Absorption
Studies in male B6C3F1 mice and Sprague-Dawley rats indicated that the burden of absorbed 14C
equivalents retained in the body following inhalation of 14C-butadiene at a concentration of 0.08–
7100 ppm was greater at lower than at higher exposure concentrations (12). For example, the
percentage of 14C absorbed and retained at 6 hours decreased from 20% to 4% in mice and from
17% to 2.5% in rats exposed to increasing concentrations. Uptake of butadiene as a percentage of
the total inhaled was found to be lower in cynomolgus monkeys than in rats and mice (13).