Elimination is the most desirable approach in the hierarchy of controls. As its name implies, the idea behind elimination is to remove the hazard. Eliminating hazards is generally easiest to accomplish at the design stage, while the material, process, and/or facility is being developed. An example of elimination in a process step might be the removal of an incoming inspection step for nanomaterials. An incoming inspection that requires opening a package containing nanomaterials leads to the potential of aerosolization of those materials and therefore a potential hazard to the inspector. Eliminating the inspection step removes the hazard, thus creating an inherently safer process.
2.2 Substitution
Within the hierarchy of controls, the purpose of substitution is to replace one set of conditions having a high hazard level with a different set of conditions having a lower hazard level. Examples of substitution could include replacing a solvent-based (i.e., flammable) material with a water-based material, substituting a highly toxic material for one of lower toxicity, or changing a process’s operating conditions so they are less severe (e.g., reduced pressure). Substitution of a nanomaterial may be difficult since it was likely introduced for its particular properties; however, some substitution may be possible. Substituting a nanomaterial slurry for a dry powder version will reduce aerosolization and provide a level of protection for workers handling the material. The specific nanomaterial should also be assessed because in some cases a less hazardous nanomaterial may provide the desired performance.
2.3 Engineering Controls
Engineering controls protect workers by removing hazardous conditions (e.g., local exhaust ventilation that captures and removes airborne emissions) or placing a barrier between the worker and the hazard (e.g., isolators and machine guards). Well-designed engineering controls can be highly effective in protecting workers and will typically be passive, that is, independent of worker interactions. It is important to design engineering controls that do not interfere with the productivity and ease of processing for the worker. If engineering controls make the operation more difficult, there will be a strong motivation by the operator to circumvent these controls. Ideally, engineering controls should make the operation easier to perform rather than more difficult. A good mantra in designing engineering controls is to “make it easier to do it the safe way.” This also applies to administrative controls that are discussed later. The initial cost of engineering controls can be higher than administrative controls or personal protective equipment (PPE); however, over the long term, operating costs are frequently lower and, in some instances, can provide a cost savings in other areas of the process. The major benefit of engineering controls over administrative controls or PPE is, however, the inherent safety of the worker under a variety of conditions and stress levels. The use of engineering controls reduces the potential for worker behavior to impact exposure levels. Thus, when elimination and substitution are not viable options, the most desirable alternative for mitigating occupational hazards is to employ engineering controls. Engineering controls are likely the most effective and applicable control strategy for most nanomaterial processes.
10 Current Strategies for Engineering Controls in Nanomaterial Production and Downstream Handling Processes
