Kills 99.9% of Germs — Sometimes

I’m a big fan of those alcohol-based gel hand sanitizers. I’m already a bit of a hypochondriac so I didn’t feel as weird this year when everyone started to use them during the H1N1 pandemic. After all, everyone knows they kill 99.9% of germs. Right? Well, um, sort of. The Wall Street Journal has a cool “Numbers Guy” column, and recently he discussed exactly what those sanitizer companies need to do to make those claims. Apparently, at least in the U.S., they must follow very strict guidelines to prove this — but not technically against viruses such as H1N1. In fact, saying 99.9% still doesn’t mean that it is effective against all germs, just against many. Plus, these tests are done in labs and not in real-world conditions. One doctor performed just such a test with perfect subjects — schoolkids. He only got 46-60% effectiveness. Of course, one big reason may be improper use of the gels (not enough time, not enough amount). It’s the same problem with birth control: the published rates of efficacy at 99% are far higher than real world effectiveness in the low 90’s.

Here are some interesting quotes from the article (Kills 99.9% of Germs — Sometimes – WSJ.com):

To cite a 99.9% fatality rate, manufacturers don’t have to kill 99.9% of all known bugs. Regulations don’t require them to disclose which bugs they exterminate, just that the products are effective against a representative sample of microbes. For instance, many products can’t kill clostridium difficile, a gastrointestinal scourge, or the hepatitis A virus, which inflames the liver. Yet by killing other, more common bugs, they can claim 99.9% effectiveness…



To claim that other microbe-unfriendly products such as household cleaners and clothing kill 99.99% of germs, companies are permitted to show such deadliness less than 99.99% of the time, according to the EPA’s rules. The standard test is run on 60 slides inoculated with a specific bug, and 59 of them treated with the product must exhibit the claimed rate of germ death. The 60th can fail to allow for a mistake on the part of testers, according to Jean Schoeni, director of research at TRAC Microbiology, which conducts EPA testing. “It’s a very fussy, particular test,” Dr. Schoeni says. Furthermore, if fewer than 59 slides show the high kill rate, manufacturers get a do-over…

The bottom line? I still think alcohol gel sanitizers are great, and even better than soap and water, but you need to do it correctly: keep rubbing your hands for up to 20 seconds. Plus, if your hands are soiled (dirt, diapers…) you still need good old fashioned soap and water.

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