Particulate Matter (PM) are small particles that contain microscopic solids and liquid droplets that are suspended in the air which can be inhaled and cause health effects. PM range in size, but particles less than 10 mm present the greatest threat. Some particles are emitted directly from a source such as, smokestacks, fires, construction sites, etc. and others are a result of complex atmospheric reactions . Today’s map of the day shows the average daily PM 2.5 by county in 2011. From the map we see a three distinct darkly shaded clusters indicating a high amount of daily exposure. The first cluster includes counties in Nevada and Utah. The second cluster includes counties within Colorado, Wyoming, Kansas and Nebraska. The third and most prominent includes counties within various southern states such as, Mississippi, Alabama, Georgia, Tennessee, Kentucky, Indiana, Illinois, Ohio, Pennsylvania, Virginia, West Virginia and North and South Carolina. In contrast, we can see states such as Oregon, Texas, California and Arizona are shaded yellow indicating a lower daily average.