OSHA formerly had no limit for diphenylamine. The proposed PEL was 10 mg/m3 as an 8-hour TWA, and the final rule adopts this limit; NIOSH (Ex. 8-47, Table N1) has indicated its concurrence. The ACGIH recommends a TLV of 10 mg/m3 TWA. Diphenylamine exists as monoclinic crystalline leaflets that discolor when exposed to light.
Acute oral toxicity data for diphenylamine are limited. A single report describes a study in which a dietary dose of 1500 mg/kg killed 2 of 20 rats within 30 days of ingestion (Griswold, Casey, Weisburger et al. 1966/Ex. 1-483). This suggests that diphenylamine is significantly less toxic than aniline (Hamblin 1963b/Ex. 1-1085). Dietary studies of rats fed 0.025, 0.1, 0.5, 1.0, or 1.5 percent diphenylamine for 226 days demonstrated nonmalignant renal cysts at the three highest doses (Thomas, Cox, and Deeds 1957/Ex. 1-873). However, rats given diphenylamine crystals encapsulated in collodion developed bladder papillomas within 125 days (Yoshida, Shimauchi, and Kin 1941, as cited in ACGIH 1986/Ex. 1-3, p. 220). Exposure to diphenylamine dust has been linked to liver, spleen, and kidney changes in experimental animals (Robert, Dervilee, and Collet 1937/Ex. 1-928).
A report of industrial diphenylamine poisoning in France described bladder symptoms, tachycardia, hypertension, and eczema (Fairhall 1957g, as cited in ACGIH 1986/Ex. 1-3, p. 220).
OSHA is establishing an 8-hour PEL of 10 mg/m3 TWA for diphenylamine. The Agency concludes that this limit will protect workers against the significant risks of liver, kidney, cardiovascular, and other systemic effects, all of which constitute material health impairments that are potentially associated with exposures to this substance at levels above the new PEL.