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ndoor Environmental Quality: particulate matter



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Particulate matter (suggested background study - How Lungs Work), The following text is an excerpt from The State of Queensland, Department of Environment and Resource Management. Copyright (c) 2006, All rights reserved.

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Particulate matter is the term used to describe particles that are suspended in the air. Particles may be solid or liquid and are one of the most obvious forms of pollution as they are visible in the hazes that cover a city or region.

Partiiculate matter and indoor air quality

Graphic adapted from the Environmental Protection Agency, Queensland

Size is the main determinant of the behaviour of an atmospheric particle. The size is usually expressed in terms of the ‘aerodynamic diameter’ which refers to unit density of spherical particles with the same aerodynamic properties, such as the falling speed.

Larger particles (greater than 50Ám) usually only remain in the air for a few minutes and settle near the source. A Ám is one millionth of a metre, or 0.000001m). Smaller particles (less than 10Ám, known as PM10) can remain in the air for several days and can be spread by winds over wide areas or long distances from the original source.

Fine particles (between 0.1-2.5Ám) may remain in the atmosphere indefinitely. Fine particles are capable of scattering light, causing a reduction in visibility.

Particles are generally removed from the atmosphere by rain or when they come into contact with surfaces. Some particles may have other pollutants attached to them, which may react with those surfaces.

Windblown dusts, pollens from plants and sea salts are natural sources of particles in the atmosphere. Bushfires, agricultural and forest hazard-reduction burning release smoke particles into the air.

Combustion processes using coal and other fossil fuels, such as power generation, industrial operations and motor vehicle fuels, emit most of the particulate matter in urban areas. Other noticeable sources of particles include agricultural burning practices (e.g. burning of sugar cane prior to harvesting) and emissions from domestic solid fuel heaters and woodstoves

Environmental effects of particulate matter Particulate air pollution can cause a wide range of damage to surfaces and materials. Merely by requiring more frequent cleaning, particulates can accelerate deterioration. If the particle is corrosive or has other pollutants, for example sulfur dioxide, attached to it then it may also react with or corrode the surface or material.

Health effects of particulate matter Under normal conditions a human respiratory tract in good health is able to deal with inhaled particles without undue stress or long-term effects. In sensitive individuals, or when high levels of particles are present, particulate matter may contribute to increased rates of respiratory illnesses and symptoms.

Studies indicate that such adverse effects are dependent on a number of factors, including:

particle size (whether particles can penetrate the lower airways), the intensity of the exposure, the chemical nature of the particles and their interaction with human tissue, the presence or absence of pre-existing conditions (especially diseases of the respiratory tract), and meteorological factors such as winds, humidity, a temperature inversion, rain or thunderstorms. Air quality goal Inhalable particles (those with diameter less than 10Ám) are commonly understood to pose the greatest risk to human health. There have been extensive studies into the health effects of different levels of particles and pollution mixes. However, no studies have yet determined a threshold value for long-term or short-term exposure below which no adverse health effects are observed.

Some facts on respirable suspended particulate (aka RSP)

The health effects of particles smaller than 10Ám are of particular concern as these particles can enter the human respiratory system and penetrate deeply into the lungs, causing adverse effects. 

PM10 is generated by diesel and petrol motor vehicles and other combustion processes that burn fossil fuels, such as power generation, industrial processes and domestic solid fuel heaters. Smoke particles from bushfires are another sporadic source of PM10 emissions. 

Of the total PM10 fraction those particles with aerodynamic diameters below 2.5 micron, or PM2.5, are now considered to be the major contributor to human health effects, as these particles can penetrate and block the very small passages of the lungs. 

PM2.5 comes from the same sources as PM10, mainly fuel combustion processes. As the particles are so small and fine they can remain suspended in the atmosphere for very long periods. These fine particles are capable of scattering sunlight, resulting in reduced visibility over long distances.

Suggested Reading

Effectiveness of Air Filters and Air Cleaners in Allergic Respiratory Diseases: A Review of the Recent Literature
James L. Sublett, Curr Allergy Asthma Rep. 2011 October; 11(5): 395–402

Exposure to Particulate Air Pollution and Risk of Deep Vein Thrombosis, A. Baccarelli et al, Arch Intern Med. 2008;168(9):920-927.
Rapid DNA Methylation Changes after Exposure to Traffic Particles, A. Baccarelli et al, American Journal of Respiratory and Critical Care Medicine Vol 179. pp. 572-578, (2009)

Particles in Practice, How Ultrafines Disseminate in the Body, B Weinhold, volume 113, number 11,  Environmental Health Perspectives, November 2005
Death by Particles, The Link Between Air Pollution and Fatal Coronary Heart Disease in Women, R. Kessler, volume 113, number 12, Environmental Health Perspectives, December 2005

Particulate Matter Air Pollution and Cardiovascular Disease, Brook, R.D. et al, Circulation. 2010;121:2331-2378

Stewart JC, Chalupa DC, Devlin RB, Frasier LM, Huang L-S, et al. 2010 Vascular Effects of Ultrafine Particles in Persons with Type 2 Diabetes. Environ Health Perspect 118(12): doi:10.1289/ehp.1002237

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