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: 1918-02-1; Chemical Formula: C6H3Cl3N2O2

OSHA formerly had no limit for picloram, but regulated it at the generic total particulate limit of 15 mg/m3 for all particulates. The ACGIH has a TLV-TWA of 10 mg/m3 and a TLV-STEL of 20 mg/m3 (both as total dust) for this white powder, which has an odor like that of chlorine; these were the limits proposed for picloram. The final rule promulgates the 10-mg/m3 TWA limit for total particulate but does not include a STEL.

Picloram has low acute oral toxicity, with LD(50) values of 3.75 g/kg for rats, 1.5 g/kg for mice, and 2.0 g/kg for rabbits (NIOSH 1979b, as cited in ACGIH 1986/Ex. 1-3, p. 489). Two-year feeding studies showed no ill effects in albino rats and beagle dogs from ingestion of doses up to and including 150 mg/kg/day (McCollister and Leng 1969, as cited in ACGIH 1986/Ex. 1-3, p. 489). At 225 mg/kg/day, rats displayed moderate liver and kidney changes and, in females, slight body weight loss after 90 days. These authors (McCollister and Leng 1969, as cited in ACGIH 1986/Ex. 1-3, p. 489) also reported no fertility, reproduction, or lactation effects in albino rats fed at levels of up to 3000 ppm (0.3 percent) in a three generational study. Although maternal toxicity in rats was reported at dietary levels of 750 and 1000 mg/kg administered during days 6 through 15 of gestation, neither teratogenic nor neonatal effects were observed when subtoxic or maternally toxic doses of picloram were administered during organogenesis (Thomson et al. 1972, as cited in ACGIH 1986/Ex. 1-3, p. 489). The National Cancer Institute (NCI) (1977d, as cited in ACGIH 1986/Ex. 1-3, p. 489) found a dose-related increase in benign liver tumors in female rats only and concluded that “under the conditions of the bioassay, the findings are suggestive of the ability of the compound to induce benign tumors in the livers of female Osborne-Mendel rats.” Based on these results, NIOSH (Ex. 8-47, Table N4) concludes that “picloram is not a nuisance particulate and is not without toxic effects.” OSHA notes that picloram must therefore be added to the list of substances formerly believed to be inert but subsequently shown to be toxic. No other comments on picloram were submitted to the rulemaking record.

At the present time, however, OSHA is establishing 8-hour TWA limits of 10 mg/m3 (total particulate) and 5 mg/m3 (respirable fraction) for picloram. The final rule does not include a short-term limit; in accordance with the policy described in Section VI.C.17 for short-term limits, OSHA has reviewed the evidence and has concluded that there is no basis for establishing a STEL for picloram, as proposed. The Agency concludes that these total and respirable particulate limits will minimize the significant risk of material health impairment in the form of systemic effects, such as liver and kidney damage, that are potentially associated with exposure to this substance at higher levels. OSHA intends to monitor the health effects literature on picloram in the future.

Page last reviewed: September 28, 2011