Particulate matter, or PM, is defined as any solid or liquid particles that are light enough to remain suspended in the air. Particulate matter is assigned size classifications based on their diameter in microns — PM10, PM2.5, PM1.
PM2.5, which is sometimes referred to as fine particulate matter, is 2.5 microns in diameter or less and can cause serious long-term health damage when inhaled. Particle pollution can come from a variety of sources, including car exhaust from traffic and wildfire smoke. Additionally, some of the respiratory droplets that are responsible for spreading the COVID-19 virus could be classified as PM2.5.
In addition to decreased cognitive function, PM2.5 has been linked to increased symptoms of conditions such as seasonal allergies, COPD, and asthma.