Disinfecting Surfaces with UV Light to Reduce Exposure to SARS-CoV-2

Results for SARS-CoV-2 Surface Disinfection with UV- November 10, 2020

Challenge

UV radiation is a well-known inactivation approach for microorganisms that offers some advantages over liquid disinfectants as it can be performed automatically, remotely, and employed to disinfect surfaces, liquids, air, and rooms. UV disinfection devices can serve as an additional method to routine cleaning practices and is commonly utilized in healthcare settings. When deployed, these UV light devices emit UVC light (200-280 nm wavelength), which is the most germicidal part of the UV spectrum by damaging nucleic acids, leading to inactivation of a pathogen. A review of the literature for efficacy data against viruses[1], including human coronaviruses, suggests that the dose necessary to inactivate 90% of SARS-CoV-2 (i.e., a one log reduction) is approximately (median of compiled data) 3.6 mJ/cm² or as high as 10 mJ/cm². Scientists, industry, and end users have noted a lack of standardized approaches related to UV light dose measurements, substrate materials, and inoculum matrices.

Experimental UVC disinfection data for SARS-CoV-2 is currently limited to specific light sources with no assessment of the impact on efficacy of critical parameters such as inoculum media and substrate material.

EPA is conducting UV disinfection efficacy measurements on surfaces common to public transportation settings. These measurements inform both the public transit agencies and the general public about the potential efficacy of UV light as part of routine cleaning and disinfection practices.

Research Objective

The overall goal of this project is to provide an assessment to transportation agencies and the general public on the effectiveness of UV light-generating devices for the disinfection of surfaces contaminated with SARS-CoV-2. The primary purpose is to evaluate the efficacy of various UVC light generating approaches by quantifying virus inactivation on surfaces common to public transportation. The data and procedures used during testing will be summarized in the form of required UV dose measurements to reach a 99.9% inactivation (3 log reduction) of the virus for easy interpretation by the end user. The secondary focus is to establish protocols for UVC efficacy studies, which will inform the potential development of standardized methods for assessing effectiveness of UV devices.

Disclaimer

EPA is conducting several studies to support the response to the COVID-19 pandemic, the results of which may be useful to the Nation. The summary here is intended to provide a simple representation of the results of on-going testing; therefore, only a brief description of the purpose of the study, methods, and interim results are provided.  This study is being conducted in accordance with an approved Quality Assurance Project Plan. The interim results have been reviewed by internal EPA technical experts, quality assurance staff, and management. No interpretation of the interim results is provided. Once complete, the study and its results will be described in detail in a publication subjected to external, expert peer review. EPA does not endorse the purchase or sale of any commercial products or services.