title: The exposure metric choices have significant impact on the association between short-term exposure to outdoor particulate matter and changes in lung function: Findings from a panel study in chronic obstructive pulmonary disease patients.
abstract: BACKGROUND
  The use of ambient air pollution data obtained from central air-monitoring stations as surrogates for participants' exposures to outdoor air pollutants in previous studies may have introduced bias in the estimation of exposure-response associations.
  
  
  OBJECTIVE
  We investigated and compared the effects of short-term exposure to outdoor particulate matter (PMout) and outdoor-originated equivalent personal PM (PMeq) on lung function in chronic obstructive pulmonary disease (COPD) patients.
  
  
  METHODS
  A total of 33 doctor-diagnosed stable COPD patients were recruited and repeatedly measured for lung function (totally 170 measurements) in 2013-2014. Daily PMout concentrations were obtained from central-monitoring stations, and daily time-weighted average PMeq concentrations were estimated based on PMout over the study. Associations of PM with lung function were estimated using mixed-effects models.
  
  
  RESULTS
  Interquartile range increases in PM2.5out (111.0 μg/m(3), 5-day) and PM10out (112.0 μg/m(3), 3-day) were associated with a 3.3% (95% confidence interval [CI]: -5.8%, -0.8%) reduction and a 2.1% (95%CI: -3.9%, -0.3%) reduction in forced vital capacity (FVC), respectively. Similar results were found for forced expiratory volume in 1s (FEV1). An interquartile range increase in PM2.5eq (45.3 μg/m(3), 3-day), but not PM10eq, was still associated with a 1.7% (95%CI: -3.3%, -0.1%) reduction in FVC.
  
  
  CONCLUSIONS
  Our study may provide a novel approach to assess the association of ambient PM with health observations with improved accuracy.
authors.affiliation: Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, Beijing, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Ni
authors.affiliation: Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, Beijing, China.
authors.forename: Shaowei
authors.initials: S
authors.lastname: Wu
authors.affiliation: Department of Building Science, School of Architecture, Tsinghua University, Beijing, China.
authors.forename: Wenjing
authors.initials: W
authors.lastname: Ji
authors.affiliation: Respiratory Department, Peking University Third Hospital, Beijing, China.
authors.forename: Yahong
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Building Science, School of Architecture, Tsinghua University, Beijing, China.
authors.forename: Bin
authors.initials: B
authors.lastname: Zhao
authors.affiliation: Department of Building Science, School of Architecture, Tsinghua University, Beijing, China.
authors.forename: Shanshan
authors.initials: S
authors.lastname: Shi
authors.affiliation: Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, Beijing, China.
authors.forename: Xingying
authors.initials: X
authors.lastname: Tu
authors.affiliation: Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, Beijing, China.
authors.forename: Hongyu
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, Beijing, China.
authors.forename: Lu
authors.initials: L
authors.lastname: Pan
authors.affiliation: Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, Beijing, China. Electronic address: lotus321321@126.com.
authors.forename: Furong
authors.initials: F
authors.lastname: Deng
authors.affiliation: Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, Beijing, China.
authors.forename: Xinbiao
authors.initials: X
authors.lastname: Guo
mesh_terms: D000328:Adult; D000368:Aged; D000393:Air Pollutants / Q000032:analysis*; D000397:Air Pollution / Q000706:statistics & numerical data*; D004781:Environmental Exposure / Q000032:analysis* / Q000706:statistics & numerical data; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D052638:Particulate Matter / Q000032:analysis*; D029424:Pulmonary Disease, Chronic Obstructive / Q000503:physiopathology*; D014797:Vital Capacity
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter
keywords: Air pollution; Chronic obstructive pulmonary disease; Exposure assessment; Lung function; Particulate matter