[Environmental and biological monitoring of occupational exposure to perchloroethylene in dry cleaning shops].

Occupational exposure to perchloroethylene (PCE) was studied in a total of 106 workers in 78 dry cleaning shops in the province of Pavia, Northern, Italy. Environmental monitoring was performed by personal passive sampling. The median time weighted average (TWA) level of PCE was 57 mg/m3, i.e., about 30% of the current Threshold Limit Value (TLV) proposed by the American Conference of Governmental Industrial Hygienists (ACGIH). However, in 12 workers exposure exceeded this limit. Biological monitoring was performed via measurement of urinary trichloroacetic acid (TCA), i.e. the exposure index currently used in Italy, and urinary excretion of unmodified perchloroethylene (PCE-U) in samples collected at the end of the half-shift. Median levels of TCA and PCE were 1.03 mg/l and 17.7 micrograms/l respectively. The correlation coefficient between environmental TWA concentrations of perchloroethylene and PCE-U was 0.755 (0.809 after logarithmic transformation), compared to 0.660 for TCA values. The subjects were then classified as "low exposed" and "heavily exposed" according to whether personal exposure was lower or higher than 57 mg/m3, the median TWA value of the whole group. PCE-U levels were significantly correlated to exposure in both subgroups whereas TCA was correlated only in the "heavily exposed subjects", but not in those with lower exposure. The results of the study show that in the majority of dry cleaning shops exposure to PCE was well below the current occupational limits. Nevertheless surveillance of dry cleaners is recommended as nearly 10% of the workers exceeded the environmental and biological limits. Urinary excretion of unmodified PCE appears to be a very reliable indicator for biological monitoring of PCE exposure in dry cleaning and is also significantly correlated to exposure at low levels. The estimated biological equivalent exposure level (BEEL) for PCE-U, corresponding to the current TLV-TWA proposed by the ACGIH, is 55 micrograms/l. Urinary TCA seems to be less suitable for assessment of individual exposure to perchloroethylene in dry cleaners as it is poorly representative of exposure to low levels of the solvent, which is a very common occurrence in this occupational group nowadays.