title: Association of short-term exposure to ground-level ozone and respiratory outpatient clinic visits in a rural location - Sublette County, Wyoming, 2008-2011.
abstract: OBJECTIVE
  Short-term exposure to ground-level ozone has been linked to adverse respiratory and other health effects; previous studies typically have focused on summer ground-level ozone in urban areas. During 2008-2011, Sublette County, Wyoming (population: ~10,000 persons), experienced periods of elevated ground-level ozone concentrations during the winter. This study sought to evaluate the association of daily ground-level ozone concentrations and health clinic visits for respiratory disease in this rural county.
  
  
  METHODS
  Clinic visits for respiratory disease were ascertained from electronic billing records of the two clinics in Sublette County for January 1, 2008-December 31, 2011. A time-stratified case-crossover design, adjusted for temperature and humidity, was used to investigate associations between ground-level ozone concentrations measured at one station and clinic visits for a respiratory health concern by using an unconstrained distributed lag of 0-3 days and single-day lags of 0 day, 1 day, 2 days, and 3 days.
  
  
  RESULTS
  The data set included 12,742 case-days and 43,285 selected control-days. The mean ground-level ozone observed was 47 ± 8 ppb. The unconstrained distributed lag of 0-3 days was consistent with a null association (adjusted odds ratio [aOR]: 1.001; 95% confidence interval [CI]: 0.990-1.012); results for lags 0, 2, and 3 days were consistent with the null. However, the results for lag 1 were indicative of a positive association; for every 10-ppb increase in the 8-h maximum average ground-level ozone, a 3.0% increase in respiratory clinic visits the following day was observed (aOR: 1.031; 95% CI: 0.994-1.069). Season modified the adverse respiratory effects: ground-level ozone was significantly associated with respiratory clinic visits during the winter months. The patterns of results from all sensitivity analyzes were consistent with the a priori model.
  
  
  CONCLUSIONS
  The results demonstrate an association of increasing ground-level ozone with an increase in clinic visits for adverse respiratory-related effects in the following day (lag day 1) in Sublette County; the magnitude was strongest during the winter months; this association during the winter months in a rural location warrants further investigation.
authors.affiliation: Epidemic Intelligence Service, Centers for Disease Control and Prevention, Atlanta, GA, USA; Wyoming Department of Health, 6101 Yellowstone Road, Suite 510, Cheyenne, WY 82002, USA. Electronic address: hgp3@cdc.gov.
authors.forename: Kerry R
authors.initials: KR
authors.lastname: Pride
authors.affiliation: Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Peel
authors.affiliation: Scientific Education and Professional Development Program Office, Office of Surveillance, Epidemiology and Laboratory Services, Centers for Disease Control and Prevention, 1600 Clifton Rd, NE, E-92, Atlanta, GA 30333, USA.
authors.forename: Byron F
authors.initials: BF
authors.lastname: Robinson
authors.affiliation: Field Support Branch, Division of Reproductive Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Wyoming Department of Health, 6101 Yellowstone Road, Suite 510, Cheyenne, WY 82002, USA.
authors.forename: Ashley
authors.initials: A
authors.lastname: Busacker
authors.affiliation: Chronic Disease Epidemiologist, Wyoming Department of Health, 6101 Yellowstone Road, Suite 510, Cheyenne, WY 82002, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Grandpre
authors.affiliation: Scientific Education and Professional Development Program Office, Office of Surveillance, Epidemiology and Laboratory Services, Centers for Disease Control and Prevention, 600 Clifton Road, NE, E-92, Atlanta, GA 30333, USA.
authors.forename: Kristine M
authors.initials: KM
authors.lastname: Bisgard
authors.affiliation: Air Pollution and Respiratory Disease Branch, Centers for Disease Control and Prevention, 600 Clifton Rd, NE, E-92, Atlanta, GA 30333, USA.
authors.forename: Fuyuen Y
authors.initials: FY
authors.lastname: Yip
authors.affiliation: Wyoming Department of Health, 101 Yellowstone Road, Suite 510, Cheyenne, WY 82002, USA.
authors.forename: Tracy D
authors.initials: TD
authors.lastname: Murphy
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000393:Air Pollutants / Q000032:analysis*; D000554:Ambulatory Care Facilities / Q000706:statistics & numerical data*; D002648:Child; D002675:Child, Preschool; D018592:Cross-Over Studies; D004781:Environmental Exposure; D004784:Environmental Monitoring; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D010126:Ozone / Q000032:analysis*; D012120:Respiration Disorders / Q000139:chemically induced* / Q000453:epidemiology*; D012423:Rural Health; D012621:Seasons; D014959:Wyoming; D055815:Young Adult
chemical_list: D000393:Air Pollutants; D010126:Ozone
keywords: Air pollution; Cold; Ozone; Rural communities; Seasons