Evaluation and Control of Perchloroethylene Exposures during Dry Cleaning

Abstract

A study was conducted at a large, commercial dry cleaner to evaluate the control of worker exposure to perchloroethylene (PERC) and provide recommendations to reduce exposure. This shop used a dry-to-dry machine that had a refrigerated condenser, which operated during the dry cycle, as the primary vapor recovery device. A small fan that was ducted to a carbon canister was the secondary vapor recovery device. When the machine door was opened, a microswitch energized the fan to draw PERC-laden air from the cylinder through activated carbon. These two controls operated independently. Three of the six employees were sampled. The machine operator, who had the highest exposures, was exposed to between 13 and 19 ppm time-weighted average (TWA) PERC, primarily from loading/unloading the dry cleaning machine. Real-time monitoring revealed that average PERC exposure while loading the machine was much higher than while unloading (846 versus 271 ppm). Real-time measurements taken near the carbon canister showed that very high concentrations of PERC (approximately 1500 ppm) were blown into the work environment each time the machine door was opened. The carbon canister was ineffective at capturing PERC in the exhausted air. The average exposure to the operator during 7 minutes of maintenance was approximately 22 ppm TWA. The highest instantaneous maintenance exposures occurred during lint trap cleaning and peaked at over 200 ppm. Controls at this shop maintained exposures to PERC below 25 ppm TWA, the exposure concentration that the Occupational Safety and Health Administration encourages dry cleaners to follow. The National Institute for Occupational Safety and Health recommends controlling PERC to the lowest feasible concentration. Several measures could be taken to reduce exposures further. Modifications to the secondary vapor recovery device or use of local exhaust ventilation could drastically reduce exposure during loading/unloading (the main source of exposure). By controlling and eliminating exposure during loading and unloading, operator exposure could be reduced approximately two-thirds. Most of the findings and recommendations provided at this shop apply to many other dry cleaning shops across the country that use similar equipment and work practices.