Indoor Air Quality

History

In the 19th century, concerns regarding indoor environmental quality centered mainly on the odors created by human occupancy. Nevertheless, even as early as 1869, concerns were expressed about the health impacts of insufficient ventilation. The early 20th century witnessed initial health code legislation to address overcrowding and high occupancy in New York City tenements. These ideas about adequate ventilation gradually began to take hold in many Western nations, to the point that the indoors was seen as a refuge from the increasing outdoor air pollution during the Industrial Age.

A culmination of the impact of polluted outdoor air was seen in the pollution inversions near Pittsburgh in 1948 and London in 1952 when polluted air trapped over these cities caused breathing problems for many residents. Some 11,000 deaths were reported during the London episode. The best advice from health authorities at that time was to stay indoors. Since the establishment of the U.S. Environmental Protection Agency's (EPA) Clean Air Act by Congress in 1970, the quality of outdoor air has improved dramatically.

The years following World War II saw significant developments impacting indoor environmental quality. The growth of organic chemistry resulted in new synthetic materials, products, and furnishings being introduced into buildings. Also, there was a boom in housing construction as returning soldiers married and started families, incorporating an increasing array of synthetics within indoor environments.

The oil embargoes of the 1970s engendered efforts to develop energy-efficient homes. Ever-tighter buildings were constructed, and it was soon [Page 392]realized that inadequate ventilation causes problems. These were frequently manifested as moisture and condensation issues, causing mold growth.

This period also witnessed a modest but growing interest within the scientific and engineering communities concerning indoor environmental quality. As this work progressed, a landmark series of studies sponsored by the EPA emerged. These studies found that the indoor levels of a certain large class of pollutants (volatile organic compounds, or VOCs) are nearly always higher than outdoor levels, suggesting that indoor sources are more significant than outdoor sources for these pollutants.

Common Indoor Pollutants

Given the wide range of possible pollutants in the indoor environment, discussion will be limited to what are perceived as the “most significant” pollutants. These can loosely be defined as those causing the most deaths, the largest number of serious injuries or impairments, or widespread irritation or discomfort.

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