Which is more efficient as a germicide: UVC, Ozone or combination and why?

Question

I've read many contradictory info about ozone vs UVC light irradiation and cannot come to a conclusion, I am totally confused.

As it commonly known UV germicidal irradiation is very effective against bacteria, virus, molds, but in the disadvantages chapter one can read

Another potential danger is the UV production of ozone, which can be harmful to one's health. The US Environmental Protection Agency designated 0.05 parts per million (ppm) of ozone to be a safe level. Lamps designed to release UVC and higher frequencies are doped so that any UV light below 254 nm wavelengths will not be released, to minimize ozone production. A full-spectrum lamp will release all UV wavelengths and produce ozone when UVC hits oxygen (O2) molecules.

OK, ozone is a bad guy which can cause mutations, cardiovascular diseases and other bad things.

But then I read about ozone magic germicide abilities, that it can destroy all types of bacteria, water treatment, air purification and even cleaning of contaminated soils, and maybe even COVID-19. So why they often advise against ozone?

I've found not so much science researches about comparative efficiency of zone and UVC, for example this which seems very dated (2003), and it says that UV is less costly but not as much universal and effective for water purification as ozone.

This one, more recent, clearly states the idea I also came to:

Vacuum-UV lamps with ozone production were found to be effective for inactivating various human pathogens.

Also I've found many comparative tables like this that confirms better ozone efficiency in all circumstances

We know that UV-lamps with wavelength below 254 nm produces ozone so why not to combine their strengths together?

So where is the truth in all these contradictory sources? How to filter out all those marketing fluff that ozone and UV-lamp sellers put into our ears?

P.S. I saw this question and it covers only part of mine.

Answer 1

Your question contains the word "efficient". The most efficient method is the one with achieves the goal with the minimum of effort or disadvantages. And that totally depends on what you want to do exactly.

• If you have a surface like a lab bench, you use ethanol or iso-propanol because its cheap, quick, relatively safe to use for that purpose and dries up quickly without remaining substance.
• If you have a cabinet to work with, you use UV irradiation because you can leave it on at night where it does not hurt your eyes/skin and it can pervade the small corners in the cabinet.
• If you have a pool, you use ozone or chlorine because you have liquid water here so ethanol does not reach the desired concentration. However UV is also an option, for example for sewage treatment
• If you have a small volume of liquid, you can use a microfilter because it's faster than using UV and does not split chemical bonds.
• If yo have a living organism, you use antibiotics which are weaker (in comparison to the measures above) and more expensive but you cannot use the other measures because they would kill the organism

So both efficiency and efficacy of desinfection have to be chosen based on the concrete situation. There is not "the most efficient" way of disinfecting.