Pollution, health concerns in the Valley

The eight counties of California's San Joaquin Valley rank high among the state's 58 counties for the burdens put upon residents by asthma and air pollution.

Each county's percentile score is the average percentile of all Census tracts within each county, representing the percentage of all Census tracts in California that have a lower score. PM 2.5 is fine inhalable particles that measure 2.5 micrometers in diameter. By comparison, the average human hair is 50 to 70 micrometers in diameter.
Chart: Tim Sheehan and Marisol Herrera / Central Valley Journalism CollectiveSource: California Office of Environmental Health Hazard Assessment's CalEnviroScreen 4.0Created with Datawrapper