OSHA formerly applied a TWA limit of 15 mg/m3 for the total particulate of crag herbicide; this was the Agency's generic total particulate limit for all particulates. The ACGIH has a total-dust TLV-TWA of 10 mg/m3 for this colorless, odorless, noncombustible solid. The proposed PEL for crag herbicide was 10 mg/m3 (total particulate), and the final rule promulgates this limit; the 5-mg/m3 limit for the respirable fraction is retained. NIOSH (Ex. 8-47, Table N4) concurs with OSHA in the selection of these limits.
An early study reported an oral LD(50) in rats of 1500 mg/kg for this herbicide (Smyth 1956/Ex. 1-759). At high concentrations, crag herbicide is a gastrointestinal irritant (NIOSH 1984, as cited in ACGIH 1986/Ex. 1-3, p. 519). Rats fed a diet containing 60 mg sesone/100 gm of diet experienced minor liver damage; when fed 20 mg sesone/100 gm of diet for two years, rats showed no adverse effects (ACGIH 1986/Ex. 1-3, p. 519). In 1984, NIOSH reported the oral LD(50) in rats to be 730 mg/kg (NIOSH 1984, as cited in ACGIH 1986/Ex. 1-3, p. 519). There are no reported incidents of human poisoning associated with the use of sesone. NIOSH submitted the only comment on this substance.
OSHA is reducing the 8-hour TWA PEL for crag herbicide (total particulate) to 10 mg/m3 and retaining the 5-mg/m3 (respirable particulate) limit. OSHA concludes that these limits will protect workers from eye, skin, gastrointestinal, and other forms of irritation caused by exposure to crag herbicide.