Will every wave length of UV work for killing bacteria? So will UV A, UV B and UV C all work? Or will only the shortest of the three, UV C, work? Also, will the average UV lamp help against bacterial growth (if it is shone on an object for 3-5 minutes for example)? What about a longer period: a bacterial colony in a petri dish under an average household UV lamp for a day? Would the growth be reduced noticeably? Or would the change be too small to notice when using the average UV lamp? Does the type of UV also matter for this (A/B/C)?

  • $\begingroup$ Can you tell us where you want to use UV as an antibacterial measure? $\endgroup$ – Chris Sep 23 '14 at 18:03
  • $\begingroup$ I'm planning on using it on two places: on my hands, and on a bacterial colony in a petri dish with nutrients. $\endgroup$ – Dasherman Sep 23 '14 at 18:57

The CDC's disinfection guidelines lists UV radiation between 328 and 210nm as effective for disinfection, with a maximum of bactericidal activity occurring between 240-280nm. At this wavelength DNA damage (Thymine dimers) is induced with a high rate.

Due to practical reasons UV light is mostly used to disinfect water, if used in rooms there is some effectiveness against microorganisms in the air and some on surfaces, but on one hand the effectiveness is reduced by square with the distance from the UV source and on the other hand you need completely empty surfaces where nothing casts shadows. The other problems are plastic materials which may get damaged by repeated UV exposure.

Have a look at this reference (only available via Google Books): "Principles and practices of disinfection, preservation and sterilization." and this subchapter.

  • $\begingroup$ I'm planning on using it both directly on my hands, with the lamp being quite close to my hands (we're talking about a distance of centimeters here). I'm also planning on shining the lamp on a bacterial colony in a petri dish with nutrients, again with quite a small distance (decimeters, this time). $\endgroup$ – Dasherman Sep 23 '14 at 18:59
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    $\begingroup$ Be very careful with your hands. This will cause sunburns in a very short time (depending on the source this might happen in minutes). $\endgroup$ – Chris Sep 23 '14 at 19:00
  • $\begingroup$ Would 3-5 minutes be harmful? Because that's how long I'm planning on exposing my own skin. The fear of getting sunburns would, however, be quite a strong reason not to. $\endgroup$ – Dasherman Sep 23 '14 at 19:58
  • $\begingroup$ With the UV sources that I know from the lab this is definitely enough to get a strong sunburn. But why do you want to expose your skin like this? $\endgroup$ – Chris Sep 23 '14 at 20:29
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    $\begingroup$ No, mo likely not. Or not completely as your hands are not a flat surface. There will be shadows and areas of low exposure. Plus the risk of sunburns (which can also occur in the eye when you look to long into the lightsource with unprotected eyes. Chemical disinfection works better. Even better is wearing gloves and disinfect them. $\endgroup$ – Chris Sep 23 '14 at 20:46

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