WADOHThis feature layer represents 5 kilometers (km) grid cell estimates of fine particulate matter (PM 2.5 ) 24-hour design values from 2022-2024 in micrograms per cubic meter (µg/m3). Spikes in PM2.5 due to wildfire smoke are not included in these calculations, since wildfire smoke exposure is scored separately. Daily average PM2.5 concentrations are estimated by combining the National Oceanic and Atmospheric Administration (NOAA) forecast model with measured concentrations from the Washington Ambient Air Monitoring Network. The NOAA forecast model accounts for emissions, meteorology, and topography. These daily averages are used to calculate 24-hour design values, which are 3-year averages of annual 98 th percentile concentrations (as defined by EPA for comparison to the federal 24-hour PM 2.5 standard). This data was created by the Washington Department of Ecology and sent to the EHD map team. Citation Washington Tracking Network, Washington State Department of Health. Web. "PM2.5 Daily Concentration". Data obtained from the Department of Ecology, 2022-2024 Data. Published September 2025. Contact us at EHDMap@doh.wa.gov if you have questions or comments.ArcGIS FeatureLayerhttps://hub.arcgis.com/datasets/fe8720475c514cc593c60acff1959e9a_0engState of Washington Geospatial Open Data PortalPublicPM2.5 Daily Concentration [Washington (State)]Web servicesWashington (State)Last Modified: 2026-01-15