title: Proximity to traffic, inflammation, and immune function among women in the Seattle, Washington, area.
abstract: BACKGROUND
  Traffic-related air pollution has been associated with adverse health outcomes, and the immune system may be a biologic mediator of health effects.
  
  
  OBJECTIVE
  We analyzed associations between living near major roads and immune status as measured by five immune assays. We hypothesized that living near a freeway, arterial, or truck route would be associated with increased inflammation and decreased immune function.
  
  
  METHODS
  We used a geographic information system (GIS) to determine residential proximity to major roads among 115 postmenopausal, overweight women in the greater Seattle, Washington (USA), area whose immunity was assessed at the baseline visit of an exercise intervention trial. We evaluated three inflammatory markers (C-reactive protein, serum amyloid A, and interleukin-6) and two functional assays of cellular immunity [natural killer (NK) cell cytotoxicity and T-lymphocyte proliferation].
  
  
  RESULTS
  Women living within 150 m of arterial roads had 21% lower NK cytotoxicity compared with women who lived farther from an arterial [mean cytotoxicity, 19.5%; 95% confidence interval (CI), 15.6-23.5%; vs. mean cytotoxicity, 24.8%; 95% CI, 22.0-27.5%], after adjustment for both individual-level and census tract-level demographic characteristics. This association was limited to women who reported exercising near traffic. Fewer women lived near freeways and truck routes. Markers of inflammation and lymphocyte proliferation did not consistently differ according to proximity to major roads.
  
  
  CONCLUSIONS
  If the observed association between residential proximity to traffic and decreased NK cytotoxicity is confirmed in other populations, our results may have implications for local land use policy.
authors.affiliation: Department of Epidemiology, School of Public Health and Community Medicine, University of Washington, Seattle, Washington 98109-1024, USA.
authors.forename: Lori A
authors.initials: LA
authors.lastname: Williams
authors.forename: Cornelia M
authors.initials: CM
authors.lastname: Ulrich
authors.forename: Timothy
authors.initials: T
authors.lastname: Larson
authors.forename: Mark H
authors.initials: MH
authors.lastname: Wener
authors.forename: Brent
authors.initials: B
authors.lastname: Wood
authors.forename: Peter T
authors.initials: PT
authors.lastname: Campbell
authors.forename: John D
authors.initials: JD
authors.lastname: Potter
authors.forename: Anne
authors.initials: A
authors.lastname: McTiernan
authors.forename: Anneclaire J
authors.initials: AJ
authors.lastname: De Roos