Cost of Air Pollution and Population Aging

The health impacts of ambient air pollution impose large costs on society. Although all people are exposed to air pollution, the older population tends to be disproportionally affected. As a result, there is growing concern about the health impacts of air pollution as many countries undergo rapid population aging. This project investigated the spatial and temporal variation in the economic cost of deaths attributable to ambient air pollution and its interaction with population aging from 2000 to 2016 at global and regional levels.

The economic cost of ambient PM2·5 borne by the older population almost doubled between 2000 and 2016, driven primarily by GDP growth, population aging, and population growth. Compared with younger people, air pollution leads to disproportionately higher health costs among older people, even after accounting for their relatively shorter life expectancy and increased disability. As the world's population is aging, the disproportionate health cost attributable to ambient PM2·5 pollution potentially widens the health inequities for older people. Countries with severe air pollution and rapid aging rates need to take immediate actions to improve air quality. In addition, strategies aimed at enhancing healthcare services, especially targeting the older population, could be beneficial for reducing the health costs of ambient air pollution.

The findings of this project were published in Lancet Planetary Health.

Hao Yin, Michael Brauer, Junfeng (Jim) Zhang, Daniel M. Kammen, Hans Joachim Schellnhuber et al., Population Ageing And Deaths attributable to Ambient PM2.5 Pollution: A Global Analysis of Economic Cost, Lancet Planetary Health, 5(6), e356-e367, 2021. 

Effects of Clean Air Act in China on Disease Burden and Health Cost

This project not only examines long-term exposure to ambient air pollution but also investigates the health effects and costs associated with short-term exposure. We discovered that national premature deaths due to long-term and short-term exposure to PM2.5 decreased by 15% and 59% between 2013 and 2018, respectively. Conversely, premature deaths attributed to long-term and short-term exposure to O3 increased by 36% and 94%. Despite a 15% reduction in deaths linked to PM2.5, its associated health costs remained relatively unchanged, influenced by GDP growth and an aging population. In contrast, health costs related to long-term exposure to O3 in 2018 were twice as high as in 2013. Moreover, the Clean Air Act in China was more effective in reducing short-term rather than long-term pollution. This underscores the need for China's air pollution regulations to prioritize the phasing out of polluting energy sources over end-of-pipe control strategies.

Jun Liu, Hao Yin (co-first author), Xiao Tang, Tong Zhu, et al. Transition in Air Pollution, Disease Burden and Health Cost in China: A Comparative Study of Long-term and Short-term Exposure, Environmental Pollution, 2021 277, 116770.

Climate actions targeting combustion sources can generate large ancillary health benefits in the form of associated air quality improvements. Therefore, understanding the health cost associated with ambient particulate matter (PM2.5) from combustion sources can guide policy design for both air pollution and climate mitigation efforts. We estimated the health costs attributable to ambient PM2.5 from six major combustion sources across 204 countries using updated concentration-response models and an age-adjusted valuation method. Global long-term exposure to ambient PM2.5 from combustion sources imposed US$1.2 (95% Uncertainty Interval: 0.8-1.6) trillion in health costs in 2019, accounting for 59% of the total health cost from all PM2.5 sources. When comparing source contributions to PM2.5 concentrations and health costs, we observed a higher share of health costs from combustion sources compared to their contribution to PM2.5 concentration across 144 countries, accounting for over 85% of the global population. This disparity was primarily attributed to the nonlinear relationship between PM2.5 concentration and its associated health costs. This finding suggests that mitigating combustion sources was more beneficial than targeting non-combustion sources in most countries. Globally, phasing out fossil fuels can generate 29% higher relative health benefits compared to their share of PM2.5 reductions. This is driven by the source’s shares of health cost for both total coal and liquid fuel & natural gas were found to be 35% and 24% higher than their contributions to corresponding PM2.5 concentrations, respectively. Other than fossil fuels, the South Asian region was expected to experience a 31% greater relative health benefit compared to the reduction in PM2.5 from the abatement of solid biofuel emissions. Mitigation efforts designed according to source-specific health costs can more effectively avoid health costs than strategies that depend solely on the source contributions to overall PM2.5 concentration.

Hao Yin, Erin McDuffie, Randall Martin, Michael Brauer, Global Health Cost of Ambient PM2.5 from Combustion Sources: Implications Air Pollution Control Strategies. Lancet Planetary Health revise & resubmit, 2024.

Challenges of Missing Data in Healthcare Facilities

Health care accounts for 9–10% of greenhouse gas (GHG) emissions in the United States. Strategies for monitoring these emissions at the hospital level are needed to decarbonize the sector. However, data collection to estimate emissions is challenging. We explored the potential of gradient boosting machines (GBM) to impute missing data on resource consumption in the 2020 survey of a consortium of 283 hospitals participating in Practice Greenhealth. GBM imputed missing values for selected variables in order to predict electricity use (R2 = 0.82) and beef consumption (R2 = 0.82) and anesthetic gas desflurane use (R2 = 0.51), using administrative and financial data readily available for most hospitals. After imputing missing consumption data, estimated GHG emissions associated with these three examples totaled over 3 million metric tons of CO2 equivalent emissions (MTCO2e). Specifically, electricity consumption had the largest total carbon footprint (2.4 MTCO2e), followed by beef (0.6 million MTCO2e) and desflurane consumption (0.03 million MTCO2e) across the 283 hospitals. The approach should be applicable to other sources of hospital GHGs in order to estimate total emissions of individual hospitals and to refine survey questions to help develop better intervention strategies.

Hao Yin, Sharma, B., Hu, H., Liu, F., Kaur, Cohen, G., McConnell, R., Eckel, S., Predicting the Climate Impact of Healthcare Facilities Using Gradient Boosting Machine. Cleaner Environmental Systems, 100155, 2023.

Estimating GHG emissions from Hospitals

The US healthcare industry has the largest carbon footprint per capita globally. Despite efforts to mitigate emissions, hospitals face challenges in achieving decarbonization targets in part because hospital-level emissions are not available. This study estimates greenhouse gas (GHG) emissions from 38 sources across seven sectors for 283 hospitals, representing approximately four percent of U.S. hospitals in 2020, that voluntarily participated in the Practice Greenhealth Environmental Excellence award program. Total GHG emissions from these hospitals were estimated to be 9·3 million metric tons CO2 equivalent (MTCO2e), corresponding to nearly two percent of U.S. healthcare’s estimated emissions. Energy, food, and waste were primary contributors to total estimated GHG emissions. While the total carbon footprint was positively correlated with the number of staffed beds, there was an inverse relationship between GHG emissions per staffed bed and the size of the hospital, suggesting that larger hospitals are more resource efficient. Additionally, smaller hospitals tended to have a higher proportion of missing reported data. Accounting for emissions at the hospital-level can help identify priorities for decarbonization strategies. Substantial variation across hospitals suggests the potential for emission reductions without compromising the quality of healthcare services. While larger hospitals contributed more to total emissions, smaller hospitals had lower resource efficiency and higher prevalence of gaps in the data. Standardized data collection is essential to empower hospitals, especially smaller health centers, to identify emission reduction opportunities. 

Hao Yin, Eckel, S.P., Liu, F., Kaur, M., Cohen, G., Hu, H., McConnell, R.S., Sharma, B., 2023a. Estimating Greenhouse Gas Emissions from Hospitals. Lancet Planetary Health under review.

Interaction between Population Aging and Spread of COVID-19 infections

COVID-19 has triggered an unprecedented public health crisis and a global economic shock. As countries and cities cautiously eased restrictions on economic activities following months of worldwide shutdown, the most effective reopening strategies may vary significantly based on their demographic characteristics and social contact patterns. In this study, we employed an extended age-specific compartment model that incorporates population mobility to investigate the interaction between population age structure and various containment interventions in New York, Los Angeles, Daegu, and Nairobi – four cities with distinct age distributions that served as local epicenters of the epidemic from January 2020 to March 2021. Our results demonstrated that individual social distancing or quarantine strategies alone cannot effectively curb the spread of infection over a one-year period. However, a combined strategy, including school closure, 50% working from home, 50% reduction in other mobility, 10% quarantine rate, and city lockdown interventions, can effectively suppress the infection. Furthermore, our findings revealed that social-distancing policies exhibit strong age-specific effects, and age-targeted interventions can yield significant spillover benefits. Specifically, reducing contact rates among the population under 20 can prevent 14%, 18%, 56%, and 99% of infections across all age groups in New York, Los Angeles, Daegu, and Nairobi, respectively, surpassing the effectiveness of policies exclusively targeting adults over 60 years old. In particular, to protect the elderly, it is essential to reduce contacts between the younger population and people of all age groups, especially those over 60 years old. While an older population structure may escalate fatality risk, it might also decrease infection risk. Moreover, a higher basic reproduction number amplifies the impact of an older population structure on the fatality risk of the elderly. The substantial disparities in susceptibility, severity, and mobility among different age groups highlight the crucial need for targeted interventions to effectively control the spread of COVID-19.

Hao Yin, Zhu Liu, Daniel M. Kammen, The Interaction between Population Age Structure and Policy Interventions on the Spread of COVID-19, Infectious Disease Modeling, 2025, https://doi.org/10.1016/j.idm.2025.03.003.

In the GBD-MAPS project, I developed a shiny application to illustrate results on the disease burden from various sources of air pollution worldwide. The objectives of this manual are to provide instructions for creating, exploring, and downloading the global air pollution source-sector databases.