NTP technical report on the toxicology and carcinogenesis studies of propylene glycol mono-t-butyl ether (CAS No. 57018-52-7) in F344/N rats and B6C3F1 mice and a toxicology study of propylene glycol mono-t-butyl ether in male NBR rats (inhalation studies).

Background: Propylene glycol mono-t-butyl ether is used as a solvent in all-purpose cleaners, inks, and nail polish lacquers. We studied the effects of propylene glycol mono-t-butyl ether on male and female rats to identify potential toxic or cancer-related hazards to humans.

Methods: We exposed groups of male and female rats and mice to air containing vapors of propylene glycol mono-t-butyl ether at concentrations of 75, 300, or 1,200 parts per million (ppm) for 6 hours per day, 5 days a week for 2 years. Untreated control animals were housed in similar exposure chambers but without chemical exposure for comparison. Tissues from more than 40 sites were examined for every animal.

Results: Rats receiving 1,200 ppm propylene glycol mono-t-butyl ether weighed less on average than the control animals. Tumors were seen in the liver and kidney of a few male rats exposed to propylene glycol mono-t-butyl ether. No increases in the numbers of tumors were seen in female rats. In male and female mice there were large increases in the numbers of liver tumors compared with the control animals.

Conclusions: We conclude that propylene glycol mono-t-butyl ether caused cancer in the liver of male and female mice. Propylene glycol mono-t-butyl ether did not cause cancer in female rats, and its effect on the liver and kidney of male rats was considered uncertain.