Regional Analysis

Nuclear Power Generation Phaseouts Redistribute U.S. Air Quality and Climate Related Mortality Risk

Abstract: Nuclear power use in the United States is projected to decline over the coming decades. We explore how nuclear phase-outs could affect air pollution, climate, and health with both existing and alternative grid infrastructure. We develop an energy grid dispatch model to estimate the emissions of CO2, NOx, and SO2 from each electricity generating unit, coupling these emissions with a chemical transport model to calculate impacts on ground-level ozone and fine particulate matter (PM2.5). 

Our yearlong scenario removing nuclear power results in compensation by coal, gas, and oil, leading to increased emissions. We find the resulting changes in PM2.5 and ozone lead to an additional 5230 annual mortalities. Changes in CO2 emissions lead to an order of magnitude higher mortalities throughout the 21st century, incurring $50.4-$220.2 of damages from one year of emissions. A scenario exploring simultaneous closures of nuclear and coal plants shifts the distribution of health impacts, and a scenario allowing for increased penetration of renewables reduces health impacts. Inequities in exposure to pollution are persistent across all scenarios– Black or African American people are exposed to the highest relative levels of pollution, even if renewable capacity is expanded.

A rise in HFC-23 emissions from eastern Asia since 2015

Authors' Short Summary: Based on atmospheric HFC-23 observations, the first estimate of post-CDM HFC-23 emissions in eastern Asia for 2008–2019 shows that these emissions contribute significantly to the global emissions rise. The observation-derived emissions were much larger than the bottom-up estimates expected to approach zero after 2015 due to national abatement activities. These discrepancies could be attributed to unsuccessful factory-level HFC-23 abatement and inaccurate quantification of emission reductions.

Executive Editor's Summary: The international Montreal Protocol was signed in 1987 in order to protect the atmospheric ozone layer by phasing out the production of halogenated hydrocarbons that deplete stratospheric ozone. The protocol was successfully implemented and, over the years, amendments and adjustments of the protocol were essential to its success. Ultimately, the protocol has resulted in a reduced halogen loading of the atmosphere since the mid-1990s. Trifluoromethane (HFC-23) is one of the substances regulated by the Montreal protocol since the Kigali amendment in 2016. HFC-23 does not deplete stratospheric ozone but is a very potent greenhouse gas. Commitments were made to reduce emissions of HFC-23 during the production of HCFC-22 as part of agreements in the protocol. However, the data presented and analysed in this paper indicate that in China more than the agreed amount of HFC-23 has been emitted since 2015, resulting either from unsuccessful factory-level HFC-23 abatement and/or inaccurate quantification of emission reductions. The analysis provides valuable data of atmospheric HFC-23. The study is also a good example of how compliance with the Montreal Protocol can be monitored.

Large mitigation potential of smoke PM2.5 in the US from human-initiated fires

Abstract: Increasing fire activity and the associated degradation in air quality in the United States has been indirectly linked to human activity via climate change. In addition, direct attribution of fires to human activities may provide opportunities for near term smoke mitigation by focusing policy, management, and funding efforts on particular ignition sources.

We analyze how fires associated with human ignitions (agricultural fires and human-initiated wildfires) impact fire particulate matter under 2.5 microns (PM2.5) concentrations in the contiguous United States (CONUS) from 2003 to 2018. We find that these agricultural and human-initiated wildfires dominate fire PM2.5 in both a high fire and human ignition year (2018) and low fire and human ignition year (2003). Smoke from these human levers also makes meaningful contributions to total PM2.5 (~5-10% in 2003 and 2018). Across CONUS, these two human ignition processes account for more than 80% of the population-weighted exposure and premature deaths associated with fire PM2.5.

These findings indicate that a large portion of the smoke exposure and impacts in CONUS are from fires ignited by human activities with large mitigation potential that could be the focus of future management choices and policymaking.

To clear the way for planting wheat in November, a farmer in Punjab, India sets aflame the left-over straw, or stubble, of a harvested rice paddy crop in October. The burning residue fills the air with carbon monoxide, ozone and fine particulate matter (PM2.5) that will make it harder to breathe for days afterward and for miles around.

A targeted approach to reducing the health impacts of crop residue burning in India
Air quality impacts of crop residue burning in India and mitigation alternatives

Abstract: Crop residue burning contributes to poor air quality and imposes a health burden on India. Despite government bans and other interventions, this practice remains widespread.

Here we estimate the impact of changes in agricultural emissions on air quality across India and quantify the potential benefit of district-level actions using an adjoint modeling approach. From 2003 to 2019, we find that agricultural residue burning caused 44,000–98,000 particulate matter exposure-related premature deaths annually, of which Punjab, Haryana, and Uttar Pradesh contribute 67–90%. Due to a combination of relatively high downwind population density, agricultural output, and cultivation of residue-intensive crops, six districts in Punjab alone contribute to 40% of India-wide annual air quality impacts from residue burning.

Burning two hours earlier in Punjab alone could avert premature deaths up to 9600 (95% CI: 8000–11,000) each year, valued at 3.2 (95% CI: 0.49–7.3) billion US dollars. Our findings support the use of targeted and potentially low-cost interventions to mitigate crop residue burning in India, pending further research regarding cost-effectiveness and feasibility.

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