Small or fine particulates are less than 2.5 micrometers in diameter. Particulates of this type are found in smoke and haze. These particles can be emitted from natural sources such as forest fires, or they can form in chemical reactions in the air with gases emitted from automobiles, power plants, and other industrial sources. Particulate matter pollution can cause respiratory illness and impair atmospheric clearness. Information source: U.S. EPA.
Small particulates contain microscopic solid or liquid droplets that can penetrate deep into lung tissue and are generally more harmful than large particulates. Health impacts include airway irritation, coughing, decreased lung function, aggravated asthma, and the development of chronic bronchitis. Information source: U.S. EPA.