Impacts of wildfire smoke PM2.5, greenspace and terrain ruggedness on life expectancy in the contiguous United States.

Abstract

Wildfire smoke PM_2.5 has been associated with many adverse health effects. However, little is known about its impact on life expectancy. This study investigated the impact of wildfire smoke PM_2.5 and its interaction with greenspace and terrain ruggedness on life expectancy in the contiguous United States. By analyzing life expectancy estimates during the 2010 to 2015 period in 66,263 census tracts with multi-level regression models adjusted for income, age, race, and population density, we found that life expectancy was negatively associated with the concentration of smoke PM_2.5 and the number of smoke days. Specifically, the increase of 1 μg/m³ in the annual daily average smoke PM_2.5 levels is associated with a decrease in life expectancy by 1.10 years (regression coefficient β = -1.10, 95 % confidence interval (CI): [-1.21, -0.99]). For every extra smoke day, life expectancy might decrease by 0.021 years (β = -0.021, 95 % CI: [-0.024, -0.018]). Additionally, the interaction of greenspace with smoke PM_2.5 negatively affected life expectancy (β = -0.29, 95 % CI: [-0.38, -0.21]). No significant relationship was observed between life expectancy and terrain ruggedness. The generalized additive model revealed that the impact of smoke PM_2.5 on life expectancy varied across concentration levels. The sensitivity analysis confirmed that the results were robust. Our study suggests that wildfires not only have a direct negative effect on life expectancy but also diminish the beneficial impact of greenspace, potentially turning its positive effects detrimental.