It seems to be ‘toxicology and nanomaterials’ season right now. In addition to the ISO (International Standards Organization) technical report on nanomaterials and toxicology which was released in early June (mentioned in my June 4, 2012 posting), the US Environmental Protection Agency (EPA) and the US National Institute of Occupational Safety and Health (NIOSH) have released new reports.
Yesterday (July 2, 2012), the EPA posted a notice on the US Federal Register about a report, a commenting period, and a public information exchange meeting for “Nanomaterial Case Study: A Comparison of Multiwalled Carbon Nanotubes and Decabromodiphenyl Ether Flame-Retardant Coatings Applied to Upholstery Textiles.”
As I noted in an Aug. 27, 2010 posting, the EPA has adopted a very interesting approach to studying possible toxicological effects due to nanomaterials (and other materials),
Such case studies do not represent completed or even preliminary assessments; rather, they are intended as a starting point in a process to identify and prioritize possible research directions to support future assessments of nanomaterials.
Part of the rationale for focusing on a series of nanomaterial case studies is that such materials and applications can have highly varied and complex properties that make considering them in the abstract or in generalities quite difficult. Different materials and different applications of a given material could raise unique questions or issues as well as some issues that are common to various applications of a given nanomaterial or even to different nanomaterials. After several individual case studies have been examined, refining a strategy for nanomaterials research to support long-term assessment efforts should be possible. (p. 19 PDF, p. 1-1 in print version of a US EPA silver nanomaterials draft report)
The July 3, 2012 news item on Nanowerk offers more detail about this latest case study (Note: I have removed a link),
EPA announces the release of the draft report, Nanomaterial Case Study: A Comparison of Multiwalled Carbon Nanotube and Decabromodiphenyl Ether Flame-Retardant Coatings Applied to Upholstery Textiles (External Review Draft), for public viewing and comment. This was announced in a July 2, 2012 Federal Register Notice along with information about the upcoming public Information Exchange Meeting scheduled for October 29, 2012. The purpose of this meeting is to receive comments and questions on the draft document, as well as provide information on the draft document and a workshop process that it will be used in, which is being conducted independently by RTI International, a contractor for EPA. The deadline for comments on the draft document is August 31, 2012. [emphases mine]
The notice on the EPA website offers details and extensive links to satisfy your information needs on this matter,
The draft document is intended to be used as part of a process to identify what is known and, more importantly, what is not yet known that could be of value in assessing the broad implications of specific nanomaterials. Like previous case studies (see History/ Chronology below [on the EPA website]), this draft case study on multiwalled carbon nanotubes (MWCNTs) is based on the comprehensive environmental assessment (CEA) approach, which consists of both a framework and a process. Unlike previous case studies this case study incorporates information about a traditional (i.e., “non-nano-enabled”) product, against which the MWCNT flame-retardant coating applied to upholstery textiles (i.e., the “nano-enabled” product) can be compared. The comparative element serves dual-purposes: 1) to provide a more robust database that facilitates identification of data gaps related to the nano-enabled product and 2) to provide a context for identifying key factors and data gaps for future efforts to evaluate risk-related trade-offs between a nano-enabled and non-nano-enabled product.
This draft case study does not represent a completed or even a preliminary assessment of MWCNTs; rather, it uses the CEA framework to structure information from available literature and other resources (e.g., government reports) on the product life cycle, fate and transport processes in various environmental media, exposure-dose characterization, and impacts in human, ecological, and environmental receptors. Importantly, information on other direct and indirect ramifications of both primary and secondary substances or stressors associated with the nanomaterial is also included when available. The draft case study provides a basis for the next step of the CEA process, whereby collective judgment is used to identify and prioritize research gaps to support future assessment efforts that inform near-term risk management goals.
Meanwhile, NIOSH has released a safety guide (from the June 29, 2012 news item on Nanowerk),
The National Institute for Occupational Safety and Health (NIOSH) has published “General Safe Practices for Working with Engineered Nanomaterials in Research Laboratories” (pdf).
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With the publication of this document, NIOSH hopes to raise awareness of the occupational safety and health practices that should be followed during the synthesis, characterization, and experimentation with engineered nanomaterials in a laboratory setting. The document contains recommendations on engineering controls and safe practices for handling engineered nanomaterials in laboratories and some pilot scale operations. This guidance was designed to be used in tandem with well-established practices and the laboratory’s chemical hygiene plan. As our knowledge of nanotechnology increases, so too will our efforts to provide additional guidance materials for working safely with engineered nanomaterials.
Here is more information from the executive summary of the General Safe Practices for Working with Engineered Nanomaterials in Research Laboratories,
Risk Management
Risk management is an integral part of occupational health and safety. Potential exposures to nanomaterials can be controlled in research laboratories through a flexible and adaptive risk management program. An effective program provides the framework to anticipate the emergence of this technology into laboratory settings, recognize the potential hazards, evaluate the exposure to the nanomaterial, develop controls to prevent or minimize exposure, and confirm the effectiveness of those controls.
Hazard Identification
Experimental animal studies indicate that potentially adverse health effects may result from exposure to nanomaterials. Experimental studies in rodents and cell cultures have shown that the toxicity of ultrafine particles or nanoparticles is greater than the toxicity of the same mass of larger particles of similar chemical composition.
Research demonstrates that inhalation is a significant route of exposure for nanomaterials. Evidence from animal studies indicates that inhaled nanoparticles may deposit deep in lung tissue, possibly interfering with lung function. It is also theorized that nanoparticles may enter the bloodstream through the lungs and transfer to other organs. Dermal exposure and subsequent penetration of nanomaterials may cause local or systemic effects. Ingestion is a third potential route of exposure. Little is known about the possible adverse effects of ingestion of nanomaterials, although some evidence suggests that nanosized particles can be transferred across the intestinal wall.
Exposure Assessment
Exposure assessment is a key element of an effective risk management program. The exposure assessment should identify tasks that contribute to nanomaterial exposure and the workers conducting those tasks. An inventory of tasks should be developed that includes information on the duration and frequency of tasks that may result in exposure, along with the quantity of the material being handled, dustiness of the nanomaterial, and its physical form. A thorough understanding of the exposure potential will guide exposure assessment measurements, which will help determine the type of controls required for exposure mitigation.
Exposure Control
Exposure control is the use of a set of tools or strategies for decreasing or eliminating worker exposure to a particular agent. Exposure control consists of a standardized hierarchy to include (in priority order): elimination, substitution, isolation, engineering controls, administrative controls, or if no other option is available, personal protective equipment (PPE).
Substitution or elimination is not often feasible for workers performing research with nanomaterials; however, it may be possible to change some aspects of the physical form of the nanomaterial or the process in a way that reduces nanomaterial release.
Isolation includes the physical separation and containment of a process or piece of equipment, either by placing it in an area separate from the worker or by putting it within an enclosure that contains any nanomaterials that might be released.
Engineering controls include any physical change to the process that reduces emissions or exposure to the material being contained or controlled. Ventilation is a form of engineering control that can be used to reduce occupational exposures to airborne particulates. General exhaust ventilation (GEV), also known as dilution ventilation, permits the release of the contaminant into the workplace air and then dilutes the concentration to an acceptable level. GEV alone is not an appropriate control for engineered nanomaterials or any other uncharacterized new chemical entity. Local exhaust ventilation (LEV), such as the standard laboratory chemical hood (formerly known as a laboratory fume hood), captures emissions at the source and thereby removes contaminants from the immediate occupational environment. Using selected forms of LEV properly is appropriate for control of engineered nanomaterials.
Administrative controls can limit workers’ exposures through techniques such as using job-rotation schedules that reduce the time an individual is exposed to a substance. Administrative controls may consist of standard operating procedures, general or specialized housekeeping procedures, spill prevention and control, and proper labeling and storage of nanomaterials. Employee training on the appropriate use and handling of nanomaterials is also an important administrative function.
PPE creates a barrier between the worker and nanomaterials in order to reduce exposures. PPE may include laboratory coats, impervious clothing, closed-toe shoes, long pants, safety glasses, face shields, impervious gloves, and respirators.
Other Considerations
Control verification or confirmation is essential to ensure that the implemented tools or strategies are performing as specified. Control verification can be performed with traditional industrial hygiene sampling methods, including area sampling, personal sampling, and real-time measurements. Control verification may also be achieved by monitoring the performance parameters of the control device to ensure that design and performance criteria are met.
Other important considerations for effective risk management of nanomaterial exposure include fire and explosion control. Some studies indicate that nanomaterials may be more prone to explosion and combustion than an equivalent mass concentration of larger particles.
Occupational health surveillance is used to identify possible injuries and illnesses and is recommended as a key element in an effective risk management program. Basic medical screening is prudent and should be conducted under the oversight of a qualified health-care professional. (pp. 9 – 11 PDF or pp. vii – ix in print)
The guidance as per the executive summary seems to rely heavily on what I imagine are industrial hygiene practices that should be followed whether or not laboratories are researching nanomaterials.
