Among the various air pollutants, particulate matter (PM) has shown
the strongest evidence for adverse health effects (Pope et al., 2006). Numerous
studies have demonstrated that short-term exposure to PM was
associated with increased risk of mortality and morbidity (Pope et al.,
2006). Because the sources and components of the PM mixture are
known to vary throughout the year, in addition to the different exposure
patterns of the population in different seasons, it is plausible that the
short-term associations between particulate air pollution and daily mortality
may change from season to season (Peng et al., 2005).