Page 438 - Fundamentals of Air Pollution 3E

388 23. Indoor Air Quality

mation in this table is not meant to be representative of typical indoor
concentrations but only examples of measurements obtained by investiga-
tors and reported in the literature.
Airborne material affecting the quality of indoor air may be classified as
gases or particulate matter. Gases which may be potential problems are
radon, CO, NO 2, and hydrocarbons. Particulate matter may come from
tobacco smoke, mold spores, animal dander, plant spores, and others as
shown in Table 23-1. Other factors interact to influence our perception of
indoor air quality, including humidity, temperature, lighting, and sound
level.

IV. EFFECTS OF INDOOR AIR POLLUTANTS

Effects of indoor air pollutants on humans are essentially the same as
those described in Chapter 7. However, there can be some additional pollut-
ant exposures in the indoor environment that are not common in the
ambient setting. From the listing in Table 23-1, radon exposures indoors
present a radiation hazard for the development of lung cancer. Environmen-
tal tobacco smoke has been found to cause lung cancer and other respiratory
diseases. Biological agents such as molds and other toxins may be a more
likely exposure hazard indoors than outside.
Radon gas is formed in the process of radioactive decay of uranium. The
distribution of naturally occurring radon follows the distribution of uranium
in geological formations. Elevated levels have been observed in certain
granite-type minerals. Residences built in these areas have the potential
for elevated indoor concentrations of radon from radon gas entering
through cracks and crevices and from outgassing from well water.
Radon gas is radioactive and emits alpha particles in the decay process.
The elements resulting from radon decay are called radon daughters or
progeny. These radon daughters can attach to airborne particles, which
can deposit in the lung. The evidence supporting the radon risk of lung
cancer comes from studies of uranium mine workers, in whom elevated
rates of lung cancer have been observed. When an analysis of the potential
exposure to radon inside homes was conducted by the U.S. Environmental
Protection Agency, an estimate of 5,000 to 20,000 excess lung cancer deaths
was projected annually (1). The risk is associated directly with increased
lifetime doses; i.e., the longer the time spent living in a residence with
elevated levels of radon, the higher the risk. Indoor levels of radon range
from less than 1 to 200 picocuries per liter (pCi/1). Levels as high as
12,000 pCi/1 have been observed but most levels are much lower. The
U.S. Environmental Protection Agency has established an action level of
4 pCi/1 for indoor radon, and if a home screening test shows concentrations
below 4 pCi/1, no remedial action is suggested.