Tuesday, 18 November 2014

Antibacterial handwash/ cleaners and cancer

A paper in late 2014 suggested a link between triclosan, the antibacterial agent in many hand washes, kitchen and bathroom cleaners, and liver cancer. This inevitably caused a fair amount of excitement in the press. But should we be abandoning these products immediately?

The trial involved mice being fed 3 grams of triclosan a day for six months. The mice suffered liver damage and as a result were more susceptible to cancer produced by other carcinogenic substances. What does this mean for us? It's almost impossible to say. To begin with, it is difficult to make a straight weight for weight comparison with animal trials. Dogs, for instance, are much more sensitive to the theobromine in chocolate than humans, weight for weight. But the best guesses we can make to see what the trial involved is that mice have a rough weight-for-weight comparison with us.

A mouse typically weighs about 20 grams, so they were receiving 3/20ths of their body weight in triclosan daily for six months. The average UK adult woman weighs about 70 kilograms, so the equivalent would be to consume 10.5 kilograms of triclosan a day for six months. A typical surface cleaner contains about 0.3 percent triclosan. So that would mean consuming the equivalent of the triclosan in 6,000 half litre bottles of cleaner every day.

This is not to say that it's a good thing to consume considerable quantities of triclosan - but this research provides no useful evidence on its lack of safety or on safe levels of use.

Let's look at the four main ways that we come across triclosan (and similar antibacterial agents).

  • It is found in antibacterial handwash. There is no evidence this removes bacteria from the hands any better than washing with ordinary soap. This being the case, it is best not to use antibacterial handwash, both because of any risk from the substance and (more likely) in case of the risk of bacteria developing resistance mentioned below.
  • It is found in antibacterial surface sprays. These do have some benefits in reducing bacterial contamination on surfaces and are probably still worth using.
  • It is found in some toothpastes, where it is suggested (with very limited evidence) that it can help with gingivitis and plaque. Best avoided. This can be difficult, as the toothpaste itself doesn't have a contents list - but search for your toothpaste and 'contents' on the web to get the information. The best-known brand containing triclosan at the time of writing is Colgate Total - though bear in mind to get equivalent quantities to the mice you would have to swallow around 12,000 tubes of toothpaste a day.
  • It is found in some cosmetics. There are no benefits other than as a preservative, but it is very difficult to discover which products contain it, and you are unlikely to consume much of your cosmetics, so this is unlikely to be a cause for concern.
Overall we ought to focus the use of antibacterial cleaners where they have the most benefit. There is limited evidence, though it hasn't been fully proven, that too high levels of antibacterial agents in the environment can trigger bacterial resistance to antibacterial agents or even antibiotics. While more evidence is required, it seems worth limiting use to surface cleaners.

You can see the original paper at the Proceedings of the National Academy of Sciences of the USA though you would need a subscription to read more than a summary. It is The commonly used antimicrobial additive triclosan is a liver tumor promoter. Mei-Fei Yueha, Koji Taniguchib, Shujuan Chena, Ronald M. Evansc, Bruce D. Hammockd,1, Michael Karinb, and Robert H. Tukeya, doi: 10.1073/pnas.1419119111

  • Chocolate
  • Hand washing

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