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Disclaimer: The material in this paper is intended for general information only. Any use of this material in relation to any specific application should be based on independent examination and determination of suitability for the application by professional qualified personnel. Those making use of or relying upon the material assume all risks and liability arising from such use or reliance.

Nanomaterials promise to transform commercial products, providing significant societal benefits. As the nanomaterials enterprise grows, so too, does the debate over environmental, health, and safety (EH&S) aspects of producing them. This article discusses nanomaterial EH&S needs and progress being made by industry, academic institutions, and government laboratories.

The long-predicted technological and societal impacts of nanomaterials are starting to be realized. Nanomaterial programs continue to be funded at local and national levels around the globe.¹ The United States invests approximately $1.4 billion per year,² with global funding being three times greater.³ Nanotechnologies are attracting new students to science and engineering. Universities are offering “nano” curricula, ranging from lectures to new degrees.⁴ Improved electronics and high-performance coatings are being developed and commericialized.⁵ These are among the positive impacts of nanotechnology.

Environmental, health, and safety (EH&S) issues of producing nanomaterials, however, remain a concern among certain segments of the technical community and the general public.^6–13 Here is a glimpse at the ongoing dialogue:

“The most attractive properties of nanomaterials for medical and technological applications, including their small size, large surface area, and high reactivity, may also lead to new and unusual toxicity.” ⁶
- “Nanotechnology–Toxicological Issues and Environmental Safety” NATO Advanced Research Workshop

“While it is by no means certain that emerging nanotechnologies will present significant risk, we can be sure that inaction in addressing risk will pave the way to public distrust and the potential for serious harm to occur.” ⁷
- Andrew D. Maynard, Woodrow Wilson International Center for Scholars

“Risks posed by nanomaterials, like risks posed by chemicals, cannot be easily generalized. Both hazard and exposure potential will vary widely for different nanomaterials and for products or applications that incorporate nanomaterials.” ⁸
- “Environmental, Health and Safety Research Needs for Engineered Nanoscale Materials” National Nanotechnology Coordination Office

“The urgency of nano-EHS research affects the entire NNI (National Nantechnology Initiative) investment . . . (as) fewer of these transformative technologies will make it into commerce if the technology transfer pipeline becomes clogged by concerns about nanoproduct safety.” ⁹
- Vicki L. Colvin, International Council on Nanotechnology

“Insurers would be prudent to consider adverse scenarios (to human health) when agreeing terms and conditions and . . . whether to exclude losses due to the reduction of property value (resulting from environmental exposure).” ¹⁰
- “Nanotechnology Recent Developments, Risks and Opportunities,” Lloyds, London

In 2008, more than $58.6 million will be spent in the United States on nanomaterials EH&S issues.^2,3 Work ranging from characterization and detection to risk assessment and communication will be funded. The fact remains, however, that nanomaterials EH&S knowledge lags commercial development of them. A systematic, coordinated approach is therefore needed to provide valuable risk management guidance while avoiding broad sweeping statements not based on fundamental scientific methods. Concurrently, current EH&S best practices must be disseminated throughout the growing nanomaterials enterprise.

This article builds upon the Environmental, Health and Safety forum at Commercialization of NanoMaterials 2007 to highlight nanomaterials EH&S issues.^14–19 Also, references to current EH&S best practices are presented to aid ongoing research, development, and commercialization efforts for nanomaterials. Links to the presentations from the EH&S forum are provided in the sidebar.

Once released into the environment, nanoparticles cannot easily be reclaimed. Nanosized particles can disperse quickly in air. Gravitational settling in water may be slowed for certain nanoparticles, potentially leading to increased contact with aquatic species. Speculation exists that nanoparticle effluents, both water-borne and atmospheric, could contaminate soil and groundwater, thus spreading into the water cycle, vegetation, and crops.²⁰ As such, ecological concerns ranging from direct contamination of food chains to crop yield are being investigated. Human exposure to nanoparticles can occur via inhalation, skin content (dermal absorption), injection, and ingestion. The retention of nanoparticles in the body and any potential detrimental effects need to be determined. Much work is needed, though, to quantify the transport and behavior of nanoparticles in living systems.

Toxicological studies on ultra-fine and nano-sized particles have mainly focused on the respiratory system. Particulate matter, especially fine particles (2.5 μm in diameter and smaller), can deposit throughout the respiratory tract, even deep in the alveolar portions of lungs. Water-soluble particles can rapidly pass into the blood stream and translocate to other organs. Furthermore, lipid soluble particles may be retained in the lungs for months or even years.¹⁴

Numerous recommendations exist on addressing nanomaterials EH&S needs.^8,19–25 Common among all of these are: nanomaterials characterization, monitoring, dose-response nanotoxicity studies, worker safety protocols, and risk assessment.

Nanoparticle behavior in the body cannot be generalized. As shown in Figure 1, the aspect ratio and surface morphology of nanoparticles can vary substantially, potentially contributing to differences in nanotoxicity. Furthermore, the state of the nanoparticle greatly affects EH&S performance. Different behavior is observed for particles in liquid, in a solid matrix, or in dry particulate form.¹⁶ Metallographic evaluations must therefore be conducted to properly categorize nanoparticle and nanomaterial toxicity.

Monitoring laboratory and production environments is important for collecting meaningful EH&S data. The American Chemistry Council has published a “reasoned approach to testing nanoscale materials” to aid materials producers.²⁶ Direct-read instruments can quantify worker exposure to nanoparticles if compensation is made for naturally occurring nanoscale particles.^15,17 In addition to individual research projects and corporate industrial hygiene programs, the U.S. National Institute of Occupational Safety and Health (NIOSH) is conducting field studies in order to develop dose-response relationships.^19,21

Engineering environmental controls and personal protective equipment (PPE) for handling nanomaterials are also being investigated. High-efficiency particulate air (HEPA) filtered vacuum systems appear to be effective for removing airborne nanoparticles.^14,16 The National Institute of Occupational Safety and Health is currently conducting nanoparticle PPE studies.¹⁹ This work has shown filtration media follows classical single-fiber theory down to 4 nm. Ongoing efforts are quantifying respirator seal effectiveness for exposure to 5 to 400 nm particles and penetration through PPE fabrics.

In 2005, NIOSH completed a thorough dose-response study to establish exposure limits for nanosized titanium dioxide particles.²⁷ This work provides a framework for developing nanoparticles and nanomaterial industrial hygiene procedures. Ongoing nanotoxicity research is focusing upon the infl uence of physical and chemical properties on nanoparticles; short- and long-term effects on organ systems and tissues; biological mechanisms for potential toxic effects; the creation of models to assist with hazard identifi cation; and toxicity correlations to mass or other appropriate measurable nanoparticle characteristics. ^21,22

In the end, nanomaterials present daunting tasks for researchers and industry, but also for those who control limited funds for EH&S activities. Coordination amongst funding agencies, such as those proposed by Vicki Colvin, executive director of the International Council on Nanotechnology (ICON),⁹ is recommended. Collaboration amongst members of the technical community is needed to develop predictive models for exposure risk. Key factors affecting worker exposure need to be quantified as do correlations between exposure potential and work processes. Also, dose-response relationships must continue to be developed with a critical focus on determining whether a given exposure will lead to bioaccumulation.^8,21,22

The environmental impact of nanoparticles and nanomaterials is another important area for continuing research. Again, characterization and monitoring studies are needed to construct meaningful models. Critical questions facing researchers are:

• Are nanomaterials more toxic than their non-nano counterparts?
• What is the fate of nanoparticles in air, water, and soil?
• What is the biodegradation potential of nanoparticles?
• Will nanoparticles transform in the environment into a more toxic form? ¹⁶

Similar to human exposure studies, much work is needed to assess the environmental impact of nanoparticles. The effects of nanoparticles on environmentally relevant species need to be quantified. The entire food chain must be considered, ranging from bottom-dwelling species (benthic) to flora and fauna to large wildlife.

Karns and Matthews^18,28 recommend paying particular attention to the beginning and end of the nanomaterials life cycle, focusing on nanoparticle emissions and product disposal. Using screening tools, such as the U.S. Environmental Protection Agency’s Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts²⁹ and life-cycles analyses, an assessment of risks and benefits can be made. In doing so, it is hoped that nanoparticle applications can be prioritized for in-depth analyses.

Consensus standards are currently being investigated by ANSI30 and ASTM.³¹ In the absence of those standards, accepted EH&S anticipation, recognition, evaluation, and control processes are being used to ensure worker safety and control environmental impact. The following builds upon this framework and discussions during the Environmental, Health and Safety Forum at Commercialization of Nano- Materials 2007.

Anticipate and Recognize
Material Safety and Data Sheets (MSDSs) are not readily available for nanomaterials. Even if an MSDS does exist for a given chemical or compound, it most likely is not applicable for nanoscale particles.

Risk assessments for respiratory, dermal, or other exposures are needed prior to initiating nanoparticle research and nanomaterial production. Past experience with other nanoparticles, including those found in nature, should be considered during this process.

Nanoparticles may represent fire and explosion concerns. The physical and chemical properties of the nanomaterials must be reviewed and procedures developed cognizant of nanoparticle combustibility, flammability, and conductivity. Handling procedures for all processes, products, and waste forms need to be implemented. Furthermore, the nature of nanoparticles and the disposition of nanomaterials are to be properly documented.

Communication is a key part of this process. All workers coming into contact with nanoparticles must be trained regarding potential hazards. Government agencies and academia must widely circulate data, models, standards, and regulations in a timely fashion. Materials and industrial hygiene professionals also need to maintain awareness of these advancements.

Evaluate
Work environment monitoring is recommended. These efforts can involve direct-read measurements, air sampling, and passive measurements.^15,17 The collected data can establish exposure potentials, verify effectiveness of engineering controls, and help establish dose-response knowledge. Nanoparticle characterization should include form, shape, chemical composition, and size distribution within a sampling.

Control
Best practices for nanomaterials EH&S have been released by various organizations.^32–39 Additionally, the following were recommended during the Environmental, Health and Safety Forum at Commercialization of NanoMaterials 2007:^15–17,19

• An EH&S audit should be conducted prior to beginning nanoparticle activities.
• Written procedures must document worker exposure potential, required engineering controls and PPE, methods for safe storage and handling, procedures to minimize exposure during production or analysis, waste disposal protocols, and spill containment practices.
• High-efficiency particulate air filtered vacuum systems should be used. Laminar flow filtered laboratory hoods and negative pressure around equipment can reduce worker exposure potential. Also, filtration on vacuum pumps for equipment can minimize air emissions and contamination.
• Personal respirators are not recommended until ongoing studies on seal effectiveness are completed.
• Personal protective clothing should be worn at all times to minimize skin contact.
• Nanoparticles in liquid or dry particulate form should be treated as hazardous or special waste. In the absence of consensus standards, best practices for asbestos disposal should be used for insoluble nanoparticles.

Currently, nanomaterials EH&S knowledge lags commercial development of them. Coordination among the technical community and funding agencies is needed to bridge knowledge gaps, ensure worker safety, and promote environmental stewardship. While nanotoxicity studies proceed, sound EH&S practices are needed for ongoing research, development, and commercialization programs. Companies, academic institutions, and government agencies engaged in the nanomaterials enterprise must anticipate the need for sound technical data for developing dose-response behavior and exposure limits for nanoparticles. They must also recognize that prioritization and coordination of efforts is needed to make meaningful progress. Nanoparticle exposure levels must be evaluated in laboratories and production facilities using effective monitoring techniques. Finally, best practices must be disseminated and adopted to control environmental impact and ensure worker safety.

Kim McDonald from Bayer MaterialScience LLC is gratefully acknowledged for organizing the Environmental, Health and Safety Forum at Commercialization of NanoMaterials 2007. Randy Ogle from Oak Ridge National Laboratory, Elizabeth McMeekin from PPG Industries, Inc., Keith Rickabaugh from RJLee Group, Inc., H. Scott Matthews from Carnegie Mellon University, and Ron Shaffer from NIOSH are also recognized for their presentations and participation in the panel discussion.

REFERENCES

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Todd M. Osman is Technical Director at TMS, 184 Thorn Hill Road, Warrendale, PA 15086; e-mail tosman@tms.org.