Childhood incident asthma and traffic-related air pollution at home and school.
BACKGROUND
Traffic-related air pollution has been associated with adverse cardiorespiratory effects, including increased asthma prevalence. However, there has been little study of effects of traffic exposure at school on new-onset asthma.


OBJECTIVE
We evaluated the relationship of new-onset asthma with traffic-related pollution near homes and schools.


METHODS
Parent-reported physician diagnosis of new-onset asthma (n = 120) was identified during 3 years of follow-up of a cohort of 2,497 kindergarten and first-grade children who were asthma- and wheezing-free at study entry into the Southern California Children's Health Study. We assessed traffic-related pollution exposure based on a line source dispersion model of traffic volume, distance from home and school, and local meteorology. Regional ambient ozone, nitrogen dioxide (NO(2)), and particulate matter were measured continuously at one central site monitor in each of 13 study communities. Hazard ratios (HRs) for new-onset asthma were scaled to the range of ambient central site pollutants and to the residential interquartile range for each traffic exposure metric.


RESULTS
Asthma risk increased with modeled traffic-related pollution exposure from roadways near homes [HR 1.51; 95% confidence interval (CI), 1.25-1.82] and near schools (HR 1.45; 95% CI, 1.06-1.98). Ambient NO(2) measured at a central site in each community was also associated with increased risk (HR 2.18; 95% CI, 1.18-4.01). In models with both NO(2) and modeled traffic exposures, there were independent associations of asthma with traffic-related pollution at school and home, whereas the estimate for NO(2) was attenuated (HR 1.37; 95% CI, 0.69-2.71).


CONCLUSIONS
Traffic-related pollution exposure at school and homes may both contribute to the development of asthma.
McConnell
Rob
R
University of Southern California, Los Angeles, California, USA. rmcconne@usc.edu
Islam
Talat
T
Shankardass
Ketan
K
Jerrett
Michael
M
Lurmann
Fred
F
Gilliland
Frank
F
Gauderman
Jim
J
Avol
Ed
E
Künzli
Nino
N
Yao
Ling
L
Peters
John
J
Berhane
Kiros
K
D000393:Air Pollutants / Q000032:analysis / Q000633:toxicity*; D001249:Asthma / Q000139:chemically induced* / Q000453:epidemiology*; D002140:California / Q000453:epidemiology; D002648:Child; D004781:Environmental Exposure; D006801:Humans; D015233:Models, Statistical; D009585:Nitrogen Dioxide / Q000032:analysis / Q000633:toxicity; D010126:Ozone / Q000032:analysis / Q000633:toxicity; D052638:Particulate Matter / Q000032:analysis / Q000633:toxicity; D012307:Risk Factors; D012574:Schools; D001335:Vehicle Emissions / Q000032:analysis / Q000633:toxicity*; D014887:Weather
D000393:Air Pollutants; D052638:Particulate Matter; D001335:Vehicle Emissions; D010126:Ozone; D009585:Nitrogen Dioxide