Cadmium, smoking, and reduced levels of exhaled nitric oxide among US adults.

Exposure to cadmium is known to be associated with reducing nitric oxide (NO) production in experimental conditions, but few studies have examined the association between environmental cadmium exposures and exhaled NO in human. We examined the association between blood cadmium levels and exhaled NO levels in a representative sample of US adults. This investigation was a cross-sectional study of 7813 adults (≥20 years) who participated in the 2007-2008 and 2009-2010 National Health and Nutrition Examination Survey and had their exhaled NO and blood cadmium measurements recorded. The geometric means of the exhaled NO and blood cadmium levels were 13.3 ppb (95% CI: 12.7, 13.9) and 0.51 μg/dL (95% CI: 0.48, 0.54), respectively. Higher blood cadmium levels were associated with decreased exhaled NO levels after adjusting for potential confounding variables. Additionally, a two-fold increase in the blood cadmium levels was associated with a 5% decrease in the exhaled NO levels. The results were significant regardless of the subjects' smoking status or serum cotinine levels, although the percent changes in the exhaled NO levels differed depending on the extent of smoking. Our findings suggest that blood cadmium levels may be associated with reduced levels of exhaled NO in a general sample of US adults. Moreover, cadmium may partially mediate the effect of smoking on exhaled NO production.