Ken D. Rosenman, M.D.
Professor, Department of Medicine
The sun has been around forever and ever, and now they are saying it is bad for us. Why?
There is increased understanding that the ultraviolet rays from the sun are a major risk factor for skin cancer. So there has been increased news about reducing exposure to ultraviolet radiation. A study in Michigan found that 3 out of 10 farmers developed skin cancer by the time they were 70.


How much sun is bad for you?
There is no dividing line to say this much is bad and below this is safe. We know that people who spend a lot of time outside, either for recreation or their work such as construction workers or farmers, have an increased risk of getting basal and squamous cell cancer. For melanoma, it's not the total amount of exposure that is thought to be important but rather episodes of sunburn. Sunburning as a child might be very important for development of melanoma years later as an adult. Skin cancers are diseases typically occurring in people over the age of 40 but are caused by exposure to ultraviolet rays from the sun that began in childhood.


What types of skin cancer are there?
There are 3 types: basal cell, squamous cell and melanoma. The first two types of cancer are very treatable with 2,000-3,000 people dying each year in the U.S. out of 800,000 people who develop it. Melanoma is harder to treat with 7,000-8,000 people dying each year in the U.S. out of the 35,000 people who develop it. For all types of skin cancer it is important to treat them early to prevent death and to have fewer complications.


I like to go outside a lot. What can I do?
There are simple things to do: stay in the shade when possible; use sun screen with sun protection factor (SPF) 15 or greater; avoid being in sunlight in the middle of the day, 10:00 a.m. - 3:00 p.m.; wear a hat that covers the top of the ears and back of the neck (baseball caps miss these areas).


What does Sun Protection Factor (SPF) mean?
This number tells you how long you can stay outside without burning, typically it is 20 minutes times the SPF number. So for example for an SPF of 15, that is 20 minutes multiplied by 15 which is 300 minutes or 5 hours. A minimum of 15 is recommended and higher numbers are usually not necessary. However, when sun screens are tested to determine the SPF number, they put the sun screen on 1/2 hour before exposure and apply more than the average user does. Waterproof means the sun screen maintains its protective level after 80 minutes in the water and water resistant means the sun screen maintains its protection after 40 minutes in the water.


If I keep sun screen on can I stay outside all day and not be at increased risk for skin cancer?
The recommendation is if you are going to be outside all day that you periodically put on more sun screen.


Sun screen prevents me from burning but will it prevent me from developing skin cancer?
Yes, sun screen used correctly as well as less expensive alternatives such as staying in shade, proper clothing and hats will reduce your risk of skin cancer as well as stop you from burning.


How does sun screen work?
Some sun screens absorb the ultraviolet rays, both type A and B, while others physically block the ultraviolet rays. The kind that absorb the rays are usually colorless. The physical sun screens that block the ultraviolet rays come in different colors. The sunscreens with the highest SPF many combine both agents that absorb and block the ultraviolet rays.


What if I'm outside and it's cloudy, am I exposed to ultraviolet radiation from the sun?
Yes, clouds do not block ultraviolet rays. You do not have to be hot in order to be exposed to the harmful ultraviolet rays.


Do you increase your risk of skin cancer if you go to tanning booths?
Probably yes. Tanning booths use ultraviolet A rays. Ultraviolet A rays are less harmful than ultraviolet B rays but exposure to them in a tanning booth probably still increases your risk of skin cancer.


Would you suggest that African-Americans use a sunscreen?
African-Americans and other people with dark skin are at very low risk of skin cancer. They are naturally protected by the melanin, the dark pigment, in their skin. However, with prolonged exposure, African-Americans can get sun burn and an African-American individual, based on their history of sun burning and how long they will be outside, might want to use sun screen or the other protective measures.


Can people have skin reactions to sun screen?
Yes. You can become allergic to sun screen.


Is skin cancer treatable?
Skin cancer is very treatable, particularly when found early. One should periodically check one's own skin and in areas one can't see have a spouse or relative check. As part of regular physical examination, remind the doctor to check. For melanoma, the ABCD's of recognition are the following: Asymmetry of the skin growth (one half doesn't match the other half); Borders of the skin growth are irregular; Color of the skin growth is not uniform and; Diameter of the skin growth is greater than a pencil eraser. Any growth the size of a mole is of concern. Sores that don't heal, red scaly patches, and nodules are other signs of skin cancer.


Is it good preventive practice to get large moles removed from your body to prevent melanoma?
Moles that change in color, height, sensation, shape, size, or texture should be checked by a doctor. If the above is not happening then there is no medical reason to remove a mole.