The Air We Breathe – Part 1
This two-part article examines indoor air quality, its health effects, its common sources, and how we can improve the quality of the air we breathe indoors. Part 1 provides an overview of indoor air quality, its main pollutants and common sources. Part 2 discusses the health effects of indoor air quality and what we can do to mitigate the ill effects of poor air quality. – Ed.
By John E. Jernstad
Mount Kisco, NY
The development of civilized societies has driven people indoors. While the problems associated with burning fossil fuels for cooking and heating indoors have been noted for thousands of years, industrial development and the call for energy efficiency has created buildings with heavy insulation and poor ventilation[1]. The result has been indoor air quality levels that can easily become more seriously polluted than outside air. While ambient air pollution is always a hot topic in both policy and public discussion, indoor air quality (IAQ) has been steadily declining as more people spend more time indoors and office technology development continues to expand the sources of indoor air pollution.
On average, people today spend approximately 90% of their time inside buildings[2]. With the exception of industrial spaces that might have a special set of circumstances, IAQ in residential, commercial and institutional buildings, of which IAQ is generally referring to, can have an immense impact on health and wellness. An adult breathes 10-20m3, or about 20 to 25kg of air, per day, compared to 3-4kg of food intake[2]. Since the human body processes far more air than food or other media through which outside elements can deliver their effects, even small concentrations of contaminants can be a cause for concern. Poor IAQ can have an especially detrimental effect on children, the elderly and other groups whose health may already be compromised.
For centuries, controlling IAQ meant dealing with bad odors, smoke, dampness and infectious diseases. In addition, indoor spaces were ventilated in order to control body odors (“bioeffluents”) since the 18th century. However, the oil crisis of the 1970’s meant building were increasingly designed to be energy efficient, a byproduct of which were tighter buildings with less ventilation[2]. Better instruments have enabled the detection of hundreds of organic compounds in the air, which can be classified into gases or particulate matter. Microbial contaminants and their organic products have also come under increasing scrutiny.
Types of Pollutants and Common Sources
Gaseous air pollutants form a major component of both outdoor and indoor air and are widely recognized to cause or exacerbate health issues. Main pollutants that often come indoors from the outside are sulfur dioxide (SO2), nitrogen dioxide (NO2), and carbon monoxide (CO) along with ozone, a byproduct of various processes[3]. The main source of SO2 is fossil fuels, while NO2 is produced from industrial sources such as power stations and CO is produced in large part by automobiles. Indoor sources, however, are often more significant contributors of pollutants. Poorly vented space heaters and gas cooking appliances produce CO, CO2 and NO2 gasses.
Another group of gaseous pollutants are volatile organic compounds (VOCs), a subgroup of organic pollutants that are one of the main causes of indoor air pollution problems and are especially prominent in indoor environments. VOCs are carbon-based compounds that exist as vapors at room temperature[1]. Hundreds of mainly hydrocarbons and hydrocarbon derivatives are present indoors, including aliphatics, aromatics, alkylbenzenes, and ketones. VOCs concentrations can be up to ten times higher indoors than outdoors[4]. VOCs can be emitted by thousands of products including paints, cleaning supplies, pesticides, building materials, office equipment, appliances, markers, and numerous other common household and office products.
Radon is another significant indoor pollutant. A colorless, odorless and radioactive gas, radon is produced through radium decay, which in turn is the product of uranium decay[1]. Uranium is ubiquitous in rocks and soil, and is the main source of indoor radon that enters homes through floors, walls and drains. Well water can also be another vector for radon. While radon itself is a gas, the danger it poses comes from the solid particles produced when radon decays, such as polonium-218 and polonium-214, which emit alpha particles and gamma rays. Particles emitted through radon decay can penetrate into the lung when inhaled and damage genetic materials and organic tissues.
Various other particulate pollutants are found in indoor environments. Tobacco smoke continues to be the leading contributor of indoor particulate pollution[5], followed by various indoor combustion sources such as space heaters, stoves and food preparation appliances. Fine particles from the outside can also readily enter indoor spaces. In addition, human activity can also increase the indoor level of particulate matter. While activities such as vacuuming do not expand the total amount of particles, it can “stir up” resting particles resulting in a higher concentration of particle pollutants suspended in the air.
Especially of concern to people working in office environments are ozone and lead. Common office equipment such as copying machines and printers as well as air cleaners and ion generators can emit ozone[5]. While lead is less of a concern today due to stricter regulations, humans can be exposed to lead through older paint and water pipes.
In addition to gases and particles, biological contaminants also form a significant class of indoor pollutants. Damp and mold are found in both residential and commercial spaces, associated with various organic matter such as wall coatings, wood, fabrics and food[5]. In addition to the obvious effects of infection, bacterial and fungi have been associated with a wide range of illnesses. Their proliferation can sometimes even be exacerbated by measures designed to control other aspects of IAQ. According to a study of IAQ levels in a condominium in Hawaii, researchers founds that air condition systems may be potential sources of microorganisms[6]. While the level of fungi present indoors and outdoors did not vary significantly, homes with air conditions systems were found to have higher concentration of bacteria. These concentrations were significant enough to appear in health assessment questionnaires.
1. Oanh, N.T.K. and Y.-T. Hung, Indoor air pollution control. Handbook of environmental engineering, ed. L.K. Wang, N.C. Pereira, and Y.-T. Hung2005, Totowa, N.J.: Humana Press. xviii, 526 p.
2. John Wiley & Sons. and Retcaco Inc., Kirk-Othmer encyclopedia of chemical technology, 1987, Wiley,: New York, NY.
3. Ayres, J.G., Health effects of gaseous air pollutants. Issues in Environmental Science and Technology: Air pollution and health, 1998. 10: p. 1-20.
4. EPA, An introduction to indoor air quality (IAQ): Volalite organic compounds (VOCs). Basic Information on Pollutants and Sources of Indoor Air Pollution, 2011.
5. Harrison, P.T.C., Health effects of indoor air pollutants. Issues in Environmental Science and Technology: Air pollution and health, 1998. 10: p. 101-125.
6. Kodama, A.M. and R.I. McGee, Airborne Microbial Contaminants in Indoor Environments. Naturally Ventilated and Air-Conditioned Homes. Archives of Environmental Health, 1986. 41(5).
It is nice post and i found some interesting information on this blog. Keep it up