title: Ambient PM2.5 and risk of emergency room visits for myocardial infarction: impact of regional PM2.5 oxidative potential: a case-crossover study.
abstract: BACKGROUND
  Regional differences in the oxidative potential of fine particulate air pollution (PM2.5) may modify its impact on the risk of myocardial infarction.
  
  
  METHODS
  A case-crossover study was conducted in 16 cities in Ontario, Canada to evaluate the impact of regional PM2.5 oxidative potential on the relationship between PM2.5 and emergency room visits for myocardial infarction. Daily air pollution and meteorological data were collected between 2004 and 2011 from provincial monitoring sites and regional estimates of glutathione (OP(GSH)) and ascorbate-related (OP(AA)) oxidative potential were determined using an acellular assay based on a synthetic respiratory tract lining fluid. Exposure variables for the combined oxidant capacity of NO2 and O3 were also examined using their sum (Ox) and a weighted average (Ox (wt)) based on their redox potentials.
  
  
  RESULTS
  In total, 30,101 cases of myocardial infarction were included in the analysis. For regions above the 90(th) percentile of OP(GSH) each 5 μg/m(3) increase in same-day PM2.5 was associated with a 7.9 % (95 % CI: 4.1, 12) increased risk of myocardial infarction whereas a 4.1 % (95 % CI: 0.26, 8.0) increase was observed in regions above the 75(th) percentile and no association was observed below the 50(th) percentile (p-interaction = 0.026). A significant 3-way interaction was detected with the strongest associations between PM2.5 and myocardial infarction occurring in areas with high regional OP(GSH) and high Ox (wt) (p-interaction < 0.001).
  
  
  CONCLUSIONS
  Regional PM2.5 oxidative potential may modify the impact of PM2.5 on the risk of myocardial infarction. The combined oxidant capacity of NO2 and O3 may magnify this effect.
authors.affiliation: Health Canada, 269 Laurier Ave West, Ottawa, K1A 0K9, Ontario, Canada. scott.weichenthal@hc-sc.gc.ca.
authors.forename: Scott
authors.initials: S
authors.lastname: Weichenthal
authors.affiliation: Health Canada, 269 Laurier Ave West, Ottawa, K1A 0K9, Ontario, Canada.
authors.forename: Eric
authors.initials: E
authors.lastname: Lavigne
authors.affiliation: University of Toronto, 200 College St, Toronto, M5S 3E5, Ontario, Canada.
authors.forename: Greg
authors.initials: G
authors.lastname: Evans
authors.affiliation: University of Massachusetts, 686 North Pleasant Street, Amherst, Massachusetts, 01003, USA.
authors.forename: Krystal
authors.initials: K
authors.lastname: Pollitt
authors.affiliation: Health Canada, 269 Laurier Ave West, Ottawa, K1A 0K9, Ontario, Canada.
authors.forename: Rick T
authors.initials: RT
authors.lastname: Burnett
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000393:Air Pollutants / Q000032:analysis*; D002648:Child; D002675:Child, Preschool; D003120:Colorado / Q000453:epidemiology; D018592:Cross-Over Studies; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D004781:Environmental Exposure / Q000009:adverse effects; D004784:Environmental Monitoring; D005390:Fires; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008875:Middle Aged; D009203:Myocardial Infarction / Q000453:epidemiology*; D016017:Odds Ratio; D010084:Oxidation-Reduction; D052638:Particulate Matter / Q000032:analysis*; D012140:Respiratory Tract Diseases / Q000453:epidemiology; D012307:Risk Factors; D055815:Young Adult
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter
keywords: Case-crossover; Myocardial infarction; Oxidative potential; Particulate matter