Air Quality

“Moderate” Air Quality the Norm for Past 10 Years

Poor air quality can aggravate the symptoms of heart and lung ailments, including asthma. It can also cause irritation and illness among the healthy population. Long-term exposure increases the risks of lung cancer, cardiovascular disease, and many other health conditions. Poor air quality can also put children’s lung development at risk. This indicator uses the Air Quality Index (AQI) to measure air quality in San Bernardino County, neighboring California counties and peer regions outside of California.

How is San Bernardino County Doing?

Over the past 10 years, the median air quality index value has not changed substantially:
  • Since 2005, a decline in “very unhealthy” and “unhealthy” days of air quality was counteracted by a rise in “moderate” days and a decline in “good” days, resulting in little change to the median air quality index value since 2005.
  • However, air quality has improved substantially from 30 years ago when the median AQI value in 1985 was 108 compared to 75 in 2014.1
  • Most days in 2014 were in the “moderate” range (221 or 61% of days).
  • Compared to air quality in neighboring and peer regions, San Bernardino County falls in the middle, with Riverside County having the fewest days of air in the “good” range and Miami Metro having the most.
Air Quality Index

The Air Quality Index is calculated for ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide. The number 100 corresponds to the national air quality standard for the pollutant.

AQI Values Health Categories
0 – 50 Good
51 – 100 Moderate
101 – 150 Unhealthy for Sensitive Groups
151 – 200 Unhealthy
201 – 300 Very Unhealthy
301 – 500 Hazardous

Source: U.S. Environmental Protection Agency (

Note: These data, accessed July 22, 2015, have been updated from data presented previously.

Source: U.S. Environmental Protection Agency, Air Data (

Note: The regions are sorted from top to bottom according the median air quality index value in each region, from highest to lowest. These data are based on hourly monitor data to assess air quality, resulting in more days of unhealthy air than data that is used by air quality management districts for regulatory compliance, which uses 24-hour monitor values. The 2014 data were accessed July 22, 2015 and are considered preliminary.

Source: U.S. Environmental Protection Agency, Air Data (

Asthma in San Bernardino County
The percentage of San Bernardino County children with an asthma diagnosis has fluctuated since 2001 but has not realized any lasting improvement, currently estimated at 14% in 2013-14. The rate for adults has also not changed dramatically since 2001, estimated at 13% in 2013-14. Poor air quality can contribute to asthma. For example, fine particle pollution can penetrate deep into the lungs and has been linked to a wide range of serious health effects, including premature death, heart attacks, and strokes, as well as acute bronchitis and aggravated asthma among children. In response to the latest research, a 2012 federal court ruling required the EPA to update the fine particle pollution standards (PM 2.5). San Bernardino County is one of seven out of over 3,000 counties nationwide that is anticipated to need to take additional steps to meet the new standard by 2020. The remaining counties can rely on air quality improvements from federal rules already on the books to meet this new standard.

Sources: California Health Interview Survey (; U.S. Environmental Protection Agency (


  1. U.S. Environmental Protection Agency, Air Data (