per billion by volume (ppbv), demonstrating that it has a significant source from
pyrolysis/combustion of biomass. We also measured HNCO at mixing ratios up to 200 pptv
(parts-per-trillion by volume) in ambient air in urban Los Angeles, CA, and in Boulder, CO,
during the recent 2010 Fourmile Canyon fire. Further, our measurements of aqueous
solubility show that HNCO is highly soluble, as it dissociates at physiological pH. Exposure …