Appendix C 409
products, decline much more slowly. Because of concerns about the
health effects of VOCs, many manufacturers have worked to reduce
the VOC emissions of their products, and some will provide emission
information to their customers.
Some VOCs are suspected or known carcinogens or causes of
adverse reproductive effects. Some VOCs also have unpleasant odors
or are irritants. VOCs are thought to be a cause of non-specific health
symptoms that are discussed subsequently.
The total volatile organic compound (TVOC) concentration, often
used as a simple, integrated measure of VOCs, is defined as the total
mass of measured VOCs per unit volume of air, exclusive of very
volatile (e.g., formaldehyde) organic compounds. Laboratory studies in
which humans have been exposed to mixtures of VOCs under controlled
conditions (Molhave et al. 1986 and 1993) have documented increased
health symptoms at TVOC concentrations of the order of milligrams
per cubic meter of air. A panel of 12 Nordic researchers reviewed the
literature on VOCs/TVOCs and health and concluded that indoor pollu-
tion including VOC is most likely a cause of health effects and comfort
problems and that the scientific literature is inconclusive with respect
to TVOC as a risk index for health and comfort (Andersson et al. 1997).
As an indicator of health effects, the TVOC concentration is inherently
flawed because the potency of individual VOCs to elicit irritancy symp-
toms varies by orders of magnitude (Tenbrinke 1995). The potency for
other potential health effects such as cancer or reproductive effects is
also highly variable among compounds.
Despite these limitations, unusually high TVOC concentrations in
commercial buildings, above one or two mg m-3 (Daisey et al. 1994), do
indicate the presence of strong VOC sources. Further investigations to
determine the composition of the VOCs and/or to identify the sources
may be warranted. The probability of adverse heath or comfort effects
caused by the high TVOC exposures will depend on the composition
of the VOC mixture and on the concentrations of odorous or harmful
compounds.
Radon is a naturally occurring radioactive gas. The primary source
of radon in most buildings is the surrounding soil and rock. Radon enters
buildings from soil as soil gas is drawn into buildings and also enters by
diffusion through the portions of buildings that contact soil. Earth-based
building materials and water from wells can also be a source of radon.
Radon exposure increases the risk of lung cancer (BEIR VI 1998).