title: Association between light absorption measurements of PM2.5 and distance from heavy traffic roads in the Mexico City metropolitan area.
abstract: OBJECTIVE
  To study the relationship between light absorption measurements of PM2.5 at various distances from heavy traffic roads and diesel vehicle counts in Mexico City.
  
  
  METHODS
  PM2.5 samples were obtained from June 2003-June 2005 in three MCMA regions. Light absorption (b abs) in a subset of PM2.5 samples was determined. We evaluated the effect of distance and diesel vehicle counts to heavy traffic roads on PM2.5 b abs using generalized estimating equation models.
  
  
  RESULTS
  Median PM2.5 b abs measurements significantly decrease as distance from heavy traffic roads increases (p<0.002); levels decreased by 7% (CI95% 0.9-14) for each 100 additional meters from heavy traffic roads. Our model predicts that PM2.5 b abs measurements would increase by 20% (CI95% 3-38) as the hourly heavy diesel vehicle count increases by 150 per hour.
  
  
  CONCLUSIONS
  PM2.5 b abs measurements are significantly associated with distance from motorways and traffic density and therefore can be used to assess human exposure to traffic-related emissions.
authors.affiliation: Centro de Investigación en Salud Poblacional, Instituto Nacional de Salud Pública, Cuernavaca, Morelos, México.
authors.forename: Marlene
authors.initials: M
authors.lastname: Cortez-Lugo
authors.forename: Consuelo
authors.initials: C
authors.lastname: Escamilla-Núñez
authors.forename: Albino
authors.initials: A
authors.lastname: Barraza-Villarreal
authors.forename: José Luis
authors.initials: JL
authors.lastname: Texcalac-Sangrador
authors.forename: Judith
authors.initials: J
authors.lastname: Chow
authors.forename: John
authors.initials: J
authors.lastname: Watson
authors.forename: Leticia
authors.initials: L
authors.lastname: Hernández-Cadena
authors.forename: Isabelle
authors.initials: I
authors.lastname: Romieu
mesh_terms: D002947:Cities; D008027:Light; D008800:Mexico; D018986:Motor Vehicles / Q000706:statistics & numerical data; D001335:Vehicle Emissions / Q000032:analysis*
chemical_list: D001335:Vehicle Emissions