Aim of the study was to investigate the potential toxic effects of di-n-butylamine (DBA), a known skin and eye irritating compound, on the respiratory tract after inhalation exposure for up to 91 days in male and female rats [Crl:(WI) WU BR]. To check whether and to what degree the no-observed-(adverse)-effect level ( NO( A) EL) decreases with increasing study duration, serial sacrifices were performed after 3 and 28 days, respectively. Based on two dose range-finding studies, the concentrations for this study were determined with 0 ( clean air), 50, 150, and 450 mg/m(3). Animals were exposed for 3 days ( 6 h/day) 28, and 91 days ( 5 days/wk, 6 h/day), respectively, and immediately sacrificed thereafter. The results show clear irritating effects only in the upper part of the respiratory tract, that is, the nasal cavities. While after 3 and 28 days effects were found only in the high-dose group, slight adaptive effects, expressed as mucous ( goblet) cell hyperplasia, could be diagnosed in the medium-and low-dose groups after 91 days of exposure. Pathological changes were most prominent after 3 days of exposure. In the lung, only marginal effects could be observed ( increased relative lung weight only in females of the high concentration after 28 days, slight, not statistically significant histopathological effects in the high concentration after 3 days, no effects on parameters of bronchoalveolar lavage fluid), while no effects were found in the remaining groups.
