Association between air pollutants and cardiovascular disease mortality in Wuhan, China

We examined the associations of daily mean concentrations of ambient air pollutants (particulate matter (PM10), sulfur dioxide (SO2), nitric oxide (NO2)) and daily cardiovascular diseases (CVD) mortality in Wuhan, China using a case-crossover design to analyze four years of data (2006-2009) collected from the Hubei Provincial Center for Disease Control and Prevention and the Wuhan Environmental Protection Bureau. From 2006 to 2009, daily average concentrations of PM10, SO2 and NO2 were 115.60 µg/m3, 53.21 µg/m3 and 53.08 µg/m3, respectively. After adjusting for temperature and relative humidity, a 10 µg/m3 increase in SO2 and NO2 over a 24-h period was associated with CVD mortality relative risk (R.R.) of 1.010 (95% CI: 1.000, 1.020) for SO2 and 1.019 (95% CI: 1.005, 1.033) for NO2, but there was no significant association between increases in PM10 and mortality. Subgroup analysis on by gender showed a significant association of 1.026 (95% CI: 1.007, 1.045) between NO2 and CVD among males, while no significant statistical effect was shown among females. Subgroup analysis by age showed that for those older than 65 years, every 10 µg/m3 increase in NO2 was associated with a 1.6% (95% CI: 0.1%, 3.1%) increase in CVD mortality. Subgroup analysis on different types of CVD showed that every 10 µg/m3 increase in PM10 and SO2 were significantly associated with an approximately 1.012 (95% CI: 1.002, 1.022) and 1.021 (95% CI: 1.002, 1.040) increase, respectively, in ischemic heart disease (ICH) mortality. In conclusion, exposure to NO2 is significantly associated with CVD mortality. Larger, multi-center studies in Chinese cities are being currently conducted to validate these findings.