Managing Your Exposure to Solar UV Radiation for Better Skin Health

With spring comes warmer weather and more opportunities to spend time outdoors exercising, recreating, gardening, etc. However, the intensity of solar radiation is also increasing, which means that precautions should be taken to reduce the likelihood of sunburns, and on the longer term, the risk of skin cancers and the photoaging of skin. Application of a sunscreen onto exposed skin surfaces is an important way of minimizing the potential for skin reddening. It should have a sun protection factor (SPF) value of 30 or higher and provide broad-spectrum protection against both ultraviolet A and B radiations. In addition, consider the use of a hat to cover your head and clothing to protect other exposed skin surfaces along with the use of sunglasses.

To enhance your skin care, though, there are additional considerations such as (1) the areas of your skin that you should focus on in reducing UV exposures and (2) whether you need to be concerned mainly about intermittent, high intensity UV exposures or long-term cumulative exposures to solar UV.

Exposure to Solar UV Radiation and the Risk of Skin Cancer

Epidemiological studies have shown that most skin cancers are concentrated on sun-exposed areas of the body, particularly the head and neck, followed by the body trunk (Narayanan et al. 2010). For example, Moan et al. (2015) reported that the relative tumor densities of squamous cell and basal cell carcinomas were much higher on the head than the body trunk for a Norwegian cohort. In contrast, they  found that the tumor densities for cutaneous melanoma were about the same on the head and torso.

These epidemiological findings suggest that the use of a hat while outdoors during periods of elevated solar UV would be an effective way of reducing UV exposures to the head and hence the risk of skin cancers. Wide-brimmed hats would provide additional protection to the neck area. Sunscreen applications to the face/neck are also beneficial for UV protection, however, Holman et al. (2015) showed that sunscreen use is fairly low for US adults--which limits its effectiveness in reducing skin cancers in the US population. Barriers to sunscreen use may be related to cost, knowledge of its benefits, inconvenience, forgetting, and a desire to tan (see Armstrong et al., 2009).

Another aspect of sun exposure that is very important to consider is that both intermittent and cumulative exposures are important risk factors in skin cancer formation! Squamous cell carcinomas are linked mainly to cumulative UV exposures, basal cell carcinomas are related to both intermittent and cumulative UV exposures, and cutaneous melanomas are primarily associated with intermittent (intense) exposures (Narayanan et al. 2010; Moan et al., 2015). 

Lifelong UV exposure-control practices should therefore be aimed at both intermittent and cumulative UV exposures in order to reduce the risks of skin cancer. Avoiding sunburns during adolescence and consciously limiting UV exposures via lifestyle choices such as wearing hats, protective clothing, applying sunscreen, etc. are all components of a healthy skin-care regimen.

Schedule Outdoor Activities to Times when the UV Index is Low

Sun-protection measures should be commensurate to the magnitude of UV solar radiation. And this means that you need to monitor UV radiation levels by time of day. For example, by limiting your time outdoors to the hours when UV radiation is low, you can dramatically cut down on exposures. Nevertheless, to ensure that UV levels are indeed low, it is imperative to monitor the expected UV Index (i.e., UVI), depicted in the next chart.

The UV Index for a given location can be simulated as a function of latitude, longitude, time of the year, surface elevation, and the level of ozone. Often the predicted values are referred to “blue sky” or “clear sky” results because the effects of cloud cover, airborne particulates, and reflected sunlight from snow, sand, etc. are not considered. Consequently, the predicted values are reasonable upper limits of the UVI for the given time and location.

The hourly UVI predicted for the location associated with the IP address of your computer or smartphone is shown in the chart below. Note the hours when the UVI is “Low” or “Moderate” in order to schedule activities outdoors for reduced exposures. If your planned outdoor activities will extend to the times when “High” to “Extreme” UVI levels are predicted to occur, then rely on sunscreen, hats, available shade, clothing, and sunglasses to control sun exposures.

Noontime UV Index Widget

Wrap Up

  • Given the elevated prevalence of skin cancers on the head and neck as well as the barriers to sunscreen use, consider wearing a hat (wide-brimmed preferred to baseball cap) as a lifestyle choice to reduce your skin cancer risk.
  • Epidemiological studies demonstrate that skin cancers are connected to both intermittent and cumulative, lifelong UV irradiation.
  • Parents should monitor their children's UV exposure to prevent sunburns, which are a risk factor for skin cancer later in life.
  • Monitoring the UV Index can help inform your daily activities and skin-care practices for avoiding UV stressors.

References

Armstrong, April W., Alice J. Watson, Maryanne Makredes, Jason E. Frangos, Alexandra B. Kimball, and Joseph C. Kvedar. 2009. “Text-Message Reminders to Improve Sunscreen Use: A Randomized, Controlled Trial Using Electronic Monitoring.” Archives of Dermatology 145: 1230–36.

Holman, Dawn M., Zahava Berkowitz, Gery P. Guy, Nikki A. Hawkins, Mona Saraiya, and Meg Watson. 2015. “Patterns of Sunscreen Use on the Face and Other Exposed Skin among US Adults.” Journal of the American Academy of Dermatology 73: 83–92.

Moan, Johan, Mantas Grigalavicius, Zivile Baturaite, Arne Dahlback, and Asta Juzeniene. 2015. “The Relationship between UV Exposure and Incidence of Skin Cancer.” Photodermatology, Photoimmunology & Photomedicine 31: 26–35.

Narayanan, Deevya L., Rao N. Saladi, and Joshua L. Fox. 2010. “Review: Ultraviolet Radiation and Skin Cancer.” International Journal of Dermatology 49: 978–86.