The quality of applied bone cement depends on the chemical composition of the application system.

UNLABELLED: The exothermal reaction of polymethylmethacrylate leads to an extensive interaction between bone cement and the synthetic material of the application system. This chemical reaction changes the structure of the cement and might generate air inclusions. METHODS AND MATERIALS: Two application systems for bone cement made of polycarbonate (PC) and polypropylene (PP) were evaluated. The application systems were mounted in a testing unit. The testing device injects a defined amount of bone cement with a certain pressure. After the injection procedure a microscopic examination was carried out. RESULTS: There were no differences in the size and the design of the used syringes. Forty procedures were carried out. The time frame for application of the cement was 5 min in the PC group and 9 min in the PP group. There was a remarkable interaction between the plastics and the cement with the appearance of numerous air inclusions in the PC group. Barely any interaction was found in the PP group. CONCLUSION: Application systems made of PP enable a prolonged application time and a reduced number of air inclusions. Further research, especially on a molecular level as well as material tests on the quality of the applied bone cement, should be carried out.

Worker exposure to perchloroethylene in the commercial dry cleaning industry.

The National Institute for Occupational Safety and Health (NIOSH) conducted industrial hygiene surveys at 44 commercial dry cleaning facilities in five states as part of an industry wide study to assess the health effects of long-term, low-level exposure to perchloroethylene (PCE). Time-weighted average (TWA) and peak exposures to PCE were determined by collecting personal air samples using activated charcoal tubes and battery-operated pumps. TWA exposures of the machine operators ranged from 4.0 to 149.0 ppm PCE. The geometric mean PCE exposure of the machine operators (22 ppm) differed significantly from the mean exposures of the pressers (3.3 ppm), seamstresses (3.0 ppm), and the concentrations in the front counter areas of the facilities (3.1 ppm). Te geometric mean 5-minute peak PCE exposure during textile transfer was 44 ppm while the mean 15-minute exposure was 33 ppm. No significant differences were found between exposures when either the TWA or the peak data were grouped by geographic location (i.e., state), or by the type of processing equipment used (i.e., "Combination" units vs. separate washing and drying units). Recommendations for work practices, ventilation, maintenance, plant layout and personal protective equipment are presented to reduce PCE exposures to lowest achievable levels.