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# Health Impacts

Air Pollution Effects on Health

Poor air quality has negative implications for human health.

• Exposure to fine particulate matter of less than 2.5 µm in width (PM2.5) is linked to heart attacks and irregular heartbeats, asthma, decreased lung function, and increased irritability of airways which can lead to coughing and difficulty breathing (EPA). [Video on PM2.5 and its health effects.]
• Exposure to surface-level ozone (O3) has similar impacts on public health as PM2.5, causing shortness of breath, coughing, airway inflammation, aggravation of existing lung diseases, such as asthma and chronic bronchitis, and chronic obstructive pulmonary disease (EPA).
• Exposure to nitrogen dioxide (NO2) also can irritate respiratory pathways, aggravating, for instance, asthma symptoms (EPA).
Exposure to outdoor air pollution is responsible for an estimated 4 million premature deaths annually with about another 3-4 million resulting from exposure to indoor air pollution; that is, air pollution is responsible for about 1 in 9 deaths worldwide (WHO, 2018;  Cohen et al., 2017). The majority of deaths are associated with PM2.5. Exposure to O3 is associated with about another 250 thousand deaths annually worldwide (Cohen et al., 2017). In the U.S., outdoor PM2.5 remains the fifth highest mortality risk factor; just in 2015, it was estimated to cause about 88,400 deaths (Cohen et al., 2017). Outdoor O3 was estimated to cause an additional 11,700 deaths (Cohen et al., 2017). For additional information, visit the State of Global Air/2018, which is produced by the Health Effects Institute and the Institute for Health Metrics and Evaluation.

Benefits of Cleaner Air: A recent study by Zhang et al. (2018) presents estimates of the concomitant health benefits (i.e., avoided deaths) of improvements in U.S. air pollution levels of PM2.5 and O3 from 1990 to 2010. Their analyses show that deaths related to air pollution exposure in the U.S. decreased by about 47 percent, dropping from about 135,000 deaths in 1990 to 71,000 in 2010. [press release]. Economically, the benefits of air pollution mitigation more than 30 times exceed the associated costs; although the U.S. dedicates roughly $65 billion annually to improve air quality, there is a resulting$2 trillion in benefits from economic production due to reduced premature mortality (US EPA, 2011). The EPA has quantified the benefits of the U.S. Clean Air Act in a report, entitled "Benefits and Costs of the Clean Air Act 1990-2020, the Second Prospective Study."

How Researchers Are Using Satellite Data in Health Studies

The spatial coverage afforded by satellite data offers increased statistical power that strengthens inference of the relation between pollutants and health outcomes. Here are just a few examples of how health researchers are using satellite-based estimates of surface-level concentrations of formaldehyde (HCHO), PM2.5, and NO2 data to estimate exposure:

• Zhu et al. (2017) used HCHO data to estimate that 6,600-13,200 people in the U.S. will develop cancer over their lifetimes by exposure to outdoor HCHO. The main HCHO source is atmospheric oxidation of biogenic isoprene. However, the HCHO yield is proporational to NOx level, so they note that NOx emission controls to reduce O3 have a co-benefit of reducing HCHO-related cancer risks. Visit the Ozone & Precursors tab for more information on HCHO.
• Brauer et al. (2016) used PM2.5 estimates to estimate the global burden of disease associated with air pollution. Visit the Particulate Matter & Precursors tab for more information.
• Clark et al. (2014) used NO2 data and the land use regression model of Novotny et al. (2011) to estimate that reducing US nonwhites' exposure to NO2 concentrations to levels experienced by whites would reduce coronary heart disease mortality by about 7,000 deaths per year. They argue that their results may aid policy-makers in identifying locations with high environmental injustice and inequality. Visit the Nitrogen Dioxide tab for more information.

For other examples, visit the References tab and the HAQAST website.

Some Milestones of Important Health Research Concerning Air Pollution

Particulate Matter

• 1989: Epidemiological study during closing of Utah Valley steel mill for a labor dispute shows that particulate pollution is associated with hospital inpatient admissions (Pope et al. 1989)
• 1995: American Cancer Society Study is largest prospective cohort study linking ambient air pollution with cardiopulmonary mortality (Pope et al. 1995)
• 1997: Harvard Six Cities Study finds that particle pollution is associated with mortality due to lung cancer and cardiopulmonary disease in 6 U.S. cities (Dockery et al. 1997)
• 2006: Harvard Six Cities Study showed that mortality went down when air quality improved in six U.S. cities (Laden et al. 2006)
• 2012: Harvard Six Cities Study reconfirmed PM2.5-mortality relationships with additional 11 years of follow up (Lepeule et al. 2012)
• 2000-2009: American Cancer Society Study is reanalyzed, updated, and extended in several studies, consistently reporting associations between particulate pollution and mortality (Krewski et al. 2000, Pope et al. 2002, Pope et al. 2004, Krewski et al. 2009)
• 2014: First study integrating epidemiological studies from around the world on ambient air pollution, household air pollution, environmental tobacco smoke, and cigarette smoking (Burnett et al. 2014)
• 2018: PM2.5 linked with diabetes (Bowe et al. Lancet Planetary Health, 2018), cognitive decline (Zhang et al. PNAS 2018), and chronic kidney disease (Bragg-Gresham et al. PLOS ONE 2018).

Ozone

• 2004: Daily O3 exposure associated with mortality in National Morbidity, Mortality, and Air Pollution Study (NMMAPS) (Bell et al. 2004)
• 2009: Longer-term exposure to O3 associated with mortality in American Cancer Society Study (Jerrett et al. 2009)
• 2016: Extended analysis of American Cancer Society study finds that long-term ambient O3 contributes to risk of respiratory and circulatory mortality

Global Burden of Disease from Air Pollution

• 2004: Surface air quality monitors used to estimate 800,000 premature deaths associated with urban PM2.5 (Cohen et al. 2004)
• 2010: Global chemical transport model used to estimate 3.7 million PM2.5 deaths and 700,000 O3 deaths globally (Anenberg et al. 2010)
• 2012: Satellite observations, global chemical transport model, and ground observations combined to estimate 3.2 million PM2.5 deaths and 152,000 O3 deaths (Lim et al. 2012)
• 2016-2018: Methods refined annually, resulting in estimates of ~4 million PM2.5 deaths deaths globally each year (Cohen et al. 201

References & Health Studies using Satellite Data