UV-C RADIATION

Knowledge and experience

WHAT IS UV-C LIGHT?

Ultraviolet germicidal radiation (UVGI) is part of the naturally occurring ultraviolet radiation from solar energy. It is completely absorbed by the ozone layer and does not reach the Earth’s surface. The current ability to emit UVGI comes only from artificial light sources. Of all the types of radiation, UV-C (falling in the band from 200 to 280nm) shows the strongest effects on biological materials. This allows UVGI to be used effectively for disinfection and decontamination of air and surfaces, preventing the spread of harmful infectious agents.

Spectrum UV

HOW UV-C INACTIVATES PATHOGENS?

The maximum UV absorption properties of biological compounds, including nucleic acids: DNA and RNA, are in the UV-C range. High-energy UV-C particles easily penetrate the cell wall of microorganisms damaging cell structures, thus deactivating them and preventing further multiplication. The germicidal effectiveness of UV-C radiation varies with the species of organisms and the wavelength range. The wavelength of 253.7nm is indicated as showing the strongest germicidal properties, corresponding to the largest range of UV absorption by bacteria, which is 260-265nm.

The cytotoxic properties of UV-C are used for sterilisation in hospitals, de-fumigation and the treatment of drinking water.

DNA molecules

  • UV-C (253.7 nm) penetrates the cell wall of the microorganism
  • High-energy UV-C photons are absorbed by cellular DNA/RNA proteins
  • UV-C damages protein structure, causing metabolic disorders
  • DNA/RNA is structurally altered so organisms cannot replicate
  • Organisms with damaged RNA/DNA are unable to metabolise and replicate, and cannot cause disease or damage to other organisms

UV-C light inactivates viruses, fungi and bacteria

 

List of bacteria, viruses, and fungi from Dr. W. Kowalski’s research on the effectiveness of UV-C in inactivating pathogens.

Bacteria

• Acinetobacter baumannii
• B. atrophaeus (B. globigii)
• Bacillus anthracis spores
• Bacillus subtilis
• Burkholderia cepacia
• Corynebacterium diphtheriae
• Escherichia coli
• Francisella tularensis
• Haemophilus influenzae
• Halobacterium sp. NRC-1
• Legionella dumoffi
• Legionella bozemanii
• Listeria monocytogenes
• Micrococcus candidus
• Mycobacterium bovis BCG
• Mycoplasma arthritidis
• Neisseria catarrhalis
• Proteus vulgaris
• Pseudomonas aeruginosa
• Salmonella enteritidis
• Sarcina lutea
• Shigella paradysenteriae
• Staphylococcus albus
• Streptococcus agalactiae

Viruses

• Adenovirus
• Bacteriophage MS2
• Coliphage X-174
• Coronavirus
• Coronavirus (SARS)
• Coxsackievirus
• Human Cytomegalovirus
• Influenza A virus
• Newcastle Disease Virus
• phage phi 6
• Poliovirus
• Poliovirus type 1
• Rauscher Murine Leukemia v.
• Rous Sarcoma virus (RSV)
• Sindbis virus
• S. aureus phage
• S. aureus phage
• Vaccinia virus

Fungi and other microorganisms

• Acanthameoba castellani
• Aspergillus amstelodami
• Aspergillus flavus
• Aspergillus fumigatus
• Blastomyces dermatitidis
• Botrytis cinerea
• Candida albicans
• Cladosporium herbarum
• C. sphaerospermum
• Cladosporium wernecki
• Cryptococcus neoformans
• Curvularia lunata
• Fusarium spp.
• Histoplasma capsulatum
• Monilinia fructigena
• Mucor mucedo
• Mucor spp.
• Penicillium chrysogenum
• Penicillium spp.
• Rhizopus nigricans
• Rhodotorula spp.
• Scopulariopsis brevicaulis
• Sporotrichum schenkii
• Torula bergeri
Kowalski, W.,
Ultraviolet Germicidal Irradiation Handbook,
UVGI for Air and Surface Disinfection,
wyd. Springer, Berlin, 2009

HOW TO CHECK THE EFFECTIVENESS OF UV-C?

The easy-to-use measuring tool provides real-time information about the disinfection performed. The delivery of the correct dose of UV-C radiation is determined by the colour of the photosensitive material on the surface of the dosimetry cards. With increasing exposure time the amount of UV-C radiation increases. The availability of the verification method is crucial to the overall process.

Dozymetr uvc

Yellow – indicates the readiness of the dosimetry card to receive UV radiation

Dozymetr uvc

Orange – means that UV-C radiation dose is received in the range 25 – 50 mJ/cm2

Dozymetr uvc

Pink – means an admission of UV-C radiation of at least 100 mJ/cm2

UV-C Radiation in international studies

01. Manual of ultraviolet bactericidal irradiation

Kowalski, W., Ultraviolet Germicidal Irradiation Handbook, UVGI for Air and Surface Disinfection, wyd. Springer, Berlin, 2009

02. Signify and Boston University confirm effectiveness of Signify’s UV-C light sources
in inactivating the virus that causes COVID-19

Signify and Boston University validate effectiveness of Signify’s UV-C light sources on inactivating the virus that causes COVID-19, 2020

03. Information from the International Ultraviolet Association on UV disinfection
with regard to COVID-19

International Ultraviolet Association (IUVA) UV disinfection for COVID-19, 2020

04. Reduction of MRSA and C.diff by 3 levels confirmed by UV-C sensitive indicators – Case University and Western Reserve in Cleveland

With exposure, the patented UV-sensitive material change from yellow to orange to pink, which can be correlated to a 3-log reduction of MRSA and C.diff – Case Western Reserve University, Cleveland

05. The UV-C dose required to achieve the incremental log reduction of bacteria, protozoa, viruses and algae.

Fluence (UV dose) Required to Achieve Incremental Log Reduction of Bacteria, Protozoa, Viruses and Algae.

06. Sterilizing Practices – guidance on disinfection and sterilisation in healthcare settings – European Centre for Disease Control and Prevention

Sterilizing Practices – Guideline for Disinfection and Sterilization in Healthcare Facilities (2008)

07. Comparison of UV-C light and chemical surface disinfection in hospital isolation units – University of Cambridge

Comparison of UV-C Light and Chemicals for Disinfection of Surfaces in Hospital Isolation Units – Cambridge University