A new study shows that climate change could cause further increases in ground-level ozone levels by 2050, leaving many parts of the United States out of compliance with air quality standards and increasing public health risks.

Ozone is a reactive gas composed of three oxygen atoms. Although natural, at ground level it often forms as a result of the interaction of volatile organic compounds (VOCs) and nitrogen oxides (NO)._X), are air pollutants.

“Climate change affects ozone formation through a number of complex factors, but rising temperatures are associated with increased ozone levels in polluted areas,” said James East, first author of the research paper. Future of the World. Doğu is a former Ph.D. student at North Carolina State University who is currently a researcher at Harvard University.

“This is in areas that already have higher levels of VOCs and NO air pollution _X As the average temperature increases, ozone content is likely to increase. “Furthermore, climate change is expected to increase natural emissions of VOCs in some regions of the United States, such as the Southeast, further exacerbating this challenge.”

Increasing ozone is important because ground-level ozone can cause a wide range of health problems, such as decreased lung function and inflammation of the airways, and causes hundreds of thousands of deaths each year.

“It’s pretty well known that climate change will increase ozone pollution, but there’s a huge amount of uncertainty about what that increase might look like,” says Fernando García Menendez, corresponding author of the paper and associate professor of environmental engineering at North Carolina State.

“Our goal in this study was to quantify the range of results and get a clearer picture of how climate change will affect ozone pollution in the United States.”

“Atmospheric chemistry is complex, and climate change affects the rate of chemical reactions, the amount of ozone precursors present, and how long ozone remains in the environment,” says García Menendez.

“We have built a number of existing models and combined statistical tools that allow us to take this wide range of variables into account to look at ozone pollution in the coming years.”

Specifically, the researchers looked at how often ozone levels would exceed air quality standards designed to protect public health, how much ozone levels would exceed standards, and how that might change by 2050.

The study’s findings are presented as a range because climate scientists still have some uncertainty about how sensitive the climate is to changes in greenhouse gas concentrations.

The best-case scenario is that the sensitivity of the climate to carbon dioxide is relatively low. If that’s the case, the new study shows that the upper limit of ozone measurements would increase by less than 0.3 parts per billion (ppb) on average. These high measurements may still be below current air quality standards for many places.

“However, even in this best-case scenario, we found that ozone levels are expected to become more variable through 2050, meaning that we still expect an increase in the number of days with extremely high increases in ozone and air quality standard violations.” says East.

The worst-case scenario is that the climate is very sensitive to carbon dioxide. In that case, high-level ozone measurements would increase by more than 2.3 parts per billion on average, the study says. Combined with increased variability, this means there will be a significant increase in the number of days when ozone levels exceed air quality standards in many parts of the country.

“In practice, our research shows that an additional 5 to 13 million people will be exposed to dangerously high ozone in 2050,” says East.

“Currently the state government and the federal government are trying to control ozone levels by reducing the emission of air pollutants,” says García Menendez. “This study suggests that current efforts to reduce emissions may be less effective at meeting ozone standards in many parts of the country, especially in places where air quality standards are already difficult to meet.”

“This study is important for two reasons,” East says. “It primarily contributes to our understanding of how climate change will affect ground-level air quality and therefore human health. Among other things, it contributes to how we evaluate the cost-benefit analysis of climate norms and related technologies.

“Second, by clarifying the spectrum of climate impacts on ozone, we provide important information that can inform policy decisions, such as EPA’s ongoing revision of the air quality standard for ozone.”