Environmental Engineering Reference
In-Depth Information
such as touch and temperature. Stimulation of trigeminal nerves produces
irritation described as burning, stinging, or smarting. Other effects include
changes in heart rate and respiratory frequency, as well as coughing, sneez-
ing, and tearing. The most important outcome of trigeminal nerve stimula-
tion (relative to explaining SBS-type symptoms) is the production of similar
qualitative symptom responses by many different chemical exposures.
2. Exposure studies
Human exposure studies using VOC mixtures have been conducted to test
the TVOC theory. In initial studies, Danish scientists exposed healthy vol-
unteers to a mixture of 22 VOCs weighted in concentration to those observed
in VOC measurements in a Danish residence in the early '80s. These VOCs
and their weighted proportions are listed in
Table 4.13
.
Groups of subjects
were exposed to 5 and 25 mg/m
3
TVOC concentrations (toluene equivalent)
in double-blind experiments for approximately 2.75 hours. Subjects exposed
to VOC mixtures at both concentrations reported significantly greater irrita-
tion than those in clean air as well as diminished performance on neurobe-
havioral tests. These results were subsequently confirmed in additional Dan-
Table 4.13
VOC Mixture Used in Danish
Human Exposure Studies
Compound
Weight ratio
n
-Hexane
1.0
n
-Nonane
1.0
n
-Decane
1.0
n
-Undecane
0.1
1-Octene
0.01
1-Decene
1.0
Cyclohexane
0.1
3-Xylene
10.0
Ethylbenzene
1.0
1,2,4-Trimethylbenzene
0.1
n
-Propylbenzene
0.1
α
-Pinene
1.0
n
-Pentanal
0.1
n
-Hexanal
1.0
Isopropanol
0.1
2-Butanol
1.0
2-Butanone
0.1
3-Methyl-3-butanone
0.1
4-Methyl-2-pentanone
0.1
n
-Butylacetate
10.0
Ethoxyethylacetate
1.0
1,2-Dichloroethane
1.0
Source:
From Molhave, L. et al.,
Atmos. Environ.
, 25A,
1283, 1991. With permission.
