Ozone exposure and cardiovascular-related mortality in the Canadian Census Health and Environment Cohort (CANCHEC) by spatial synoptic classification zone

• Published in: Environmental pollution (1987) Vol. 214; pp. 589 - 599
• Main Authors: Cakmak, Sabit, Hebbern, Chris, Vanos, Jennifer, Crouse, Dan L., Burnett, Rick
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.07.2016
• Subjects: Air Pollutants - analysis; Air Pollutants - toxicity; Air pollution; Air Pollution - analysis; Canada; Cardiovascular; Cardiovascular Diseases - mortality; Censuses; cerebrovascular disorders; chronic exposure; Climate; Climate zones; death; Environmental Exposure; Environmental health; Female; Humans; Male; Mortality; myocardial ischemia; ozone; Ozone - analysis; Ozone - toxicity; Particulate Matter - analysis; particulates; Proportional Hazards Models; risk; Socioeconomic Factors; Time Factors; Weather; ANW, Canada; Canada; Air pollution; Cardiovascular; Climate zones; Mortality; Environmental health
• ISSN: 0269-7491; 1873-6424; 1873-6424
• DOI: 10.1016/j.envpol.2016.04.067

Our objective is to analyse the association between long term ozone exposure and cardiovascular related mortality while accounting for climate, location, and socioeconomic factors. We assigned subjects with 16 years of follow-up in the Canadian Census Health and Environment Cohort (CanCHEC) to one of seven regions based on spatial synoptic classification (SSC) weather types and examined the interaction of exposure to both fine particulate matter (PM2.5) and ground level ozone and cause of death using survival analysis, while adjusting for socioeconomic characteristics and individual confounders. Correlations between ozone and PM2.5 varied across SSC zones from −0.02 to 0.7. Comparing zones using the most populated SSC zone as a reference, a 10 ppb increase in ozone exposure was associated with increases in hazard ratios (HRs) that ranged from 1.007 (95% CI 0.99, 1.015) to 1.03 (95% CI 1.02, 1.041) for cardiovascular disease, 1.013 (95% CI 0.996, 1.03) to 1.058 (95% CI 1.034, 1.082) for cerebrovascular disease, and 1.02 (95% CI 1.006, 1.034) for ischemic heart disease. HRs remained significant after adjustment for PM2.5. Long term exposure to ozone is related to an increased risk of mortality from cardiovascular and cerebrovascular diseases; the risk varies by location across Canada and is not attenuated by adjustment for PM2.5. This research shows that the SSC can be used to define geographic regions and it demonstrates the importance of accounting for that spatial variability when studying the long term health effects of air pollution. •We assign geographic zones in Canada based on SSC and identified 7 climate zones.•Ozone risk on CV mortality varies by zone HR of 1.007–1.058 using zone 3 as reference.•Correlations between parameter estimates of ozone and PM2.5 reduced from −0.73 to −0.57 with spatial model.•The mortality risk due to ozone remains after adjustment for PM2.5.•Regional differentiation can be achieved using the spatial synoptic classification. Cardiovascular and related mortality risk due to long term exposure to ozone varies by climate zone in Canada and in select climate zones remains significant after adjustment for PM2.5.