Sunday, August 26, 2012

Hawaii and sun protection

Every year we visit our dermatologist and  wonder if something will have to be cut off, frozen off, or sampled for cancer.  Even though we pour on high-SPF sunscreen every day, having fair skin in the tropical Hawaiian sun increases our risk of getting skin cancer.  This year, the Doctor told some things about sunscreen and skin cancer that we did not know.

The SPF (skin protection factor) number used for sunscreen is based on a “fractional calculation” of the amount of sunlight being blocked which is 1 divided by the SPF number. So, SPF 15  allows 1/ 15th of the sunlight through which means it blocks about 93% of the sunlight.  SPF 30 allows 1/30th of the sunlight through, which blocks 96% of the sunlight. We didn’t realize that doubling the SPF number only meant that 3% more of the sunlight was blocked. 

The SPF number on sunscreen is only related to blocking Ultra Violet B (UVB) rays which cause sunburns.  We use sunscreen and usually stay inside from 9AM-4PM in Hawaii when UVB is the strongest.  Though that protects us from sunburn,  it turns out that UVB is not the primary cause of skin cancer. 

Ultra Violet A (UVA) rays have been known to damage the skin, but it also responsible for giving you a great tan.  Only recently was it was discovered that UVA exposure is the primary cause of skin cancer.  This is a problem because UVA is the same strength all day, so doing our walks later in the afternoon is not providing us any protection from it.  We assumed that the thick vog (volcanic emissions) in Kona was filtering out all the UV rays, but UVA goes right through clouds and vog.  We are even exposed behind a glass window inside our house or car. Researchers believe that this is one of the reasons workers in offices with large windows have increased rates of skin cancer. Our Hawaii tans and freckles are from five years of UVA, even though we thought we were minimizing our sun exposure.
The  FDA has not approved a SPF-like rating for UVA, so using sunscreen does not necessarily provide any protection. There are some ingredients that are thought to help block UVA such as oxybenzone, titanium dioxide, and zinc oxide, however it is not known how much protection they really offer.

We like spending time on the beach and soaking up the Hawaiian sunlight, so keeping track of how much time we are outside as well as wearing hats and covering up is our best protection. Meanwhile, we hope that more is learned about the risks and benefits of UVA.  


city said...

thanks for sharing.

Art Brown said...

Sun protection is nothing to take lightly. It's better safe than sorry. I also burn way too easily so I try to remember to put on sunblock before I go out. I know of some great dermatologists as well that give great suggestions.