filling, including minimizing leak paths by securing the bag to the outlet spout and wetting the outside of the bag to prevent surface dust from becoming airborne. Research over the years in a variety of industrial settings has shown that water spray application is effective in lowering respirable dust levels [Mukherjee et al. 1986]. The use of atomization nozzles was shown to be one of the most effective water-spray delivery systems in dust knockdown performance tests. Water sprays lower respirable dust concentrations by knocking down the dust, fibers, and particles, and they also can induce airflow to direct the remaining dust away from the workers.
Other nonventilation engineering controls include many devices developed for the pharmaceutical industry, including isolation containment systems [Hirst et al. 2002]. One of the most common flexible isolation systems is glove box containment, which can be used as an enclosure around small-scale powder processes, such as mixing and drying. Rigid glove box isolation units also provide a method for isolating the worker from the process and are often used for medium-scale operations involving transfer of powders. Glove bags are similar to rigid glove boxes, but they are flexible and disposable. They are used for small operations for containment or protection from contamination. Another nonventilation control used in this industry is the continuous liner system, which allows the filling of product containers while enclosing the material in a polypropylene bag. This system is often used for off-loading materials when the powders are to be packed into drums.
2.4 Administrative Controls
Administrative controls and PPE are frequently used with existing processes where hazards are not well controlled. This could occur when engineering control measures are not feasible or do not reduce exposures to an acceptable level. Administrative controls (which include training, job rotation, work scheduling, and other strategies to reduce exposure) and PPE programs may be less expensive to establish but, over the long term, can be very costly to sustain. These methods for protecting workers have also proven to be less effective than other measures and often require significant effort by the affected workers [ACGIH 2013; DiNardi 2003]. A valuable application of administrative controls is as a redundancy to engineering controls. While the engineering controls provide the primary protection for the worker, the administrative controls serve as back-up should the engineering control fail.
NIOSH recommends that facilities implement the following work practices as part of an overall strategy to control worker exposure to nanomaterials: (1) Educate workers on the safe handling of engineered nanomaterials to minimize the likelihood of inhalation exposure and skin contact. (2) Provide information on the hazardous properties of the materials being handled with instructions on how to prevent exposure. (3) Encourage workers to use handwashing facilities before eating, smoking, or leaving the worksite. (4) Provide additional control measures (e.g., use of a buffer area, decontamination facilities for workers if warranted by the hazard) to ensure that engineered nanomaterials are not transported outside of the work area. (5) Where there is the potential for area or personnel contamination, provide facilities for showering and changing clothes to prevent the inadvertent contamination of other areas (including take-home) caused by the transfer of nanomaterials on clothing and skin. (6) Avoid handling nanomaterials in the open air in a “free particle” state. (7)
Current Strategies for Engineering Controls in Nanomaterial Production and Downstream Handling Processes
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