Environmental Engineering Reference
In-Depth Information
The aldehydes are a group of VOCs that have received special attention
in indoor environments because of their irritant effects at relatively low
concentrations. The aldehydes, however, represent only a fraction of a larger
group of organic compounds found to contaminate air in residential and
nonresidential indoor environments. Concentrations of individual VOCs and
SVOCs as described below are very low and, therefore, it is generally
believed that exposure to any individual VOC (other than HCHO) poses
little or no risk of causing acute symptoms in building occupants. Neverthe-
less, because of the large number of VOCs, and to a lesser extent SVOCs,
present, health concerns have been expressed relative to the collective effect
(i.e., additive, synergistic) of exposures to a large number of substances, as
well as substances which are potentially carcinogenic in humans.
A. VOCs in residential buildings
VOCs detected and quantified in U.S. residences include aromatic hydrocar-
bons such as toluene, ethyl benzene,
- isomers of xylene, naphtha-
lene, and methylnapthalene, alkanes such as nonane, decane, undecane,
dodecane, tridecane, tetradecane, pentadecane, and hexadecane, as well as
compounds such as mesithylene, cumene, limonene, and benzaldehyde. Tol-
uene was observed in the highest concentrations (45 to 160
m
- and
p
). With the
exceptions of toluene, xylene, and benzaldehyde, average concentrations of
other individual VOCs were <20
µ
g/m
3
.
Volatile organic compounds and their levels have been characterized in
hundreds of randomly selected German houses. The 57 individual VOCs
identified included straight (
µ
g/m
3
-), branch-chained, and cyclic alkanes, aro-
matic hydrocarbons, chlorinated hydrocarbons, terpenes, carbonyls, and
alcohols. Concentration ranges of individual compounds varied by three
orders of magnitude. With the exception of toluene, mean concentrations
were <25
n
(low ppbv range expressed as mixing
ratios). The average sum of identified VOCs was approximately 0.4 mg/m
µ
g/m
, with most <10
µ
g/m
3
3
,
3
with a range of 0.07 to 2.67 mg/m
. In a study of new and older occupied
apartments, Danish investigators reported summed VOC concentrations in
newer apartment units to average 6.2 mg/m
3
and 0.4 mg/m
in older units.
3
3
B.
VOCs in nonresidential buildings
A number of investigations have been conducted to characterize VOCs in
nonresidential buildings such as offices, schools, and other institutional envi-
ronments. Concentrations of individual VOCs in California office buildings
have been reported to range from 3 to 319
. Major identified com-
pounds included straight, branch-chained, and cyclic alkanes, followed by
a variety of aromatic hydrocarbons, with toluene the most common and
abundant VOC. Chlorinated hydrocarbons, such as tetrachloroethylene,
1,1,1-trichloroethane, and trichloroethylene, were also commonly measured.
µ
g/m
3
