The weather page shows the daily air quality and often the critical pollutant is particulates. What are they?
Karen Mostek, Chicago
Dear Karen,The EPA defines particulate matter as the mixture of solid particles and droplets that are suspended in the air. Some, such as dust, dirt and smoke are large enough to be seen, while others can only be viewed through an electron microscope. These particles are released from sources that include construction sites, dirt or gravel roads, smokestacks and fires. Others, such as sulfur dioxide and nitrogen oxides, form as a product of chemical reactions and are emitted from power plants, industries and automobiles. The smallest particles can cause health problems when inhaled because they can enter the bloodstream. These very fine particles are a main component of atmospheric haze that greatly cuts visibility.