Effect of the Interaction Between Outdoor Air Pollution and Extreme Temperature on Daily Mortality in Shanghai, China

Yuexin Cheng,Haidong Kan

doi:10.2188/jea.je20110049

Abstract

BackgroundBoth outdoor air pollution and extreme temperature have been associated with daily mortality; however, the effect of their interaction is not known.MethodsThis time-series analysis examined the effect of the interaction between outdoor air pollutants and extreme temperature on daily mortality in Shanghai, China. A generalized additive model (GAM) with penalized splines was used to analyze mortality, air pollution, temperature, and covariate data. The effects of air pollutants were stratified by temperature stratum to examine the interaction effect of air pollutants and extreme temperature.ResultsWe found a statistically significant interaction between PM10/O3 and extreme low temperatures for both total nonaccidental and cause-specific mortality. On days with “normal” temperatures (15th–85th percentile), a 10-µg/m3 increment in PM10 corresponded to a 0.17% (95% CI: 0.03%, 0.32%) increase in total mortality, a 0.23% (0.02%, 0.44%) increase in cardiovascular mortality, and a 0.26% (−0.07%, 0.60%) increase in respiratory mortality. On low-temperature days (<15th percentile), the estimates changed to 0.40% (0.21%, 0.58%) for total mortality, 0.49% (0.13%, 0.86%) for cardiovascular mortality, and 0.24% (−0.33%, 0.82%) for respiratory mortality. The interaction pattern of O3 with lower temperature was similar. The interaction between PM10/O3 and lower temperature remained robust when alternative cut-points were used for temperature strata.ConclusionsThe acute health effects of air pollution might vary by temperature level.

Highlights

Short-term exposure to outdoor air pollution has been linked to adverse health effects, including increased mortality, higher rates of hospital admissions and emergency department visits, exacerbation of chronic respiratory conditions, and decreased lung function.[1]
Epidemiologic evidence of an interaction between air pollution and extreme temperature is scarce and the question remains unanswered. In this time-series analysis we examined the effect of the interaction between outdoor air pollutants—ie, particulate matter less than 10 μm in diameter
The use of alternative cut-points for temperature strata yielded similar trends. In this community-based time-series analysis we found a statistically significant interaction between air pollution and lower temperature in their effects on daily mortality

Summary

Introduction

Katsouyanni et al analyzed the potential interaction between air pollution and high temperature and found evidence of an interaction effect.[7] Roberts suggested that the interaction between daily particulate air pollution and daily mean temperature should be considered in epidemiologic studies of air pollution.[8] Recent analyses of the season-specific effects of air pollution highlight the need for comprehensive investigation of the interaction between air pollution and temperature, because season is obviously related to temperature.[9,10,11,12,13,14] Both outdoor air pollution and extreme temperature have been associated with daily mortality; the effect of their interaction is not known. Conclusions: The acute health effects of air pollution might vary by temperature level

Methods

Results

Conclusion