Abstract
Pathogen-free Sprague-Bawley rats (SPF) were exposed to automotive exhaust gas from 2 ½ months to lifetime (two years) for six hours per day, five days each week. The exhaust gas contained 50 ppm of carbon monoxide and two different concentrations of nitrogen oxides (NOx) (0.2 and 23.0 ppm), carbon dioxide (0.065% and 0.370%), and aldehydes (0.1 and 2.0 ppm). Only the dilution with the highest content of NOx (23 ppm) produced biological effects: decrease of body weight, diminution of the sound avoiding reflexes, and increase in the number of spontaneous tumors. However, this dilution does not influence heart rate, ventricular complex (QRS) II electrocardiographic deflection, the rats’ survival, or the renal and aortic lesions resulting from aging processes, although the emphysematous process may be accelerated.