UV dosimeter badges

And the secrets they reveal ...

If you really want to know how much UV your skin is getting exposed to, you need to wear a device that measures it during your normal day-to-day activities. A couple of my colleagues here in New Zealand - Martin Allen and Zim Sherman - have been instrumental (if you’ll excuse the pun) in developing such devices. We call them UV dosimeters, though pedants may argue the name is slightly misleading because they measure the UV available outside the skin rather than the UV received inside it (i.e., the actual ‘dose’).

But ‘dosimeters’ works fine for me. At first sight they look like wrist-watches. But instead of the face showing a clock dial or digital readout, it’s made of a piece of blank white teflon that transmits UV radiation. Hidden behind that face is a sensor designed to measure skin-damaging UV. Further electronics amplify and log the data, which is later downloaded for computer analysis. Martin and Zim have now gone their separate ways. You can find details of their products here and here.

Results from such devices can be surprising. Our group at Lauder has assisted with calibrating them and interpreting the data. A study we were involved with a few years back showed how useless fixed instruments are in estimating real-life personal UV exposure. Dosimeter data taken over several weeks involving about 500 participants in Auckland and Dunedin showed that those Kiwis typically got only around 3 percent of the available UV. Admittedly, somewhat more than our (noctural!) emblematic namesakes, but not by nearly as much as we expected. This shows that - for these city-dwellers at least - behavioural differences are potentially far more important than geographical differences or long term changes UV. I suppose the good news is that this group was practising Sun-Smart behaviour.

But not so for all groups. Especially outdoor sports-people. Studies with similar sensors worn by marathon runners, skiers, or cyclists, for example, show that their personal UV exposures can far-exceed safe limits. Sunscreen-use is a must for those groups.

Don’t assume - in your youthful exuberance (if you’re lucky enough to be there) - that you’re bulletproof. These things tend to catch up with you in later life. I heard last week that my cousin’s hubby in Auckland had just succumbed to melanoma. He was a good guy, too young to die. And he’s just the most recent victim in a long line from my acquaintances.

The message needs to get out.

Perhaps these dosimeters can help. The inexpensive sensors used in them can also be used in static UV displays at high-risk locations like beaches, sports arenas, and children’s play areas.

Here’s an example from a multi-sport event I was helping with a few years back. Unfortunately, although the sensors are inexpensive, the other engineering isn’t. So we made only a few of them before settling on smart phone apps instead.

If you hunger for more about the innards of the UV dosimeters, read all the gory details here.