The effect estimates per unit change of air pollutant concentrations
observed in this study were smaller than those reported in
developed countries, which likely reflects the differences in air
pollution levels and chemical components, as well as differences in the socioeconomic susceptibility of the populations. One hypothesized
explanation is that a much steeper slope may be expected at
low pollutant levels than at high pollutant levels in the exposureresponse
function curve (Pope et al., 2011). Despite the smaller
unit effect per an absolute change in air pollutant concentrations in
this study, the total impact of air pollution in triggering OHCD still
needs to be highlighted in China because the level of air pollution is
higher and the exposed population is large.