Handbook of Solvents - George Wypych - ChemTech - Ventech!

15.2.1 Use of breath monitoring 1089
15.2.1.7.1 PERC
Tetrachloroethylene (PERC) is used extensively in the textile industry as a dry cleaning aid
and in metal processing as a metal degreaser. The major concern is on occupational exposures,
but elevated indoor air concentrations of PERC have also been documented. 49 As a result,
the potentially exposed population is very large, with a wide range of exposures. The
uptake of PERC by the lung is high 51,52 because of its high solubility in blood and adipose.
Most of it is eliminated via the lung, with very small amounts metabolized to trichloroacetic
acid (TCA) and eliminated in the urine. 51,52 Even smaller amounts of trichloroethanol in the
urine have been reported. 52
A number of field studies have been published with similar designs, in which breathing
zone air, blood, breath and urine were measured in groups of workers. In addition,
chamber studies allowed measurements under predetermined consistent conditions. The
emerging patterns formed the basis for recommendations for biologic monitoring.
In a study of thirty two workers, 9 end-exhaled air was measured at the beginning of the
first shift of the week, after 15-30 min after the end of the shift on the 3 rd and 5 th day of the
same week, and at the beginning of the first shift of the subsequent week. The authors required
the subjects to hold their breaths for 5 seconds and collected only the last part of the
breath to obtain alveolar air. These measurements correlated with personal breathing zone
samples collected each day. The highest correlation was found between PERC and TCA in
blood at the end of the workweek and the average exposure for the entire week (R 2 =0.953).
Among the non-invasive techniques, PERC in exhaled air collected 15-30 min after the end
of the shift at the end of the week had an R 2 of 0.931, and was followed by TCA in urine
(R 2 =0.909).
In a field study of workers employed in dry cleaning, 53 twenty-four female and two
male subjects were monitored. End-exhaled air and blood samples were collected at the beginning
and at 30 minutes after the end of the 3 rd workday of the week. On that same day,
personal, shift-long, breathing zone samples were also collected from each worker. Urine
samples were collected before and after the shift on a daily basis and analyzed for TCA.
With a mean exposure of 20.8 ppm, no TCA was detected in any of the urine samples (no
detection limit was reported). Among the three exposure parameters (breathing zone air,
blood and end-exhaled air) only the correlation between the PERC concentration in the
blood and in the breath was reported as statistically significant by the authors (R 2 =0.77).
The authors concluded that if the concentration of PERC in blood, 16 hours after the end of
exposure, was below 1000 µg/L, the average exposure was likely to have been below 50
ppm.
A group of thirteen male dry cleaners 40 was followed for a week with daily shift-long
personal (badge) monitoring; mixed-exhaled air collected daily before- and after-shift; and
mixed-exhaled air, blood and urine measurements on the morning after the last shift. Results
indicated strong correlations between PERC concentrations in mixed-exhaled air and
blood (R 2 =0.944), as well as mixed-exhaled air and personal air samples collected either after
the shift (R 2 =0.885), or on the following morning (R 2 =0.770). Mixed-exhaled air measurements
collected either at the end of the last shift of the week (R 2 =0.814) or in the
morning following the last shift (R 2 =0.764) were better indicators of exposure over the entire
week than either blood (R 2 =0.697) or urine (R 2 =0.678). The authors recommended consideration
of mixed-exhaled air as a potential BEI.
In addition to field studies, controlled human exposures to PERC have been reported.
In this type of studies, subjects were exposed to various constant levels of PERC for different
lengths of time with or without exercise. Samples of blood, exhaled air and urine were
collected according to a variety of schedules both during exposure and for varying lengths