Health assessment of gasoline and fuel oxygenate vapors: Micronucleus and sister chromatid exchange evaluations

- Cytogenetic tests performed with gasoline or gasoline/oxygenate vapor condensates.
- Inhalation exposure of rats was 2000, 10,000 or 20,000 mg/m3 over 28 days.
- No cytogenetic damage was seen in the bone marrow micronucleus test.
- Sister chromatid exchange in peripheral blood was seen for gasoline, G/MTBE, G/TAME.

Micronucleus and sister chromatid exchange (SCE) tests were performed for vapor condensate of baseline gasoline (BGVC), or gasoline with oxygenates, methyl tert-butyl ether (G/MTBE), ethyl tert butyl ether (G/ETBE), t-amyl methyl ether (G/TAME), diisopropyl ether (G/DIPE), t-butyl alcohol (TBA), or ethanol (G/EtOH). Sprague Dawley rats (the same 5/sex/group for both endpoints) were exposed to 0, 2000, 10,000, or 20,000 mg/m3 of each condensate, 6 h/day, 5 days/week over 4 weeks. Positive controls (5/sex/test) were given cyclophosphamide IP, 24 h prior to sacrifice at 5 mg/kg (SCE test) and 40 mg/kg (micronucleus test). Blood was collected from the abdominal aorta for the SCE test and femurs removed for the micronucleus test. Blood cell cultures were treated with 5 μg/ml bromodeoxyuridine (BrdU) for SCE evaluation. No significant increases in micronucleated immature erythrocytes were observed for any test material. Statistically significant increases in SCE were observed in rats given BGVC alone or in female rats given G/MTBE. G/TAME induced increased SCE in both sexes at the highest dose only. Although DNA perturbation was observed for several samples, DNA damage was not expressed as increased micronuclei in bone marrow cells. Inclusion of oxygenates in gasoline did not increase the effects of gasoline alone or produce a cytogenetic hazard.