Associations Between Simulated Future Changes in Climate, Air Quality, and Human Health

Neal L Fann,Christopher G Nolte,Nicholas J Nassikas,Marcus C Sarofim,Jeremy Martinich

doi:10.1001/jamanetworkopen.2020.32064

Abstract

Future changes in climate are likely to adversely affect human health by affecting concentrations of particulate matter sized less than 2.5 μm (PM2.5) and ozone (O3) in many areas. However, the degree to which these outcomes may be mitigated by reducing air pollutant emissions is not well understood. To model the associations between future changes in climate, air quality, and human health for 2 climate models and under 2 air pollutant emission scenarios. This modeling study simulated meteorological conditions over the coterminous continental US during a 1995 to 2005 baseline and over the 21st century (2025-2100) by dynamically downscaling representations of a high warming scenario from the Community Earth System Model (CESM) and the Coupled Model version 3 (CM3) global climate models. Using a chemical transport model, PM2.5 and O3 concentrations were simulated under a 2011 air pollutant emission data set and a 2040 projection. The changes in PM2.5 and O3-attributable deaths associated with climate change among the US census-projected population were estimated for 2030, 2050, 2075, and 2095 for each of 2 emission inventories and climate models. Data were analyzed from June 2018 to June 2020. The main outcomes were simulated change in summer season means of the maximum daily 8-hour mean O3, annual mean PM2.5, population-weighted exposure, and the number of avoided or incurred deaths associated with these pollutants. Results are reported for 2030, 2050, 2075, and 2095, compared with 2000, for 2 climate models and 2 air pollutant emissions data sets. The projected increased maximum daily temperatures through 2095 were up to 7.6 °C for the CESM model and 11.8 °C for the CM3 model. Under each climate model scenario by 2095, compared with 2000, an estimated additional 21 000 (95% CI, 14 000-28 000) PM2.5-attributable deaths and 4100 (95% CI, 2200-6000) O3-attributable deaths were projected to occur. These projections decreased to an estimated 15 000 (95% CI, 10 000-20 000) PM2.5-attributable deaths and 640 (95% CI, 340-940) O3-attributable deaths when simulated using a future emission inventory that accounted for reduced anthropogenic emissions. These findings suggest that reducing future air pollutant emissions could also reduce the climate-driven increase in deaths associated with air pollution by hundreds to thousands.

Highlights

Future changes in the climate will affect the level and distribution of common air pollutants, including ground-level ozone (O3) and fine particles sized 2.5 μm and smaller (PM2.5) in the United States.[1,2,3,4,5] The climate can affect pollutant concentrations through 2 broad pathways
These projections decreased to an estimated 15 000 PM2.5-attributable deaths and 640 O3-attributable deaths when simulated using a future emission inventory that accounted for reduced anthropogenic emissions
These findings suggest that reducing future air pollutant emissions could reduce the climate-driven increase in deaths associated with air pollution by hundreds to thousands

Summary

Introduction

Future changes in the climate will affect the level and distribution of common air pollutants, including ground-level ozone (O3) and fine particles sized 2.5 μm and smaller (PM2.5) in the United States.[1,2,3,4,5] The climate can affect pollutant concentrations through 2 broad pathways. The human health risks associated with these pollutants are well established in controlled human exposure studies and toxicology and epidemiology literature.[10,11,12] Myocardial infarctions, strokes, and respiratory diseases, such as chronic obstructive lung disease, acute lower respiratory tract infections, and lung cancer, are the primary drivers of mortality associated with air pollution.[12,13] The mechanisms of these deaths are likely due to oxidative stress, alterations in host immune defense, increased permeability of endothelial cells, and localized and systemic inflammation.[10,14] Applying a suite of tools to model the pathways from climate to air quality and human health, researchers have quantified estimated counts of air pollution-related premature death and illness attributable to future climate change.[15,16] Often, these analyses run a global or regional climate model for 1 or more climate scenarios, projecting climate-induced changes in meteorological variables.[17] Downscaled meteorological projections are input to photochemical air quality models, which simulate the concentrations of air pollutants. These model-projected changes in pollutants are input to a human health impact assessment

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