Modeling the effect of temperature on ozone-related mortality

TL;DR

This study develops a semi-parametric spatial model to analyze the joint effects of ozone and temperature on mortality, revealing nonlinear and synergistic interactions especially at high levels.

Contribution

It introduces a novel monotone semi-parametric model for joint ozone-temperature risk surfaces, capturing nonlinear and nonadditive effects in urban mortality data.

Findings

Evidence of nonlinear ozone effects on mortality

Detection of ozone-temperature interactions at high levels

Model outperforms additive linear models

Abstract

Climate change is expected to alter the distribution of ambient ozone levels and temperatures which, in turn, may impact public health. Much research has focused on the effect of short-term ozone exposures on mortality and morbidity while controlling for temperature as a confounder, but less is known about the joint effects of ozone and temperature. The extent of the health effects of changing ozone levels and temperatures will depend on whether these effects are additive or synergistic. In this paper we propose a spatial, semi-parametric model to estimate the joint ozone-temperature risk surfaces in 95 US urban areas. Our methodology restricts the ozone-temperature risk surfaces to be monotone in ozone and allows for both nonadditive and nonlinear effects of ozone and temperature. We use data from the National Mortality and Morbidity Air Pollution Study (NMMAPS) and show that the proposed model fits the data better than additive linear and nonlinear models. We then examine the synergistic effect of ozone and temperature both nationally and locally and find evidence of a nonlinear ozone effect and an ozone-temperature interaction at higher temperatures and ozone concentrations.