Long-term Trends in Ozone Exposure and Attributable Burden in Urban-Rural Areas Worldwide and in the United States from 2000 to 2019

Background: Tropospheric ozone is a harmful air pollutant that is associated with both short- and long-term respiratory and cardiovascular diseases. Ozone exposure is increasing globally, and is expected to continue to worsen, especially in low- and middle-income nations, driven by both emission increases and climate change. While some regions have successfully implemented ozone management policies and consequently seen reductions in ozone and ozone precursor emissions, harmful levels of ozone persist and are expected to worsen in most regions. While estimates of ozone concentrations and attributable health impacts are available at national and regional levels, spatiotemporal and demographic patterns at the subnational levels, especially for urban-rural areas remain limited, particularly for low and middle-income countries. Purpose: To improve understanding of the range in ozone concentrations and associated disease burden within countries, including at the urban-rural and county scales, and how ozone exposure varies by demographic groups. Results of this dissertation may inform national and city governments, international organizations, and global sustainability networks for the purposes of planning, standard and policy setting, and public education.Methods: This dissertation leveraged the recent availability of an ozone surface concentration dataset with sufficient global coverage and at relatively fine spatial resolution (0.1°) to conduct three analyses, in which ozone-attributable mortality for urban-rural areas worldwide and at the county-level in the United States were estimated and spatiotemporal and demographic trends in ozone exposure and attributable burden were evaluated. Each analysis used an epidemiologically-derived health impact function and concentration-response functions and risk information from the Global Burden of Disease Study (GBD) 2019, which conducted a meta-regression of five cohorts from Canada, the United Kingdom, and the United States. In the first analysis, fine resolution ozone concentration estimates, along with fine resolution population estimates, national and subnational baseline disease rate estimates from the GBD 2019 Study, and epidemiologically-derived risk information were used to calculate ozone-attributable mortality in 2019 for urban areas worldwide (including 12,946 cities and densely-populated towns), and their surrounding peri-urban, peri-rural, and rural areas (URCAs or urban-rural catchment areas). Spatial boundaries for cities and urban-rural catchment areas were derived from existing datasets and modified for the analysis. The second analysis similarly estimated ozone exposure and attributable mortality across URCAs worldwide and by region over a 20-year period of 2000 to 2019 and evaluated long-term trends using regression methods. The third analysis evaluate county-level ozone exposure and attributable mortality in the United States, including long-term trends from 2000 to 2019, demographic differences in exposure by race, ethnicity, educational attainment, health insurance status, and income, and examined long-term ozone health risks for areas both in and out of attainment status with EPA’s 2015 short-term ozone standard. This analysis used county-averaged ozone concentrations, baseline disease rates from U.S. vital statistics data, estimates of population from the U.S. Census Bureau, and other demographic data from National Center for Health Statistics. Results: The first analysis estimated 423,100 estimated global ozone-attributable deaths, of which 37% (147,100) occurred in urban areas, where 40% of the world’s population resides, and 56% (254,000) occurred in peri-urban areas (<1 hour from an urban area), where 47% of the world’s population resides. In 2019, three quarters of the ozone-attributable deaths worldwide (77%; 112,700) were found in cities of South and East Asia. City-level ozone-attributable mortality rates varied by a factor of 10 across world regions. The second analysis estimated that ozone-attributable mortality worldwide increased by 46% (n=132,900) from 2000 [290,400 deaths (95%: 151,800, 457,600)] to 2019 [423,100 deaths (95% CI: 223,200, 659,400)]. The fraction of global ozone-attributable mortality occurring in peri-urban areas remained unchanged from 2000 to 2019 (56%), whereas urban areas gained in their share of global ozone-attributable burden (from 35% to 37%; 54,000 more deaths). Cities with concentrations above the World Health Organization peak season ozone standard (60 µg/m3) increased from 89% (n=11,568) in 2000 to 96% (n=12,433) in 2019. The third analysis found that despite decreasing ozone concentrations nationwide from 2000 to 2019, in 2019 the entire U.S. population resided in counties with county-average ozone levels above the World Health Organization peak season ozone standard of 60 µg/m3 (~30 ppb) and are associated with an estimated 14,100 (95% CI: 12,300, 16,100)] deaths nationwide. Compared with other racial and ethnic groups in 2019, Asian and Native Hawaiian/Other Pacific Islander populations had the greatest proportion of population (49%) residing in counties with the highest quintile of U.S. ozone concentrations (56 ppb to 67 ppb), followed by Americans with two or more races and Hispanic populations (45%). Large urban, followed by suburban areas of large urban, areas had the highest ozone concentrations (46 and 43 ppb, respectively) and proportions of ozone-attributable mortality nationwide (30% and 24%). Lastly, ozone concentrations declined more in counties considered to be in attainment with EPA’s 8-Hour Ozone (2015) NAAQS than in nonattainment areas, however ozone-attributable mortality rates were the same magnitude in both areas in 2019 (7 deaths/100,000 population) because of the influence of higher chronic respiratory disease (CRD) rates in attainment areas (140 vs. 100 deaths/100,000 population).Conclusions: These analyses provide much needed and consistent characterization of spatiotemporal trends in ozone concentrations and attributable mortality at subnational scales, including for nearly 13,000 cities worldwide and U.S. demographic groups, over a 20-year period, and the findings provide several valuable public health insights. Results from the first two analyses indicate that ozone exposure is increasing wriorldwide, contributing to disproportionate ozone mortality in peri-urban areas and increasing attributable mortality in urban areas. Ozone levels and attributable mortality were greatest in regions and cities of Asia and African cities; however, higher-income regions, like high-income Asia Pacific and North America, continue to experience high ozone concentrations and attributable mortality rates. This result was further examined in analysis 3, which found that despite decreasing ozone concentrations across the U.S. from 2000 to 2019, ozone exposure continues to contribute to substantial public health burden. Ozone exposure also differed substantially by racial and ethnic groups by U.S. region. All three analyses highlight a need for lowering seasonal average ozone concentrations globally to reduce the global ozone-attributable public health burden. Additionally, prioritizing consideration of demographic factors, including race, ethnicity, and baseline disease in ozone mitigation strategies is important to ensure their equitable public health benefit. Furthermore, strategies aiming to reduce ozone precursor emissions worldwide in areas affecting urban and peri-urban exposure can yield substantial public health benefits. Future work should use more highly resolved estimates of exposure and baseline disease risk to further explore spatiotemporal patterns by population subgroups. Additional studies are also needed to examine both short- and long-term ozone exposure and health impacts.

Author

• Malashock, Daniel

Language

• en

Keyword

• air pollution
• mortality
• cities
• ozone
• urban-rural
• disease burden

Date created

• 2023

Type of Work

• Dissertation

License

• All rights reserved

Rights statement

• In Copyright

GW Unit

• Environmental & Occupational Health

Degree

• Ph.D.

Advisor

• Anenberg, Susan

Committee Member(s)

• Michaels, David
• Gray, George

Persistent URL

•  https://scholarspace.library.gwu.edu/etd/8k71nh850