Particulate matter

Particulate matter is a mixture of tiny solid particles and liquid droplets suspended in air. Its effects depend strongly on particle size, composition, and how long it remains airborne.

PM2.5: Airborne particles with aerodynamic diameters of 2.5 micrometers or less. This fine-particle fraction can penetrate deep into the respiratory tract.
Air quality index: A public reporting scale that communicates how polluted air is and its potential health effects. Many versions use particulate concentrations to summarize short-term air quality.
Particulate-matter size fractions: Categories of airborne particles defined by aerodynamic diameter cutoffs. Size fractions distinguish fine, coarse, and ultrafine particles in monitoring and health studies.
Air pollution and health: The study of health effects caused by exposure to polluted air. Particulate exposure is associated with respiratory and cardiovascular illness.
PM10: Airborne particles with aerodynamic diameters of 10 micrometers or less. This broader size fraction includes coarse particles that are usually trapped higher in the airways.
Air quality monitoring: The systematic measurement of pollutants in ambient air. Monitoring stations track particle concentrations for forecasts, regulation, and research.
Black carbon: A light-absorbing component of soot produced by incomplete combustion. It is a combustion-related particle component with distinct climate and health effects.
Lung deposition: The settling and retention of inhaled particles in different regions of the lungs. Particle size helps determine which parts of the respiratory system receive exposure.
Aerosol: A suspension of fine solid particles or liquid droplets in a gas. Particulate matter is the particle component of an atmospheric aerosol.
Air pollution: The presence of substances in air at concentrations that harm health or the environment. Particulate matter is one major class of air pollutant.

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