Respiratory and Cardiovascular Effects of NO 2 in Epidemiological Studies

Nitrogen dioxide (NO 2 ) is generally considered a useful indicator for measuring and judging air pollution stemming from motor vehicle sources. Toxicity or health effects related to exposure to NO 2 have been debated as NO 2 usually occurs in the same environment as particulates, and the relative contribution of individual components of the mixture is difficult to disentangle. Epidemiological studies suggest that nitrogen dioxide enhances short-term effects of particular matter (PM 10 ) as observed in time series studies on mortality and hospital admissions. Also recent reviews are related to possible effects on human immune system – experimental animal studies and studies on controlled human exposures suggest that allergenic properties might be enhanced in the presence of NO 2 . Long-term effects are rarely investigated; a few studies show that reduction of lung function in children and adults can be found in those with higher NO 2 exposure. Recent research also suggests effects on the heart. And some studies in children find decreasing respiratory symptoms when NO 2 levels are reduced. World Health Organization (WHO) therefore retains short- and long-term guideline values for NO 2 needed to protect population's health and these might have to be reduced in view of new research results.