Norman Horn, Ph.D., chemical engineer, Seal Shield, LLC
Over the past year, a focus group from IUVA partnered with the US National Institute of Standards and Technology (NIST) to produce a special section of the Journal of Research of the National Institute of Standards and Technology focused on ultraviolet (UV) technology for public health, with an emphasis on healthcare-associated infections (HAIs). The genesis of this project was the January 2020 workshop hosted at the NIST headquarters in Gaithersburg, Maryland, and the group initially convened to produce conference proceedings of the event.
But the year 2020, of course, proceeded to be a time dominated by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (COVID-19), and UV technology’s importance to combatting COVID-19 became increasingly evident in the ensuing months. This led the focus group to change from merely publishing proceedings to creating a unique opportunity for NIST and the UV industry.
Normally, the Journal of Research of the National Institute of Standards and Technology publishes the work of NIST scientists and their collaborators. With this opportunity to publish peer-reviewed, open-access articles, the journal opened a call for papers dedicated to UV technologies for public health. Besides the extraordinary circumstances of the global pandemic, this also indicates just how far the UV industry has come in its importance to the future of public health.
The journal section, like all of the publications from NIST, will be available to the public via the NIST website (https://www.nist.gov/nist-research-library/journal-research-nist) and through PubMed Central. Anyone with the drive to learn about UV science, standards and applications will find a wealth of knowledge in this special section. It is particularly notable that we have not seen a book-level treatment of advancements in UV science in nearly a decade (I could find only one in the literature), and thus to have such an assembled work in one place available to all is an exciting prospect for our field.
To whet the appetites of UV Solutions readers to what they will find in the journal, I would invite you to traverse the contents with me in summary. The focus group responsible for organizing the special section (myself included) bookended the volume with two papers. The lead paper (Poster et al.) kicks the journal off with a review of the recent history of UV technology in the context of our tumultuous times, and the concluding article (also Poster et al., to be published) presents a case and potential model for a UV technology consortium involving industry, academia and government participation. Everything in between can be categorized roughly into three areas:
- UV science fundamentals
- Design and use of UV applications
- Metrology and measurement of UV energy
The research presented will bridge these sections, naturally, but all are important contributions in their own way.
UV Science Fundamentals
The papers surveying UV science include contributions in UV mechanisms, optics and biological responses to UV energy. Dan Spicer surveys the field of photonic disinfection in a paper well-suited for both the uninitiated curious person and seasoned professionals wanting to review and solidify their understanding. (In other words, send this one to your friends and family!) The fundamental mechanism of UV-C inactivation of microorganisms is explained in detail, as well as the types of sources and tools available in the marketplace today to combat HAI proliferation.
Stojalowski and Fairfoull contributed an investigation into materials that can reflect UV-C light and describe a useful device for obtaining reflection measurements using color-changing paper dosimeters to compare reflected dosage. Their presented results are relative rather than absolute, but the method presented is a clever way of comparing different materials side by side.
Blatchley, Petri and Sun present an explanation of available UV-C dose-response data and action spectra for viruses in general and coronaviruses in particular. Then, they apply this knowledge to argue that SARS-CoV-2 similarly will be inactivated by UV-C, and that this is consistent with the limited data available at the time. Since the science has proceeded rather quickly over the past year, even more data are available now, demonstrating this as well. Nonetheless, this paper establishes important context for our understanding of virus inactivation behavior.
Dr. Art Kreitenberg and Dr. Richard Martinello, both respected physicians and IUVA members, provide a carefully considered perspective on standards for whole-room UV disinfection of a healthcare environment. They review at a high level the scope of what whole-room UV disinfection aims to do and the criteria for evaluating successful performance.
A crucial contribution and unique addition to this volume is the work of Mahsa Masjoudi, Madjid Mohseni and James Bolton on the “Sensitivity of Bacteria, Protozoa, Viruses and Other Microorganisms to Ultraviolet Radiation.” I call special attention to this paper not only because it is the longest article in the issue (when you count all the pages of tables) but also because it has a significant history within the IUVA. For over a decade, Professor Bolton has maintained a white paper, publicly available on the IUVA website, that easily has been the largest compilation of UV fluence (dosage) data ever assembled. His team’s work has been a trusted resource for numerous researchers and now its inclusion in the peer-reviewed literature is a celebratory occasion.
Designing and Using UV Applications
Understanding the basic science of UV is important, but delving into applications often can lead us into many unanticipated issues and, thus, new research problems. Among the many difficult situations the pandemic put before us, an early hurdle to overcome was extending the lifetime of personal protective equipment (PPE) through disinfection. Disinfecting N95 respirators with UV received major attention throughout the broader healthcare industry, and a few papers in this volume seek to address this.
Geldert et al. explain the unique considerations needed to disinfect N95 respirators with UV-C, noting that effective and reproducible results depend greatly on understanding the UV-C dosage and that the porous nature of N95s makes measuring the delivered dose a complicated endeavor. Chandran et al. present design considerations for UV-C devices, especially as they relate to disinfecting difficult objects such as N95 respirators. Claytor et al. describe their work designing a portable UV-C disinfection chamber to disinfect PPE for re-use, taking a detailed look at source selection, mechanical and electrical design, and testing procedures.
Finally, Yates et al. contributed a study of UV-C degradation effects of materials used in aircraft interiors. Their work sought to demonstrate if and how these materials could perhaps discolor, become weakened or lose critical flame retardance upon repeated exposure to UV-C sources. They find that it is important for them to set a limit of exposure before significant changes occur but that this limit does not prohibit them from getting sufficient dosage for adequate disinfection.
Metrology and Measurement of UV Energy
UV measurement is a subtle but important science, as the following contributions to this special section emphasize. Obeng et al. have developed a method of measuring the electrical resistance of biological thin films using microwave broadband dielectric spectroscopy. These films and measurements then can become a biological indicator for assessing whole-room UV-C surface disinfection.
Fredes et al., recognizing the challenge of predicting minimum irradiation times for disinfection, present a new mathematical model to estimate irradiance distributions given various technical parameters of UV-C sources. Zong et al. have pioneered a new technique to measure emissions from LEDs and laser diodes that they term a mean differential continuous pulse (DCP) method. It improves upon existing DCP methodology by reducing the major sources of error in prior iterations of DCP.
The depth and breadth of UV science and technology is remarkable, and we are only beginning to tap the full potential for UV disinfection technology to reduce the impact of HAIs and improve patient outcomes. This special section of the Journal of Research of the National Institute of Standards and Technology is an excellent contribution to the field, and every contributor to this volume is to be commended for their efforts. n
Special thanks to the authors who contributed papers to the special section, and thank you to Dr. Ron B. Goldfarb, Chief Editor, Journal of Research of NIST; Kathryn Miller, NIST Information Services Office; Anika Newell, copy editor; all the anonymous peer reviewers of the articles; and the members of the focus group: Dianne Poster, NIST (co-chair); Troy Cowan, IUVA; Rick Martinello, Yale School of Medicine and Yale New Haven Health; Cameron Miller, NIST; and Michael Postek, University of South Florida, for supporting this effort.
Contact: Norman Horn, [email protected]