How are we doing?
This year the air quality indicator received a mixed rating. San Diego's air quality is shaped by local pollution emissions and regional conditions. Major sources of pollution include vehicle traffic, freight and shipping, and wildfire smoke. San Diego County had fewer poor air quality days overall in 2025 compared to 2024. However, the annual level of particulate matter increased to its highest level in 10 years and exceeded the EPA standard. In 2024, the region had 53.4 pediatric, asthma-related emergency visits per 10,000 children compared to California’s 60.7 visits. Climate change and rising temperatures increase the likelihood of unhealthy air quality caused by wildfire smoke. Wildfires in San Diego were more frequent in 2025-2025 than in 2023, but not as dangerous compared to historical seasons. Efforts to reduce air pollution and mitigating wildfires will improve public health and ensure that the San Diego region can enjoy better air quality.
Rating: Mixed Results
Some improvements alongside ongoing challenges of pollution and wildfires
Air quality index
The U.S. Air Quality Index (AQI) categorizes air quality into six levels, ranging from Good (0-50) to Hazardous (301+), reflecting increasing concerns about pollution. The Equinox Dashboard tracks the number of days each year when San Diego County experiences air quality rated as “Unhealthy for Sensitive Groups”, “Unhealthy”, or “Very Unhealthy”. Sensitive groups include individuals with lung disease, outdoor workers, children, and older adults, though others may also be affected. While the general public is less likely to be impacted by air quality rated as “Unhealthy for Sensitive Groups”, caution is still advised.
In 2024, San Diego County had no days rated as “Very Unhealthy”. However, the number of days rated as “Unhealthy” increased from 0 to 4, while days rated as “Unhealthy for Sensitive Groups” rose from 44 in 2023 to 48 in 2024, indicating that more days posed a risk to the most vulnerable populations.
Increases in days with poorer air quality could be due to a variety of factors. Pollution sources include factories, power plants, vehicles, and wildfires. Heat and droughts can exacerbate polluted conditions because ozone is more efficiently produced in sunny and warm conditions, and wildfires and dust storms are more likely to occur during droughts.
Children's asthma cases in the region
Asthma is a disease that affects the lungs and can be caused by genetic and environmental factors. Poor air quality is known to significantly increase the risk of asthma attacks and subsequent emergency visits. Asthma rates can be a good indicator for understanding a population’s sensitivity to environmental stressors. According to the California Department of Public Health, there were 3,733 cases of asthma-related emergency visits in 2022 among children under 18. The areas of Campo (157.5), College Grove (100.7), Encanto (95.4), Alpine (94.4), and El Cajon (92) had the highest number of emergency visits per 10,000 children. These areas may deal with higher rates of asthma due to exposure to environmental pollution and hazards, such as vehicle exhaust, waste, and hazard sites, as well as challenged socioeconomic conditions, such as poverty and unemployment.
A closer look at particulate matter
PM2.5 (particulate matter) consists of tiny airborne particles or droplets that are thirty times smaller than the diameter of human hair. At high concentrations, PM2.5 can pose health risks, particularly for the respiratory system. Major sources of PM 2.5 include the combustion of fuels such as gasoline, oil, and wood. In San Diego, PM2.5 levels peak between 6 and 9 p.m., likely due to heavy evening traffic.
Concentrations of PM2.5 can vary daily due to factors such as wildfires, drought conditions, traffic levels, weather, and fireworks. To determine annual averages, monthly PM 2.5 readings were summarized. For 2024, the average annual PM 2.5 level in San Diego County was 9.2 µg/m³ (micrograms per cubic meter). Historically, average PM2.5 levels in the San Diego region have remained below the federal standard. However, in February 2024, the Environmental Protection Agency (EPA) updated its standards for PM2.5, lowering it from 12.0 µg/m³ to 9.0 µg/m³ in response to new research linking air pollution to serious health effects.
Understanding other aspects of air quality
Other common pollutants include carbon monoxide, sulfur dioxide, nitrogen dioxide, and ozone. According to the American Lung Association’s 2025 State of the Air report , the region fares poorly due to high annual PM 2.5 rates and recurring high ozone days, making the region rank as the 8th worst county in the nation for ozone pollution.
University of San Diego undergraduate student, Madeline Sit (‘23), developed a historical analysis of types of air pollution in San Diego County and how it relates to car traffic, wildfire, and rainfall. Click on a card below to explore:
Wildfires
San Diego's arid climate and Santa Ana winds create prime conditions for wildfires. Wildfires are a natural part of the region’s ecosystem, but poorly managed land and precarious infrastructure can lead to disastrous wildfires. Wildfire smoke contains particulate matter, carbon monoxide, and nitrogen oxides, all of which can threaten human health. Wildfires can play a significant role in the quick rise of short-term PM 2.5 levels. The tiny, ultrafine particulate matter can irritate the lungs and eyes and enter the human bloodstream. Wearing masks and running ventilation systems that can filter out these particles can help protect against wildfire smoke.
This map shows large wildfires that occurred in the San Diego region between 2001 and 2021. The 2003 and 2007 wildfire seasons were particularly catastrophic. More recently, the San Diego region experienced large wildfires and related poor air quality in 2020.
Related Indicators
- Renewable Energy
- Electric Vehicles
- Outdoor Access
Alternatives to fossil fuels and gas-powered technology help us have a cleaner energy consumption, curbing the emissions of greenhouse gasses and toxic emissions.
Why is air quality important?
High quality of life means the region boasts a thriving economy and a healthy environment accessible to all in the community.
Economy
Poor air quality negatively impacts the economy by reducing labor productivity, increasing health expenditures, and causing crop yield losses. In California, the rising frequency and intensity of wildfires further strain the economy. These events damage infrastructure, crops, and water quality. Additionally, the heightened risk of wildfires has resulted in higher insurance premiums for homeowners.
Environment
Air quality is crucial due to the short- and long-term effects on public health. Air quality measurements reflect air pollution caused by industrial and commercial facilities and individual fossil fuel use, especially for transportation.
Wildfires are a natural part of San Diego’s ecology, but their increasing frequency in recent years is a growing concern for both residents and scientists. Smoke can spread to surrounding neighborhoods, harming the health of residents and local wildlife, significantly impacting short-term air quality over a wide area. Frequent wildfires can also damage habitats faster than they can recover.
Equity
People in urban communities are affected disproportionately by various public health issues such as air quality. Low-income and disadvantaged communities in California experience higher levels of air pollution and negative health effects compared to wealthier communities. These communities also often have higher proportions of people of color. For instance, freeways built directly through low-income neighborhoods expose residents of color to noise and air pollution, adversely affecting their health. The Barrio Logan neighborhood is an example and ranks among the top five most polluted areas in California.
Regional Response
Policies
On February 7, 2024, the EPA strengthened the National Ambient Air Quality Standard.The annual PM₂.₅ standard changed from 12 µg/m³ to 9 µg/m³ to reflect new scientific evidence revealing the serious effects of particulate matter on human health. This change holds many California counties to a tougher standard, including San Diego County.
The California Air Resources Board sets air quality standards that are often more protective than federal standards. However, not all counties meet federal standards for all pollutants. The 2026 Extreme Ozone SIP Revision is a statewide plan designed to help the state attain federal ozone standards.
Rules and regulations by the San Diego County Air Pollution Control District (SDCAPD) can be viewed online.
Projects
The San Diego County Air Pollution Control District’s Office of Environmental Justice leads efforts to reduce community exposure to pollutants. The prioritized communities are Portside Communities and International Border Communities.
The Metropolitan Transit System’s Zero Emissions Bus Program plans to fully transition to zero emission buses by 2040.
The Rooted in Communidad, Cultivating Equity (RICCE) initiative aims to improve air quality, improve road safety, and implement urban greenery in the Barrio Logan, Logan Heights, Sherman Heights, Shelltown, Stockton, Grant Hill, Mount Hope, and Southcrest neighborhoods.
Partnerships
San Diegans come together each year to participate in Clean Air Day which is supported by numerous government agencies, including San Diego Gas & Electric, The San Diego Foundation, San Diego Association of Governments (SANDAG) and many more organizations and community leaders.
The San Diego-Tijuana Air Quality Task Force is a binational initiative for developing measures to improve air quality in the border region.
What are we tracking?
We report air quality by tracking the number of days when San Diego County’s air is considered unhealthy or very unhealthy for the total population as well as when it is unhealthy for sensitive groups as recorded in the EPA Air Quality Index Report. Air pollution levels measured at a particular monitoring site are not necessarily representative of the air quality for an entire county or urban area. We also measure children’s asthma hospitalization rates by ZIP code throughout the county and report on those areas with 5 or more events. For air pollutants, we specifically focus on annual average PM 2.5 levels in the county.