| Nitrous Acid, Nitrogen Dioxide, and Ozone Concentrations in Residential Environments Kiyoung Lee,1 Jianping Xue,2,* Alison S. Geyh,3 Halûk Özkaynak,2,* Brian P. Leaderer,4 Charles J. Weschler,5 and John D. Spengler2 1University of California, School of Medicine, Davis, California, USA; 2Harvard University, School of Public Health, Boston, Massachusetts, USA; 3Johns Hopkins University, School of Hygiene and Public Health, Baltimore, Maryland, USA; 4Yale University, School of Medicine, New Haven, Connecticut, USA; 5University of Medicine and Dentistry of New Jersey/Robert Wood Johnson
Medical School, New Brunswick, New Jersey, USA Abstract
Nitrous acid (HONO) may be generated by heterogeneous reactions of nitrogen dioxide and direct emission from combustion sources. Interactions among nitrogen oxides and ozone are important for outdoor photochemical reactions. However, little is known of indoor HONO levels or the relationship between residential HONO, NO2, and O3 concentrations in occupied houses. Six-day integrated indoor and outdoor concentrations of the three pollutants were simultaneously measured in two communities in Southern California using passive samplers. The average indoor HONO concentration was 4.6 ppb, compared to 0.9 ppb for outdoor HONO. Average indoor and outdoor NO2 concentrations were 28 and 20.1 ppb, respectively. Indoor O3 concentrations were low (average 14.9 ppb) in comparison to the outdoor levels (average 56.5 ppb) . Housing characteristics, including community and presence of a gas range, were significantly associated with indoor NO2 and HONO concentrations. Indoor HONO levels were closely correlated with indoor NO2 levels and were about 17% of indoor NO2 concentrations. Indoor HONO levels were inversely correlated with indoor O3 levels. The measurements demonstrated the occurrence of substantial residential indoor HONO concentrations and associations among the three indoor air pollutants. Key words: indoor air, indoor/outdoor concentrations, nitrogen dioxide, nitrous acid, ozone, residence. Environ Health Perspect 110:145-149 (2002) . [Online 10 January 2002] http://ehpnet1.niehs.nih.gov/docs/2002/110p145-150lee/ abstract.html Address correspondence to K. Lee, Department of Epidemiology and Preventive Medicine, School of Medicine, University of California at Davis, One Shields Avenue, Davis CA 95615 USA. Telephone: (530) 754-8164. Fax: (530) 752-5047. E-mail: lee@ucdavis.edu *Current address: U.S. Environmental Protection Agency, Research Triangle Park, NC, USA. We thank the children and their families for their participation and cooperation in this study. This study was partially funded by National Institute of Environmental Health Sciences grants R01-ES06370 and R01-ES05410. Received 14 May 2001 ; accepted 9 August 2001.
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