A number of test animal studies have also been conducted on the absorption of benzene
from inhalation exposure. Schrenk et al. (1941) noted a linear relationship between benzene
concentration (200–1300 ppm [639–4153 mg/m3
]) and the equilibrium concentration of benzene
in the blood of dogs. A steady-state blood level was attained within 30 minutes at these
exposure concentrations. Exposure concentration appears to affect the retention of inhaled
radioactivity, as demonstrated by Sabourin et al. (1987) in rats and mice. The retention of
benzene by rats and mice during a 6-hour exposure decreased as exposure concentration
increased: 33 ± 6% to 15 ± 9% for rats, and 50 ± 1% to 10 ± 2% for mice, as exposure
concentration increased from 26 to 2600 mg/m3
 (10 to 1000 ppm). This study also showed
species variability in the uptake and retention of inhaled benzene. At all exposure
concentrations, uptake was higher in mice. At exposure concentrations below 350 mg/m3
, mice
retained approximately 50% more radioactivity per kilogram body weight than did rats, but there
was no significant difference at the highest (2500 mg/m3
) concentration. In general, mice
inhaled greater amounts of benzene per kilogram body weight due to their higher relative minute
volume per kilogram than other species.