Hexavalent chromium exposures and exposure-control technologies in American enterprise: results of a NIOSH field research study.

The National Institute for Occupational Safety and Health (NIOSH) conducted 21 field surveys in selected industries to characterize workers' exposures to hexavalent chromium-containing airborne particulate and to evaluate existing technologies for controlling these exposures. Hexavalent chromium Cr(VI) is a respiratory irritant and chronic inhalation may cause lung cancer. Primary evaluation methods included collection of full work shift, personal breathing-zone (PBZ) air samples for Cr(VI), measurement of ventilation system parameters, and documentation of processes and work practices. This study emphasized evaluation of engineering exposure control measures, so PBZ exposures were measured on the outside of personal protective equipment, for example, respirators. Field surveys were conducted in two chromium electroplating facilities, including one where full-shift PBZ exposures to Cr(VI) ranged from 3.0 to 16 times the 1 micro g/m(3)NIOSH recommended exposure limit (REL) despite several engineering controls on the plating tanks. At a painting and coating facility that used Cr(VI)-containing products, full-shift exposures of painters and helpers (2.4 to 55 micro g/m(3)) exceeded the REL, but LEV effectiveness was limited. Other operations evaluated included welding in construction; metal cutting operations on chromium-containing materials in ship breaking; chromate-paint removal with abrasive blasting; atomized alloy-spray coating; foundry operations; printing; and the manufacture of refractory brick, colored glass, prefabricated concrete products, and treated wood products. NIOSH researchers concluded that, in many of the evaluated processes, Cr(VI) exposures at or below the current NIOSH REL are achievable. However, for some processes, it is unclear whether controlling exposures to this range is consistently achievable without respirator use. Some operations involving the application of coatings and finishes may be among those most difficult to control to this range. Most operations judged to be moderately difficult to control to this range involve joining and cutting metals with relatively high chromium content. Nonetheless, exposures in a wide variety of other processes were judged more easily controllable to the current REL or below, or were found to be minimal, including some operations meeting the general descriptions named above but with different specific operating parameters producing lower Cr(VI) exposures.

Factors affecting emission collection by surgical smoke evacuators.

Gaseous and particulate emissions from laser surgery are often controlled by the use of smoke evacuators. Thus it is important that factors affecting the performance of these evacuators be understood. In this study, a tracer gas technique was used to examine a number of factors affecting the performance of smoke evacuators, including evacuator flow rate, distance from the evacuator nozzle to the surgical site, and direction and speed of external air flow in relation to nozzle flow. The tracer gas technique allowed the release of emissions to be visualized with infrared imaging and also allowed the collection efficiency to be assessed quantitatively. The results were demonstrated with the use of a surgical laser system. It was found that the collection efficiency of the smoke evacuator was affected by all the factors studied. Increasing the evacuator flow rate allowed the collection of emissions under conditions in which lower evacuator flow rates had less efficient collection. The speed and direction of external air flow affected collection of emissions greatly. If the air flow was in the same direction as the nozzle flow, efficient collection of emissions at a distance from the emission release point was observed. However, at other angles relative to nozzle flow, the efficiency degraded rapidly with distance from the emission release site. With the use of the surgical laser system, at laser powers of 30 W, the tracer system predicted the collection of emissions. At 60 and 100 W of laser power, higher external air flows and greater attention to nozzle positioning were necessary. Based on the results of this study, conclusions are drawn on how to improve the collection efficiency of smoke evacuators used in laser surgery.