethion report oral LD(50)s of 87.4 + 0.16 mg/kg for albino rats and 24.4 mg/kg for female rats (Niagara Chemical Division, FMC Corp., as cited in ACGIH 1986/Ex. 1-3, p. 236). Inhalation studies report LC(50) values of 710 mg/m3 for female rats exposed to 25-percent wettable powder dust for one hour, and 7200 mg/m3 for male rats similarly exposed. Dermal exposure studies, employing technical ethion, report a median acute dermal lethal dose in rabbits of 915 mg/kg, demonstrating ethion's ability to penetrate skin; instillation of 0.05 ml ethion in the rabbit eye is immediately irritating but does not cause corneal scarring (Niagara Chemical Division, FMC Corp., as cited in ACGIH 1986/Ex. 1-3, p. 236). Dietary studies of rats fed 600, 1000, or 1500 ppm reported complete cholinesterase inhibition; 300 ppm in the diet produced marked cholinesterase inhibition (Association of American Pesticide Control Officials, Inc. 1969, as cited in ACGIH 1986/Ex. 1-3, p. 236).
Ethion poisonings have been reported in workers harvesting grapes and peaches (State of California Department of Industrial Relations, as cited in ACGIH 1986/Ex. 1-3, p. 236). Only NIOSH commented on ethion.
OSHA is establishing a PEL of 0.4 mg/m3 for ethion as an 8-hour TWA, with a skin notation. The Agency concludes that these limits will protect exposed workers from the significant risks of organophosphate poisoning and cholinesterase inhibition formerly permitted by the absence of any OSHA limit. The Agency notes this substance's potential for dermal absorption in laboratory animals and is establishing a skin notation to protect against the risk of systemic toxicity by this route of exposure. OSHA finds that the systemic poisoning and cholinesterase inhibition caused by overexposure to ethion constitute material health impairments.