Science Inventory

Evaluating the impact of ultraviolet C exposure conditions on coliphage MS2 inactivation on surfaces

Citation:

Ratliff, K., L. Oudejans, Michael Calfee, A. Abdel-Hady, M. Monge, AND D. Aslett. Evaluating the impact of ultraviolet C exposure conditions on coliphage MS2 inactivation on surfaces. Letters in Applied Microbiology. Blackwell Publishing, Malden, MA, 75(4):933-941, (2022). https://doi.org/10.1111/lam.13770

Impact/Purpose:

The COVID-19 pandemic has raised interest in using devices that emit ultraviolet-C (UVC) radiation as an alternative approach to disinfecting surfaces, and an increasing number UVC devices are being marketed. Research to determine how effective these different UVC sources are against microorganisms and viruses is often conducted using different methods and laboratory conditions, which can make it difficult to compare results between studies and understand how effective UVC devices will be in real-world settings. In this research, we compare how some of these different experimental factors affect the efficacy of UVC light for disinfecting surfaces. We propose that microscopic differences between even smooth materials can potentially shield microorganisms and viruses from UVC light, making the surface an important factor in determining how effective the light can be, and that the UVC dose reported to achieve a 90% reduction cannot always be linearly extrapolated to predict the 99.9% reduction dose.

Description:

Ultraviolet-C (UVC) radiation has long been used to disinfect air, water, and surfaces. The COVID-19 pandemic has recently raised interest in using UVC devices as an alternative approach for disinfecting surfaces and materials, as an increasing number of UVC devices come to market. Studies investigating the efficacy of UVC radiation against pathogens on surfaces use a wide range of laboratory methods and experimental conditions that can make cross-comparison of results and extrapolation of findings to real world settings difficult. Here, we use three different UVC-generating sources – a broad spectrum pulsed xenon light, a continuous light-emitting diode (LED), and a low-pressure mercury vapor lamp – to evaluate the impact of different experimental conditions on UVC efficacy against the coliphage MS2 on surfaces. We find that a nonlinear dose-response relationship exists for all three light sources, meaning that linear extrapolation of doses resulting in a 1-log10 (90%) reduction does not accurately predict the dose required for higher (e.g., 3-log10 or 99.9%) reductions. In addition, our results show that the underlying substrate plays an important role in determining UVC efficacy. Variations in microscopic surface topography across four different smooth, nonporous materials (301 stainless steel, 304 stainless steel, glass, and ABS plastic) may shield MS2 from UVC radiation to different degrees, which impacts UVC device efficacy. These findings are important to consider in comparing results from different UVC studies and in estimating device performance in field conditions.