The degree of inactivation by ultraviolet radiation is directly related to the UV dose applied. The UV dose is the product of UV intensity [I] (expressed as energy per unit surface area) and exposure time [T].
Therefore: DOSE = I x T
This dose, sometimes referred to as fluence, is commonly expressed as millijoule per square centimeter (mJ/cm2). The units "J/m2" are used in most parts of the world except for North America, where "mJ/cm2" are used.
The reduction of micro-organisms is classified using a logarithmic scale. A single log reduction is a 90% reduction of organisms. A two log reduction is a 99% reduction of organisms, followed by a three log reduction (99.9%), etc. The UV-C exposure dosage needed for each level of reduction is shown in the table along with the published reference where the data came from.
| Persistence Bacteria On Dry Inanimate Surfaces | |
| Organism | Persistence |
| Acinetobacter spp. | 3 days to 5 months |
| Bordetella pertussis | 3-5 days |
| Campylobacter jejuni | Up to 6 days |
| Clostridium difficile (spores) | 5 months |
| Chlamydia pneumoniae | Up to 6 days |
| Chlamydia psittaci | 5 months |
| Chlamydia pneumoniae | Up to 30 hours |
| Chlamydia psittaci | 15 days |
| Corynebacterium diphtheria | 7 days – 6 months |
| Corynebacterium pseudotuberculosis | 1-8 days |
| Escherichia coli | 1.5 hours – 16 months |
| Enterococcus spp. including VRE and VSE | 5 days – 4 months |
| Haemophilus influenza | 12 days |
| Helicobacter pylori | Up to 90 minutes |
| Klebsiella spp. | 2 hours – 30 months |
| Listeria spp. | 1 day – 4 months |
| Mycobacterium bovis | Up to 2 months |
| Mycobacterium tuberculosis | 1 day – 4 months |
| Neisseria gonorrhoeae | 1-3 days |
| Proteus vulgaris | 1-2 days |
| Pseudomonas aeruginosa | 6 hours – 16 months; 5 weeks on dry floor |
| Salmonella typhi | 6 hours – 4 weeks |
| Salmonella typhimurium | 10 days – 4.2 years |
| Salmonella spp. | 1 day |
| Serratia marcescens | 3 days – 2 months; 5 weeks on dry floor |
| Shigella spp. | 2 days – 5 months |
| Staphylococcus aureus, including MRSA | 7 days – 7 months |
| Streptococcus pneumoniae | 1-20 days |
| Streptococcus pyogenes | 3 days – 6.5 months |
| Vibrio cholera | 1-7 days |
We compiled several links to studies made by top scientists, virologist and UV lighting experts around the world. Their work contributed to many major breakthroughs in UV lighting sterilization technologies and disinfection processes in a multitude of applications, including air, water and surface treatments using UVC lighting.
Evaluation of an Ultraviolet C (UVC) Light-Emitting Device for Disinfection of High Touch Surfaces in Hospital Critical Areas at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6801766/
UVC LED Irradiation Effectively Inactivates Aerosolized Viruses, Bacteria, and Fungi in a Chamber-Type Air Disinfection System at https://aem.asm.org/content/84/17/e00944-18#:~:text=UVC%20light%20is%20well%20known,materials%20(16%2C%2017).
Welch, D., Buonanno, M., Grilj, V. et al. Far-UVC light: A new tool to control the spread of airbornemediated microbial diseases. Sci Rep 8, 2752 (2018). https://doi.org/10.1038/s41598-018-21058-w
Tseng, CC, Li, CS. (2007). Inactivation of viruses on surfaces by ultraviolet germicidal irradiation. Journal of Occupational and Environmental Hygiene, 4(6): 400-5. Retrieved from https://www.tandfonline.com/doi/full/10.1080/15459620701329012
Nature of UV. (n.d.). Retrieved from American Air and Water at https://www.americanairandwater.com/uv-facts/uv-light.htm
Crosta, P. (2017). What to know about viruses. Retrieved from Medical News Today at https://www.medicalnewstoday.com/articles/158179
Krug, R. M. & Wagner, R. R. (2020). Virus: General Features, Definition. Retrieved from Encyclopedia Britannica at https://www.britannica.com/science/virus
Silverman, J. & Kiger, P. J. (2020). How Can Light Kill Viruses? Retrieved from How Stuff Works: Science at https://science.howstuffworks.com/life/cellular-microscopic/light-virus1.htm
UV Basics: How UV Disinfection Works (n.d.). Retrieved from Trojan UV at https://www.trojanuv.com/uv-basics?acceptCookies=1
Crosta, P. (2017). What to know about viruses. Retrieved from Medical News Today at https://www.medicalnewstoday.com/articles/158179
Geiger, D. (2020, April 28). UV Light Helps Duke Hospitals Fight Transmission of Superbugs. Retrieved from Duke Health website at https://www.dukehealth.org/blog/uv-light-helps-duke-hospitalsfight-transmission-of-superbugs
Mishra, M. (2019, December 4). UV lights in hospitals could help limit bacteria on phones. Retrieved from Reuters website at https://www.reuters.com/article/us-health-hospitals-uv-sanitizers/uvlights-in-hospitals-could-help-limit-bacteria-on-phones-idUSKBN1Y82L4
Tseng, CC, Li, CS. (2007). Inactivation of viruses on surfaces by ultraviolet germicidal irradiation. Journal of Occupational and Environmental Hygiene, 4(6): 400-5. Retrieved from https://www.tandfonline.com/doi/full/10.1080/15459620701329012
Ultraviolet and HVAC: Keys to reducing hospital acquired infections. (n.d.). Retrieved from Hospital News website at https://hospitalnews.com/ultraviolet-hvac-keys-reducing-hospital-acquiredinfections/
