Human exposure to oxides of nitrogen at ambient and supra-ambient concentrations.

Oxides of nitrogen (NOx) are a ubiquitous group of air pollutants found in outdoor air as well as indoor environments. The main source of these contaminants is from the combustion of biofuel. Low level and chronic exposure occurs mainly in indoor environments. Acute and high level exposure can occur in a variety of industrial, agricultural, mining, and military settings. The adverse effect of chronic and low level exposure on lung function has been suggested by several epidemiologic studies. However, the results of controlled human exposure to ambient concentrations of NOx have been inconsistent. On the other hand, acute exposure to high levels of NOx has a relatively predictable clinical response in the form of airway irritation, development of pulmonary edema and, in some cases chronic airway disease. There are several lines of evidence to support the role of nutritional antioxidants in amelioration of oxidant lung damage induced by NOx.