Observation of the Sri Lanka College of Microbiologists on the use of UVC air purifiers
There are three types of UV rays. UVA (315 nm to 400 nm), UVB (280 nm to 315 nm) and UVC (200 nm to 280 nm) (Figure 1). All UV types (UVA, UVB and UVC) create different risks for humans. The only type of UV light which can reliably inactivate bacteria and viruses is UVC which is the most dangerous type for humans 1. UVC from sunlight is filtered out by the ozone layer in the atmosphere, so that humans are naturally protected from UVC 2.
Figure 1: Ultraviolet portion of the electromagnetic spectrum (Taken from reference 3)
UVC is detrimental to DNA/RNA and can destroy genetic materials in humans and viral particles within seconds of exposure. Exposure to UV radiation is damaging to the cells. While the effect of exposure of human cells to UVC is still being studied, the American Cancer Society has identified UVC as “reasonably anticipated to be a carcinogen” 4. Some of the devices that produce UV light also produce ozone as part of their cycle 5. Ozone can also be hazardous to humans if exposed, causing damage to lungs and worsening of chronic respiratory conditions. The World Health Organization warns against using ultraviolet disinfection lamps to sanitize hands or other areas of the skin 5.
Therefore, considering the above health hazards, UVC light should only be applied to vacant, unoccupied, closed environments where all proper safety precautions are strictly observed. There should not be any leaks/ penetration of UV light into spaces where people are present 6. These devices must be used properly to be safe to ensure that no one is exposed during the time of disinfection. Hence, to use UVC safely, specialist equipment and training is essential. Strict controls such as sensors should be in place to assure that no person is entering into a space when UV light is in operation 7.
UVC light has been in use for disinfection and sterilization of air in various applications such as in air purifiers to “scrub” the air in health care facilities and industries and also as a surface disinfection method8. Though UVC is known to inactivate bacteria and viruses, there is less evidence for its activity against SARS-CoV-2, the virus that causes COVID-19. It has been proven to be effective for other corona viruses (SARS-CoV and MERS-CoV) under controlled conditions in the laboratory 9,10. However, the effectiveness of UV light in practice depends on factors such the exposure time and the ability of the UV light to reach virus particles in air, and in the folds and crevices of materials and surfaces 11. In a recent study which looked at whether UVC could be used to disinfect Personal Protective Equipment (PPE), the authors found that of all the viruses that have been investigated so far, SARS-CoV-2 needed the highest exposure of UV light 12. Further, humidity can reduce the effectiveness of germicidal effect of UVC. Moreover, when UVC is used in ducts in the air purification systems, it is less effective in preventing person-to-person transmission in a room where both an infectious source and other susceptible persons share the same air 13.
Given the wide array of UVC devices marketed by various companies and the lack of uniform performance standards, with highly variable degree of validation and performance testing, these devices should be certified and tested by a local expert agency for their effectiveness and safety before use in the local setting. Currently, there is no authoritative organization/ agency to test the performance and safety of these devices and do validation or commissioning. Potential occupational exposure from poor installation and human errors can have serious health issues 12.
The WHO and CDC specifically state that these devices can be used as a complementary system to HEPA filtered air exchange systems 7,14. In the local context, in public health care settings, the use of such a system is not practical. However, they may have a place in terminal cleaning of separate rooms or isolation rooms with attached toilets once a patient is discharged.
Considering the above, the SLCM does not recommend the use of UVC light for air sterilization in the local setting until:
- further research/ guidelines prove its effectiveness against COVID-19
- a safer method of applying UVC is devised as applicable to local health care unit designs
- all engineering and administrative controls are in place to effectively monitor hazard levels using UVC in these institutions
- it is shown to significantly contribute to break the chain of transmission considering the expenses associated
- it is demonstrated to be have significant advantages over simpler and less hazardous and less expensive methods used to clean and disinfect healthcare environment
Further, we have noted that certain private vendors are marketing germicidal devices containing UV light for home use during this tragic pandemic. The following is a quote from the report by IES Committee on germicidal Ultraviolet (GUV);
“Compact GUV products are sold but are considered a serious safety concern in a general household environment, where children, pets, or careless adults can easily be overexposed. These products are typically less than 10 watts, with open and exposed mercury lamps”.
As a professional body, SLCM advises the public to be aware of the harmful effects of these devices as described above.
The Sri Lanka College of Microbiologists is a professional body established with the goal of promoting the advancement of Medical Microbiology in Sri Lanka and has no conflict of interest either financial or otherwise regarding content presented in this document.
- World Health Organization. Ultraviolet radiation and the INTERSUN Programme. https://www.who.int/uv/faq/whatisuv/en/index2.html . Accessed on 08/05/2020
- World Health Organization. Protection Against Exposure to Ultraviolet Radiation. Available at https://www.who.int/docstore/peh-uv/pub/whoehg95-17.htm Accessed on 07/05/2020
- Forrest FENCL, How UV-C energy works in HVAC applications: Part 1. Available from https://www.csemag.com/articles/how-uv-c-energy-works-in-hvac-applications-part-1/ Accessed on 08/05/2020
- Ultraviolet (UV) Radiation. https://www.cancer.org/cancer/cancer-causes/radiation-exposure/uv-radiation.html. Accessed on 07/05/2020
- IUVA Fact Sheet on UV Disinfection for COVID-19. Available at http://www.iuva.org/IUVA-Fact-Sheet-on-UV-Disinfection-for-COVID-19. Accessed on 07/05/2020
- World Health Organization. Ultra-violet (UV) lamps should not be used to disinfect hands or other areas of your skin. Available at https://www.who.int/emergencies/diseases/novel-coronavirus-2019/advice-for-public/myth-busters Accessed on 07/05/2020
- World Health Organization. Severe Acute Respiratory Infections Treatment Centre Practical manual to set up and manage a SARI treatment centre and a SARI screening facility in health care facilities. March 2020. Available from https://www.who.int/publications-detail/severe-acute-respiratory-infections-treatment-centre
- Memarzadeh F, Olmsted R, Bartley J. Applications of ultraviolet germicidal irradiation disinfection in health care facilities: Effective adjunct, but not standalone technology. Am J Infect Control 2010;38:S13-24
- Bedell K, Buchaklian AH, Perlman S. Efficacy of an automated multiple emitter whole-room ultraviolet-C sisinfection system against Coronaviruses MHV and MERS-CoV. Infect Control Hosp Epidemiol. 2016 May;37(5):598-9. doi: 10.1017/ice.2015.348.
- Darnell ME, Subbarao K, Feinstone SM, Taylor DR. Inactivation of the coronavirus that induces severe acute respiratory syndrome, SARS-CoV. J Virol Methods. 2004 Oct;121(1):85-91. PubMed PMID: 15350737; PubMed Central PMCID: PMC7112912.
- CDC-a, Decontamination and Reuse of Filtering Facepiece Respirators https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/decontamination-reuse-respirators.html Accessed on 07/05/2020
- Derraik JG, Anderson WA, Connelly EA, Anderson YC. Rapid evidence summary on SARS-CoV-2 survivorship and disinfection, and a reusable PPE protocol using a double-hit process. medRxiv preprint. doi: https://doi.org/10.1101/2020.04.02.20051409.t this version posted April 6, 2020.
- IES Committee Report: Germicidal Ultraviolet (GUV) – Frequently Asked Questions. IES CR-2-20-V1. Available at https://www.ies.org/standards/committee-reports/ies-committee-report-cr-2-20-faqs/ Accessed on 07/05/2020
- CDC. Environmental Infection Control Guidelines, Available at https://www.cdc.gov/infectioncontrol/guidelines/environmental/background/air.html#table7 Accessed on 08/05/2020