Source Attribution of PM2.5 Health Benefits Over Northern Hemisphere Using Adjoint of Hemispheric CMAQ

Y B Oztaner; S Zhao; B Henderson; R Mathur; A Hakami

doi:10.1029/2025GH001533

Source Attribution of PM_2.5 Health Benefits Over Northern Hemisphere Using Adjoint of Hemispheric CMAQ

Geohealth. 2026 Jan 20;10(1):e2025GH001533. doi: 10.1029/2025GH001533. eCollection 2026 Jan.

Authors

Y B Oztaner¹, S Zhao¹, B Henderson², R Mathur², A Hakami¹

Affiliations

¹ Department of Civil and Environmental Engineering Carleton University Ottawa ON Canada.
² U.S. Environmental Protection Agency Research Triangle Park NC USA.

Abstract

The adjoint of the U.S. EPA's Community Multiscale Air Quality (CMAQ) model is extended for hemispheric scale applications and is used to estimate location-specific health impacts from primary PM_2.5, and PM_2.5 precursor emissions (NH₃, NO_X and SO₂). We estimate the monetized health burden due to mortality caused by chronic PM_2.5 exposure among adults living in the northern hemisphere, using a generalized concentration-response function. The health impact sensitivities show large spatial variability over the northern hemisphere and exhibit a great deal of seasonal variability, especially for inorganic precursor emissions. The largest marginal impacts are seen for NH₃ and primary PM_2.5. The estimated health impacts for a 10% reduction in emissions reveal a hemispheric burden of 513,700 avoided mortality and monetized health benefits at above 1.2 trillion USD₂₀₁₆. The largest regional contribution to hemispheric mortality is found to be in East and South Asia, particularly China and India (183,760 and 123,440 for a 10% reduction in emissions, respectively). Monetized health burdens are estimated to be highest in China and Europe (∼365 and ∼252 million USD for a 10% reduction in emissions) while it is relatively similar in India (∼175 million USD) as in Canada and the United States (∼177 million USD). Sectoral source contribution analysis demonstrates that the agriculture (19%) and residential (15%) sectors are the largest contributors to the northern hemispheric scale health burden, however, regional differences exist in the results. Examining location- and sector-specific health impacts can inform more effective regulatory measures.

Keywords: PM2.5 health impacts; adjoint sensitivity analysis; northern hemisphere.

Plain language summary

Chronic exposure to outdoor PM_2.5 is one of the highest mortality risk factors. We used an air quality model to understand how reducing air pollution could improve health across the Northern Hemisphere. We estimated how many deaths could be avoided and the economic value of these health benefits if emissions were reduced. We looked at primary PM_2.5 emissions and gases like ammonia, nitrogen oxides, and sulfur dioxide, which can form PM_2.5 in the air. Using a sophisticated sensitivity analysis, we linked emissions to health outcomes and economic impacts in specific locations. Our results show that health impacts vary by season and region, and that ammonia and primary PM_2.5 emissions cause the greatest harm. Reducing emissions by 10% could prevent more than 500,000 premature deaths each year and save over $1.2 trillion (USD 2016). East and South Asia had the highest number of deaths, while China and Europe faced the greatest economic burden. Emissions from agriculture and residential sources were the biggest contributors to health impacts. Identifying where pollution reductions would bring the most health benefits can support the development of more targeted and effective air quality policies.