Ambient Concentration Trends
Ozone Concentrations
A design value is used to compare the ambient concentrations to the air quality standard. For ozone, the design value is calculated by taking the average of the 4th highest annual 8-hour ozone concentration over three consecutive years. Ozone concentrations are usually highest in the summer. The figure below shows the peak 8-hour ozone design values from 2000 – 2022 in the Sacramento region.
Particulate Matter Concentrations
Particulate Matter – 2.5 microns or less (PM2.5)
For particulate matter for 2.5 microns or less, the design value is calculated using the 3-year average of the 98th percentile of 24-hour PM2.5 concentrations. The figure below shows the PM2.5 concentrations from 2000 to 2021. For federal air quality planning purposes, the figure excludes unusually high fine particulate matter concentrations in 2018 and 2020 due to wildfire smoke impacts. The region has made significant progress in reducing ambient PM2.5 concentrations since 2007, after implementation of the District's wood burning prohibition rule also known as the "Check Before You Burn" program. PM2.5 concentrations are normally higher during the winter months in Sacramento due to the increase in residential wood burning activities (except during wildfire events). Excluding wildfire impacted days, concentrations have remained at or below the federal standard since 2013.
