Lynda M. Ewers

Clean-up of Lead in Household Carpet and Floor Dust

Methods to remove lead-containing dust were tested on carpets from homes of children with high blood lead and on new carpets artificially contaminated in the laboratory. The household carpets could not be cleaned effectively by repetitive vacuuming with HEPA-filtered cleaners. The lead concentration in the removed dust remained about the same from the initial cleaning (1 min/m2) to the final cleaning (total cleaning time of 10 min/m2). The lead loading on the surface of the carpets often increased during cleaning because vacuuming brought lead from deeper in the carpet to the surface. Over 95% of the total dust was removed from bare wooden floors by dry vacuuming (5 min/m2). For linoleum, more than 75% was removed by vacuuming for 5 min/m2. However, little was removed in vacuuming after the initial two minutes and about 20% was removed in a final wet-washing step. HEPA-vacuuming of the laboratory-contaminated carpets revealed that two of the commercially available vacuum cleaners tested were essentially equivalent and each removed significantly more dust than a third vacuum during a total cleaning time of 10 min/m2. Cleaning for 6 min/m2 was necessary to remove more than 70% of the embedded dust by the two more efficient vacuums. Cleaning efficiencies were about the same for short pile and sculptured carpets. It was concluded that it may be more practical to replace rather than clean carpets. HEPA-vacuum cleaning of carpets was shown to increase lead dust on the surface under some conditions.

A Field Method for Near Real-Time Analysis of Perchloroethylene in End-Exhaled Breath

The field method for near real-time analysis of perchloroethylene (Perc) in breath is simple, fast, and reproducible for Perc breath analysis in field settings and should prove useful in industrial hygiene practice. The method allows Perc monitoring with good specificity to the sub-part per million (ppm) level within minutes of exposure. A commercially available, portable gas chromatograph with a photoionization detector was used in these analyses. Gas chromatograph settings were optimized in the laboratory for measurement of Perc in Tedlar™ bags. Laboratory development of the method included evaluation of the sensitivity, specificity, precision, and speed of analysis for Perc. Replicate aliquots of Perc at concentrations ranging from 0.01 to 100 ppm were used to construct a calibration curve. The mean retention time for Perc was 238 sec. The impact of potential interference by acetone, toluene, isoprene, methanol, ethanol, acetaldehyde, carbon tetrachloride, benzene, or chloroform was evaluated by mixing Perc with each compound and performing analyses. Measurements of Perc in human breath samples collected in Tedlar bags in a workplace setting were made and compared to measurements of the same samples made by an established analytical method using charcoal tubes (National Institute of Occupational Safety and Health [NIOSH] Method 1003). The accuracy, precision, and speed of the gas chromatograph method were determined. Measurements made with the new method were within a margin of ±8.8% (95% CI, n = 6) of measurements made according to NIOSH Method 1003 for field samples in the range of 0.9 to 6 ppm. Method precision was determined by calculating the pooled coefficient of variation for all measurements (replicates = 3) made in the field and was found to be 5.8%.

An Evaluation of Retrofit Engineering Control Interventions to Reduce Perchloroethylene Exposures in Commercial Dry-Cleaning Shops

Real-time monitoring was used to evaluate the ability of engineering control devices retrofitted on two existing dry-cleaning machines to reduce worker exposures to perchloroethylene. In one dry-cleaning shop, a refrigerated condenser was installed on a machine that had a water-cooled condenser to reduce the air temperature, improve vapor recovery, and lower exposures. In a second shop, a carbon adsorber was retrofitted on a machine to adsorb residual perchloroethylene not collected by the existing refrigerated condenser to improve vapor recovery and reduce exposures. Both controls were successful at reducing the perchloroethylene exposures of the dry-cleaning machine operator. Real-time monitoring was performed to evaluate how the engineering controls affected exposures during loading and unloading the dry-cleaning machine, a task generally considered to account for the highest exposures. The real-time monitoring showed that dramatic reductions occurred in exposures during loading and unloading of the dry-cleaning machine due to the engineering controls. Peak operator exposures during loading and unloading were reduced by 60 percent in the shop that had a refrigerated condenser installed on the dry-cleaning machine and 92 percent in the shop that had a carbon adsorber installed. Although loading and unloading exposures were dramatically reduced, drops in full-shift time-weighted average (TWA) exposures were less dramatic. TWA exposures to perchloroethylene, as measured by conventional air sampling, showed smaller reductions in operator exposures of 28 percent or less. Differences between exposure results from real-time and conventional air sampling very likely resulted from other uncontrolled sources of exposure, differences in shop general ventilation before and after the control was installed, relatively small sample sizes, and experimental variability inherent in field research. Although there were some difficulties and complications with installation and maintenance of the engineering controls, this study showed that retrofitting engineering controls may be a feasible option for some dry-cleaning shop owners to reduce worker exposures to perchloroethylene. By installing retrofit controls, a dry-cleaning facility can reduce exposures, in some cases dramatically, and bring operators into compliance with the Occupational Safety and Health Administration (OSHA) peak exposure limit of 300 ppm. Retrofit engineering controls are also likely to enable many dry-cleaning workers to lower their overall personal TWA exposures to perchloroethylene.