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Indoor Air Quality (IAQ)

Indoor Particulate Matter

The National Academies of Sciences, Engineering, and Medicine (NASEM) was tasked by EPA to convene a public workshop on February 10-11, 2016 to discuss the state of the science on the health effects of indoor exposure to particulate matter and any associated health impacts. Topics discussed included:

  • Sources of indoor particulate matter
  • Particulate dynamics and chemistry
  • Exposure levels and characterization
  • Exposure mitigation
  • Identified and emerging health concerns
  • Interventions and risk communication

For more information, click below for:

For more information, contact Indoor-PM@NAS.edu.

Particulate matter (also referred to as PM or particle pollution) is a complex mixture of solid and/or liquid particles suspended in air. These particles can vary in size, shape and composition. EPA is especially concerned about particles that are 10 micrometers in diameter or smaller because these particles are inhalable. Once inhaled, particles can affect the heart and lungs and in some cases cause serious health effects. The human health effects of outdoor PM are well-established and are used to set health-based standards for outdoor air (National Ambient Air Quality Standards, NAAQS). PM is also found in all indoor environments. Indoor PM levels have the potential to exceed outdoor PM levels and the NAAQS. However, less is known about the specific impacts of indoor PM on health.

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Health Effects of Inhalable Particles

Exposure to inhalable particles can affect both your lungs and your heart. Many studies directly link the size of particles to their potential for causing health problems. Small particles (less than 10 micrometers in diameter) can get deep into your lungs, and some may even get into your bloodstream. People with heart or lung diseases such as coronary artery disease, congestive heart failure, and asthma or chronic obstructive pulmonary disease (COPD), children and older adults may be at greater risk from PM exposure. Scientific studies have linked PM exposure to a variety of health impacts, including:

  • Eye, nose and throat irritation;
  • Aggravation of coronary and respiratory disease symptoms; and
  • Premature death in people with heart or lung disease.

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Indoor PM Sources


PM found indoors will include particles of outdoor origin that migrate indoors and particles that originate from indoor sources. Indoor PM can be generated through cooking, combustion activities (including burning of candles, use of fireplaces, use of unvented space heaters or kerosene heaters, cigarette smoking) and some hobbies. Indoor PM can also be of biological origin.
For more information on major indoor combustion related sources see also:

  • Stoves, Heaters, Fireplaces and Chimneys
  • Environmental Tobacco Smoke

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Levels of PM Indoors

Indoor PM levels are dependent on several factors including outdoor levels, infiltration, types of ventilation and filtration systems used, indoor sources, and personal activities of occupants. In homes without smoking or other strong particle sources, indoor PM would be expected to be the same as, or lower than, outdoor levels.

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Steps to Reduce Exposure to Indoor PM

  • Vent all fuel-fired combustion appliances to the outdoors (including stoves, heaters and furnaces)
  • Install and use exhaust fans vented to the outside when cooking
  • Avoid the use of unvented stoves, fireplaces or space heaters indoors. If you must use unvented appliances follow manufacturers’ instructions especially related to ventilation..
  • Choose properly sized woodstoves, certified to meet EPA emission standards; make certain that doors on all woodstoves fit tightly.
  • Use appropriate wood in stoves and fireplaces. Check EPA’s BurnWise program for Safe Wood-burning Practices
  • Have a trained professional inspect, clean and tune-up central heating system (furnace, flues and chimneys) annually. Repair any leaks properly.
  • Change filters on central heating and cooling systems and air cleaners according to manufacturer's directions.​

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Additional Resources

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