Several factors affect exposure to nanomaterials:
The concentration, duration, and frequency of exposure to nanoparticles all affect user exposure.
In addition, the ability of nanoparticles to be easily dispersed as a dust (e.g. a powder) or an airborne spray or droplets will impact exposure of the users.
Use of protective measures such as engineering controls (e.g. fume hoods) and personal protective equipment (e.g. gloves) can reduce user exposure.
Job-related activities may also influence user exposure:
Active handling of nanomaterials as powders on the benchtop pose the greatest risk for inhalation exposure; NIOSH recommends the use of HEPA filters, either in respirators or local ventilation equipment to control such powders
Tasks that generate aerosols of nanomaterials from slurries, suspensions, or solutions pose a potential for both inhalation and dermal exposure. In some cases, it has been found that nanomaterials have penetrated both gloves and skin.
Clean-up and waste disposal of nanomaterials may result in exposure if not properly handled. Maintenance and cleaning of production systems or dust collection systems may result in exposure if deposited nanoparticles are disturbed.
Machining, sanding, drilling, or other mechanical disruptions of materials containing nanomaterials may lead to aerosolization.
Measurement of Nanomaterials
Traditional industrial hygiene sampling methods such as airborne dust measurements have been used to measure airborne nanomaterials. However, these methods require careful interpretation. Scientists are developing more sensitive and specific sampling techniques to evaluate occupational exposures. Sampling in the workplace should include background measurements and measurements before, during, and after production or handling of these materials. These measurements can determine if emissions and possible exposures are occurring.
Exposure Controls
Elimination or substitution of a less hazardous substance is a basic principle of laboratory safety and health. Certain aspects of a process may be changed and result in a less hazardous situation to exist.
Reducing user exposures to nanomaterials can be achieved by Engineering Controls such as source enclosure (isolating the generation source from the user) and local exhaust ventilation systems. Exhaust ventilation systems that use high-efficiency particulate air (HEPA) filters are very effective in removing nanomaterials. In Table 16.1 (provided by NIOSH), recommendations of installing control measures depending on the nanomaterial used in specific activities are presented.
By means of engineering controls, operational procedures, such as reducing the time the employee is handling the material, specifying good housekeeping and other good work practices, training employees, and implementing proper labeling and storage of materials, limit the exposure to nanomaterials.
If engineering and administrative controls cannot control exposures, personal protective equipment, such as respirators and appropriate gloves and coveralls, should be considered.
Recommended safety procedures for handling nanomaterials:
- Use good general laboratory safety practices as found in Chemical and Biological Safety sections of this handbook and individual laboratory operating procedures. Wear gloves, lab coats, safety glasses, face shields, closed-toed shoes. Avoid getting nanoparticles in eyes, mucous membranes, on skin, or in respiratory tract.
- Wash your hands BEFORE you leave the lab.
- Be sure to consider the hazards of precursor materials in evaluating process hazards. (For example, some powders are more dangerous until they are mixed into a solution, whereby they become safer to handle and there is less possibility of inhalation of floating particles.)
- Avoid skin contact with nanoparticles or nanoparticle-containing solutions by using appropriate personal protective equipment. Do not handle nanoparticles with your bare skin.
- Handle nanoparticles only inside a HEPA-filtered powered-exhaust laminar flow hood, wear appropriate respiratory protection. If this is not possible, consult with LSS on obtaining respiratory protection.
- Use fume hoods to expel fumes from tube furnaces or chemical reaction vessels.
- Place the waste that contains nanoparticles in puncture-proof sealable containers, or double bag in 6 mL plastic, clearly mark with contents, and disposed of through hazardous waste channels.
- Clean up spilled nanoparticles accomplished with a HEPA-filtered vacuum or call LSS.
- Become familiar with the SDS associated with the basic material; be alert for the onset of any symptoms associated with the chronic effects of these materials.
No certain set of rules will cover all situations.
Given the differing synthetic methods and experimental goals, no blanket recommendation can be made regarding aerosol emissions controls. This should be evaluated on a case-by-case basis.
Consideration should be given to the high reactivity of some nanopowder materials with regard to potential fire and explosion hazards (Table 16.1).
| Table 7.1 Biosafety levels | ||||
|---|---|---|---|---|
| Biosafety Level | 1 | 2 | 3 | 4 |
| Infectious Agents | Unlikely to cause
Low individual and | Can cause human
Moderate individual risk,
Effective treatments | Cause serious human
High individual risk,
| Cause very
High individual risk, |
| Examples of infectious agents in this risk level | E. coli, California encephalitis viruses, many influenza viruses | Anthrax, Q fever, tuberculosis, Hantaviruses, human immuno-deficiency viruses | Ebola viruses, Herpes B virus (Monkey virus), foot and mouth disease | |
| Facilities | Standard well-designed experimental animal and laboratory facilities | Level 1 plus: Separate laboratory, room surfaces impervious and readily cleaned, biohazard sign | Level 2 plus: Controlled access double door entry and body shower, air pressure must be negative at all times, no recirculation, HEPA filtration, backup power | Specialized, secure, completely self-contained unit with specialized ventilation, fully monitored; air lock entry and exit, |
| Safety Equipment | Handwashing facilities, laboratory coats | Level 1 plus: autoclave, HEPA-filtered class I or II biological safety cabinet, personal protective equipment | Level 2 plus: Autoclave, HEPA-filtered class II biological safety cabinet, personal protective equipment to include solid front laboratory clothing, head covers, dedicated footwear, and gloves, appropriate respiratory protection | Class III biological safety cabinets, positive pressure ventilated suits |
| Procedures | Basic safe laboratory practices | Use of personal protective equipment laboratory coat worn only in the laboratory, gloves, decontamination | Users fully trained, written protocols; showers, wastes disposed of as contaminated, use of biological safety cabinets, personal protective devices | Access only to certified staff, rigorous sterilization/decontamination procedures |
Adopted from The University of North Carolina at Chapel Hill, Environmental Health & Safety Department.
References and sources for information from the relevant websites and documentation of different universities, NGOs and government agencies used in the preparation of this website are provided at references.