Air Quality

Unhealthy Air Quality Days

Worsened more than 1 percent from
2015 to 2016

How are we doing?

Air quality received a thumbs-down because the combined number of unhealthy air days and unhealthy air days for sensitive groups increased from 2015 (41 days) to 2016 (42 days). Asthma hospitalization rates for children, an indicator of poor air quality, varied throughout the county with the highest rates in Barrio Logan, Logan Heights and surrounding areas. See more information.


In 2016, unhealthy air days for sensitive groups (people with lung disease, older adults and children) in San Diego County remained at 40 days. Unhealthy air days increased slightly from 1 in 2015 to 2 in 2016 and very unhealthy air days remained at 0. Note that the daily air quality rating is based off the worst of 18 monitoring stations throughout San Diego County each day.

Data Source: Data Source: U.S. Environmental Protection Agency, Air Quality Index Report, 2017

Why is it important?

  • In the San Diego region, a majority of air pollutants come from vehicle emissions. When engines burn fuel, they release chemicals such as nitrogen oxides (a precursor to smog), metals, acids, benzene and formaldehyde. Electric vehicles and increased public transportation can combat these problems.
  • According a report by, some 400,000 San Diegans have lung diseases such as asthma and chronic obstructive pulmonary disease (COPD) and are at heightened risk from air pollution.

Children’s Asthma Hospitalization Rates by ZIP Code

(San Diego County ZIP codes with five or more events, rate per 100,000 children, 2015)

Asthma hospitalization rates for children, an indicator of poor air quality, varied throughout the county with the highest rates registered in Barrio Logan, Logan Heights and surrounding areas.

Data Sources: California Breathing, 2017; Environmental Health Coalition, 2017; 2015 American Community Survey 5-year estimates, 2016

  Idea for Change

Cities should prioritize increasing urban tree cover, especially in low-income and urban areas. Urban tree canopy is shown to improve air quality by intercepting airborne particulates, reducing smog and enhancing respiratory health. The city of San Diego's Climate Action Plan establishes the goal to increase urban tree canopy cover with targets of 15 percent urban tree canopy coverage by 2020 and 35 percent by 2035. The City Council also unanimously approved the Urban Forestry Program Five Year Plan in January 2017. According to the plan, each year 100 large, mature trees have the potential to remove 7 tons of carbon dioxide, 328 pounds of other air pollutants and catch approximately 215,000 gallons of rainwater. Learn more.

  Bright Spot

A network of air quality monitors in San Ysidro operated by Casa Familiar, San Diego State University and the University of Washington is examining exposure to air pollution from idling vehicles at the port of entry as well as the migration of pollutants from Tijuana. The project is funded by the California Office of Environmental Health Hazard Assessment with the goal that data may inform future solutions to environmental justice problems within the area, including reducing vehicle emissions at the port of entry, as well as informing children and other sensitive groups in the community on ways to reduce their exposure to harmful air pollutants. Learn more.

  What are we measuring?

We measure the 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 when it is unhealthy just for sensitive groups as recorded in the EPA Air Quality Index Report. We also measure children’s asthma hospitalization rates by ZIP code throughout the county. Learn more about the data.