Targeted Regulation Can Reduce the Frequency of High-Ozone Events
Author: Christoher Holt and Joshua Linn
Ground-level ozone causes smog, exacerbates asthma and other respiratory conditions, and damages ecosystems. Under the Clean Air Act, the US Environmental Protection Agency sets standards for ozone concentrations, and EPA may strengthen those standards this year. Cap-and-trade programs, which put a limit on the emissions that are allowed in a given jurisdiction, also have been an important tool in reducing ozone levels by reducing emissions of nitrogen oxides (NOx), a key chemical ingredient in ozone formation. Yet, although EPA standards and cap-and-trade programs have reduced NOx emissions and ozone levels, many parts of the country continue to violate the ozone standards. To reduce ozone violations, EPA could continue tightening emissions caps and expanding the group of emitters to whom the caps apply. round-level ozone forms through a complicated process. Under hot and sunny conditions, volatile organic compounds react with NOx to form ozone. The amount of ozone that forms depends on concentrations of these volatile organic compounds and NOx, as well as weather conditions. Major sources of NOx emissions include power plants, industrial facilities, and vehicles. EPA set the current ozone standard in 2015. An area’s air quality violates the standard if the ozone concentration exceeds a certain limit too frequently. Over the past two decades, NOx emissions from power plants have decreased substantially, thanks partly to the EPA cap-and-trade programs that now cover most of the eastern United States. The precipitous decline in NOx emissions has, as intended, reduced ozone levels and high-ozone events