Temperature as a modifier of the effects of fine particulate matter on acute mortality in Hong Kong

Interactions between particulate matter with aerodynamic diameter less than or equal to 2.5 μm (PM_2.5) and temperature on mortality have not been well studied, and results are difficult to synthesize. We aimed to assess modification of temperature on the association between PM_2.5 and cause-specific mortality by stratifying temperature into low, medium, and high stratum in Hong Kong, using data from 1999 to 2011. The mortality effects of PM_2.5 were stronger in low temperature stratum than those in high. The excess risk (%) per 10 μg/m³ increase in PM_2.5 at lag 0–1 in low temperature stratum were 0.94% (95% confidence interval: 0.65, 1.24) for all natural, 0.88% (0.38, 1.37) for cardiovascular, and 1.15% (0.51, 1.79) for respiratory mortality. We found statistically significant interaction of PM_2.5 and temperature between low and high temperature stratum for all natural mortality. Our results suggested that temperature might modify mortality effects of PM_2.5 in Hong Kong. - Highlights: • Mortality effects of PM_2.5 in different temperature strata were examined. • Stronger mortality effects of PM_2.5 in low temperature stratum than those in high. • We examined interactions between PM_2.5 and temperature for causes of mortality. - Statistically significant interaction of PM_2.5 and temperature between low and high temperature strata was found for all natural mortality in Hong Kong