| Traffic, Susceptibility, and Childhood Asthma Rob McConnell,1 Kiros Berhane,1 Ling Yao,1 Michael Jerrett,1 Fred Lurmann,2 Frank Gilliland,1 Nino Künzli,1 Jim Gauderman,1 Ed Avol,1 Duncan Thomas,1 and John Peters1 1Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California, USA; 2Sonoma Technology Inc., Petaluma, California, USA Abstract
Results from studies of traffic and childhood asthma have been inconsistent, but there has been little systematic evaluation of susceptible subgroups. In this study, we examined the relationship of local traffic-related exposure and asthma and wheeze in southern California school children (5-7 years of age) . Lifetime history of doctor-diagnosed asthma and prevalent asthma and wheeze were evaluated by questionnaire. Parental history of asthma and child's history of allergic symptoms, sex, and early-life exposure (residence at the same home since 2 years of age) were examined as susceptibility factors. Residential exposure was assessed by proximity to a major road and by modeling exposure to local traffic-related pollutants. Residence within 75 m of a major road was associated with an increased risk of lifetime asthma [odds ratio (OR) = 1.29 ; 95% confidence interval (CI) , 1.01-1.86], prevalent asthma (OR = 1.50 ; 95% CI, 1.16-1.95) , and wheeze (OR = 1.40 ; 95% CI, 1.09-1.78) . Susceptibility increased in long-term residents with no parental history of asthma for lifetime asthma (OR = 1.85 ; 95% CI, 1.11-3.09) , prevalent asthma (OR = 2.46 ; 95% CI, 0.48-4.09) , and recent wheeze (OR = 2.74 ; 95% CI, 1.71-4.39) . The higher risk of asthma near a major road decreased to background rates at 150-200 m from the road. In children with a parental history of asthma and in children moving to the residence after 2 years of age, there was no increased risk associated with exposure. Effect of residential proximity to roadways was also larger in girls. A similar pattern of effects was observed with traffic-modeled exposure. These results indicate that residence near a major road is associated with asthma. The reason for larger effects in those with no parental history of asthma merits further investigation. Key words: air pollution, asthma, child, epidemiology, traffic. Environ Health Perspect 114:766-772 (2006) . doi:10.1289/ehp.8594 available via http://dx.doi.org/ [Online 16 February 2006]
Address correspondence to R. McConnell, Department of Preventive Medicine, USC Keck School of Medicine, 1540 Alcazar St., CHP 236, Los Angeles, CA 90033 USA. Telephone: (323) 442-1096. Fax: (323) 442-3272. E-mail: rmcconne@usc.edu Supplemental material is available online at http://www.ehponline.org/members/2006/8594/suppl.pdf We thank J. Samet for helpful comments on the manuscript, E. Rappaport and J. Manila for data management, and B. Penfold and S. Raffuse for assisting with the assessment of traffic-related exposures. This study was supported by the National Institute of Environmental Health Science (grants 5P30ES007048, 5 P01 ES009581, and 5 P01 ES011627) , the U.S. Environmental Protection Agency [grants R 826708, RD831861-01, and R82735201 (the Southern California Particle Center) ], the South Coast Air Quality Management District, the National Heart, Lung, and Blood Institute (grant 5R01HL61768) , and the Hastings Foundation. The authors declare they have no competing financial interests. Received 17 August 2005 ; accepted 16 February 2006.
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