title: Air pollution and activity during transportation by car, subway, and walking.
abstract: BACKGROUND
  Little evidence exists about the health risks and benefits associated with using public buses and subways rather than cars. The objective of the current study was to assess the magnitude and variance of personal exposure to particulate matter 2.5 microns or smaller (PM(2.5)) and concomitant physical activity energy expenditure (PAEE) for transportation by car, subway, or walking.
  
  
  METHODS
  Twenty nonsmoking volunteers from New York City traveled on predetermined routes by car, subway, and walking, for up to 8 hours on 3 different days, between October 2007 and February 2008. Outfitted with a personal monitor with PM(2.5) aerosol inlet, and a GPS receiver, they completed a detailed physical activity diary for each route. Both metabolic equivalent (MET) and PAEE rates (Kcal/min) were computed from GPS-derived activity durations and speeds, activity-specific METs, and measured body weight.
  
  
  RESULTS
  Total PM(2.5) exposures did not differ among car, subway, and walking arms (respectively, 21.4, 30.6, and 26.5 microg/m(3) x min, p=0.19); but average MET values (respectively, 1.51, 2.03, and 2.60 Kcal/kg x hr, p<0.0001) and PAEE rates (1.74, 2.35, and 3.04 Kcal/min, p<0.0001) did. After correction for the humidity factor, exposure to PM(2.5) appeared to be lower for the car arm (13.1 microg/m(3) x min) than for the subway (19.6 microg/m(3) x min) or walking (23.9 microg/m(3) x min, p=0.004) arms.
  
  
  CONCLUSIONS
  Driving cars was associated with less physical activity but not necessarily less exposure to PM(2.5) than riding subways or walking in an urban environment. These effect sizes and variances can be used to design larger experiments assessing the health effects of urban transportation.
authors.affiliation: Center for the Biology of Natural Systems, Queens College, Queens, New York, USA. alfredo.morabia@qc.cuny.edu
authors.forename: Alfredo
authors.initials: A
authors.lastname: Morabia
authors.forename: Philippe N
authors.initials: PN
authors.lastname: Amstislavski
authors.forename: Franklin E
authors.initials: FE
authors.lastname: Mirer
authors.forename: Tashia M
authors.initials: TM
authors.lastname: Amstislavski
authors.forename: Holger
authors.initials: H
authors.lastname: Eisl
authors.forename: Mary S
authors.initials: MS
authors.lastname: Wolff
authors.forename: Steven B
authors.initials: SB
authors.lastname: Markowitz
mesh_terms: D000328:Adult; D000397:Air Pollution / Q000032:analysis*; D001334:Automobile Driving; D004734:Energy Metabolism / Q000502:physiology*; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D008297:Male; D055686:Metabolic Equivalent / Q000502:physiology*; D008875:Middle Aged; D052638:Particulate Matter / Q000032:analysis*; D011890:Railroads; D013997:Time Factors; D014186:Transportation; D014505:Urban Population; D016138:Walking
chemical_list: D052638:Particulate Matter