The Multiple Benefits of Removing Major Outdoor Air Pollution Point Sources

Children’s health is a public health priority, and environmental health is a core tenant of public health. Environmental quality is critical for protecting, sustaining, and promoting human and ecological health. Outdoor air quality is vital to our respiratory, cardiovascular, and neurologic health. Although many natural sources as well as human (or anthropogenic) sources of pollutants are in the air, the largest identifiable outdoor point source of multiple pollutants in our modern society is coal-fired power plants. Their emissions are known to have impacts on local, community, regional, national, and global scales. Power plants simultaneously impact surface water bodies, groundwater aquifers, and soil and sediment downwind and downstream.

Copious research appears in peer-reviewed clinical, public health, environmental sciences, and engineering journals concerning exposure to environmental asthma triggers found in outdoor air. Many triggers also are found in indoor air from outdoor sources and separate indoor sources in homes, schools, and childcare centers. Extensive research also appears in the same peer-reviewed literature concerning associations between those exposures and various measures of adverse outcomes defining asthma-related conditions. Susceptible, vulnerable subpopulations include children and adults across multiple age groups. Moreover, disparities—and thus extra vulnerabilities—have existed among racial and ethnic minorities, between urban and suburban and rural areas, and by gender identity. Documented adverse, asthma-related conditions range from daily and nighttime exacerbations of classic symptoms of asthma—cough, wheezing, chest tightness, shortness of breath—to use of controller and rescue or emergency inhaler prescription medication, to more severe metrics such as emergency room or emergency department visits, hospitalizations, and, sadly, deaths. Documented cases include infants and toddlers (i.e., preschool-age children), in whom making a formal diagnosis is harder.^1–6

The long-term University of Southern California Children’s Health Study cohort of school-age children provided evidence of the increased relative risk for developing asthma when boys and girls lived and played outdoors—three or more team sports (i.e., approximately one per season)—in relatively more polluted communities versus in cleaner communities.⁷ The study researchers also reported similar evidence specific to estimated traffic-related outdoor air pollution exposure at home and at school but did not report any other specific outdoor point, area, or mobile sources of known environmental asthma triggers.⁸

With respect to large point sources of outdoor air pollution, such as coal-fired power plants, studies have been conducted in the United States with respect to respiratory health, including childhood asthma.^9–11 However, evidence remains limited, and, on more serious adverse outcome measures (e.g., asthma hospitalizations),⁹ this evidence does not include indicators of more frequent symptom exacerbation caused by everyday exposure to outdoor air environmental asthma triggers emitted by specific sources, even if controller medications are prescribed and used based on asthma action plans.¹²

REDUCE POTENTIAL EXPOSURE SOURCES TO IMPROVE A CHILD’S LUNGS

In this issue of AJPH, Komisarow and Pakhtigian (p. 881) contribute to the public health and environmental health literature by capitalizing on an opportunity for a “natural experiment.” In their retrospective differences-in-differences study design, the authors examined nearly a decade of data (2009–2017) surrounding the period from March to August 2012, when three large coal-fired power plants closed within the city of Chicago, Illinois. The adverse outcome of interest was emergency department visits for asthma-related conditions (e.g., uncontrolled symptom episodes) among children aged zero to four years. Authors used annual data available at the zip-code level for areas within Chicago. They also determined which zip codes (based on their centroid) were within 10 kilometers (“near”) of one of the three coal-fired power plants versus more than 10 kilometers (“far”) from each of the power plants. Overall, emergency department visits for children aged zero to four years who lived in zip codes closer to one of the three coal-fired power plants in Chicago declined in the years 2014 to 2017 (similar crude and adjusted rates 2012–2014). This finding is notable, even after considering broader economic factors likely affecting crude and adjusted rates for 2009 to 2011. (Similar trends appeared for “near” versus “far” zip codes even if crude rates were approximately twice as high for “near” versus “far” zip codes.)

EVERY STUDY INFORMS FUTURE WORK

In the study by Komisarow and Pakhtigian, the estimated population exposure was limited and ecologic in nature because it explicitly considered only one major outdoor point source of pollution and no other outdoor (e.g., waste incinerators) or known indoor combustion sources of the same (and other) pollutants. However, the point source was properly described and could be repeated—and ideally improved upon—in future research. The authors used government agency data on daily average wind speed and direction (for each day’s fastest two-minute reading at nearby Chicago Midway Airport) and annual reported source emissions, in tons, of multiple targeted criteria pollutants subject to regulation in the United States. The pollutants addressed in this study were particulate matter or PM_2.5 (particulate matter ≤ 2.5 µm), nitrogen dioxide (as emissions of nitrogen oxides or NO_x), and sulfur dioxide. It can be noted how lead, carbon monoxide, and ozone (secondary pollutant not directly emitted by coal-fired power plants) were purposely excluded.

The authors also did not assess other important environmental asthma triggers found indoors and outdoors in typical urban communities. Nevertheless, the study in a major Midwestern US city has merit. The study provided more public health scientific evidence in support of our nation’s decision to move away from larger fossil fuel–based sources of electricity to meet the ever-growing population’s daily demands for energy. The authors also generate ideas for future research in the United States involving more people, especially lower-income racial and ethnic minority subpopulations, who live within shorter distances of power plants planned to be decommissioned or which are already shut down. (Note: Sierra Club’s Beyond Coal Campaign provides updated information for free online at https://coal.sierraclub.org.) Such studies will not prove causation but, at best, statistically significant associations; however, they reemphasize the value of “natural experiments” conducted with appropriate statistical methods and good data. Future research could combine reported source emissions data and more detailed data on power plant operating capacity with daily and annual average government monitoring station data on outdoor air quality and weather as well as similarly available geographic, population, and hospital-based demographics and health data.

FINAL THOUGHTS FOR PUBLIC HEALTH

In their study in AJPH, Komisarow and Pakhtigian reiterated, “Exposure to ambient [outdoor] air pollution, especially among young children, is a serious public health concern” (p. 881). The current federal administration, building on recent federal court decisions, plans to implement and enforce the US Clean Air Act and strengthen regulations concerning emissions of criteria pollutants, toxic air contaminants such as heavy metals, and greenhouse gases from coal- and fuel-fired power plants. As public health professionals—researchers, practitioners, and policy advocates—we must do our part to hold agencies accountable. We must stand by the science (i.e., the peer-reviewed published literature to date) and continue to advance the evidence base with more epidemiologic research with refined exposure assessments. We can support local and state initiatives that work to move away from use of fossil fuels in our society. Efforts include energy efficiency, resource conservation, and sustainable low-carbon, low-emission practices. As a result, we can protect children aged zero to four years before they enter schools, where they will learn how to be safer and healthier citizens of the Earth they inherit.