No targets are currently set for this indicator.
Particle pollution, also called particulate matter (PM), is a mixture of tiny solids or liquid droplets that includes smoke, soot, dirt, and dust floating in the air. PM2.5 (particles less than 2.5 micrometers) is identified as a pollution problem in many Washington communities and is associated with a number of adverse health impacts. This indicator tracks the percent of the Puget Sound population exposed to air quality that does not meet the state healthy air goal for PM2.5 (20 µg/m3).
Percentage of the Puget Sound population exposed to air quality that does not meet Ecology’s healthy air goal for fine particulate matter (PM2.5) of 20 µg/m3.
Exposure to PM2.5 pollution causes a number of adverse health impacts, particularly to the pulmonary and cardiovascular systems. Its impacts are especially harmful for those with chronic heart and lung diseases such as asthma, bronchitis, and emphysema. PM2.5 exposure can exacerbate these conditions, which can lead to hospitalization or premature mortality. Sensitive populations, such as children and the elderly, also face greater risks of health impacts from PM2.5 exposure.
In 2022, smoke from several fires in Washington’s Cascade Range caused intermittent periods of impaired air quality across the state, with an unusually late and severe smoke episode in western Washington in October. PM2.5 monitors in Clallam, King, Mason, Pierce, Skagit, Snohomish, and Whatcom counties recorded 98th percentile concentrations above the Washington healthy air goal of 20 μg/m3. All monitors representing Island, Jefferson, Kitsap, San Juan, and Thurston counties met the healthy air goal.
In 2021, western Washington experienced a relatively mild wildfire smoke season with only a few summer days with smoke impacts at most monitoring sites. Only three Puget Sound communities recorded a 98th percentile PM2.5 concentration over Washington's healthy air goal of 20 μg/m3: Darrington, Marysville, and South Tacoma. Exceedances of Washington's health air goal were primarily observed during brief episodes of cold and stagnant weather in the winter months. During such conditions, residential wood combustion is a leading source of PM2.5 in these communities.
In 2020, greater than 99% of the Puget Sound population was exposed to impaired air quality. An extensive and severe wildfire smoke episode in late summer caused unhealthy air quality across the state, with many areas reaching the very unhealthy and hazardous ranges of PM2.5 for several days. All but one monitoring site in the Puget Sound watershed (Neah Bay) recorded 98th percentile PM2.5 concentrations above Washington's healthy air goal of 20 μg/m3. During this smoke event, many monitoring sites set records for their highest concentrations ever recorded. Outside of the wildfire season, PM2.5 concentrations were relatively low.
After two consecutive years of prolonged wildfire smoke impacts in 2017 and 2018, calendar year 2019 was marked by a mild wildfire season with very few smoke-impacted days. The exceedances of Washington's healthy air goal of 20 μg/m3 were primarily observed during brief episodes of cold and stagnant weather in the winter months. These episodes occurred with moderate frequency relative to other years. Residential wood combustion is a dominant source of PM2.5 during cold, stagnant weather.
Washington State Department of Ecology Ambient Air Monitoring Network
Washington State Department of Ecology Ambient Air Monitoring Network
Washington Office of Financial Management April 1 Population Estimates
PM2.5 concentrations are measured continuously at monitoring sites throughout the Puget Sound region by the Washington Department of Ecology and its partner agencies. Each site reports a daily average PM2.5 concentration that the surrounding population may be exposed to. Every year, 98th percentile daily concentrations are calculated for each active monitoring site following the process described in 40 C.F.R. Part 50 Appendix N. This metric is the basis of the 24-hour National Ambient Air Quality Standard for PM2.5. The 'exposure to impaired air quality' indicator shows where the 98th percentile of the daily average PM2.5 measurements exceed Washington’s healthy air goal for PM2.5 (20 µg/m3) for a particular year. The 98th percentile is the 8th highest day in a year with complete data, therefore, areas not meeting the healthy air goal have impaired air quality for at least eight days out of the year.
Each of the twelve counties adjoining Puget Sound (Clallam, Island, Jefferson, King, Kitsap, Mason, Pierce, San Juan, Skagit, Snohomish, Thurston, and Whatcom) is assigned the highest 98th percentile PM2.5 concentration of the monitoring sites in that county. This approach is consistent with EPA's treatment of summary PM2.5 data by county where multiple monitoring sites exist in one county (see EPA's Air Quality Design Values). San Juan County, which has no monitoring sites, is assigned the 98th percentile PM2.5 concentration from the Anacortes-O Ave monitor, as a 2019 PM2.5 study by the Department of Ecology indicated that this Anacortes monitor is adequately representative of air quality conditions in San Juan County.
Annual populations for each county are obtained from the Washington Office of Financial Management's April 1 Population Estimates. The percent of the Puget Sound population exposed to air quality that does not meet the state healthy air goal for PM2.5 (20 µg/m3) is calculated as the population of Puget Sound counties with 98th percentile PM2.5 concentrations over 20 µg/m3 divided by the total population of the twelve Puget Sound counties.
PM2.5 refers to fine particulate matter smaller than 2.5 micrometers in aerodynamic diameter.
Daily values refer to the 24-hour average concentrations of PM2.5 measured from midnight to midnight from suitable monitors.
98th percentile is the 8th highest daily value in a year with complete monitoring data.
Future work on this indicator will attempt to develop a complementary measure of air quality that examines trends among environmental justice communities and/or tribal reservations. Identifying whether specific demographic groups are more exposed to poor air quality than others will help provide a more complete understanding of environmental and public health issues experienced across Puget Sound.
PM2.5 concentrations fluctuate year-to-year based on changes in meteorology and emissions. The severity of local and regional wildfires has been a key driver of changes in PM2.5 concentrations in recent years. Outside of wildfire smoke events, air quality is generally improving over time. Successful interventions such as wood stove replacements have lead to reduced PM2.5 concentrations in many communities most impacted by smoke from residential wood combustion. However, when summarizing PM2.5 conditions annually, such progress is masked by the increasing frequency and severity of wildfire smoke events.
The Washington Department of Ecology conducts a number of programs to reduce particle pollution in Washington.
For more information about air quality monitoring in Washington, see the Department of Ecology's Air Quality Monitoring Network webpage and map of current air quality conditions.
EPA's AirNow Fire and Smoke map displays agency PM2.5 air monitoring data along with publicly available air sensor data calibrated using a national correction equation.
Department of Ecology (2009) Health Effects and Economic Impacts of Fine Particle Pollution in Washington
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