| Title: | The impact of nitrogen oxides concentration decreases on ozone trends in the USA |
| Author(s): | Jhun I; Coull BA; Zanobetti A; Koutrakis P; |
| Address: | "Department of Environmental Health, Harvard School of Public Health, 401 Park Drive, Landmark 4 West (Rm 412J), Boston, MA 02215, USA. Department of Biostatistics, Harvard School of Public Health, 655 Huntington Avenue, Boston, MA 02115, USA" |
| DOI: | 10.1007/s11869-014-0279-2 |
| ISSN/ISBN: | 1873-9318 (Print) 1873-9326 (Electronic) 1873-9318 (Linking) |
| Abstract: | "Ozone (O(3)) has harmful effects on human health and ecosystems. In the USA, significant reductions of O(3) precursors-nitrogen oxides (NO(x)) and volatile organic compounds (VOCs)-have not yielded proportionate decreases in O(3). NO(x) is a major precursor of O(3) as well as a quencher of O(3) through NO(x) titration, which is especially important during the night and wintertime. In this study, we investigated the potential dual impact of NO(x) concentration decreases on recent O(3) trends by season and time of day. We analyzed hourly O(3) and NO(x) measurement data between 1994 and 2010 in the continental USA. Nationally, hourly O(3) concentrations decreased by as much as -0.38 ppb/year with a standard error of 0.05 ppb/year during the warm season midday, but increased by as much as +0.30+/-0.04 ppb/year during the cold season. High O(3) concentrations (>/=75th percentile) during the warm season decreased significantly, however, there were notable increases in the cold season as well as warm season nighttime; we found that these increases were largely attributable to NO(x) decreases as less O(3) is quenched. These O(3) increases, or 'penalties', related to NO(x) reductions remained robust at a wide range of O(3) concentrations (5th to 99th percentile), and even after accounting for VOC reductions and meteorological parameters, including temperature, wind speed, and water vapor pressure. In addition, we observed O(3) penalties across rural, suburban, and urban areas. Nonetheless, peak O(3) concentrations (99.9th percentile) were mitigated by NO(x) reductions. In addition, there was some suggestive evidence that VOC reductions have been more effective in reducing O(3)" |
| Keywords: | Air pollution Nitrogen oxides Ozone Trends; |
| Notes: | "PubMed-not-MEDLINEJhun, Iny Coull, Brent A Zanobetti, Antonella Koutrakis, Petros eng P01 ES009825/ES/NIEHS NIH HHS/ Netherlands 2015/06/01 Air Qual Atmos Health. 2015 Jun; 8(3):283-292. doi: 10.1007/s11869-014-0279-2" |
