The Difference Between Chronic and Intermittent Sun Exposure
Your risk of skin cancer depends, in large part, on your level of sun exposure. But, did you know that there are different types of sun exposure and what type of skin cancer you are most at risk for depends on how you are exposed to the sun?
Intermittent sun exposure is sporadic and often intense bursts of sun exposure. It is usually associated with indoor workers who spend weekends and vacations out in the sun. Acute sun exposure, which can result in sunburn, is more common in those who have intermittent sun exposure.
Chronic sun exposure is consistent and repetitive sun exposure. Outdoor workers and those who participate in outdoor activities on a daily or regular basis have chronic sun exposure.
Intermittent Sun Exposure and Melanoma
It is those who have intermittent sun exposure that are most at risk for developing melanoma, the most lethal form of skin cancer. Intermittent sun exposure includes using tanning salons on a irregular basis, for example, going to a tanning salon prior to a vacation or a major event. One of the reasons melanoma is much more common than in the past is that our society has moved from spending more time outdoors to spending more time indoors. Since intermittent sun exposure is associated with melanoma, it would stand to reason that as more people work and spend time indoors and then spend time in the sun on the weekends, the rate of melanoma would increase.
Besides sun exposure, there are other risk factors for developing melanoma:
- Having fair skin and/or red hair
- A large number of moles
- Having unusually shaped moles
- Weakened immune system
- Family history of melanoma
- Living at a high elevation or close to the equator
Scientists believe that melanoma develops because of a combination of factors. Certain people might have a higher risk because of their skin color or a family history of melanoma; these factors, added to intermittent sun exposure, might explain why some people get melanoma and others don't.
Chronic Sun Exposure and Non-Melanoma Skin Cancer
Basal cell carcinoma and squamous cell carcinoma are more apt to develop after years of chronic sun exposure. The cummulative affect of the sun is closely associated with the non-melanoma skin cancers. Many people use sun protection, such as sunscreen, when they plan to be outside for hours, for example if they are spending the day at the beach but don't use it on a daily basis, allowing the cummulative affects of the sun to continue building.
Researchers in one study explain that "over a lifetime, a person will receive tens of thousands of minimal erythema doses of UVR through normal, daily, incidental exposure." That includes the 15 minutes you stood outside talking to your neighbor, the short walk you took during your lunch break, the time you walked from your car to your home, and the time you sat in your car (UV rays can penetrate car windows.) The recommendations for sunscreen are that it should be reapplied every few hours. But, when spending most of the day indoors, this is rarely done.
Even when you think you aren't getting sun exposure, you are. The effects slowly add up over time, leaving you at risk of developing basal cell or squamous cell carcinoma. Using even a minimum sunscreen (SPF 4 -10) on a daily basis, can reduce your lifetime exposure by one-half.
Chronic sun exposure, according to some studies, might help protect individuals from melanoma or, at the very least, does not seem to increase your risk of developing melanoma. This is where "getting a suntan helps protect you from skin cancer" comes from. Scientists believe that as your body is constantly exposed to the sun, your skin develops ways to protect it and repair damaged cells. But this approach leaves you at a higher risk of developing basal cell or squamous cell carcinomas.