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How Helpful is Sunscreen?

 

 

 

 Kathleen Souweine

Date: 11/16/2005

 

At one point, each and every one of us has gotten the sunscreen lecture: “If you use sunscreen you won’t get skin cancer, and you won’t end up all wrinkly at the age of 45.”  But how much truth does this statement really hold?  The purpose of this website is to find out the real reason why we wear sunscreen (or why everyone tells us we should) and how helpful it really is.   

How does sunscreen work?
 

 

 

 

 


First of all, we all know that without sun protection most people will get a sunburn, causing redness.  A sunburn is the result of cellular damage from ultraviolet radiation.  The human body is built to deal with damage by trying to repair it.  Thus, when you get a sunburn, your body increases blood flow to the skin in order to send in cells to repair the damaged ones.  This increased blood flow explains the redness of the skin.  The chemicals in sunscreens work by blocking, absorbing, or reflecting ultraviolet light, thus decreasing the chance of sun damage. 

  

What’s the big deal about sun damage?                                                                                                        

 

Repeated sun damage is linked to premature wrinkling, skin damage, and several types of skin cancer including melanoma, basal, and squamous cell carcinoma.  Studies indicate that severe sunburns early on in life may increase chances for melanoma later in life.     

 

How effective is sunscreen against skin cancer?   


 

         Unfortunately, wearing sunscreen does not guarantee that you will never get skin cancer.  Sunscreen helps prevent skin damage and skin cancer but there are other factors to take into consideration. 

First of all, you must wear sunscreen correctly.  Liberally apply SPF 15 sunscreen or higher a half an hour before going out into the sun.  Reapply about every one and a half hours or after swimming, towel drying, or sweating.  What does SPF mean?  SPF stands for sun protection factor and acts as a multiplying factor.  If you are normally safe in the sun for ten minutes, then with an SPF 10 sunscreen you will be safe in the sun for one hundred minutes.  A higher SPF means a stronger sunscreen. 

Furthermore, the U.S. Environmental Protection Agency recommends avoiding the sun during its strongest hours between 10 a.m. and 4 p.m. and wearing a hat, protective clothing and sunglasses during prolonged periods in the sun. 

Finally, there may be one more somewhat surprising thing to consider.  The sun produces three types of rays; UVA, UVB, and UVC.  UVC rays are filtered out by the atmosphere, but the longer wavelengths of UVA and UVB reach us on the Earth.  However, most sunscreens do not offer protection from UVA wavelengths.  In fact, SPF applies only to UVB wavelengths.  Although some websites claim UVA rays are not harmful and can be considered a safe way to tan, most emphasize the fact that no UV light is safe.  Products that claim “all day protection” and “broad spectrum sunblock” offer protection from both UVA and UVB rays.  

 

         The above information and more about sun protection can be found at the following websites:

www.aad.org/pamphlets/sunscreen.html

www.travel.howstuffworks.com/sunscreen.htm

www.pueblo.gsa.gov/cic_text/health/sun_uv/sun-uv-you.htm

www.healthlink.mcw.edu/article/964647970.html

 

                                                                                                                      

Sunscreen Use, Melanoma and Sun Exposure

 

Melanoma is a cancer of the pigment-producing cells in your body.  Over the past forty years, the incidence of melanoma has shown an increasing trend worldwide.  Melanoma is the severest of the skin cancers due to its high lethality. Due to results showing sunscreen use has the ability to reduce UVB – induced skin cancers, sunscreen has become an important part of melanoma prevention.  However, it is difficult to draw conclusions on the degree of protection sunscreen offers from preventing melanoma because of several confounding variables.  These confounding variables may include different risk factors, improper sunscreen use and human behavior towards the sunlight. 

The two major risk factors for melanoma are skin sensitivity and exposure to ultraviolet radiation from the sun.  Other risk factors include age, sex, family history of melanoma, number of moles, and exposure to artificial ultraviolet radiation.  Risk factors are confounding variables that may affect a sunscreen user’s chance of getting melanoma.  However, while people with more sensitive skin are at a greater use for melanoma, these same people are more likely to use sunscreen.  In this example, sunscreen use cannot be linked with lower melanoma risk.

Improper sunscreen use is another important confounding variable.  A person may use sunscreen to protect against sunburn, thus allowing themselves long sunbathing hours.  However, sunscreens do not protect the skin during prolonged exposure to the sun and thus sunscreen use without a reduction in sun contact may not lessen risk for skin cancer.  In one experiment, “the group that received sunscreen with an SPF of 30 had higher cumulative exposure to sun and longer daily sunbathing than did the group that used sunscreen with an SPF of 10” (Dennis).  This result proves that sunscreen use is a confounding variable of sun exposure.  Other factors of improper sunscreen use involve persons not applying generous enough amounts of sunscreen and not reapplying when necessary.

It should be mentioned that improper sunscreen use may be the result of certain behaviors towards sunbathing.  In our day and age, suntans are considered more attractive and healthy looking than paler skin.  “A literature review carried out for the period between 1977 and 1998 showed that intentional sun exposure is highly prevalent among youths, despite their awareness of the risks involved in excessive exposure to ultraviolet radiation and their knowledge on skin protection measures” (Souza).  This type of excessive sun exposure can cause the types of burns associated with melanoma.

Scientists limited knowledge of UVA rays influence in development of melanoma also adds difficulty to the sunscreen-melanoma relationship.  Until fairly recently, UVB rays were considered the cancer causing rays while UVA rays were left out of that equation.  Now, the cause UVA rays have in premature aging is increasingly recognized, as well as the acceptance that UVA rays do play some part in melanoma risk.  Since most sunscreens are only UVB protective, sunscreen protected bathers may still be putting themselves at risk for melanoma.  However, to what effect UVA rays effect melanoma risk is unknown.

In conclusion, although wearing sunscreen will clearly lower one’s risk of developing melanoma, there are many confounding variables to take into account when linking sunscreen to melanoma.  Because of these variables as well as new data on UVA rays, there haven’t been any recent experiments that have clearly stated how much wearing sunscreen reduces melanoma risk.  In the future, I expect someone will conduct an experiment with many controlling variables that will be able to answer this question for us.

 

Autier, P., Dore, J.F., Renard, F., Luther, H., Cattarazza, M.S., Gefeller, O., Grivegnee, A. (1997) Melanoma and Sunscreen Use: Need for Studies Representative of Actual Behaviours.  European Institute of Oncology, Suppl 2: 115-20

Dennis, L., Freeman, L.E., & VanBeek, M. (2003) Sunscreen Use and the Risk for

Melanoma: A Quantitative Review. Annals of Internal Medicine, Vol. 139, Issue 12, 966-978

         Souza, S., Fischer, F., Souza, J. (2004) Suntanning and Risk of Cutaneous Melanoma: a Literature Review. Revista de Saude Publica, vol.38, no.4

 

 

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