Ultraviolet Radiation Technologies and Healthcare-Associated Infections: Standards and Metrology Needs

Abstract

The National Institute of Standards and Technology (NIST) hosted an international workshop on ultraviolet-C (UV-C) disinfection technologies on January 14-15, 2020, in Gaithersburg, Maryland, in collaboration with the International Ultraviolet Association (IUVA). This successful public event, as evidenced by the participation of more than 150 attendees, with 65% from the ultraviolet technology industry, was part of an ongoing collaborative effort between NIST and the IUVA and its affiliates to examine the measurement and standards needs for pathogen abatement with UV-C in the healthcare whole-room environment. Prior to and since this event, stakeholders from industry, academia, government, and public health services have been collaboratively engaged with NIST to accelerate the development and use of accurate measurements and models for UV-C disinfection technologies and facilitate technology transfer. The workshop served as an open forum to continue this discussion with a technical focus centered on the effective design, use, and implementation of UV-C technologies for the prevention and treatment of healthcare-associated infections (HAIs) in complex hospital settings. These settings include patient rooms, operating rooms, common staging areas, ventilation systems, personal protective equipment, and tools for the reprocessing and disinfecting of instruments or devices used in medical procedures, such as catheters and ventilators. The critical need for UV-C technologies for disinfection has been amplified by the outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus that causes coronavirus disease 2019 (COVID-19), stimulating an even greater emphasis on identifying testing and performance metrology needs. This paper discusses these topics based on the international workshop and community activities since the workshop, including a public World-Wide-Web-based seminar with more than 500 registered attendees on September 30, 2020; an international conference on UV-C technologies for air and surface disinfection, December 8-9, 2020; and a webinar on returning to normalcy with the use of UV-C technologies, April 27 and 29, 2021. This article also serves as an introduction to a special section of the Journal of Research of the National Institute of Standards and Technology, where full papers address recent technical, noncommercial, UV-C technology and pathogen-abatement investigations. The set of papers provides keen insights from the vantage points of medicine and industry. Recent technical developments, successes, and needs in optics and photonics, radiation physics, biological efficacy, and the needs of future markets in UV-C technologies are described to provide a concise compilation of the community's efforts and the state of the field. Standards needs are identified and discussed throughout this special section. This article provides a summary of the essential role of standards for innovation and implementation of UV-C technology for improved patient care and public health.

Keywords: UV-C; disinfection; dose; efficacy; hospitals; innovation; light; metrology; optics; public health; standards; ultraviolet-C radiation.

Fig. 1. Number of deaths for the leading causes of death for the total population of the United States in 2015 compared to hospital-associated infections (bar in yellow), with heart disease and cancer being the top two causes of death, with 633,842 and 595,930 deaths, respectively (capped at 200,000 on the scale of the graph for illustration purposes). Data from Refs. [–15]).

Fig. 2. The sun’s electromagnetic energy travels in waves and spans a broad spectrum from very long radio waves (left) to very short gamma rays (right), with most waves being filtered by Earth’s atmosphere, except in the radio and optical windows, where the atmosphere is not opaque to those wavelengths. The human eye can detect only a small portion of this spectrum, called visible light. UV radiation is a very small portion of the sun’s electromagnetic spectrum, and the portion that disinfects does not transmit through the small atmospheric window shown for the UV region [27]. Figure credit: Science Mission Directorate, National Aeronautics and Space Administration (NASA).

Fig. 3. The electromagnetic spectrum from the sun, which includes various types of UV and other electromagnetic radiations and highlights the region for the optimal UV disinfection range [29]. Figure credit: Division of Technical Resources, Office of Research Facilities, U.S. National Institutes of Health.

Fig. 4. Historical measurements of the bactericidal action of UV radiation published by Gates in 1930 [39] using “methods of isolating and measuring monochromatic radiations, of preparing and exposing the bacteria, and of estimating the effects of exposure” [40]. (A) Curve of incident energies involved in the destruction of 50% of S. aureus. (B) Curve of the reciprocals of A. The curve on the left is described as a demonstration that “less incident energy is required between 260 nm and 270 nm than in any other region of the bactericidal zone examined and point toward a second minimum below 230 nm. The presence of a sharp peak in the energy requirement near 240 nm appears to be equally significant” [39]. Used with permission.

Fig. 5. Specific absorption cross section versus wavelength for proteins and nucleotides within the cell of a microorganism. Here, the dry weight percentages are protein (70%), nucleotides (20%), and other components (10%) (e.g., lipids). This figure was constructed per Bolton and Cotton [25] using average spectra for proteins and nucleotides along with the respective mass ratios. Used with permission.

Fig. 6. Absorption spectra of nucleotides and of DNA (from Bolton and Cotton [25], adapted from Harm, 1980³). Used with permission.⁴

Fig. 7. Advanced water treatment process at the Water Replenishment District of Southern California (WRD) Leo J. Vander Lans Water (LVL) Treatment Facility [57]. Stage 3 includes the use of UV radiation for the disinfection of microorganisms and other components that are broken down due to advanced oxidation processes catalyzed by photolysis reactions of water with UV radiation. Figure credit: WRD LVL.

Fig. 8. Recommended research directions from the NIST–IUVA workshop on UV technologies for healthcare, January 14−15, 2020, NIST, Gaithersburg, Maryland.