A recent study by the American Lung Association found the Los Angeles and Long Beach area had the worst ozone air pollution in the country.

According to the 2023 State of the Air report published April 19, nearly 120 million people across the United States live in counties that received an F for either ozone or particle pollution in 2023. An F rating indicates a failing level as per the National Ambient Air Quality Standards for PM 2.5, which refers to fine inhalable particles. People of color and those of lower income are disproportionately affected by air pollution and thus at a higher risk for illness, the study found.

When sunlight heats certain compounds found in the atmosphere – many of which can come from human-made pollutants – it forms ozone or smog. These gases are oftentimes byproducts in the combustion process, said Yasmine Agelidis, an attorney at EarthJustice, a nonprofit that represents frontline environmental justice communities.

The American Lung Association also revealed that ozone exposure leads to respiratory infections in the short term, and cardiovascular and lung diseases over time.

Yifang Zhu, professor at the Fielding School of Public Health, said ozone levels are hard to predict or control as they are not directly emitted from a particular source, unlike other climate-warming greenhouse gases. This complicates addressing ozone formation because its levels may also vary based on meteorological conditions, Zhu added.

The issue of ozone in LA is complicated by its mountainous coasts, which prevent pollutants from reaching the atmosphere, said Jochen Stutz, a professor of atmospheric and oceanic sciences.

Zhu said concerns for worsening air pollution in LA will increase with climate change and also economic and population growth. This year will be LA’s second year as the city with the highest ozone levels, according to the 2022 State of the Air report.

“More people – basically more personal use products, more emission sources – it’s gonna all add to this problem in the future,” Zhu said.

Federal and local officials have started to view ozone pollution as an urgent issue.

The Environmental Protection Agency has expressed concern about LA’s level of pollutants since the 1990s when the agency announced the Clean Air Act, which seeks to regulate greenhouse gas emissions. Under the Clean Air Act, California has standardized restrictions on vehicle emissions, which has led to innovative strategies for vehicle electrification and the use of catalytic converters, according to CNBC.

In LA, there has also been an emphasis on sustainable development goals, otherwise known as the 2030 Agenda, with areas focusing on sustainable cities and communities as well as climate action.

Stutz said one of the most significant changes in California is the introduction of the catalytic converter, which suppresses ozone production in cars, but regulations show slow progress toward a final solution. Additionally, in January, Gov. Gavin Newsom has banned the sale of new gas cars by 2035 in order to make a full shift to electric vehicles.

Agelidis said the California Air Resources Board approved the Advanced Clean Fleets Rule as well, which mandates the use of zero-emissions trucks. Agelidis added that she would like to see this commitment for other industry sectors as well.

“It is costing us a lot more now to wait than it would be if we just invested upfront and cleaned up,” Agelidis said.

Zhu said reducing greenhouse gas emissions is a broader concept and that decarbonization – the transition to renewable energy – will bring about lower carbon dioxide emissions alongside the decrease of many other atmospheric pollutants involved in the combustion of fossil fuels. For example, electric vehicle use has reduced tailpipe emissions from vehicles, she added.

Urban forestry through the addition of greenery and alternatives to driving in LA can create a more sustainable landscape as well as reduce emissions and ozone production, said Dustin Herrmann, principal scientist at TreePeople.

“So you make greening a part of creating a streetscape, right? That’s more amenable for walking and biking and cooling bus stops,” Hermann said. “Basically making life outside of a car safe and inviting.”

Zhu said it is still important to protect oneself from the adverse health effects of ozone in the meantime. For one example, he said people should try to avoid exercising at high ozone hours during the late afternoon or move some of their exercises indoors.

“(The) public does have options to protect themselves from being exposed to a high level of ozone concentration, so they can protect their health right to do that,” Zhu said.

Though structural changes will take time to implement, Agelidis said a positive attitude toward zero emissions is necessary for a green future.

“Instead of operating according to the status quo and allowing combustion to continue by just having incremental reductions in pollution, we’re talking about a zero-emissions future. That’s going to require quite a bit of work,” Agelidis said. “It takes an innovative, can-do attitude to persist when you’re dealing with a big structural shift like that.”