Evaluation of biological significance of nitrogen oxides exposure.

This paper attempts to assess health risks associated with nitrogen oxides (NOx) exposures. Experimental animal studies show that continuous or intermittent exposures to concentration of 0.04 to 0.5 ppm nitrogen dioxide (NO2) produce a number of pulmonary and systemic effects. Controlled human exposure studies show that short-term exposures to 0.3 to 0.5 ppm NO2 or 1.0 ppm nitric oxide produce bronchoconstriction and blood biochemical changes in some subjects. When we consider together both findings of the animal and human exposure studies, we may suggest with some reliability that the concentrations of NOx in ambient and indoor air pollutions may have adverse health effects on some subjects, and may partly contribute to the respiratory symptoms or illness and reduced pulmonary function observed in the epidemiological studies.