Never heard of it. Granted haven't checked for writups on websites about it. Sure, I and a few others I know may be some exception to the rule but I'm 54 and my friends are about the same age. All of us veteran growers who have spent our fair share of time (since our early 20s) in our grow rooms and neither of us have had or heard anything of the sort occur.I think you're missing the point. You can't see or feel the damage being done but there's been a lot written about the cumulative skin and eye damage from the UV and IR from HID bulbs. Even some the manufacturers of these bulbs place warnings on their websites. Baseball caps may be of some help but I'm guessing not too much compared to long sleeves and good glasses. I guess it's similar to the sun........not much will show up as a teenager or young adult, but when you're in you 50's and 60's, it may be a different story. Fair skinned people probably have more to worry about than darker skinned growers too. Remember, it's proven to be cumulative and the issues compound as we get older.