Current Strategies for Engineering Controls in Nanomaterial Production and Downstream Handling Processes/Conclusions and Recommendations

by National Institute of Occupational Safety and Health

CHAPTER 5

Conclusions and Recommendations

Engineered nanomaterials are materials that are intentionally produced and have at least one primary dimension less than 100 nanometers (nm). Nanomaterials have properties different from those of the bulk material, making them unique and desirable for specific processes. These same properties may also cause adverse health effects in workers. Currently, the toxicity of many nanomaterials is unknown, but initial research indicates that there may be health concerns related to occupational exposures. Due to the potential for health effects, it is important to control worker exposures to the extent possible. The following are conclusions and recommendations for reducing the potential for employee exposures during nanomanufacturing processes based on current knowledge.

5.1 General

• Hazards involved in processing and manufacturing nanomaterials should be managed as part of a comprehensive occupational safety and health management plan. Preliminary hazard assessments (PHAs) should be conducted to determine the need for control measures during the planning stage. Hazard assessments should be done during the operation of a facility and regularly updated when any processes change.

• The concept of Prevention through Design (PtD) is to design out or minimize hazards early in the design process. When PtD is implemented, the control hierarchy is applied by designing safety into the work environment to prevent work-related injuries and illnesses.

5.2 Control Banding

• With the absence of OELs, control banding is a potentially useful concept in the risk management of nanomaterials. Control banding is not intended to be a substitute for OELs and does not alleviate the need for environmental monitoring or industrial hygiene expertise.

5.3 Hierarchy of Controls

• The hierarchy of controls should be followed when controlling potential occupational hazards from nanoparticles. Elimination and substitution are at the top of the hierarchy. However, eliminating nanomaterials may not be possible as the nanomaterials were likely chosen because of their unique properties. The manner in which these materials are handled and processed can largely affect the overall safety of the process.

• The substitution of less hazardous materials for those that are a higher hazard should be considered to reduce the risk to workers. Substitution also applies to the form of the product used; for example, a slurry with less exposure potential could be used to replace a dry powder.

5.4 Engineering Controls

• If elimination and substitution are not feasible to reduce hazards, engineering controls should be implemented. These could include local exhaust ventilation, isolation measures, and application of water or other material for dust suppression.

• Engineering controls are likely the most effective control strategy for nanomaterials. Common controls used in the nanotechnology industry include fume hoods, biological safety cabinets, glove box isolators, glove bags, bag dump stations, and directional laminar flow booths. Each of these controls should be carefully designed and operated properly to be effective.

• Preventative maintenance schedules should be developed to ensure that engineering controls are operating at design conditions.

• Non-ventilation engineering controls cover a range of controls (e.g., guards and barricades, material treatment, or additives). These controls should be used in conjunction with ventilation measures to provide an enhanced level of protection for workers. Many devices developed for the pharmaceutical industry, including isolation containment systems, may be suitable for the nanotechnology industry.
  • The continuous liner system allows filling product containers while enclosing the material in a polypropylene bag. This system should be considered for off-loading materials when the powders are to be packed into drums.
  • Water sprays may reduce respirable dust concentrations generated from processes such as machining (e.g., cutting, grinding). Machines and tooling, as well as the material being cut or formed, must be compatible with water. If a fluid other than water is used, attention should be given to the fluid being applied to avoid creating a health hazard to workers.

• A variety of controls are currently commercially available for use.

• A checklist that collects basic process information (e.g., capacity, location, and usage) and control operation and maintenance parameters can optimize and improve existing exposure control. An example checklist is provided in Table 4.

5.5 Administrative Controls

Administrative controls and PPE are frequently used with existing processes where hazards cannot be effectively controlled solely with engineering controls. This could occur when control measures are not feasible or do not reduce exposures to an acceptable level. Administrative controls 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 proven to be less effective than other measures and require significant efforts by the affected workers. A program that addresses the hazards present, employee training, and PPE selection, use, and maintenance should be in place when PPE is used.

Administrative controls and PPE can also be useful for redundancy, especially in high-hazard situations. While engineering controls serve as primary controls, the administrative and PPE controls provide backup.

Employers should implement the following work practices to control worker exposure to nanomaterials:

• Educate workers on the safe handling of engineered nanomaterials to minimize the likelihood of inhalation exposure and skin contact.

• Provide information to workers on the hazardous properties of the nanomaterials being produced or handled with instruction on how to prevent exposure.

• Obtain the material safety data sheets (MSDS) when using nanomaterials from an outside source and review the information with employees who may come in contact with the materials. Given the lack of complete health information of many nanomaterials, the MSDS may not provide adequate guidance and should be assessed by the health and safety office.

• To reduce the potential for release of nanomaterials, consider transferring powdered materials to a slurry, where possible.

• Clean up spills of nanomaterials immediately and in accordance with written procedures. Appropriate PPE should be donned while performing clean-up tasks.

• Provide additional control measures (e.g., a buffer area, decontamination facilities located by the hazard) to ensure that engineered nanomaterials are not transported outside the work area. Place a sticky mat at the exits of production areas to reduce the likelihood of spreading nanomaterials.

• Encourage workers to use hand-washing facilities before eating, smoking, or leaving the worksite.

• 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.

• Prohibit the consumption of food or beverages in work areas where nanomaterials are handled.

• Ensure work areas and equipment, e.g., balance, are cleaned at the end of each work shift, at a minimum, using either a HEPA-filtered vacuum cleaner or wet wiping methods. Dry sweeping or compressed air should not be used to clean work areas. Cleanup should be conducted in a manner that prevents worker contact with wastes. Disposal of all waste material should comply with all applicable federal, state, and local regulations.

• Store nanomaterials, whether suspended in liquids or in a dry particle form, in closed (tightly sealed) containers whenever possible.

• Conduct routine industrial hygiene and medical monitoring to ensure that work practices and engineering controls are effective.

5.6 Personal Protective Equipment

• Because nanoparticles have been found to penetrate the skin, items such as gloves, gauntlets, and laboratory clothing or coats should be worn when working with nanoparticles. Good hygiene practices for wearing the protective equipment should be followed.
• Gloves made of neoprene, nitrile, or other chemical-resistant gloves should be used and changed frequently or whenever they are visibly worn, torn, or contaminated.
• Respiratory protection should be used to reduce worker exposures to acceptable levels in the absence of effective engineering controls, during the installation or maintenance of engineering controls, for short-duration tasks that make engineering controls impractical, and during emergencies.
• Respirators in the workplace should be used as part of a comprehensive respiratory protection program. The program should include written standard operating procedures; workplace monitoring; hazard-based selection; fit-testing and training of the user; procedures for cleaning, disinfection, maintenance, and storage of reusable respirators; respirator inspection and program evaluation; medical qualification of the user; and the use of NIOSH-certified respirators.