This indicator measures the average amount of ozone (often called smog) in the air during the most polluted 8 hours of summer days. Ground level ozone is formed when pollutants such as nitrogen oxides (NO_X) and reactive organic gases react with sunlight.

Everyone should be able to live in neighborhoods where it is safe to breathe. When ozone levels in the air are high, it can cause lung inflammation and more serious respiratory issues. Prolonged exposure to high ozone levels can increase the risk of cardiovascular and respiratory diseases, poor birth outcomes, and premature death. People who spend a lot of time outdoors are especially at risk of high ozone exposure, including outdoor workers and adults and children participating in sports and exercise.^{110, 111} For more information on research on Ozone and Health, see the California Air Resources Board and U.S. Environmental Protection Agency’s web resources.

To address high levels of ozone, jurisdictions should adopt a range of strategies to reduce emissions of the chemicals that react with sunlight to become ozone (ozone precursors), reduce urban heat islands that speed ozone formation, and protect residents from pollution.

While local jurisdictions do not have regulatory authority over most smokestack (stationary source) and tail pipe (mobile source) emissions, there are many actions local jurisdictions can take to reduce pollution. They can incentivize or require Low-Emission Vehicles and Freight Facilities in many situations. They can also limit ozone production by helping Reduce Car Use—decreasing tail pipe emissions and other particles released from wear and tear on breaks and tires, and also investing in sidewalks, biking, public transportation, ridesharing and other mobility options. Smart Growth strategies, in particular, can help reduce driving by allowing people to live close to jobs, services and other destinations. They can also work with their local Air Quality Management District to Reduce Emissions from Other Sources, like generators, lawncare equipment, and other stationary sources.

In addition to reducing pollution, it is essential to find ways to protect residents from ozone and other pollutants. Where pollution and people must co-exist, jurisdictions can Reduce Exposure to Pollution by encouraging accurate information collection and developing appropriate responses to air risks. Jurisdictions can promote Cool Communities where buildings, pavement, and other dark surfaces capture heat. Increased temperatures in urban areas speed the process that generates ozone from precursor pollutants. They can use natural systems and heat-reflective materials to keep buildings, pavements, and the urban environment cooler. Finally, jurisdictions should Build Community Power and Connection and partner with communities to address air quality and health issues.

For all strategies, jurisdictions should direct and prioritize efforts for places already overburdened by air pollution, and work to address existing inequities in health. In addition to relieving existing burdens, jurisdictions should identify opportunities to maximize additional health or quality of life benefits that can be achieved in addition to decreased pollution. For instance, Weatherization Programs can improve indoor air quality, reduce asthma triggers, provide job training opportunities, and save residents money. Local governments should prioritize interventions that minimize risk in vulnerable communities, while maximizing co-benefits that meet community needs.