Abstract
BackgroundRegional differences in the oxidative potential of fine particulate air pollution (PM2.5) may modify its impact on the risk of myocardial infarction.MethodsA 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 (OPGSH) and ascorbate-related (OPAA) 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 (Oxwt) based on their redox potentials.ResultsIn total, 30,101 cases of myocardial infarction were included in the analysis. For regions above the 90th percentile of OPGSH each 5 μg/m3 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 75th percentile and no association was observed below the 50th 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 OPGSH and high Oxwt (p-interaction < 0.001).ConclusionsRegional 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.Electronic supplementary materialThe online version of this article (doi:10.1186/s12940-016-0129-9) contains supplementary material, which is available to authorized users.
Highlights
Regional differences in the oxidative potential of fine particulate air pollution (PM2.5) may modify its impact on the risk of myocardial infarction
Some evidence suggests that regional differences in PM2.5 oxidative potential may be explained in part by differences in particle composition as a European study of 19 cities reported strong correlations between the copper, iron, and zinc content of PM2.5 and ascorbate-related oxidative potential (OPAA) whereas aluminium and copper were associated with glutathionerelated oxidative potential (OPGSH) [13]
Daily PM2.5 mass concentrations were low and oxidative potential varied substantially across sites with values ranging from 0.06–0.35 % depletion/μg PM2.5 for glutathione-related oxidative potential (OPGSH) and 0.12–0.39 % depletion/μg PM2.5 for OPAA (Additional file 1: Table S1; Additional file 3: Figure S2)
Summary
Regional differences in the oxidative potential of fine particulate air pollution (PM2.5) may modify its impact on the risk of myocardial infarction. Some evidence suggests that regional differences in PM2.5 oxidative potential may be explained in part by differences in particle composition as a European study of 19 cities reported strong correlations between the copper, iron, and zinc content of PM2.5 and ascorbate-related oxidative potential (OPAA) whereas aluminium and copper were associated with glutathionerelated oxidative potential (OPGSH) [13] Other compounds such as polycyclic aromatic hydrocarbons and quinones likely contribute regional differences in PM2.5 oxidative potential [7, 14, 18]. To our knowledge this is the first study to examine how regional differences in oxidative potential may modify the acute health effects of PM2.5
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