title: Ambient ozone exposure and children's acute asthma in New York City: a case-crossover analysis.
abstract: BACKGROUND
  Childhood asthma morbidity has been associated with ambient ozone in case-crossover studies. Varying effects of ozone by child age and sex, however, have been less explored.
  
  
  METHODS
  This study evaluates associations between ozone exposure and asthma emergency department visits and hospitalizations among boys and girls aged 5-17 years in New York City for the 2005-2011 warm season period. Time-stratified case-crossover analysis was conducted and, for comparison, time-series analysis controlling for season, day-of-week, same-day and delayed effects of temperature and relative humidity were also performed.
  
  
  RESULTS
  We found associations between ambient ozone levels and childhood asthma emergency department visits and hospitalizations in New York City, although the relationships varied among boys and girls and by age group. For an increase of interquartile range (0.013 ppm) in ozone, there was a 2.9-8.4% increased risk for boys and 5.4-6.5% for girls in asthma emergency department visits; and 8.2% increased risk for girls in hospitalizations. Among girls, we observed stronger associations among older children (10-13 and 14-17 year age groups). We did not observe significant modification by age for boys. Boys exhibited a more prompt response (lag day 1) to ozone than did girls (lag day 3), but significant associations for girls were retained longer, through lag day 6.
  
  
  CONCLUSIONS
  Our study indicates significant variance in associations between short-term ozone concentrations and asthma events by child sex and age. Differences in ozone response for boys and girls, before and after puberty, may point towards both social (gendered) and biological (sex-linked) sources of effect modification.
authors.affiliation: Icahn School of Medicine at Mount Sinai, 1 Gustave L. Levy Pl., Box 1057, DPM, New York, NY, 10029, USA. perry.sheffield@mssm.edu.
authors.forename: Perry Elizabeth
authors.initials: PE
authors.lastname: Sheffield
authors.affiliation: Department of Environmental and Occupational Health, University of Pittsburgh Graduate School of Public Health, 100 Technology Drive, Pittsburgh, PA, 15219, USA. jiz102@pitt.edu.
authors.forename: Jiang
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Department of Environmental and Occupational Health, University of Pittsburgh Graduate School of Public Health, 100 Technology Drive, Pittsburgh, PA, 15219, USA. jlcshmool@pitt.edu.
authors.forename: Jessie Loving Carr
authors.initials: JL
authors.lastname: Shmool
authors.affiliation: Department of Environmental and Occupational Health, University of Pittsburgh Graduate School of Public Health, 100 Technology Drive, Pittsburgh, PA, 15219, USA. jcloughe@pitt.edu.
authors.forename: Jane Ellen
authors.initials: JE
authors.lastname: Clougherty
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000393:Air Pollutants / Q000633:toxicity*; D001249:Asthma / Q000139:chemically induced / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D018592:Cross-Over Studies; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D009519:New York City / Q000453:epidemiology; D010126:Ozone / Q000633:toxicity*; D012306:Risk; D012621:Seasons
chemical_list: D000393:Air Pollutants; D010126:Ozone