Background

The link between particulate matter (PM) and cardiovascular morbidity has been investigated in numerous studies. Less evidence exists, however, about how age, gender and season may modify this relationship. The aim of this study was to evaluate the association between ambient PM_2.5 (PM ≤ 2.5 µm) and daily hospital emergency room visits (ERV) for cardiovascular diseases in Beijing, China. Moreover, potential effect modification by age, gender, season, air mass origin and the specific period with 2008 Beijing Olympic were investigated. Finally, the temporal lag structure of PM_2.5 has also been explored.

Methods

Daily counts of cardiovascular ERV were obtained from the Peking University Third Hospital from January 2007 to December 2008. Concurrently, data on PM_2.5, PM₁₀ (PM ≤ 10 µm), nitrogen dioxide and sulfur dioxide concentrations were obtained from monitoring networks and a fixed monitoring station. Poisson regression models adjusting for confounders were used to estimate immediate, delayed and cumulative air pollution effects. The temporal lag structure was also estimated using polynomial distributed lag (PDL) models. We calculated the relative risk (RR) for overall cardiovascular disease ERV as well as for specific causes of disease; and also investigated the potential modifying effect of age, gender, season, air mass origin and the period with 2008 Beijing Olympics.

Results

We observed adverse effects of PM_2.5 on cardiovascular ERV—an IQR increase (68 μg/m³) in PM_2.5 was associated with an overall RR of 1.022 (95 % CI 0.990–1.057) obtained from PDL model. Strongest effects of PM_2.5 on cardiovascular ERV were found for a lag of 7 days; the respective estimate was 1.012 (95 % CI 1.002–1.022). The effects were more pronounced in females and in spring. Arrhythmia and cerebrovascular diseases showed a stronger association with PM_2.5. We also found stronger PM-effects for stagnant and southern air masses and the period of Olympics modified the air pollution effects.

Conclusions

We observed a rather delayed effect of PM_2.5 on cardiovascular ERV, which was modified by gender and season. Our findings provide new evidence about effect modifications and may have implications to improve policy making for particulate air pollution standards in Beijing, China.