The COVID-19 Pandemic & More: Actions by all of us protect public healthSep 19, 2022
Colorado’s air quality problems were in the news last week, as the Environmental Protection Agency shifted the status of the Denver Metro/Northern Front Range ozone non-attainment region to severe. The problem of ozone air pollution emerged in Los Angeles with the first documented episode taking place on July 26, 1943. At the time, the genesis of ozone air pollution was unknown and occurring during World War II, there was concern about chemical warfare. Crops were an early victim of the rising ozone problem. The chemist Arie J. Haagen-Smit identified the unknown pollutant as ozone in 1950 and described the chemical reactions leading to its formation as a secondary pollutant in 1952. The key ingredients for ozone formation are nitrogen oxides, emitted by engines; hydrocarbons, emitted by engines and also by some industries, including the oil and gas industry; and sunlight—does that sound like Denver and the Front Range? The kinetics of ozone generation are well worked out—higher temperatures coming with climate change mean more ozone.
Once thought to be a pollution problem unique to Southern California, ozone was soon found in other locations as vehicles became ever more common. Read Smogtown for more on the colorful history of pollution in Los Angeles. Now, ozone is a nationwide problem. Denver ranked seventh nationally in terms of the severity of its ozone problem in the 2022 State of the Air report from the American Lung Association. Our worsening ozone problem can be readily explained: rising emissions of precursors with population growth and more traffic; increasing numbers of oil and gas wells; and summer sunlight and warmer temperatures. Furthermore, the National Ambient Air Quality Standard (NAAQS) for ozone has been tightened.
With regard to the NAAQS promulgated under the Clean Air Act, ozone is the indicator for the complex mixture of photochemical pollutants generated by chemical reactions, as worked out by Haagen-Smit. There is a rich literature on the adverse consequences of exposure to ozone specifically and exposure to photochemical pollution generally. Those familiar with Los Angeles decades ago will recall the throat and eye irritation experienced on landing in Southern California. Experimental exposure to ozone causes reversible reduction of lung function in some people, and that reduction occurs at levels that are found in many locales, including Denver. Evidence also suggests that ozone is associated with mortality, including a time-series study from my Johns Hopkins team that was published in 2004. The most recent comprehensive review by the Environmental Protection Agency found the evidence to be strongest, and supporting causality for a short-term effect, on respiratory health.
Colorado has been taking steps to grapple with ozone pollution. The downgrading of its non-attainment status means that new measures are needed, potentially including use of reformulated gasoline blended to burn more cleanly. Whether use of more costly reformulated gasoline is necessary in summer months is a point of contention between the State and the Environmental Protection Agency. The State Implementation Plan, required to move towards attainment, does not include use of such gasoline based on modeling results.
Protection of public health necessarily involves actions that affect all of us, and sometimes actions that we must all take. Reducing ozone pollution across the Front Range may require paying more for gasoline during the summer months and perhaps reducing vehicle usage. While there may be costs for all, we can anticipate the benefits of cleaner air and fewer ozone alert days. The scientific evidence on the adverse consequences of ozone pollution is certain enough to warrant action.
The COVID-19 pandemic led to government measures with a purpose similar to that of ozone regulation—promoting individual actions by all to protect public health. Mask wearing stands out as exemplary. Face coverings provided protection to others against sprayed droplets and smaller aerosols to a degree. Those wearing N95 or equivalent respirators gained protection for themselves against inhaling infectious aerosols. The degree of protection afforded and the beneficiaries of the protection vary by the risk context set by the state of the pandemic and the exposure circumstances. In the September 8 issue of the New England Journal of Medicine, Dupont and Galea describe these trade-offs using the example of COVID-19 and masking. Their article’s title captures the complexities—Science, Competing Values, and Trade-offs in Public Health. This is a title that can be used over and over again.
On Friday, September 23, the Colorado School of Public Health will have its first Research Exchange Day, organized by Associate Dean Cathy Bradley and Michelle Kuba. Alonzo Plough, Chief Scientific Officer and Vice-President of the Robert Wood Johnson Foundation is the keynote speaker—not to be missed.
Jonathan Samet, MD, MS
Dean, Colorado School of Public Health