This section details the ways that you can protect yourself when working with nanomaterials. Though there are still gaps in the safety and health knowledge literature, this section describes prudent use and handling practices that can protect you not just from nanomaterials, but other potentially harmful substances in the lab.
The most significant exposure route in laboratory settings would be inhalation, and this is the route with the most toxicity data. Respirable exposures would be most likely during the creation or handling of nanomaterials in aerosol, powder, or colloidal suspension. Nanomaterials in composites are not as likely to result in respirable exposures unless they are cut, ground, or degraded. As with all potential exposures, the best place to start is the OSHA “hierarchy of controls”, which goes from engineering controls to work practice controls to personal protective equipment. Engineering controls always come first, since they have the potential to remove the exposure from the work area. Do not consider using personal protective equipment until you have considered all engineering and work practice controls.
A. Engineering Controls
It is a sound assumption that local exhaust ventilation systems (such as laboratory hoods) would effectively remove nanomaterials from the air, based on research about the capture of ultrafine particles by these systems.
To avoid re-entrainment of nanomaterials, EHS recommends High-Efficiency Particulate Air (HEPA) systems in conjunction with local exhaust ventilation. Filtration systems must be able to capture at least 99.97% of monodispersed 300 nm aerosols in order to qualify for HEPA rating. The 300 nm diameter is the most penetrating particle size. Particles smaller than 300 nm (including the nanoscale of 1-100 nm) are actually captured more effectively due to diffusion or electrostatic attraction, and particles larger than 300 nm are captured by impaction and interception. Thus, HEPA filters should effectively capture nanomaterials, however, the filter must sit properly in the housing, or nanomaterials will bypass it and take the path of least resistance.
B. Work Practice Controls
The most effective work practice control is product substitution, with a safer product used in place of a more hazardous one. For nanomaterial research, this is generally not feasible, since the experiment requires the unique nanoscale properties. However, other work practice controls are feasible. Try to use “wet” materials whenever possible, since dry materials are much more likely to cause respirable exposures. Make sure to clean up work areas effectively; use wet methods (not dry sweeping!) and consider the purchase of a HEPA vacuum. As with all laboratory substances, designate food and drink areas far from where you handle materials. If necessary, provide for adequate hand washing, showering, and clean clothes storage areas. Good work practice controls can minimize your exposure potentials from all major routes (respirable, skin contact, and ingestion).
C. Personal Protective Equipment
Earlier, under the Engineering Controls section, it was noted that HEPA filtration systems on ventilation systems could remove more than 99.97% of airborne nanomaterials. Similarly, properly fitted elastomeric respirators with HEPA cartridges (Figure 18.4a) should be able to prevent respirable exposure to airborne nanomaterials. Proper fit is critical, since a poor face seal means the particles and their airstream take the path of least resistance through the seal gaps into the breathing zone. See Chapter 5: Protective Clothing and Equipment for more information about the medical evaluation and fit testing requirements for tight-fitting respirators. Remember that you cannot consider respiratory protection or any other personal protective equipment until feasible engineering and work practice controls are exhausted.
Filtering facepiece respirators such as the N-95 (Figure 18.4b) are capable of filtering nanomaterials, but are prone to gaps and inward leakage. These respirators are not personal protective equipment from exposure to nanoaerosols.
There is currently very little data to indicate whether skin protective equipment such as gloves, Tyvek® sleeves and suits, etc., can protect from nanomaterials. Most available data is from bloodborne pathogen protective equipment, which is challenge-tested with a 27 nm bacteriophage per ANSI (the American National Standards Institute).
Currently, it is unknown whether the skin is a significant route of exposure to nanomaterials. Until more data becomes available, you should use gloves (double gloving for extensive skin contact) and sleeves to prevent skin contact, and change gloves frequently. When handling nanomaterials in solution you should wear gloves that are chemically resistant to the solution or solvent nanomaterials are suspended in.