Organic contaminants - Indoor Environmental Quality - page 117

Table 4.14 Dose-Response Model Relationship Between TVOC Exposures and

Discomfort/Health Effects

TVOC concentration
(mg/m 3 ) Response Exposure range

<0.20 No effects Comfort range

0.20-3.0 Irritation/discomfort possible Multifactorial exposure

range

3.0-25.0 Irritation and discomfort;

headache possible

Discomfort range

>25.0 Neurotoxic effects Toxic range

Source: From Molhave, L., Proc. 5th Internatl. Conf. Indoor Air Qual. & Climate , Toronto, 5,
15, 1990.

ish studies, and in part, by USEPA studies at 25 mg/m 3 . Though USEPA
scientists observed a significant increase in headache and a feeling of dis-
comfort, they were unable to confirm neurobehavioral changes. Concentra-
tions of 5 mg/m 3 and 25 mg/m 3 would be approximately 1 and 5 ppmv
toluene-equivalent concentrations. The threshold for acute effects on expo-
sure to submixtures of six to nine of the original 22 VOCs has been reported
to be <1.7 mg/m 3 .

3. TVOC theory application
Danish scientists have proposed a dose-response model to relate exposures
to TVOCs and health effects. These model relationships are summarized in
Table 4.14 . At TVOC exposure concentrations <0.2 mg/m 3 , no acute health
effects are expected, whereas irritant symptoms would be expected in all
exposure cases >3 mg/m 3 . Neurotoxic effects other than headache would be
expected above an exposure concentration of 25 mg/m 3 . In the exposure
range of 0.2 to 3.0 mg/m 3 , both irritation and discomfort would be expected
to occur if other factors, such as temperature and other contaminant expo-
sures, interacted with TVOC exposures. Because of the limited number and
unique nature of contaminants used in their study (buildings vary widely
in VOC types and concentrations), Danish scientists have cautioned that the
TVOC concept should not be used as a generic indicator of potential health
risks in buildings. At best, TVOC concentrations are an indicator of the risk
of nonspecific sensory irritation to relatively unreactive VOCs with a limited
range of vapor pressures.

4. Systematic building studies
A number of investigators have attempted to determine whether SBS-type
symptoms are associated with exposure to TVOCs. No apparent relation-
ships were observed in non-problem Danish municipal and California office
buildings. However, in problem Swedish school buildings, significant posi-
tive correlations were observed between SBS-type symptom prevalence and
the logarithmic value of TVOC concentrations ( Figure 4.6 ) . Significant