title: Saturation sampling for spatial variation in multiple air pollutants across an inversion-prone metropolitan area of complex terrain.
abstract: BACKGROUND
  Characterizing intra-urban variation in air quality is important for epidemiological investigation of health outcomes and disparities. To date, however, few studies have been designed to capture spatial variation during select hours of the day, or to examine the roles of meteorology and complex terrain in shaping intra-urban exposure gradients.
  
  
  METHODS
  We designed a spatial saturation monitoring study to target local air pollution sources, and to understand the role of topography and temperature inversions on fine-scale pollution variation by systematically allocating sampling locations across gradients in key local emissions sources (vehicle traffic, industrial facilities) and topography (elevation) in the Pittsburgh area. Street-level integrated samples of fine particulate matter (PM2.5), black carbon (BC), nitrogen dioxide (NO2), sulfur dioxide (SO2), and ozone (O3) were collected during morning rush and probable inversion hours (6-11 AM), during summer and winter. We hypothesized that pollution concentrations would be: 1) higher under inversion conditions, 2) exacerbated in lower-elevation areas, and 3) vary by season.
  
  
  RESULTS
  During July - August 2011 and January - March 2012, we observed wide spatial and seasonal variability in pollution concentrations, exceeding the range measured at regulatory monitors. We identified elevated concentrations of multiple pollutants at lower-elevation sites, and a positive association between inversion frequency and NO2 concentration. We examined temporal adjustment methods for deriving seasonal concentration estimates, and found that the appropriate reference temporal trend differs between pollutants.
  
  
  CONCLUSIONS
  Our time-stratified spatial saturation approach found some evidence for modification of inversion-concentration relationships by topography, and provided useful insights for refining and interpreting GIS-based pollution source indicators for Land Use Regression modeling.
authors.affiliation: Department of Environmental and Occupational Health, University of Pittsburgh Graduate School of Public Health, Pittsburgh, PA, USA. jlcarr@pitt.edu.
authors.forename: Jessie Lc
authors.initials: JL
authors.lastname: Shmool
authors.forename: Drew R
authors.initials: DR
authors.lastname: Michanowicz
authors.forename: Leah
authors.initials: L
authors.lastname: Cambal
authors.forename: Brett
authors.initials: B
authors.lastname: Tunno
authors.forename: Jeffery
authors.initials: J
authors.lastname: Howell
authors.forename: Sara
authors.initials: S
authors.lastname: Gillooly
authors.forename: Courtney
authors.initials: C
authors.lastname: Roper
authors.forename: Sheila
authors.initials: S
authors.lastname: Tripathy
authors.forename: Lauren G
authors.initials: LG
authors.lastname: Chubb
authors.forename: Holger M
authors.initials: HM
authors.lastname: Eisl
authors.forename: John E
authors.initials: JE
authors.lastname: Gorczynski
authors.forename: Fernando E
authors.initials: FE
authors.lastname: Holguin
authors.forename: Kyra Naumoff
authors.initials: KN
authors.lastname: Shields
authors.forename: Jane E
authors.initials: JE
authors.lastname: Clougherty
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D002244:Carbon / Q000032:analysis; D002947:Cities; D004784:Environmental Monitoring / Q000379:methods*; D040362:Geographic Information Systems; D009585:Nitrogen Dioxide / Q000032:analysis; D052638:Particulate Matter / Q000032:analysis; D010414:Pennsylvania; D012044:Regression Analysis; D012621:Seasons; D013696:Temperature; D013997:Time Factors
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D002244:Carbon; D009585:Nitrogen Dioxide
references.citation: Circulation. 2006 Dec 5;114(23):2443-8
references.pmid: 17101851
references.citation: Environ Sci Technol. 2012 Oct 16;46(20):11195-205
references.pmid: 22963366
references.citation: J Expo Sci Environ Epidemiol. 2006 Mar;16(2):106-14
references.pmid: 16047040
references.citation: Indoor Air. 2011 Feb;21(1):53-66
references.pmid: 20887392
references.citation: J Toxicol Environ Health A. 2007 Feb 1;70(3-4):200-12
references.pmid: 17365582
references.citation: Inhal Toxicol. 2007;19 Suppl 1:127-33
references.pmid: 17886060
references.citation: Environ Health Perspect. 2012 Oct;120(10):1385-90
references.pmid: 22784691
references.citation: Environ Health Perspect. 2007 Feb;115(2):278-84
references.pmid: 17384778
references.citation: Sci Total Environ. 2009 Sep 1;407(18):5085-95
references.pmid: 19540568
references.citation: J Air Waste Manag Assoc. 2002 Sep;52(9):1032-42
references.pmid: 12269664
references.citation: Environ Sci Technol. 2009 Apr 1;43(7):2407-11
references.pmid: 19452894
references.citation: Epidemiology. 2003 Mar;14(2):228-39
references.pmid: 12606891
references.citation: J Expo Sci Environ Epidemiol. 2013 May-Jun;23(3):223-31
references.pmid: 23321861
references.citation: Sci Total Environ. 2010 Oct 1;408(21):5086-96
references.pmid: 20705328
references.citation: J Expo Anal Environ Epidemiol. 2005 Mar;15(2):185-204
references.pmid: 15292906
references.citation: Environ Health. 2012 Oct 10;11:76
references.pmid: 23051204
references.citation: Environ Health. 2013 Jun 27;12:51
references.pmid: 23802774
references.citation: Environ Res. 2008 Jan;106(1):7-16
references.pmid: 17961539
references.citation: Epidemiology. 2005 Nov;16(6):727-36
references.pmid: 16222161
references.citation: Environ Health. 2008 May 16;7:17
references.pmid: 18485201
references.citation: Annu Rev Public Health. 1994;15:107-32
references.pmid: 8054077
references.citation: Am J Respir Crit Care Med. 2002 Oct 15;166(8):1092-8
references.pmid: 12379553
references.citation: J Expo Sci Environ Epidemiol. 2013 May-Jun;23(3):232-40
references.pmid: 23361442
references.citation: Environ Sci Technol. 2010 Jul 15;44(14):5334-44
references.pmid: 20560612
references.citation: Sci Total Environ. 2000 May 15;253(1-3):151-67
references.pmid: 10843339
references.citation: Res Rep Health Eff Inst. 2009 May;(140):5-114; discussion 115-36
references.pmid: 19627030