title: Regional PM2.5 and asthma morbidity in an agricultural community: a panel study.
abstract: BACKGROUND
  Elevated pediatric asthma morbidity has been observed in rural US communities, but the role of the ambient environment in exacerbating rural asthma is poorly understood.
  
  
  OBJECTIVE
  To investigate associations between particulate matter less than 2.5 μm in diameter (PM2.5) and pediatric asthma exacerbations in an agricultural community of Washington State.
  
  
  METHODS
  School-aged children with asthma (n=58) were followed for up to 25 months with repeated measures of respiratory health. Asthma symptoms and quick-relief medication use were assessed biweekly through phone administered surveys (n=2023 interviews). In addition, subjects used home peak flow meters on a daily basis to measure forced expiratory volume in one second (FEV1) (n=7830 measurements). Regional PM2.5 was measured at a single air monitor located centrally in the study region. To assess relationships between PM2.5 and these outcomes we used linear regression with generalized estimating equations, adjusting for meteorological and temporal confounders. Effect modification by atopy was explored as well.
  
  
  RESULTS
  An interquartile increase (IQR) in weekly PM2.5 of 6.7 μg/m(3) was associated with an increase in reported asthma symptoms Specific symptoms including wheezing, limitation of activities, and nighttime waking displayed the strongest associations. FEV1 as a percent of predicted decreased by 0.9% (95%CI: -1.8, 0.0) for an IQR increase in PM2.5 one day prior, and by 1.4% (95%CI: -2.7, -0.2) when restricted to children with atopic asthma.
  
  
  CONCLUSIONS
  This study provides evidence that PM2.5 in an agricultural setting contributes to elevated asthma morbidity. Further work on identifying and mitigating sources of PM2.5 in the area is warranted.
authors.affiliation: Department of Epidemiology, School of Public Health, University of Washington, Box 357236, Seattle, WA 98195, United States. Electronic address: cloftus@uw.edu.
authors.forename: Christine
authors.initials: C
authors.lastname: Loftus
authors.affiliation: Department of Environmental and Occupational Health Sciences, School of Public Health, University of Washington, Box 357234, Seattle, WA 98195, United States.
authors.forename: Michael
authors.initials: M
authors.lastname: Yost
authors.affiliation: Department of Statistics, College of Arts and Sciences, University of Washington, Box 354322, Seattle, WA 98195, United States.
authors.forename: Paul
authors.initials: P
authors.lastname: Sampson
authors.affiliation: Yakima Valley Farm Workers Clinic, Yakima, WA, United States.
authors.forename: Griselda
authors.initials: G
authors.lastname: Arias
authors.affiliation: Northwest Education Center, Radio KDNA, 121 Sunnyside Avenue, Granger, WA 98932, United States.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Torres
authors.affiliation: Pacific Northwest Agricultural Safety and Health Center, School of Public Health, University of Washington, Box 357234, Seattle, WA, United States.
authors.forename: Victoria Breckwich
authors.initials: VB
authors.lastname: Vasquez
authors.affiliation: Department of Epidemiology, School of Public Health, University of Washington, Box 357236, Seattle, WA 98195, United States.
authors.forename: Parveen
authors.initials: P
authors.lastname: Bhatti
authors.affiliation: Department of Epidemiology, School of Public Health, University of Washington, Box 357236, Seattle, WA 98195, United States; Department of Environmental and Occupational Health Sciences, School of Public Health, University of Washington, Box 357234, Seattle, WA 98195, United States; Department of Pediatrics, School of Medicine, University of Washington, Box 356320, Seattle, WA 98195, United States.
authors.forename: Catherine
authors.initials: C
authors.lastname: Karr
mesh_terms: D000383:Agriculture; D001249:Asthma / Q000139:chemically induced / Q000453:epidemiology* / Q000503:physiopathology; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D052638:Particulate Matter / Q000633:toxicity*; D012129:Respiratory Function Tests; D014861:Washington / Q000453:epidemiology
chemical_list: D052638:Particulate Matter
keywords: Agricultural air quality; Asthma exacerbations; PM2.5; Pediatric asthma; Rural asthma