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Comment by alexandros | Hacker News Reader

What I'm more worried about is the claim that they kill 99.9% of germs. This would mean that the most resistant 0.1% get all the free space to grow. We're not disinfecting our world, we're creating evolutionary pressure on the germs to become resistant to our countermeasures.

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Some things are easier to evolve a resistance to than others. The antibacterial measures we apply externally (rather than internally) tend to be more of the "would kill anything living" variety than the "targets specific, removable weakness of this organism". Hence, hard to adapt to.

Hand sanitizers, for example, work by immersing bacteria in alcohol, a potent organic solvent. It dissolves cell membranes and denatures proteins.

While there are bugs that can live in some pretty harsh conditions, to my mind, worrying about the bacteria in your kitchen sink spontaneously developing resistance to alcohol is like worrying about them spontaneously developing resistance to boiling water.

Possible, on the millions-of-years scale. Not exactly a big concern in this lifetime.

Another big reason resistance to alcohol (and boiling water) doesn't develop is that neither is persistent in the environment, and thus the selective pressure vanishes fairly quickly. The mutations required to resist either likely have downsides in normal environments, and thus will normally be selected against.

Does that mean they kill 99.9% of known germ types (i.e. some are resistant). Or that it is able to kill 99.9% of germs on a known object (i.e. some random subset of germs will escape destruction for whatever reason).

I suppose the former but I've never researched.

That's interesting. I always interpret it to be 99.9% of the population on a given surface. It could be read as types also I guess.

EDIT: the article posted here http://news.ycombinator.com/item?id=1031922 seems to support the 'types' theory, although it also casts significant doubt on the validity of the claims.

...and the other 0.1% kill you...

"we're creating evolutionary pressure on the germs to become resistant to our countermeasures"

I thought that's what we were doing anyway.

It's an arms race.

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