There is growing concern that human exposure to respirable grain dust contaminated with aflatoxin B1 (AFB1), a potent hepatocarcinogen, may be a risk factor for a number of human diseases. The objective of this study was to determine if liver DNA adduct formation occurs in rats following either intratracheal injection or nose-only aerosol inhalation exposure to AFB1. Male Fischer 344 rats were exposed by both routes of administration, and in preliminary data using intratracheal instillation, up to 2% of the administered dose became bound to liver DNA. In the nose-only aerosol inhalation experiments, rats were exposed for up to 120 min. Immediately after exposure, four animals were killed at each time point and their livers removed, DNA isolated and purified and analyzed for aflatoxin-DNA adducts by HPLC. A linear dose-response relationship was observed with a correlation coefficient of 0.96 between increasing length of exposure, and the amount of aflatoxin-N7-guanine adducts formed per mg DNA, the mean values and standard errors were 4.2 +/- 0.18, 15.3 +/- 4.3, 21.6 +/- 2.8 and 56.8 +/- 4.6 pmol aflatoxin-DNA adducts per mg DNA for the 20, 40, 60 and 120 min exposures respectively. The amounts of aflatoxin-DNA adducts formed were statistically significantly different (P less than 0.01) among the treated groups. These results indicate that aerosol inhalation is an effective route of exposure to AFB1 in rats that results in genotoxic damage in the liver.