Absence of Hydrocarbon-Induced Nephropathy in Rats Exposed Subchronically To Volatile Hydrocarbon Mixtures Pertinent To Gasoline

Ninety-day inhalation studies were conducted on 50:50 weight per cent (wt %) mixtures of n-butane:n-pentane and isobutane:isopen tane, respectively, and on a distillation cut boiling below 145° F of a reference unleaded gasoline blend to assess the nephrotoxicity of these volatile mixtures. The mixtures of butanes and pentanes were selected because these four hydrocarbons are the most prevalent components of gasoline vapors encountered under typical occupa tional exposures. The 0-145° F gasoline distillation fraction was tested because it reasonably approximates the composition of gaso line vapors measured under occupational settings. Male and female F-344 rats were exposed to 2 levels of each mixture, 6 hours per day, 5 days per week, for 13 weeks. The target concentrations for the butane:pentane mixtures were 4500 and 1000 parts per million (ppm), while 5200 and 1200 ppm were set for the gasoline distilla tion fraction. An interim sacrifice was conducted after 28 days. The rats were not significantly affected by the exposures, and there was no evidence of hydrocarbon-induced nephropathy in either sex at the termination of each study. However, at the 28-day interim sac rifice period for both butane:pentane mixtures, mild, transient treatment-related but not exposure-related kidney effects were observed in the male rats. These perturbations were absent at the interim sacrifice period for the gasoline distillation fraction.