Sources of Chemicals in Indoor Air

This example illustrates several things (1) long-term exposure can lead to effects where short-term exposure to the same chemical at the same concentration may not, (2) indoor air quality can adversely affect health, and (3) national regulations are not consistent with regard to protecting indoor air quality. 

In addition to these common sources from consumer products, chemicals can also volatilize from the soil and groundwater beneath structures into indoor air, as shown in figure 10.6. These volatile chemicals are present in the subsurface from releases associated with industrial activities, including leaking underground fuel tanks (e.g., benzene, MTBE, and other petroleum-related chemicals), surface spills (followed by downward percolation of chemicals to groundwater and lateral transport beneath structures), and other environmental releases. 

Historically, evaluation of indoor air quality has been slow to develop, and difficult to quantify. Most of the work done in this area has focused on radon, a naturally occurring radionuclide that can move upwards from the soil as a vapor (i.e., volatilization) and enter the indoor environment, where it can then be inhaled, in much the same way that steam rises from a pot of boiling water. 

This is even more complex when a site is being considered for redevelopment in an impacted area (e.g.. Brownfield sites) where buildings are yet to be constructed. In these cases, all building-related pcu cimeters used in the model must be based on relatively conservative assumptions to ensure protection of human health. Indoor air concentrations have been measured at mcmy of the locations where the model has been used, and predicted concentrations have been shown to be between one and three orders of magnitude (e.g., ten to one thousand times) different from actual measured concentrations. The best the model can work is to be within a factor of 10 of actucd concentrations in indoor ciir. 

Nevertheless, modeling is typically conducted before any indoor air sampling is conducted, largely because of the complexities involved with other contributing sources of chemicals in indoor air (see table 10.3). Public perception is also a consideration, as the need to sample indoor air quality raises the issue of health concerns by those who frequent the building. 

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