A formulation of tobacco extract containing 4% nicotine (TE) and similar nicotine formulation containing vehicle and 4% nicotine (NF) were evaluated using animal inhalation assays. Two 4-h inhalation exposures at 1 and 2 mg/L aerosol exposure concentrations, respectively, of the tobacco extract with 4% nicotine formulation showed that the LC50 was greater than 2 mg/L, the maximum concentration tested. All inhalation exposures were conducted using the capillary aerosol generator (CAG). Increasing aerosol TPM concentrations (0, 10, 50, 200, 1000 mg/m(3) TE and 0, 50, 200, 500, 1000 mg/m(3) NF) were generated via the CAG and used to expose groups of male and female rats for 4-h per day for 14 days. In life monitors for potential effects included clinical observations, weekly body weights and food consumption. Post mortem evaluations included gross tissue findings, hematology, clinical chemistry, serum plasma and nicotine levels, absolute and normalized organ and tissue weights, and histopathology of target organs. Treatment-related changes were observed in body weights, hematology, clinical chemistry, organ weights and histopathological findings for TE at the 200 and 1000 mg/m(3) exposure levels, and in the 500 and 1000 mg/m(3) exposure groups for NF. Under the conditions of these studies, the no-observed-adverse-effect level in the rat was approximately 50 mg/m(3) for the TE aerosol-exposed groups, and approximately 200 mg/m(3) in the NF aerosol-exposed groups.