A pen you can lend without fear of passing on bugs?

My last post concerned Asking for Evidence about chia seeds and ended with a thrilling cliffhanger: what happened when I started asking questions about anti-bac pens? I’ll bet you’ve been biting your nails (you shouldn’t, bad habit) just dying to hear about it. Well the wait is finally over…

First of all, in case you’ve never heard of an ‘anti-bac’ pen, allow me to enlighten you. These are pens made of a special plastic that has been treated to be antibacterial. That pen you lent your mate only to suspect they might have been sticking it in their mouth, and possibly even more disturbing bodily orifices? Fear no more, if it’s an anti-bac pen no germs will adhere to its plastic barrel, and you can continue to chew it yourself with impunity.

Well that’s the theory anyway. A quick look at the website http://www.anti-bac.ltd.uk throws up a number of interesting claims. In particular, “The active agent is moulded into the pen and is effective 100% of the time for the entire lifetime of the pen.” and “kills 99.9% of harmful bacteria and viruses” (hey biologists, can you kill a virus?)

The anti-bac website also mentions BS EN 20645, and after a bit of studious googling (I believe I’m correctly following official guidance in using that verb) I discovered this standard relates to the antibacterial activity of textiles, specifically “woven, knitted and other flat textiles”. At the risk of stating the obvious, these pens aren’t knitted. Although apparently the standard can be applied to other materials, providing it’s “adapted accordingly”.

So, how was the test adapted? Are the results published somewhere? Does it really last for the ‘entire lifetime’ the pen (and what is that?) Exactly how much bacterial and viral genocide actually occurs on contact with this shiny white plastic?

I emailed the company to ask them about these questions. What did they say?

Wait for it…

Nothing, nil, nada. No answer. I even used the ‘sales’ address, as companies often actually check that one.

Huh. Well obviously this would be a very short piece if I’d stopped there. So I went in search of another expert, and quickly managed to dig up the contact details of Professor Ian Jones at the University of Reading.

A molecule of triclosan; bacteria beware!

Unlike Anti-bac Ltd he was very quick to reply to my emails, and told me that these pens work in a similar way to anti-bacterial chopping boards. They incorporate a disinfectant into the plastic, usually triclosan. Triclosan is an antibacterial and antifungal agent. It’s actually quite a small molecule, falling into a group called polychloro phenoxy phenol. Sounds good doesn’t it? For the non-chemists out there, things with benzene rings (those hexagon thingies) and phenols (hexagon thingies with OH attached) are often not especially good for one’s health.

And so we find the fire diamond for triclosan… now if you’re a regular reader you’ll be an expert with these by now. If not, just a quick reminder, the higher the number the nastier it is. That 2 in the blue section means that continued exposure could cause possible residual injury. Other substances with a 2 include the old-fashioned anaesthetic ether, and anti-freeze ingredient ethylene glycol. Of course, this is referring to significant quantities of the free chemical, not minute amounts embedded in plastic. And the Environmental Protection Agency concluded that exposure to triclosan – which turns up in lots of things, including anti-bacterial soaps – doesn’t present significant risks to human health. It might not even be triclosan in the anti-bac pens (the company didn’t get back to me, so we don’t know). Still… it raises an interesting point, given how paranoid many people are about chemical exposure. Which is riskier? Bacterial exposure or chemical exposure? Especially taking into account the findings from the University of Michigan School of Public Health that washing with plain soap is actually more effective than using those with antibacterial agents such as triclosan.

Anyway, back to the anti-bac pen claims. Professor Jones went on to say that these pens “have their place, especially in situations which are very sensitive to contamination issues like hospital wards and surgeries. The downside is a false feeling of safety when in fact everything else you touch has not been sanitised in the same way and the fact that their use detracts a little from the real challenge which is to get people to adopt routine hygiene measures such that their hands are not likely to be sources of infection in the first place.”

I asked him more about the ‘lifetime of the pen’ issue, and he explained that the disinfectant is built into the plastic, so organisms are indeed killed when they come into contact with it. As the grip wears down fresh plastic is revealed, so theoretically the anti-bacterial properties never wear out. The problem is that that, of course, pens are picked up by sticky, greasy, sweaty fingers all the time and stuffed into icky pockets and less-than-pristine pencil cases. Once the plastic gets covered in a layer of grime, the whole thing will stop working.

He finished by telling me that “these materials never completely kill organisms, they reduce numbers between 100 and 1000 times. However that can still leave a significant number of organisms alive.”

So in summary, chances are the active ingredient won’t really be effective for the lifetime of the pen under normal handling conditions. It might be true that active ingredient kills 99.9% of bacteria, but that could still leave quite a lot on the pen. Worth spending your money on? Maybe in places such as hospital wards, where the people handling them already (we hope) have scrupulously clean hands, but in your child’s grubby pencil case? Probably not.

Want more? The third part of my Ask For Evidence work was recently published on the Sense About Science website, you can read it here.