title: Associations between ozone, PM2.5, and four pollen types on emergency department pediatric asthma events during the warm season in New Jersey: a case-crossover study.
abstract: BACKGROUND
  Asthma is one of the most common chronic diseases among school-aged children in the United States. Environmental respiratory irritants exacerbate asthma among children. Understanding the impact of a variety of known and biologically plausible environmental irritants and triggers among children in New Jersey - ozone, fine particulate matter (PM2.5), tree pollen, weed pollen, grass pollen and ragweed - would allow for informed public health interventions.
  
  
  METHODS
  Time-stratified case-crossover design was used to study the transient impact of ozone, PM2.5 and pollen on the acute onset of pediatric asthma. Daily emergency department visits were obtained for children aged 3-17 years with a primary diagnosis of asthma during the warm season (April through September), 2004-2007 (inclusive). Bi-directional control sampling was used to select two control periods for each case for a total of 65,562 inclusion days. Since the period of exposure prior to emergency department visit may be the most clinically relevant, lag exposures were investigated (same day (lag0), 1, 2, 3, 4, and 5 as well as 3-day and 5-day moving averages). Multivariable conditional logistic regression controlling for holiday, school-in-session indicator, and 3-day moving average for temperature and relative humidity was used to examine the associations. Odds ratios are based on interquartile range (IQR) increases or 10 unit increases when IQR ranges were narrow. Single-pollutant models as well as multipollutant models were examined. Stratification on gender, race, ethnicity and socioeconomic status was explored.
  
  
  RESULTS
  The associations with ozone and PM2.5 were strongest on the same day (lag0) of the emergency department visit (RR IQR=1.05, 95% CI 1.04-1.06) and (RR IQR=1.03, 95% CI 1.02-1.04), respectively, with a decreasing lag effect. Tree and weed pollen were associated with pediatric ED visits; the largest magnitudes of association was with the 5-day average (RR IQR=1.23, 95% CI 1.21-1.25) and (RR 10=1.13, 95% CI 1.12-1.14), respectively. Grass pollen was only minimally associated with the outcome while ragweed had a negative association.
  
  
  CONCLUSIONS
  The ambient air pollutant ozone is associated with increases in pediatric emergency department asthma visits during the warm weather season. The different pollen types showed different associations with the outcome. High levels of tree pollen appear to be an important risk factor in asthma exacerbations.
authors.affiliation: Environmental and Occupational Health Surveillance Program, New Jersey Department of Health, 135 East State Street, P.O. Box 369, Trenton, NJ 08625, USA. Electronic address: jessie.gleason@doh.state.nj.us.
authors.forename: Jessie A
authors.initials: JA
authors.lastname: Gleason
authors.affiliation: Robert Wood Johnson University Hospital, Center for Environmental Prediction, Rutgers University, 14 College Farm Road Room 243, New Brunswick, NJ 08901, USA. Electronic address: drlbielory@gmail.com.
authors.forename: Leonard
authors.initials: L
authors.lastname: Bielory
authors.affiliation: Environmental and Occupational Health Surveillance Program, New Jersey Department of Health, 135 East State Street, P.O. Box 369, Trenton, NJ 08625, USA. Electronic address: jerald.fagliano@doh.state.nj.us.
authors.forename: Jerald A
authors.initials: JA
authors.lastname: Fagliano
mesh_terms: D000293:Adolescent; D000393:Air Pollutants / Q000009:adverse effects*; D001249:Asthma / Q000139:chemically induced / Q000453:epidemiology* / Q000276:immunology; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D009515:New Jersey / Q000453:epidemiology; D010126:Ozone / Q000009:adverse effects*; D052638:Particulate Matter / Q000009:adverse effects*; D011058:Pollen / Q000009:adverse effects* / Q000276:immunology; D012621:Seasons
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D010126:Ozone
keywords: Asthma; Case-crossover; Ozone; PM(2.5); Pollen