Air Quality

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AIR QUALITY TRENDS ARE MIXED FROM YEAR-TO-YEAR, BUT SOME OVERALL IMPROVEMENT 

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.  

TREND

The most common air quality status for San Bernardino County is the “moderate” range.  In 2023, more than half of the days in the year (54%) were in the “moderate” range. Since 2015, the percentage of days in the moderate range has been generally decreasing. These are being replaced with more days in the “good” range, but also more in the “unhealthy” range.  The median AQI value, where a higher value represents poorer air quality, improved in 2023 compared to the 10-year high in 2020 (71 and 93, respectively).  Both values are in the “moderate” range. 

Air Quality Index Key

Index ValueNameAdvisory
0 to 50GoodNone
51 to 100ModerateUnusually sensitive individuals should consider limiting prolonged outdoor exertion
101 to 150Unhealthy for Sensitive GroupsChildren, active adults and people with respiratory disease, such as asthma, should limit prolonged outdoor exertion
151 to 200UnhealthyChildren, active adults and people with respiratory disease, such as asthma, should avoid prolonged outdoor exertion; everyone else should limit prolonged outdoor exertion
201 to 300Very UnhealthyChildren, active adults and people with respiratory disease, such as asthma, should avoid prolonged outdoor exertion; everyone else should limit outdoor exertion
301 to 500HazardousEveryone should avoid all physical activity outdoors
MIXED AIR QUALITY RATINGS OVER TIME, BUT MEDIAN AQI IS GENERALLY IMPROVING
Percentage of Days When Air Quality Index Was Good, Moderate, Unhealthy for Sensitive Groups, Unhealthy, Very Unhealthy or Hazardous in San Bernardino County, 2015-2024

* Data for 2024 are preliminary and all data have been updated by the data source since previously published on this site. The percentages were calculated on 245 days with AQI data in 2024, whereas the remainder of the years shown were calculated with 365 (or 366) days with AQI data.

Source: U.S. Environmental Protection Agency, Air Data (www.epa.gov/outdoor-air-quality-data)

GEOGRAPHIC COMPARISON

Within peer regions, there is variation in the number of days each region experiences in the six AQI categories – from “good” to “hazardous.” However, the median AQI value, which takes into account all daily AQI readings in a given year, was higher in San Bernardino County in 2023 than all regions compared except Phoenix and Riverside County.  

SAN BERNARDINO AIR QUALITY POORER THAN PEERS, EXCEPT PHOENIX
Regional Comparison of the Number of Days in 2023 when the Air Quality Index was Good, Moderate, Unhealthy for Sensitive Groups, Unhealthy, Very Unhealthy, or Hazardous

Note: The regions are sorted from left to right according to the median AQI 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. Data for 2023 are used to show regional comparisons since 2024 data are preliminary.
Source: U.S. Environmental Protection Agency, Annual AQI by County and Metro Area (https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual)