Nanotechnology

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• Directors' Message
• Executive Summary

Thank you.

John Howard, M.D.
Director, National Institute for Occupational Safety and Health
Centers for Disease Control and Prevention

The following is a summary of findings and key recommendations:

Potential Health Concerns

• The potential for nanomaterials to enter the body is among several factors that scientists examine in determining whether such materials may pose an occupational health hazard. Nanomaterials have the greatest potential to enter the body if they are in the form of nanoparticles, agglomerates of nanoparticles, and particles from nanostructured materials that become airborne or come into contact with the skin.
• Based on results from human and animal studies, nanoparticles can be inhaled and deposit in the respiratory tract; and based on animal studies, airborne nanomaterials can enter the blood stream, and translocate to other organs.
• Experimental studies in rats have shown that equivalent mass doses of insoluble ultrafine particles (smaller than 100 nm) are more potent than large particles of similar composition in causing pulmonary inflammation and lung tumors in those laboratory animals. However, toxicity may be mitigated by surface characteristics and other factors. Results from in vitro cell culture studies with similar materials are generally supportive of the biological responses observed in animals.
• Cytotoxicity and experimental animal studies have shown that changes in the chemical composition, structure of the molecules, or surfaces properties of certain nanomaterials can influence their potential toxicity.
• Studies in workers exposed to aerosols of manufactured microscopic (fine) and nanoscale (ultrafine) particles have reported lung function decrements and adverse respiratory symptoms; however, uncertainty exists about the role of ultrafine particles relative to other airborne contaminants (e.g., chemicals, fine particles) in these work environments in causing adverse health effects.
• Engineered nanoparticles whose physical and chemical characteristics are like those of ultrafine particles need to be studied to determine if they pose health risks similar to those that have been associated with the ultrafine particles. 

Potential Safety Concerns

• Although insufficient information exists to predict the fire and explosion risk associated with nanoscale powders, nanoscale combustible material could present a higher risk than coarser material with a similar mass concentration, given its increased particle surface area and potentially unique properties due to the nanoscale.
• Some nanomaterials may initiate catalytic reactions depending on their composition and structure that would not otherwise be anticipated from their chemical composition alone.

Working with Engineered Nanomaterials

• Nanomaterial-enabled products such as nanocomposites and surface coatings, and materials comprised of nanostructures such as integrated circuits are unlikely to pose a risk of exposure during their handling and use. However, some of the processes (formulating and applying nanoscale coatings) used in their production may lead to exposure to nanoparticles.
  
• Processes generating nanomaterials in the gas phase, or using or producing nanomaterials as powders or slurries/suspensions/solutions pose the greatest risk for releasing nanoparticles. Maintenance on production systems (including cleaning and disposal of materials from dust collection systems) is likely to result in exposure to nanoparticles if it involves disturbing deposited nanomaterial.
• The following workplace tasks may increase the risk of exposure to nanoparticles:

• working with nanomaterials in liquid media without adequate protection (e.g., gloves) will increase the risk of skin exposure.
• working with nanomaterials in liquid during pouring or mixing operations, or where a high degree of agitation is involved, will lead to an increase likelihood of inhalable and respirable droplets being formed.
• generating nanoparticles in the gas phase in non-enclosed systems will increase the chances of aerosol release to the workplace.
• handling nanostructured powders will lead to the possibility of aerosolization.
• maintenance on equipment and processes used to produce or fabricate nanomaterials or the clean-up of spills or waste material will pose a potential for exposure to workers performing these tasks.
• cleaning of dust collection systems used to capture nanoparticles can pose a potential for both skin and inhalation exposure.
• machining, sanding, drilling, or other mechanical disruptions of materials containing nanoparticles can potentially lead to aerosolization of nanomaterials.

Exposure Assessment and Characterization

• Until more information becomes available on the mechanisms underlying nanoparticle toxicity, it is uncertain as to what measurement technique should be used to monitor exposures in the workplace. Current research indicates that mass and bulk chemistry may be less important than particle size and shape, surface area, and surface chemistry (or activity) for nanostructured materials.
• Many of the sampling techniques that are available for measuring airborne nanoaerosols vary in complexity but can provide useful information for evaluating occupational exposures with respect to particle size, mass, surface area, number concentration, composition, and surface.  Unfortunately, relatively few of these techniques are readily applicable to routine exposure monitoring. 
• Regardless of the metric or measurement method used for evaluating nanoaerosol exposures, it is critical that background nanoaerosol measurements be conducted before the production, processing or handling of the nanomaterial/nanoparticle.
• When feasible, personal sampling is preferred to ensure an accurate representation of the worker’s exposure, whereas area sampling (e.g., size-fractionated aerosol samples) and real-time (direct reading) exposure measurements may be more useful for evaluating the need for improvement of engineering controls and work practices.

Precautionary Measures

• Given the limited amount of information for determining if engineered nanoparticles pose an occupational health risk, it is prudent to take precautionary measures to minimize worker exposures.
• For most processes and job tasks, the control of airborne exposure to nanoaerosols can be accomplished using a wide variety of engineering control techniques similar to those used in reducing exposure to general aerosols.
• The implementation of a risk management program in workplaces where exposure to nanomaterials exists can help to minimize the potential for exposure to nanoaerosols. Elements of such a program should include:

• evaluating the hazard posed by the nanomaterial based on available physical and chemical property data and toxicology or health effects data.
• assessing potential worker exposure to determine the degree of risk.
• the education and training of workers in the proper handling of nanomaterials (e.g., good work practices).
• the establishment of criteria and procedures for installing and evaluating engineering controls (e.g., exhaust ventilation) at locations where exposure to nanoparticles might occur.
• the development of procedures for determining the need and selection of personal protective equipment (e.g., clothing, gloves, respirators).
• the systematic evaluation of exposures to ensure that control measures are working properly and that workers are being provided the appropriate personal protective equipment.

• Engineering control techniques such as source enclosure (i.e., isolating the generation source from the worker) and local exhaust ventilation systems should be effective for capturing airborne nanoparticles.  Current knowledge indicates that a well-designed exhaust ventilation system with a high-efficiency particulate air (HEPA) filter should effectively remove nanoparticles.
• The use of good work practices can help to minimize worker exposures to nanomaterials.  Examples of good practices include; cleaning of work areas using HEPA vacuum pickup and wet wiping methods, preventing the consumption of food or beverages in workplaces where nanomaterials are handled, and providing hand-washing facilities and facilities for showering and changing clothes.
• No guidelines are currently available on the selection of clothing or other apparel (e.g. gloves)for the prevention of dermal exposure to nanoaerosols. However, some clothing standards incorporate testing with nanoscale particles and therefore provide some indication of the effectiveness of protective clothing with regard to nanoparticles.
• Respirators may be necessary when engineering and administrative controls do not adequately prevent exposures. Currently, there are no specific exposure limits for airborne exposures to engineered nanoparticles although occupational exposure limits exist for larger particles of similar chemical composition. The decision to use respiratory protection should be based on professional judgment that takes into account toxicity information, exposure measurement data, and the frequency and likelihood of the worker’s exposure. Preliminary evidence shows that for respirator filtration media there is no deviation from the classical single-fiber theory for particulates as small as 2.5 nm in diameter. While this evidence needs confirmation, it is likely that NIOSH certified respirators will be useful for protecting workers from nanoparticle inhalation.