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Published June 11, 2009 | Supplemental Material
Journal Article Open

Absorption of Inhaled NO_2


Nitrogen dioxide (NO_2), a sparingly water-soluble π-radical gas, is a criteria air pollutant that induces adverse health effects. How is inhaled NO_2(g) incorporated into the fluid microfilms lining respiratory airways remains an open issue because its exceedingly small uptake coefficient (γ 10^(−7)−10^(−8)) limits physical dissolution on neat water. Here, we investigate whether the biological antioxidants present in these fluids enhance NO_2(g) dissolution by monitoring the surface of aqueous ascorbate, urate, and glutathione microdroplets exposed to NO_2(g) for 1 ms via online thermospray ionization mass spectrometry. We found that antioxidants catalyze the hydrolytic disproportionation of NO_2(g), 2NO_2(g) + H_2O(l) = NO_3^−(aq) + H^+(aq) + HONO, but are not consumed in the process. Because this function will be largely performed by chloride, the major anion in airway lining fluids, we infer that inhaled NO_2(g) delivers H^+, HONO, and NO_3^− as primary transducers of toxic action without antioxidant participation.

Additional Information

© 2009 American Chemical Society. Received: March 24, 2009; Revised Manuscript Received: May 5, 2009. Publication Date (Web): May 15, 2009. S.E. thanks the Japan Society for the Promotion of Science Research Fellowship for Young Scientists. This project was supported by the National Science Foundation (ATM-0534990). Supporting Information: Additional data, data analysis, and experimental details. This material is available free of charge via the Internet at http://pubs.acs.org.

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