Effects of atmospheric ammonia (NH3) on the nasal mucosa and somatic growth were investigated in pigs exposed to 4 NH3 concentrations (0; 25; 50; and 100 ppm) for 6 days in a specifically designed air-pollutant exposure chamber. Nasal lavage (NAL) was applied to quantify the ammonia-induced inflammatory response by measuring the number of neutrophils and the albumin (porcine serum albumin) concentration in the NAL liquid. In control pigs, these variables remained unchanged throughout the exposure period. In all other groups, an important ammonia concentration-related increase was recorded. The equation of the linear regression line established between the mean values of the number of neutrophils (x 10(3)) per milliliter of NAL liquid (y) recorded at the end of the exposure period and the ammonia concentrations (ppm) was: y = 69.7 + 3.3 [NH3] (r = 0.979; P < 0.020). The increase in the neutrophil count was significant (P < 0.05) at concentrations as low as 25 ppm. For albumin concentration nanograms per milliliter, the corresponding equation was: y = 574 + 14.3 [NH3] (r = 0.953; P < 0.045). However, the first significant change (P < 0.05) in this variable was only obtained for the higher concentration (100 ppm). In exposed pigs, a concentration-related depression of somatic growth was observed. The equation of the regression line plotted relating the individual values of the changes in body weight gain recorded over the exposure period expressed as percentage of the initial body weight (y) and the ammonia concentration was: y = 3.507-0.203 [NH3] + 0.001 [NH3]2 (r = 0.55; P < 0.010).(ABSTRACT TRUNCATED AT 250 WORDS)