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Carcinogenicity

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Description of key information

A two part carcinogenicity study was conducted on both rats and mice to determine the oncogenic effects of inhalation exposure of commercial hexane solvent.  
No NOAEC level was calculated for local irritation effects. The LOAEC level for both sexes was 900 ppm. No oncogenic effects were seen in the exposure groups. The NOAEC for systemic effects was 9016 ppm in rats of both sexes.

Key value for chemical safety assessment

Additional information

In a two part study the oncogenic effects of inhalation exposure of commercial hexane solvent (~52% n-hexane) was conducted on male and female mice and male and female rats (Daughtrey, 1999; Klimisch score =1). In Part I of the study groups of 50 male and 50 female rats were exposed to 0, 900, 3000, or 9016 ppm of test substance for 6 hrs/day, 5 days/week, for 2 yrs. Mortalities of exposure groups were consistant with control groups. Body weight gain was significantly reduced in exposure groups. Histopathology revealed dose-related effects in the nasoturbinal tissue in all exposure groups. Therefore, there was no NOAEC level for local irritation effects. The LOAEC level for both sexes was 900 ppm. No oncogenic effects were seen in the exposure groups. The NOAEC for systemic effects was 9016 ppm in rats of both sexes.

In Part II of the study groups of 50 male and 50 female mice were exposed to 0, 900, 3000, or 9018 ppm (0, 3168, 10560, 31680 mg/m3) of test substance for 6 hrs/day, 5 days/week, for 2 yrs. Mortalities of exposure groups were consistant with control groups. Histopathology revealed increased liver masses and nodules in female mice at the 9018 ppm exposure group. As referenced in NTP, 2004, liver tumors in B6C3F1 mice are known to be sensitive to body weight changes, especially in female B6C3F1 mice. Therefore, the increased incidence of liver masses and nodules in female mice should be interpreted with care. The NOAEC level for oncogenic effects in female mice is 3000 ppm (10560 mg/m3). The LOAEC for female mice was 9018 ppm (31680 mg/m3). No oncogenic effects were seen in male mice. The NOAEC level for oncogenic effects in male mice is 9018 ppm (31680 mg/m3).

This study directly informs the DNEL.

Justification for classification or non-classification

Commercial hexane solvent containing between 5 and 80% n-hexane is not classified for carcinogenicity.