PM2.5 (Fine Particulate Matter)
Also known as: PM2.5
What is PM2.5?
PM2.5 refers to atmospheric particulate matter with a diameter of less than 2.5 micrometers. These tiny particles are about 30 times smaller than the width of a human hair and can penetrate deep into your lungs and even enter your bloodstream.
Sources
Major sources include combustion from vehicles, power plants, residential wood burning, forest fires, agricultural burning, and some industrial processes. Indoor sources include tobacco smoke, cooking, burning candles or oil lamps, and fireplaces.
Health Effects
Short-term exposure can cause irritation of the eyes, nose, and throat, coughing, sneezing, runny nose, and shortness of breath. Long-term exposure is linked to premature death in people with heart or lung disease, nonfatal heart attacks, irregular heartbeat, aggravated asthma, decreased lung function, and increased respiratory symptoms.
Protecting Yourself
The most reliable way to reduce your exposure is to monitor the Air Quality Index before spending extended time outdoors. On days when the AQI for PM2.5 is elevated, consider moving strenuous exercise indoors and keeping windows closed if outdoor air is worse than indoor air.
Sensitive groups — including children, older adults, and people with asthma or heart disease — should take extra precautions at lower AQI thresholds than the general public. High-quality air purifiers with HEPA and activated carbon filters can significantly reduce indoor concentrations. You can track current PM2.5 levels for any US city using the search on this site, which pulls directly from EPA AirNow monitoring stations.
EPA Standard
Annual average standard set by the EPA to protect public health.
AQI Scale
US Cities Most Affected by PM2.5
Cities with the most days where PM2.5 was the primary pollutant driving AQI.