α-Pinene is the main component in turpentine and is used as a fragrance and flavoring ingredient. Due to widespread exposure potential and a lack of available toxicity data, male and female F344/N rats and B6C3F1/N mice were exposed to α-pinene (96% pure) by inhalation for 2 weeks or 3 months. Genetic toxicology studies were conducted in Salmonella typhimurium, Escherichia coli, and mouse peripheral blood erythrocytes.
In the 2-week studies, groups of five male and five female rats and mice were exposed to α-pinene by whole body inhalation at concentrations of 0, 100, 200, 400, 800, or 1,600 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 16 (rats) or 17 (mice) days. There was significantly decreased survival in the 800 and 1,600 ppm male and female rats and mice, clinical signs of toxicity in rats exposed to 400 ppm or greater and mice exposed to 800 or 1,600 ppm, and increased liver weights (up to 21%) in both species. Histopathologic lesions noted in the 2-week studies were confined to minimal olfactory epithelial degeneration of nasal tissue in male and female mice exposed to 800 and 1,600 ppm (data not presented).
In the 3-month studies, groups of 10 male and 10 female rats and mice were exposed to α-pinene by whole body inhalation at concentrations of 0, 25, 50, 100, 200, or 400 ppm, 6 hours plus T90 (10 minutes) per day, 5 days per week for 14 weeks. All exposed male rats and male and female mice survived to the end of the studies, while six 400 ppm female rats died before the end of the study The major targets for α-pinene toxicity were the liver, urinary system, and male reproductive system. The absolute liver weights were significantly greater than those of the chamber controls in 400 ppm male rats (13%), male mice (21%), and female mice (18%), and female rats exposed to 50, 100, or 200 ppm (14%, 14%, and 17%, respectively); however, accompanying treatment-related histopathologic lesions did not occur in the liver of male or female rats or mice. Absolute kidney weights were increased in male rats exposed to 100 ppm or greater (up to 25%) and 50 and 200 ppm female rats (10%); in males, these increases were accompanied by histopathologic lesions including granular casts and hyaline droplet accumulation at all exposure concentrations, as well as exposure concentration-dependent increases in the severity of nephropathy, which is a common spontaneous lesion observed in male rats. Exposure concentration-dependent increased incidences of transitional epithelium hyperplasia of the urinary bladder occurred in male and female mice exposed to 100 ppm or greater (males: 100 ppm, 70%; 200 ppm, 100%; 400 ppm, 100%; females: 60%, 100%, 100%). There were also significantly lower numbers of sperm per cauda compared to the chamber controls in 200 and 400 ppm male rats (19%) and 100, 200, and 400 ppm male mice (24%, 33%, and 40%, respectively).
α-Pinene was not mutagenic in S. typhimurium strains TA98 or TA100 or in E. coli, with or without exogenous metabolic activation. No increase in micronucleated erythrocytes was seen in male or female mice in the 3-month study.
The current permissible exposure limit and recommended airborne exposure limit for α-pinene is 100 ppm (as turpentine) and the threshold limit value is 20 ppm averaged over an 8-hour workshift.
Under the conditions of the 3-month inhalation studies, there were treatment-related lesions in male and female rats and mice. The major targets from α-pinene exposure in rats and mice included the liver, urinary system (kidney of rats and urinary bladder of mice), and cauda epididymal sperm. The most sensitive measures of α-pinene exposure in each species and sex were increased incidences of kidney lesions in male rats [lowest-observed-effect level (LOEL)=25 ppm], increased relative liver weights in female rats (LOEL=25 ppm) without accompanying histopathologic changes, decreased sperm per cauda and increased incidences of transitional epithelium hyperplasia of the urinary bladder in male mice (LOEL=100 ppm), and increased incidences of transitional epithelium hyperplasia of the urinary bladder in female mice (LOEL=100 ppm).
National Toxicology Program (NTP). 2016. NTP technical report on the toxicity studies of α-pinene (CASRN 80-56-8) administered by inhalation to F344/N rats and B6C3F1/N mice. Research Triangle Park, NC: National Toxicology Program. Toxicity Report 81. https://doi.org/10.22427/NTP-TOX-81