What is ultraviolet light?
Ultraviolet is an invisible spectrum of light that primarily comprises wavelengths from 100 nm to 400 nm – UV-A, UV-B, and UV-C. All three of these types of UV light can be used for disinfecting, however, we’ll get into more detail about why UV-C is most effective against harmful pathogens.
UV lamps have been in use for water, air, and surface disinfection for nearly 100 years. We’ll focus on surface disinfection for this article. To better understand the difference between varying types of UV lamps, it’s important to know the 3 ultraviolet light spectrums and wavelength positives and negatives in relation to UV disinfection.
UV-A: UV-A is radiation that is in the region of the ultraviolet spectrum which is nearest to visible light and extends from about 320 to 400 nm in wavelength and that causes tanning and contributes to aging of the skin.
UV-B: UV-B is radiation that is in the region of the ultraviolet spectrum which extends from about 280 to 320 nm in wavelength and is primarily responsible for sunburn, aging of skin, and the development of skin cancer.
UV-C: Ideal for disinfection. UV-C is radiation that is in the region of the ultraviolet spectrum which extends from about 200 to 280 nm in wavelength and is more hazardous than UV-B but is completely absorbed by earth’s upper atmosphere.
Effectiveness of the 3 ultraviolet light types
Here is an example of the efficiency of these three types of ultraviolet rays (AIMS Microbiology Study). This study compares the effectiveness of UV-A, UV-B, and UV-C light in inactivating Phi6 and SARS-CoV-2m, and addresses whether Phi6 is a suitable SARS-CoV-2 surrogate for testing virus inactivation by ultraviolet radiation. Like coronaviruses, Phi-6 is an enveloped RNA virus, but one that is nonpathogenic. This study focuses on log reduction data compared to these three types of UV light.
All UV spectral ranges examined in the present work show antiviral properties towards Phi6, with UVC proving to be the most effective and UVA the least one (Source: UVC, UVB, and UVA susceptibility of Phi6 and its suitability as a SARS-CoV-2 surrogate).
In this study, the Phi6 bacteriophage and its host Pseudomonas syringae were propagated under controlled conditions. The virus was diluted to 10⁷ PFU/mL and exposed to UV-C (254 nm), UV-B (311 nm), and UV-A (365 nm) light at a 32 cm distance. Irradiation intensity was measured with a calibrated UV-VIS spectroradiometer, ensuring uniform exposure. Post-irradiation, virus concentrations were measured using a double agar overlay plaque assay. The study included three replicates per wavelength and assessed the effects of UV light on virus inactivation, offering insights into UV efficiency across different spectra.
Based on data from the test results, here is how long it took to achieve a 3 Log reduction with UV-A, UV-B, and UV-C:
- UV-A: 36 Hours
- UV-B: 8 Hours
- UV-C: 5 Minutes
The study concluded that “all UV spectral ranges examined in the present work show antiviral properties toward Phi6, with UVC proving to be the most effective and UVA the least one.” This is compelling data and can be used to better understand the efficiency and effectiveness of different wavelengths, and comparisons of different UV disinfection products.
In conclusion, while all ultraviolet light types demonstrate antiviral properties, UV-C light stands out as the most potent for disinfection, delivering rapid and effective pathogen inactivation. Its efficiency, compared to the much slower UV-A and UV-B, underscores the importance of selecting the right UV wavelength for optimal germicidal outcomes. When paired with key factors such as intensity, exposure time, and direct line of sight, UV-C light emerges as a powerful tool in modern disinfection, offering a compelling solution for mitigating harmful pathogens in various environments.
Reference Sources:
Log Reduction of UV-C, UV-B, UV-A, https://www.aimspress.com/article/doi/10.3934/microbiol.2022020?viewType=HTML
Melanie Turner, Some household products email unhealthy levels of ozone, study finds, https://ww2.arb.ca.gov/news/some-household-products-emit-unhealthy-levels-ozone-study-finds
Ultraviolet C Light at 222 nm, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10684113/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9281457/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8136854/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7894148/
https://sanuvox.com/en/blog/effect-of-germicidal-uv-on-plastic-materials/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2230791/
https://www.ccohs.ca/oshanswers/phys_agents/ultravioletradiation.html
https://pubmed.ncbi.nlm.nih.gov/33534912/
https://www.epa.gov/ground-level-ozone-pollution/health-effects-ozone-pollution
