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Posted: Jul 27, 2012
Safe handling of advanced nanomaterials
(Nanowerk News) In the last five years, research and development activities in the field of nanotechnology have shifted to include advanced nanomaterials. The main feature of advanced nanomaterials that distinguishes them from simpler nanomaterials, such as carbon black and nanoscale TiO2 used primarily as additives, is the ability of advanced nanomaterials to change or evolve properties during their use, as a result of intended and unintended reactions to the external environment. Examples of advanced nanomaterials include nanomaterials functionalized for specific applications, such as nanoscale gold used in cancer treatment therapies, quantum dots used in medical imaging of the body, and carbon nanotubes and graphene used in electronics. Depending on the type of nanomaterial and the conditions of exposure, such a change of properties may result in health risks to workers handling advanced nanomaterials if exposure is not adequately controlled.
Although scientists do not have all the information necessary for detailed risk assessment, several factors demonstrate the need to pursue the necessary research and, in the meantime, to take prudent steps to control exposures. The factors include characteristics of advanced nanomaterials that are similar to those of simpler nanomaterials, where we can apply the risk assessment and risk management principles that we applied to simpler nanomaterials. The factors also include the characteristics unique to advanced nanomaterials that present an additional level of concern.
The characteristics that we also face with simpler nanomaterials include the ability of advanced nanomaterials to reach and interact with human internal organs if inhaled. Similar to simpler nanomaterials, advanced nanomaterials may pose health concerns associated with their dissolution, their shape (if they are in the form of fibers) and contaminants adsorbed on their surface. Similar to simpler nanomaterials, some advanced nanomaterials can be present in the workplace air environment due to residual or fugitive emissions, even when they are manipulated within enclosures. To our knowledge, data describing the types, levels, and conditions of actual workplace exposures to advanced nanomaterials have not been published to date in the scientific literature.
The characteristics unique to advanced nanomaterials include an enhanced ability of nanomaterials to reach internal organs through inhalation, ingestion or skin penetration, and subsequent transport in the blood to other body organs depending on the way the nanomaterial is constructed. For example, to optimize performance for certain applications, advanced nanomaterials can be designed to remain as single particles, which can enhance their bioavailability and increase their risk potential. There could also be hazardous properties unique to advanced nanomaterials which originate from their ability to convert energy from one form to another. For example, the ability of gold nanomaterials to convert light into thermal energy is under investigation for application in cancer therapy. However, such a property could be hazardous when exposure to an advanced nanomaterial occurs simultaneously and unintentionally with an external field which activates the property, raising the risk of damage to healthy tissues.
A traditional hierarchy of controls to reduce occupational risks may be applied to advanced nanomaterials. The hierarchy of controls starts with elimination or substitution of hazards. Preventing a potential risk to workers from a particular advanced nanomaterial by eliminating that potential hazard at the design phase of development is the most effective means of risk management and can support the safe progression of nanotechnology from simple to more advanced nanomaterials. Prevention of harm through safe design includes: (1) avoiding incorporating hazardous elements such as lead and other heavy metals into the nanomaterial; (2) designing “safer” nanomaterials, which would disintegrate into non-toxic and easily biodegradable components; and (3) designing safer nanomanufacturing processes.
Safe design of nanomaterials is included in the National Nanotechnology Initiative’s Signature Initiative on Nanotechnology Knowledge Infrastructure (pdf) announced in May of 2012. Specifically, the Signature Initiative states that “a focused national emphasis on nanoinformatics* will provide a strong basis for the rational design of nanomaterials and products, prioritization of research, and assessment of risk throughout product lifecycles and across sectors.” Safe design will be also a focus of an upcoming workshop on Safe Nano Design: Molecule • Manufacturing • Market co-sponsored by NIOSH.
If it is not possible to eliminate or reduce hazards through substitution or design, engineering controls are used to reduce the potential for exposure. Automated and enclosed processes to avoid contamination and ensure quality are already employed in certain manufacturing processes for nanomaterials and could be further expanded to other operations. However, potential for exposure would still exist during maintenance and transfer operations, as well as in the event of an unintended release. Potential for exposure would also exist for non-enclosed processes. In such situations, other engineering controls such as extraction ventilation and, finally, personal protective equipment, have proven effective in reducing exposures to simpler nanomaterials. Workplace exposure-management practices along with good manufacturing practices in the pharmaceutical industry, and specific relevant guidelines such as those for health care workers handling hazardous drugs, could be further adapted for manufacturing and handling of active nanomaterials in the workplace.
Due to their complex nature, advanced nanomaterials present a challenge in occupational risk assessment and risk management. However, they also present an opportunity to proactively assess the potential occupational risks from their development and use before they enter mainstream manufacturing. Therefore, risk assessment studies specifically directed at these materials in the workplace need to be conducted. NIOSH’s Nanotechnology Research Center is well poised to expand its work to include assessing the potential occupational exposures and hazards of advanced nanomaterials, and developing guidance for their safe handling in the workplace. An updated strategic plan for NIOSH nanotechnology program will include market forecasting and review of available surveillance data to identify emerging commercial advanced nanomaterials for toxicological testing and field evaluation of workplace exposures. We would also like to invite readers’ comments on the sorts of issues that they want NIOSH to examine in the area of occupational safety and health of advanced nanomaterials.
Dr. Murashov is a Special Assistant for Nanotechnology to the NIOSH Director. He is a member of the U.S. Nanoscale Science, Engineering, and Technology subcommittee. He also leads projects for the ISO Technical Committee 229 (Nanotechnologies), World Health Organization and the Organization for Economic Cooperation and Development’s Working Party on Manufactured Nanomaterials.
Dr. Schulte is the Director of the NIOSH Education and Information Division and Manager of the Nanotechnology Research Center.
Dr. Howard is the Director of the National Institute for Occupational Safety and Health.
Source: By Vladimir Murashov, Paul Schulte, John Howard; NIOSH