title: PM mass concentration and PM oxidative potential in relation to carotid intima-media thickness.
abstract: BACKGROUND
  There is limited evidence on whether particulate matter (PM) can augment the progression of atherosclerosis; furthermore, the specific attributes of PM responsible for health effects are unclear. We developed models to predict exposure to PM <10 μm (PM10) and also to predict a measure of oxidative potential (the capacity of particles to induce oxidative damage). Our objectives were (1) to estimate the association between PM10 and carotid intima-media thickness, a measure of subclinical atherosclerosis, and (2) to compare this association with that of PM10 weighted by its oxidative potential (PM10*OP).
  
  
  METHODS
  Analysis was based on 2348 participants of the Whitehall II cohort of British civil servants who had intima-media thickness measured between 2003 and 2005 and lived in Greater London. Weekly PM10 and PM10*OP were predicted at each participant's residence. Primary exposure metrics were defined as PM10 and PM10*OP averaged over the year before scan. We estimated associations between exposure metrics and intima-media thickness using generalized linear regression models.
  
  
  RESULTS
  An interquartile range increase (5.2 μgm(-3)) in PM10 was associated with a 5.0% (95% confidence interval = 1.9% to 8.3%) increase in intima-media thickness after covariate adjustment. The association for an interquartile range change in PM10*OP (1.5 m(-3)) was weaker: 1.2% (0.2% to 2.2%).
  
  
  CONCLUSIONS
  These findings support a relationship between PM exposure and atherosclerosis. PM weighted by this particular measure of oxidative potential was not more predictive of the extent of atherosclerosis than PM mass concentration.
authors.affiliation: Department of Social and Environmental Health Research, London School of Hygiene and Tropical Medicine, London, United Kingdom. cathryn.tonne@lshtm.ac.uk
authors.forename: Cathryn
authors.initials: C
authors.lastname: Tonne
authors.forename: Jeff D
authors.initials: JD
authors.lastname: Yanosky
authors.forename: Sean
authors.initials: S
authors.lastname: Beevers
authors.forename: Paul
authors.initials: P
authors.lastname: Wilkinson
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Kelly
mesh_terms: D000368:Aged; D000393:Air Pollutants / Q000032:analysis / Q000633:toxicity*; D000397:Air Pollution / Q000009:adverse effects* / Q000032:analysis; D050197:Atherosclerosis / Q000139:chemically induced* / Q000000981:diagnostic imaging / Q000503:physiopathology; D059168:Carotid Intima-Media Thickness; D015331:Cohort Studies; D005260:Female; D006801:Humans; D019570:Inhalation Exposure / Q000009:adverse effects* / Q000032:analysis; D016014:Linear Models; D008131:London; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D018384:Oxidative Stress; D052638:Particulate Matter / Q000032:analysis / Q000633:toxicity*
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter