On Friday, April 19, 2019 at 3:30:55 PM UTC-7, Dan Marotta wrote:
Earlier in this thread someone reported that he'd used a UV meter to
check various canopies and found that they blocked UV radiation.Â* He
also stated that other tests showed the same results.

My guess is that the most sun exposure occurs before flying, you know,
all that time spent standing around in the sun.Â* All of that sunscreen
and those solar protective garments are really great protection while
you're standing around or working in the sun.Â* I doubt they cause any
harm during flight, either.

On 4/19/2019 12:40 PM, wrote:
Best option, though expensive, would be a canopy with the UV screen built in.

The following info has been obtained from various, readily available sources.
1) Skin Cancer rates among the Pilot Population are 50% higher than the general population.
2) Our exposure to UV Radiation, a leading cause of Skin Cancer, increases by 3% to 5% for each 1,000 ft of altitude gain. Just wonderful news for high altitude work.

My Dad, who flew from 1942 to 2015, died from Melanoma which first developed on his chest. Dad was never one to go around without a shirt on but did typically wear very thin shirts while flying and soaring. Draw your own conclusions. In early 2016 I had all of the glass in my 172 replaced with green tint with the built-in UV screen. The cabin is more comfortable and safer as well.

--
Dan, 5J

Isn't there a time component too. The amount of UV under a canopy might be pretty low but you are continuously exposed to it for hours upon hours. That to me seems like it will make the impact on your skin from what would normally be considered a low exposure much higher. Personally I use 70+ sunscreen, I've heard that anything over ~35 is overkill but I like to be safe and don't want to reapply it every couple of hours. I would love to wear long sleeves but I am in the Southwest US and it gets HOT, even at reasonably high altitudes.