Additive effect of nitrogen oxides and cold stress on circulating leukocyte counts in rats

To study the combined effect of nitrogen oxides (NOx) and cold stress on circulating leukocyte counts, the numbers of total leukocytes, neutrophils, lymphocytes, and eosinophils were counted in rats after 3 h exposure to NOx and/or cold stress. There was a tendency for both NOx and cold stress to increase the total leukocyte count and the neutrophil count, and to decrease the eosinophil count. The data indicated that the effects of NOx and cold stress were additive when they acted simultaneously.