DIURON

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: 330-54-1; Chemical Formula: C₉H₁₀Cl₂N₂O

OSHA previously had no limit for diuron. The Agency proposed an 8-hour TWA PEL of 10 mg/m³ for diuron, and this limit is established by the final rule. NIOSH (Ex. 8-47, Table N1) agrees that this limit is appropriate. The ACGIH has a TLV of 10 mg/m³ TWA for this white crystalline solid.

Hodge and Associates (1967/Ex. 1-911; 1968/Ex. 1-912) have reported that diuron has a low order of acute and chronic toxicity. For male rats, the oral LD(50) is 3400 mg/kg. In two-year feeding studies of rats and dogs, the no-effect levels were reported to be 250 and 125 ppm, respectively. A concentration of 125 ppm in the diet did not cause reproductive or carcinogenic effects in a three-generational study of rats (Hodge, Downs, Panner et al. 1967/Ex. 1-911; Hodge, Downs, Smith et al. 1968/Ex. 1-912); 1400 ppm did not have carcinogenic effects in mice (Innes, Ulland, Valerio et al. 1969/Ex. 1-270). Skin irritation and sensitization test findings in guinea pigs have been negative (ACGIH 1986/Ex. 1-3, p. 228). However, repeated doses of this pre-emergence herbicide produced anemia in rats and methemoglobinemia after hydrolysis to dichloroaniline in the body (Condensed Technical Information, duPont 1961).

OSHA is establishing an 8-hour TWA limit of 10 mg/m³ for diuron. OSHA concludes that this limit will protect workers from the significant risks potentially associated with workplace exposure to this substance at the levels permitted in the absence of any OSHA PEL. These risks include anemia and methemoglobinemia, both of which constitute material impairments of health. The final rule’s 10-mg/m³ PEL will substantially reduce these risks.