Table 4 shows that the effects of air pollution on OHCD mortality
varied considerably at different temperature levels, suggesting that
there may be interactions between air pollutants and temperature.
For all air pollutants, the strongest effects occurred when the daily
temperature was low. For PM10, PM2.5 and O3, the effects were
larger at high temperatures than at moderate temperatures.
Results from sensitivity analyses of air pollution and OHCD
mortality (data not shown) demonstrated that the effect estimate
decreased appreciably when the df used were increased from 4 df
to 7 df per year, and then remained stable when using 7e10 df per
year. Additionally, the estimated effect decreased slightly but was
still statistically significant after controlling for more lag days of
temperature (0e3, 0e7 and 0e14 days). The effect estimate
increased slightly when we excluded days of extremely severe air
pollution.