How climate change could mess up your future run goals
Ozone pollution could worsen under more extreme conditions, scientists warn
Last Tuesday, the day before Global Running Day, New York City saw unhealthy ground levels of ozone. Ozone is a gas made up of three oxygen atoms. You can’t see it or smell it.
In response to these conditions, the National Weather Service’s local station issued an advisory. During specified hours, sensitive groups like children, seniors, and those with asthma were instructed to avoid strenuous activities — like exercise.
That station said the combination of temperatures in the high seventies, sunny skies, and light winds allowed for ozone levels to rise. But, there are other contributing factors to rising levels.
New York City is the largest city in the country. The U.S. Environmental Protection Agency (EPA) says unhealthy levels of ozone are more likely in urban environments: where approximately 80% of Americans live, according to recent Census Bureau data. The harmful, or “bad,” ozone can also be transported from place to place by winds, bringing similar conditions to rural areas.
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Ground level ozone, the ozone that chokes citydwellers, is created by chemical reactions: nitrogen oxides (NOx) and volatile organic compounds (VOCs) reacting in sunlight and heat.
Ozone can be “good” when occurring naturally in the Earth’s upper atmosphere. It helps to shield the planet from the sun’s harsh UV rays. But “bad” ozone is a pollutant, affecting both humans and our ecosystems.
For example, exposure to unhealthy levels of ozone can reduce photosynthesis: the critical process necessary for plants to grow. It can also change water and nutrient cycles and habitat quality: all key components of survival for Earth’s biodiversity. For these reasons and more, it is federal law for the National Park Service to protect air quality resources in America’s parks.
For humans, the pollutants can damage our airways, make our lungs more vulnerable to infection, increase the occurrence of asthma attacks, make it difficult for us to breathe, and cause coughing and sore throats. Ozone exposure can even lead to premature death, when combined with other risk factors.
While unhealthy ozone levels can threaten people of all ages, the EPA says children are at the greatest risk because they are more likely to be active outdoors, have asthma, and have lungs that are still forming.
Still, people with specific genetic traits and those with a reduced intake of nutrients like vitamins C and E are at a greater risk, as well.
To prevent these effects, the EPA advises individuals in these categories closely monitor local conditions (the air quality index), and reduce outdoor active time. “For example, go for a walk instead of a jog,” the agency instructs. That can be kind of a bummer if you’re, say, training for a marathon and have no access to treadmills. There are other steps to take at AirNow.gov.
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Fortunately, air quality trends have shown progress, as reported by the EPA last year. Emissions of most key air pollutants continue to decline from 1990, with VOCs falling to 11.9 million tons. In a separate report from the American Lung Association (ALA), the organization said this year that — for the fourth consecutive year — the number of people living in counties with a failing ozone grade declined by 2.4 million people.
But the ALA report also highlights continuing challenges. Ozone air pollution continues to make breathing harder for more Americans than any other single pollutant. More than 131 million people live in places with failing grades for unhealthy levels of ozone or particle pollution. “This is 11.7 million more people breathing unhealthy air compared to last year’s report,” the report says.
Many of the top cities for ozone pollution are listed in my home state of California, with others in the Southwest.
This pollution is regulated across the country, according to the EPA, using what they call “national ambient air quality standards (NAAQS).” Ozone is one of six air pollutants in the Clean Air Act known as a “criteria air pollutant.” The EPA’s NAAQS apply to the concentration of these criteria air pollutants in outdoor air.
Specific locations are designated by the EPA as “attainment” or “nonattainment” areas based on their levels of air quality. Nonattainment areas need work to improve air quality. To do so, states must draft their own plans to control air pollution and meet standards.
The Clean Air Act requires that the EPA reviews these standards and updates them as needed. In 2020, the EPA decided to retain ozone standards set in 2015. In its “National Ambient Air Quality Standards for Ozone,” the EPA said that it was revising primary and secondary NAAQS for ozone to 0.070 parts per million during an average period of eight hours. The state governments help to track this data, to ensure the health of residents.
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But, other factors are at play. Anthropogenic climate change is worsening droughts, increasing the frequency and intensity of wildfires, and turning up the heat: especially across the West. This year, scientists expect a shift to a La Niña climate pattern, ensuring an even hotter and drier conditions in the West. Plus, ground-level ozone pollution is also a greenhouse gas that can contribute to climate change by trapping heat in Earth’s atmosphere.
The EPA also predicts that higher levels of greenhouse gas emissions from human sources that contribute to the planet’s warming — like vehicle and plant emissions — could increase ozone levels. In a study from 2022, EPA researchers projected scenarios for emissions back in 2011 and in 2040 under current air regulations. While the influences of climate change on air quality were varied based on region and emissions, the agency said its results showed current air pollution control measures can lower ozone concentrations even with climate warming. An analysis using the same future scenarios found a projected increase in deaths that could be attributed to climate impacts on air pollution — but just how many died were based on exposure.
Just over a week ago, researchers at North Carolina State University forecast more dire possibilities. In a new study published in nonprofit American Geophysical Union’s journal “Earth’s Future,” the authors used emissions scenarios — also bias correcting and evaluating modeled and observed ozone “episodes” — to find that climate change could increase the magnitude of the highest annually occurring ozone concentrations by over 2.3 parts per billion on average across the U.S. at mid-century under a high climate sensitivity and moderate emissions scenario. Under a lower climate sensitivity scenario, the rise was held to less than 0.3 parts per billion. The authors also say areas currently meeting standards risk being “pushed into non-compliance due to a climate-induced increase in frequency of high ozone days.”
The study acknowledges that assessing changes is complicated due to uncertainties related to climate sensitivity, climate model response, and internal variability in simulations. The results of the study were presented as a range because of uncertainty about how sensitive the climate is to changes in the concentration of greenhouse gases.
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So, if scientists are worried, have been worried: what’s our takeaway now? I’ve yet to see reaction to this study in many larger outlets (the associated press release was also tweeted out by the United Nations Office for Disaster Risk Reduction), but this headline from earth.com is pretty big for a study and topic with so much underlying uncertainty: “Ozone pollution will harm tens of millions of people at current pace.”
And, while we may be hurdling toward shifts in ozone pollution levels as temperatures rise around the world (we just hit 12 straight months of record high temperatures), lowering emissions and others steps can be taken to determine the scale of unhealthy events.
Before any of these daunting scenarios come to pass, the EPA, scientists, and federal government will hopefully evaluate our understanding of the situation and develop a clearer picture of these ties and how they could shape our future under climate change. We already have seen glimpses of this in China and India, and with wildfire smoke bringing a yellowish haze to the Big Apple last summer.
“Current forecast models indicate Quebec and Ontario have a low to moderate predicted risk of wildfires, with a higher risk of fires, and their corresponding particulate matter, in the western states and Canadian provinces. However, New Yorkers should expect to see elevated ozone levels at least a few more times this summer,” New York State Department of Environmental Conservation Interim Commissioner Sean Mahar said in a statement on Tuesday.
Running outside was one of my only forms of remaining sane during the beginning of the COVID-19 pandemic. I’m sure hikers, skaters, and basketball players can relate. Getting outside is good for everyone: from toddlers to seniors.
Maintaining healthy air — especially in our cities and parks — starts with us.
