Air Quality

Unhealthy Air Quality Days

Worsened more than 1 percent from
2016 to 2017

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 42 days in 2016 to 62 days in 2017 (a 48% increase). Asthma hospitalization rates for children, an indicator of poor air quality, varied throughout the county with the highest rates in downtown San Diego, Barrio Logan, Logan Heights and surrounding areas. See more information.


In 2017, total unhealthy air days for all groups increased from 42 days in 2016 to 62 days. The number of unhealthy air days for sensitive groups (people with lung disease, older adults and children) increased by 16 days in 2017, while unhealthy air days increased by 4 days and very unhealthy air days remained at zero. Note that the daily air quality rating is based on the worst monitoring results among 18 stations throughout San Diego County. While unhealthy air quality days fell significantly from 2008 to 2010, the numbers have increased during the past few years.

*2017 data is preliminary.

Data Sources: U.S. Environmental Protection Agency, Air Quality Index Report, 2018

Why is it important?

  • In the San Diego region, a majority of air pollutants come from vehicle emissions and include nitrogen oxides (a precursor to smog), metals, acids, benzene and formaldehyde. Increased public transportation and electric vehicles and can reduce these emissions.
  • According a report by California Breathing, 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.
  • The American Lung Association’s 2017 State of the Air report gave San Diego County an “F” for ozone pollution and a “D” for short-term levels of particle pollution.
  • Want to see today’s air quality in San Diego? Check out the Environmental Protection Agency’s AirNow website.

Children’s Asthma Hospitalization Rates by ZIP Code

(San Diego County ZIP codes with five or more events, rate per 100,000 children, 2016)

0.01 to 50.00
50.01 to 100.00
100.01 to 125.00
125.01 to 150.00
150.01 to 200.00
200.01 to 250.00
250.00 or higher
Less than 5 hospitalizations
No Reported Population Data

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; 2016 American Community Survey 5-year estimates, 2018

  Idea for Change

Air quality is degraded by smog and ozone pollution from transportation. In the American Lung Association’s State of the Air report, San Diego was ranked the seventh dirtiest city in the country, with respect to ozone pollution. Although progress has been made in recent years, local governments must continue to monitor ozone levels in the region, and take proactive policy steps when necessary. Specifically, data provided from the California Environmental Protection Agency, and local air pollution control districts should be utilized more extensively to inform decision-making on transportation and air quality initiatives.

  Bright Spot

The Port of San Diego kicked off a $24 million modernization project to upgrade the Tenth Avenue Marine Terminal in Barrio Logan in order to handle more cargo, create more jobs while also protecting the environment through the installation of smart technology. The project will transition the port’s ground fleet to electric vehicles by installing 30 charging stations and offering incentives to tenants that deploy clean vessels and trucks. The plan also includes converting certain on-site equipment to electrical power to reduce air pollution and noise impacts on the Barrio Logan community.

  What are we measuring?

We measure 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. We also measure children’s asthma hospitalization rates by ZIP code throughout the county. Learn more about the data.