Mad Dogs and Englishmen ..
Go out in the midday sun ...
Today has been another beautiful sunny Central Otago summer’s day (even if rather too warm by afternoon).
I played nine holes of golf this morning. I got up early and applied sunscreen before I went. I put on my wide-brimmed sunhat, and three of us teed off at 8:30 am. The course was beautiful, but the golf was mixed. We finished shortly after 10:00 am, and repaired for a cup of coffee.
Here’s how the UVI varied over the day, taken from the free UVNZ smartphone app that my friend Jerry Burke produced.
As you can see from the plot, when we finished our game, the UVI was about 5, and rising steeply. The app also tells you the dose of UV received on a horizontal surface (like a bald pate). By that time of the day, the total UV received was 2 MED, which is twice the amount needed to cause visible damage to the skin (1 MED = 1 Minimum Erythema Dose = 1 dose of skin-damaging UV). So it was good that we took precautions. For sensitive skins, those doses are much larger. I’d set the app to display the doses for skin type III, which is rather insensitive to UV damage.
Perhaps we should have played even earlier. But if we’d instead played for the same time interval over the peak UV period (encompassing 2 pm), the dose would have been 5 times as much!. It would have exceeded 10 MED. That sunscreen and hat would be indispensable.
And, if we’d loitered outside all day, the total damaging dose we’d received would have been close to 30 MED. So even if we’d applied sunscreen of SPF 30, we still would have received skin damage (because sunscreen are rarely applied thickly enough to achieve advertised performance).
By playing early, we avoided the worst. The peak UVI was 11.7 at 2 pm when the sun elevation is highest. The maximum temperature exceeded 32 degrees celsiua, so in the heat of the afternoon I sought refuge inside the comfort of our house. Here’s a view out the window of a thundercloud forming.
As I finish writing, it’s about 6:30 pm. Another good time to play golf. Nice and cool too (and dry if that thunder-clump doesn’t develop). There’s still plenty of time. It’ll still be light at 9:00 pm.
Sadly, the Saturday competition golf in Alexandra tees off around 1 pm. Exactly the wrong time!
If you’re in New Zealand, download the UVNZ app so you can plan your own days to minimize your UV-exposure risk. It costs nothing and may save your life. If you live outside New Zealand, install the GlobalUV app.
Thank you for listening. For more occasional free posts on the intersection of UV, Health and Climate, please click below