Toxicology of Industrial Compounds

F.A.DE WOLFF ET AL. 5
Figure 1.1 The mean minute volume (1 min −1 ) and the percentage of the minute
volume cleared from solvent (shaded area) during exposure to styrene (left) and 1,1,
1-trichloroethane (right) at increasing degree of workload.
coefficients determine the absorption through the alveolar membrane and
the distribution over the body. Furthermore, exercise is an important
physiological determinant. With increasing exercise, ventilation increases
and, therefore, also the availability of the vapour to the lung per unit of
time. In addition, cardiac output increases during exercise, and this may
affect absorption, distribution and metabolism through enhanced blood
flow.
Finally, the elimination of a solvent which occurs during exposure may
significantly affect the uptake rate. The percentage of the vapour not
retained by the body but exhaled again is dependent on, again,
physicochemical factors such as solubility, but also on the rate of
metabolism (Fiserova-Bergerova, 1985).
In order to demonstrate the different factors which may affect
pulmonary absorption of vapours we have constructed Figure 1.1, based
on earlier work of Astrand et al. (Astrand, 1975). In their studies,
volunteers were exposed to different vapours such as styrene or 1,1,1trichloroethane
at increasing degrees of workload during 2 h.
The first 30 min they were exposed at rest, and then the workload was
increased every 30 min with 50 W. The minute volume, here referred to as
‘supply’, was measured and expressed in 1 min −1 , and the exhaled solvent
concentration was also measured at regular intervals. The shaded area of
the vertical bars in Figure 1.1 indicate the percentage of minute volume
cleared from the solvent, averaged over the observation period. This is
considered to be a measure for pulmonary uptake.