How Can We Solve Our Air Quality Problem in the Face of Climate Change? | Environmental Health | JAMA Network Open | JAMA Network
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Invited Commentary
Environmental Health
January 4, 2021

How Can We Solve Our Air Quality Problem in the Face of Climate Change?

Author Affiliations
  • 1Boston University School of Public Health, Boston, Massachusetts
JAMA Netw Open. 2021;4(1):e2035010. doi:10.1001/jamanetworkopen.2020.35010

Climate change is on course to disrupt nearly every aspect of the way we live, as the Intergovernmental Panel on Climate Change makes clear to us every few years.1 Of the many impacts we can expect on human health, those mediated by changing air pollution concentrations are especially well documented.2,3 Air pollution and climate change are intimately connected, with impacts in both directions. Climate-active pollutants, such as CO2, black carbon, and methane, either directly harm health or come from sources that emit pollutants that harm health. In addition, weather and climate have profound impacts on the levels and spatial patterns of air pollution to which we are exposed. Research over the past 2 decades has confirmed that, holding all else constant, climate change tends to worsen air pollution problems, a concept that Jacob and Winner4 described as the “climate penalty.” This effect is most pronounced for ground-level ozone, which forms on warm sunny days downwind of regions with high emissions of nitrogen oxides and volatile organic compounds (eg, metropolitan areas). Particulate matter smaller than 2.5 μm in aerodynamic diameter (PM2.5) is also affected by climate change, but in more complex ways. The climate penalty means that, for any given level of air pollution emissions, pollution exposures and resulting health impacts will be made worse in a warming climate.5

What has been less clear is how much leverage we will have during this century to mitigate the climate penalty in the continental US via more stringent air pollution control policies. This is the question that Fann and colleagues address.6 Their approach follows a health impact assessment framework, which computes projected changes in air pollution–attributed deaths as a function of changes in air pollution levels over the current century, driven by changes in both climate and air pollution emissions. They start by running a complex air pollution simulation model over the US in 5 decadal periods, centered around 2005, 2030, 2050, 2075, and 2095. Outputs from that model are then fed into health impact functions, drawn from epidemiological studies, that relate changing air pollution concentrations to changing death rates. The authors appropriately focus on PM2.5 and ozone, the 2 regulated air pollutants that continue to reach unhealthy levels in many parts of the world,7 including the US. High ozone and PM2.5 levels have consistently been associated with a wide range of adverse health outcomes, including premature death.

Holding air pollution emissions constant at 2011 levels, the authors6 estimate that a rapid climate change scenario could lead to approximately 25 000 additional pollution-attributed deaths annually by 2095, compared with the 2005 baseline year. This case isolates the health impacts of the climate penalty on air pollution as it plays out over the century. By contrast, when air pollution emissions are reduced following already-promulgated regulatory actions through 2040, projected mortality impacts are reduced by approximately 40% in 2095, to just under 16 000 additional deaths compared with 2005. These results demonstrate the substantial health benefits of additional investments in air pollution emission reduction policies. More troubling, however, is the estimate that the climate penalty will still result in additional air pollution-attributed deaths in 2095 vs 2005 even if air pollution emissions are substantially reduced.

To be sure, substantial uncertainties underlie complex modeling studies of this kind. Different climate models (Fann et al6 include 2) offer markedly different views of the timing, magnitude, and spatial pattern of future changes in temperature, PM2.5 and ozone. Projections of future population, baseline age-specific mortality rates, and air pollution–health impact functions through 2095 are fraught with unknowns. Although most of these inputs are amenable to sensitivity analyses, it can be difficult in practice to play out the full range of scenarios because of the computational expense of running air pollution simulation models. Constraints of this kind meant that Fann et al6 only included 1 climate change scenario, Representative Concentration Pathway 8.5 (simulating 8.5 W/m2 radiative forcing), which is generally considered to be a worst case. It would be intriguing to explore the potential benefits of more aggressive carbon reduction scenarios in reducing the climate penalty, or to capture a fuller range of uncertainties by including additional climate models. The authors offer a potential way out of this constraint by offering a novel reduced form model to enable direct estimation of the air pollution climate penalty on the basis of temperature outputs of climate models. If proven reliable, this simple approach could open the door to a broad range of future impact studies.

Modeling studies like those of Fann et al6 serve a critical role in helping society to anticipate, prepare for, and ideally mitigate adverse health impacts of our rapidly changing climate. Although it is encouraging that the potential health benefits that Fann et al6 show could be attained by implementing the regulations already on the books through 2040, we will need to do even more to reduce air pollution-attributed health impacts even further while also addressing the looming climate crisis.

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Article Information

Published: January 4, 2021. doi:10.1001/jamanetworkopen.2020.35010

Open Access: This is an open access article distributed under the terms of the CC-BY License. © 2021 Kinney PL. JAMA Network Open.

Corresponding Author: Patrick Kinney, ScD, Boston University School of Public Health, 715 Albany St, Rm 443, Talbot 4W, Boston, Massachusetts 02118 (

Conflict of Interest Disclosures: None reported.

Intergovernmental Panel on Climate Change. AR5 climate change 2014: impacts, adaptation, and vulnerability. Published 2014. Accessed December 8, 2020.
Fiore  AM, Naik  V, Leibensperger  EM.  Air quality and climate connections.   J Air Waste Manag Assoc. 2015;65(6):645-685. doi:10.1080/10962247.2015.1040526PubMedGoogle ScholarCrossref
Fann  N, Brennan  T, Dolwick  P,  et al. Air quality impacts. In: Crimmins  A, Balbus  JL, Gamble  CB,  et al, eds.  The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment. US Global Change Research Program; 2016:69-98. doi:10.7930/J0GQ6VP6
Jacob  DJ, Winner  DA.  Effect of climate change on air quality.   Atmospher Environ. 2009;43(1):51-63. doi:10.1016/j.atmosenv.2008.09.051Google ScholarCrossref
Kinney  PL.  Interactions of climate change, air pollution, and human health.   Curr Environ Health Rep. 2018;5(1):179-186. doi:10.1007/s40572-018-0188-xPubMedGoogle ScholarCrossref
Fann  NL, Nolte  CG, Sarofim  MC, Martinich  J, Nassikas  NJ.  Associations between simulated future changes in climate, air quality, and human health.   JAMA Netw Open. 2021;4(1):e2032064. doi:10.1001/jamanetworkopen.2020.32064Google Scholar
Cohen  AJ, Brauer  M, Burnett  R,  et al.  Estimates and 25-year trends of the global burden of disease attributable to ambient air pollution: an analysis of data from the Global Burden of Diseases Study 2015.   Lancet. 2017;389(10082):1907-1918. doi:10.1016/S0140-6736(17)30505-6PubMedGoogle ScholarCrossref
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