Every year on October 9th we celebrate National Nanotechnology Day. The date 10-9 pays homage to the nanometer scale: 10^–9 (one billionth of a meter). Anything that can be measured in nanometers is extremely small! For instance, the width of a strand of human hair is about 90,000 nanometers, bacteria are between 300–5,000 nanometers, viruses are 5–300 nanometers, the diameter of deoxyribonucleic acid (DNA) is 2.5 nanometers, and a single atom is 0.1–0.5 nanometers. A healthy young adult’s fingernail grows an average of just over 1 nanometer per second (3.47 millimeters per month on average)!¹ National Nanotechnology Day was created to help raise awareness of nanotechnology, to show how it is currently used in products that enrich our daily lives and to consider future challenges and opportunities.

What are engineered nanomaterials?

Engineered nanomaterials (ENMs) are materials intentionally produced to have particle sizes between 1 and 100 nanometers in at least one dimension. These materials can be nanoparticles, nanotubes, or nanoplates, depending on their shape. ENMs typically have new or unique properties different from those of larger forms of the same material, making them desirable for specific product applications. These properties can contribute to increased elasticity, tensile strength, electrical conduction, and reactivity. Increasingly, they are added into existing materials to give these properties to bulk materials (such as plastics or metals). Consumer products using ENMs include cosmetics, sunscreen, food storage products, appliances, clothing, electronics, computers, sporting goods, and coatings. ENMs are also used in state-of-the-art sensors and biomedical technologies. COVID-19 research and the development of vaccines depend heavily on nanotechnology, and many vaccines use nanotechnology to improve their effectiveness. You probably are interacting with nanotechnology-enabled products every day!

What are the potential health effects of ENM exposure to workers?

As with every new technology, the potential risks associated with the production and use of nanomaterials need to be considered along with the benefits. Workers can be exposed to nanomaterials when they inhale aerosolized nanomaterials or touch contaminated surfaces or materials. Aerosolization happens when energy is applied to ENMs: dry powders can easily become airborne while being handled or by the air of a blowing fan. ENMs suspended in liquid need more energy to be made airborne, such as being agitated or misted, while ENMs bound in solid material need to be cut or ground to be released. Touching dry powders, ENM-containing liquids, or solids containing bound ENMs adds the potential for dermal exposure.

The potential adverse health effects, or toxicologic effects, of ENMs depend on many factors, including the ENM itself and the route of exposure. There aren’t many large-scale studies of human exposures to ENMs, so we primarily rely on the results of cell- and animal-based studies. These studies show that inhaling some ENMs may be potentially carcinogenic² or allergenic³, and dermal exposures may be sensitizing.³ Additionally, ENMs are often modified by coatings or by the presence of other chemicals, creating complex “coexposures” whose effects can be difficult to study. Because of the challenge in modeling the risk of so many different ENMs, safe nanotechnology places an emphasis on minimizing unintended exposures.

How is NIOSH helping ENM workers?

Since the early 2000s, NIOSH has been at the forefront of efforts to characterize potential workplace hazards for those working with ENMs and to ensure safe and healthy workplaces, including the creation of the NIOSH Nanotechnology Research Center in 2004. Since then, NIOSH has published a quantitative risk assessment and an elemental mass-based recommended exposure limit (REL) for each of the following: carbon nanotubes/nanofibers,⁴ nanoscale titanium dioxide, ⁵ and silver nanomaterials.⁶ In addition, the poster Controlling Health Hazards When Working With Nanomaterials: Questions to Ask Before You Start is a helpful and easy-to-use visual resource for the workplace.

Performing an exposure assessment and control verification can determine the potential for workplace exposure to ENMs. The NIOSH Nanomaterial Exposure Assessment Technique (NEAT 2.0)⁷ can also be used to identify the potential for exposure to anENM in the workplace. NEAT 2.0 makes use of an array of industrial hygiene methods including filter-based samples and particle counters. This sampling strategy places a strong emphasis on full workday exposures, incorporates background monitoring, and emphasizes the importance of integrated filter sampling in the worker’s breathing zone over the use of direct reading instruments (such as a condensation particle counter). This sampling strategy consists of the following important steps:⁷

1. Collect Basic Workplace Information
   • Workflow, number of workers, tasks performed, materials used, other indicators of potential exposure
2. Design and Implement the Sampling Plan
   • Full-shift and task-based integrated filter-based sampling, direct reading instruments, engineering controls evaluation
3. Risk Assessment
   • Evaluate background and engineering controls data
   • Use the hierarchy of controls to develop mitigation strategies for exposure potential
   • Communicate potential risks
4. Risk Management
   • Confirm ongoing control of risk by performing additional measurements, if necessary

By performing the steps above, a comprehensive exposure assessment can be performed to assist with the identification of potential nanomaterial exposures in an occupational setting. By determining exposure potential, the facility can then work to control exposure using mitigation strategies and the hierarchy of controls.

The separate NIOSH workplace sampling guidance documents for carbon nanotubes/nanofibers, titanium dioxide, and silver contain a lot of information. Occupational health and safety professionals expressed a need for one document explaining all the available nanomaterial sampling techniques. In response, NIOSH published a technical report in 2022 entitled Occupational Exposure Sampling for Engineered Nanomaterials⁸ that explains all the nanomaterial sampling techniques available to date in one resource.

Are we having an impact?

In collaboration with RTI International, NIOSH administered a survey developed by the RAND Corporation to North American companies working with nanomaterials to assess health and safety practices and the impact of efforts made by NIOSH to protect worker health and safety.⁹ Forty-five companies in the United States and Canada that fabricate, manufacture, handle, dispose, or otherwise use nanomaterials completed the online survey in 2019. The survey included research questions about nanomaterials in use and the overall occupational health and safety culture at the companies. Additionally, other questions asked about whether the companies interacted with NIOSH or used NIOSH resources to inform their health and safety practices and policies. More than a third (37.8%) of the 45 respondents reported using at least one NIOSH resource for information about safe handling of nanomaterials. Larger companies were more likely to report using NIOSH resources than companies employing fewer than 50 employees. While the survey was limited by the small sample size, it provided valuable insight, including that future NIOSH outreach should specifically target small businesses that use or handle nanomaterials.

We hope you find a way to celebrate National Nanotechnology Day! The National Nanotechnology Initiative (nano.gov) suggests running a 100 Billion Nanometer Dash. Sounds like quite a distance, but it is just 100 meters (328 feet) or 6.2% of a mile. As we continue to provide guidance and recommendations to keep workers safe when working with ENMs, we will be right there with you until you cross the finish line… one nanometer at a time. Good luck!

LCDR Adrienne Eastlake, MS, RS/REHS, MT (ASCP), is a research industrial hygienist with the NIOSH Division of Science Integration Science Applications Branch.

Gary Roth, PhD, MS, is a researcher with the NIOSH Division of Science Integration Emerging Technologies Branch.

Nicole Neu-Baker, MPH, is a researcher with the State University of New York Polytechnic Institute Colleges of Nanoscale Science and Engineering and a NIOSH Intergovernmental Personnel Act assignee.

References

¹ Yaemsiri S, Hou N, Slining MM, He K. [2010] Growth rate of human fingernails and toenails in healthy American young adults. J Eur Acad Dermatol Venereol. Apr;24(4):420-3. https://doi.org/10.1111/j.1468-3083.2009.03426.x

² Fraser K, Kodali V, Yanamala N, Birch ME, Cena L, Casuccio G, Bunker K, Lersch TL, Evans DE, Stefaniak A, Hammer MA, Kashon ML, Boots T, Eye T, Hubczak J, Friend SA, Dahm M, Schubauer-Berigan MK, Siegrist K, Lowry D, Bauer AK, Sargent LM, Erdely A [2020]. Physicochemical characterization and genotoxicity of the broad class of carbon nanotubes and nanofibers used or produced in U.S. facilities. Part Fibre Toxicol 17(62), https://doi.org/10.1186/s12989-020-00392-w.

³ Roach KA, Stefaniak AB, Roberts JR [2019]. Metal nanomaterials: immune effects and implications of physicochemical properties on sensitization, elicitation, and exacerbation of allergic disease, J Immunotoxicol 16(1):87–124, https://doi.org/10.1080/1547691X.2019.1605553.

⁴ NIOSH [2013]. Occupational exposure to carbon nanotubes and nanofibers. By Zumwalde R, Kuempel E, Birch E, Trout D, Castranova V. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2013-145, https://www.cdc.gov/niosh/docs/2013-145/.

⁵ NIOSH [2011]. Occupational exposure to titanium dioxide. By Dankovic D, Kuempel E, Geraci C, Gilbert S, Rice F, Schulte P, Smith R, Sofge C, Wheeler M, Lentz TJ, Zumwalde R, Maynard A, Attfield M, Pinheiro G, Ruder A, Hubbs A, Ahlers H, Lynch D, Toraason M, Vallyathan V. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2011-160, https://www.cdc.gov/niosh/docs/2011-160/.

⁶ NIOSH [2021]. Health effects of occupational exposure to silver nanomaterials. By Kuempel E, Roberts JR, Roth G, Dunn KL, Zumwalde R, Drew N, Hubbs A, Trout D, Holdsworth G. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2021-112, https://www.cdc.gov/niosh/docs/2021-112/.

⁷ Eastlake A, Beaucham C, Martinez K, Dahm M, Sparks C, Hodson L, Geraci C [2016]. Refinement of the Nanoparticle Emission Assessment Technique into the Nanomaterial Exposure Assessment Technique (NEAT 2.0). J Occup Environ Hyg 13(9):708–717, http://doi.org/10.1080/15459624.2016.1167278.

⁸ NIOSH [2022]. Occupational exposure sampling for engineered nanomaterials. By Hodson L, Eastlake A. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2022-153, https://doi.org/10.26616/NIOSHPUB2022153.

⁹ Neu-Baker NM, Eastlake A, Hodson L [2022]. Results of the 2019 survey of engineered nanomaterial occupational health and safety practices. Int J Environ Res Public Health 19(13):7676. https://doi.org/10.3390/ijerph19137676