[ type to search... ]

US population-weighted PM2.5 exposure, by county

Each bar is one U.S. county. Bar width is its population; bar height is its annual mean PM2.5 in µg/m³. Counties are sorted from highest exposure on the left to lowest on the right.

PM2.5: County Health Rankings 2024 release (CDC EPHT, data year 2019 — a pre-COVID, pre-2020-wildfire-surge baseline). Populations: U.S. Census Bureau Vintage 2019 estimates (as of July 1, 2019). Source breakdown on hover/click: EPA's 2020 National Emissions Inventory.

Find your county

Click any bar for a full source breakdown. The pop-weighted mean line shows what the average American actually breathes.

Important caveats

The source breakdown shown on hover and click is primary PM2.5 emitted inside that county, in tons per year, from the EPA's National Emissions Inventory. That is not the same as what determines the concentration on the y-axis.

  • Secondary PM2.5 — sulfates, nitrates, and organic aerosols formed in the atmosphere from SO2, NOx, ammonia, and VOC precursors — is a large share of ambient PM2.5 across most of the US but doesn't appear in primary-emissions inventories.
  • Long-range transport moves smoke and aerosols across state lines. A county's local emissions can be a minor share of the air people in that county actually breathe.
  • Fire/dust years swing the "Wildfires & prescribed burns" and "Dust" categories enormously year over year. The PM2.5 values shown are for 2019 — chosen as a pre-COVID, pre-2020-wildfire-surge baseline so the chart reflects typical exposure rather than a single bad smoke year.
  • Coverage is 3,115 of the ~3,144 U.S. counties and county-equivalents. CHR omits a number of sparsely-populated Alaska boroughs and a few other small areas where PM2.5 monitoring data isn't available — only 4 of Alaska's 29 boroughs and census areas are represented here.