Asthma in exercising children exposed to ozone: a cohort study.
BACKGROUND
Little is known about the effect of exposure to air pollution during exercise or time spent outdoors on the development of asthma. We investigated the relation between newly-diagnosed asthma and team sports in a cohort of children exposed to different concentrations and mixtures of air pollutants.


METHODS
3535 children with no history of asthma were recruited from schools in 12 communities in southern California and were followed up for up to 5 years. 265 children reported a new diagnosis of asthma during follow-up. We assessed risk of asthma in children playing team sports at study entry in six communities with high daytime ozone concentrations, six with lower concentrations, and in communities with high or low concentrations of nitrogen dioxide, particulate matter, and inorganic-acid vapour.


RESULTS
In communities with high ozone concentrations, the relative risk of developing asthma in children playing three or more sports was 3.3 (95% CI 1.9-5.8), compared with children playing no sports. Sports had no effect in areas of low ozone concentration (0.8, 0.4-1.6). Time spent outside was associated with a higher incidence of asthma in areas of high ozone (1.4, 1.0-2.1), but not in areas of low ozone. Exposure to pollutants other than ozone did not alter the effect of team sports.


CONCLUSIONS
Incidence of new diagnoses of asthma is associated with heavy exercise in communities with high concentrations of ozone, thus, air pollution and outdoor exercise could contribute to the development of asthma in children.
McConnell
Rob
R
Department of Preventive Medicine, University of Southern California School of Medicine, Los Angeles, CA 90089-9011, USA. mcconne@hsc.usc.edu
Berhane
Kiros
K
Gilliland
Frank
F
London
Stephanie J
SJ
Islam
Talat
T
Gauderman
W James
WJ
Avol
Edward
E
Margolis
Helene G
HG
Peters
John M
JM
D000293:Adolescent; D000393:Air Pollutants / Q000032:analysis; D001250:Asthma, Exercise-Induced / Q000209:etiology*; D002140:California; D002648:Child; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D010083:Oxidants, Photochemical / Q000009:adverse effects* / Q000032:analysis; D010126:Ozone / Q000009:adverse effects* / Q000032:analysis; D012923:Social Class; D013177:Sports
D000393:Air Pollutants; D010083:Oxidants, Photochemical; D010126:Ozone