title: Isocyanic acid in the atmosphere and its possible link to smoke-related health effects.
abstract: We measured isocyanic acid (HNCO) in laboratory biomass fires at levels up to 600 parts 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 levels > 1 ppbv provide a direct source of isocyanic acid and cyanate ion (NCO(-)) to humans at levels that have recognized health effects: atherosclerosis, cataracts, and rheumatoid arthritis, through the mechanism of protein carbamylation. In addition to the wildland fire and urban sources, we observed HNCO in tobacco smoke, HNCO has been reported from the low-temperature combustion of coal, and as a by-product of urea-selective catalytic reduction (SCR) systems that are being phased-in to control on-road diesel NO(x) emissions in the United States and the European Union. Given the current levels of exposure in populations that burn biomass or use tobacco, the expected growth in biomass burning emissions with warmer, drier regional climates, and planned increase in diesel SCR controls, it is imperative that we understand the extent and effects of this HNCO exposure.
authors.affiliation: National Oceanic and Atmospheric Administration, Earth System Research Laboratories, Chemical Sciences Division, R/CSD7, 325 Broadway, Boulder, CO 80305, USA. james.m.roberts@noaa.gov
authors.forename: James M
authors.initials: JM
authors.lastname: Roberts
authors.forename: Patrick R
authors.initials: PR
authors.lastname: Veres
authors.forename: Anthony K
authors.initials: AK
authors.lastname: Cochran
authors.forename: Carsten
authors.initials: C
authors.lastname: Warneke
authors.forename: Ian R
authors.initials: IR
authors.lastname: Burling
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Yokelson
authors.forename: Brian
authors.initials: B
authors.lastname: Lerner
authors.forename: Jessica B
authors.initials: JB
authors.lastname: Gilman
authors.forename: William C
authors.initials: WC
authors.lastname: Kuster
authors.forename: Ray
authors.initials: R
authors.lastname: Fall
authors.forename: Joost
authors.initials: J
authors.lastname: de Gouw
mesh_terms: D000393:Air Pollutants; D001272:Atmosphere; D018533:Biomass; D002140:California; D002244:Carbon / Q000737:chemistry; D002248:Carbon Monoxide / Q000737:chemistry; D002384:Catalysis; D003120:Colorado; D003485:Cyanates / Q000032:analysis* / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D005390:Fires; D006863:Hydrogen-Ion Concentration; D009569:Nitric Oxide / Q000737:chemistry; D011522:Protons; D012906:Smoke; D012995:Solubility; D013696:Temperature
chemical_list: D000393:Air Pollutants; D003485:Cyanates; D011522:Protons; D012906:Smoke; D009569:Nitric Oxide; D002244:Carbon; D002248:Carbon Monoxide; C005057:isocyanic acid