Sun smarts for runners.

The American Cancer Society estimates that greater than 1 million cases of non-melanoma skin cancer are diagnosed each year, and in 2005 the American Cancer Society predicted that almost 60,000 cases of melanoma would occur (1). Because ultraviolet radiation (UVR) exposure is a major risk factor for the development of these cutaneous tumors, athletes involved in outdoor sports experience a heightened risk. In one study of professional cyclists in the Tour de Suisse, researchers found that cyclists endured more than 30 times the upper limits of UVR exposure set by the International Commission for Nonionizing Radiation Protection (2). Other studies have found comparable exposure levels in professional triathletes and skiers (3,4). These findings suggest that runners who experience significant exposure to UVR would benefit from photoprotective measures.

The American Academy of Dermatology offers a number of recommendations to the population-at-large for protection from harmful UVR. Some of the recommendations include avoiding activity outdoors between the hours of 10 am and 4 pm, seeking shade when possible, wearing protective clothing along with hats and sunglasses, and using a sunscreen with an SPF of at least 15 (5). Beyond these basic measures, the runner should be aware of particular considerations in choosing and using a sunscreen as well as the factors influencing the ability of clothing to provide UVR protection. The following review of these factors will aid the runner in making educated choices for protection.

A) Sunscreen

Daily sunscreen reduced the number of incident actinic keratoses, precursors to squamous cell carcinoma in two double-blind, randomized, controlled clinical trials (6,7). Importantly, effective protection from UVR depends upon the sunscreen's spectrum of protection and water resistance, as well as upon the ability of the athlete to apply the sunscreen appropriately.

i) Spectrum of protection

When choosing a sunscreen it is most important to ensure the product provides broad-spectrum protection against both UVA and UVB. The spectrum of UV light that reaches the earth's surface includes UVA and UVB rays, with the majority being UVA as most of the UVB is filtered by the ozone layer. Sunburns are caused by UVB, while the aging effects of the sun are caused by UVA. Therefore, sunscreens only blocking UVB provide a false sense of security in the athlete who is free of sunburn, as penetrating UVA can cause significant damage. Importantly, both UVA and UVB have been implicated in the development of skin cancers (8). The majority of sunscreens achieve broad-spectrum coverage through a combination of physical blocking agents, such a magnesium oxide or titanium dioxide, and UV absorbing agents such as cinnamate derivatives and dibenzoylmethanes (9).

ii) Delivery Medium

Characteristics of sunscreen products vary widely. Newer sunscreen formulations exist and include less greasy versions and even "spray-on" sunscreens. Personal preference should dictate this decision, as no studies yet promulgate superiority of one vehicle over another.

iii) Water/Sweat Resistance

Runners must recognize the importance of water-resistance when choosing a sunscreen. One study found that those sunscreens with labels of "water resistant" and "water proof" showed only gradual decrease in protection with water immersion compared to sunscreens without these descriptors which were readily washed away (10). Of note, the FDA requires water resistant sunscreens to meet certain standards. "Water resistant" products must retain their designated SPF level after 40 minutes of water exposure, while "water proof" products must maintain their SPF after 80 minutes of water exposure (9). Importantly, reapplication every few hours is necessary if the athlete is outdoors for extended periods. During periods of intense sweating, runners may need to reapply sunscreen even more frequently since this type of sweating is clearly more intensive than the studies to determine a sunscreen's water tolerability.

iv) Appropriate Application

Quite commonly, inadequate application of sunscreen results in less protection than the listed SPF (11). The American Academy of Dermatology suggests that users apply at least an amount that could fill a shot glass. The Academy also recommends applying sunscreen 15 to 30 minutes before going outdoors and reapplying every two hours as well as after swimming (5).

B) Clothing

In addition to sunscreen, clothing possesses UVR protective properties as well; however, not all clothing types provide equal levels of protection. Analogous to the SPF of sunscreen, UPF or ultraviolet protection factor designates the level of protection provided by a particular piece of clothing as determined by laboratory measurements. UPF can be affected by multiple factors including inherent characteristics of the material, dyes and chemical additives, laundering, and wetness (see Table 1).

i) Fabric type and construction

In general, polyester provides superior protection over fabrics composed of cotton, linen, and rayon (12). Other factors also contribute to a fabric's overall UPF. Heavier fabrics and a tighter weave contribute to decrease the size of holes in the fabric, thereby increasing the UPF (12,13,14). Tight clothing that stretches with wear provides decreased UVR protection due to the increase in hole size associated with stretch (15).

ii) Dyes/UVR Absorbers

Dyed clothing and UVR absorbers added to the fabric in production also serve to increase the UPF. In general, darker colors provide better protection. In one study, blue dye and yellow dye added to white cotton t-shirts increased the UPF from a mean value of 5.2 before treatment to mean values of 16.5 (yellow) and 33.2 (blue) after treatment. In the same study, researchers laundered white cotton t-shirt swatches with a mean UPF of 4.8 with a UVR-absorbing agent. A significant increase in UPF after each wash was observed such that after one wash the UPF increased to 10.9 and after five washes the UPF rose to 23.0 (16).

iii) Effect of Washing

Another study required 20 volunteers to wear a cotton jersey-knit t-shirt for four to eight hours each week for 10 weeks with weekly washes. The UPF of the t-shirts increased from a mean value of 19 to 40.6. Examination of the t-shirts under a light microscope showed a measurable decrease in hole area, postulated to be due to shrinkage from laundering (17). A different study showed a similar trend (16).

iv) Wetness

In general, the UPF of most fabrics decreases with wetness (18,19,20); however, exceptions do exist. One study showed that the fabrics modal and polyester crepe treated with UVR absorbers (titanium dioxide) actually have increased UPF values in the wet state. Other fabrics in this particular study such as linen, viscose, and polyester proved to have no significant change in UPF when wet (20).

In summary, the tighter the weave of the fabric, the better protection it provides. Traditionally, polyester has been shown to provide more effective protection than cotton; however, the addition of chemicals to garments during the production process may null the discrepancy. Darker colors, in general, have increased UVR protection, but increased perspiration in these shades may prove counterproductive. Typically, when garments become wet (through sweating during exercise) UVR protection goes down. Laundering clothes will increase the UV protection, which is attributed to the shrinking of the fibers. Stretching of garments due to a tight-fit will increase the space between the weave thereby decreasing its photoprotective properties.

In view of the extensive UVR exposure runners can encounter, it is important to incorporate appropriate protective measures into daily running routines as a preventive measure against skin aging and carcinogenesis. Proper application and reapplication of broad-spectrum, waterproof sunscreens and the use of appropriate protective clothing are vital components of skin health for runners.

REFERENCES

1. American Cancer Society. Cancer Facts & Figures 2005.

2. Moehrle M, Heinrich I., Schmid A, Garbe C. Extreme UV exposure of professional cyclists. Dermatology 2000; 201: 44-45.

3. Moehrle M. Ultraviolet exposure in the Ironman triathlon. Med Sci Sports Exerc. 2001; 33(8): 1385-1386.

4. Rigel EG, Lebwohl MG, Rigel AC, Rigel DS. Ultraviolet radiation in alpine skiing. Arch Dermatol. Jan 2003; 139: 60-62.

5. American Academy of Dermatology website: www.aad.org

6. Naylor MF, Boyd A, Smith DW, Cameron GS, Hubbard D, Neldner KH. High sun protection factor sunscreens in the suppression of actinic neoplasia. Arch Dermatol. Feb 1995; 131: 170-175.

7. Thompson SC, Jolley D, Marks R. Reduction of solar keratoses by regular sunscreen use. N Engl J Med. Oct 1993; 329: 1147-51.

8. Nole G, Johnson AW. An analysis of cumulative lifetime solar ultraviolet radiation exposure and the benefits of daily sun protection. Dermatol Ther. 2004; 17: 57-62.

9. Moloney FJ, Collins S, Murphy GM. Sunscreens: safety, efficacy, and appropriate use. Am J Clin Dermatol. 2002; 3(3): 185-91.

10. Stokes RP, Diffey BL. The water resistance of sunscreen and day-care products. Br J Dermatol. 1999; 140: 259-63.

11. Sternberg C, Larko O. Sunscreen application and its importance for the sun protection factor. Arch Dermatol. 1985; 121: 1400-2.

12. Davis S, Capjack L, Kerr N, Fedosejevs R. Clothing as protection from ultraviolet radiation: which fabric is most effective? Int J Dermatol. 1997; 36: 374-379.

13. Gambichler T, Altmeyer P, Hoffman K. Role of clothes in sun protection. Recent Results Cancer Res. 2002; 160: 15-25.

14. Morison W. Photoprotection by clothing. Dermatol Ther. 2003; 16: 16-22.

15. Kimlin MG, Parisi AV, Meldrum LR. Effect of stretch on the ultraviolet spectral transmission of one type of commonly used clothing. Photodermunol Photoimmunol Photomed 1999; 15: 171-74.

16. Wang SQ, Kopf AW, Marx J, Bogdan A, Polsky D, Bart RS. Reduction of ultraviolet transmission through cotton t-shirt fabrics with low ultraviolet protection by various laundering methods and dyeing: clinical implications. J Am Acad Dermatol. May 2001; 44(5): 767-774.

17. Stanford DG, Georgouras KE, Pailthorpe MT. Sun protection by a summer-weight garment: the effect of washing and wearing. Med J Aust. Apr 1995; 162(8): 422-425.

18. Parisi AV, Kimlin MG, Mulheran L, Meldrum LR, Randall C. Field-based measurements of personal erythemal ultraviolet exposure through a common summer garment. Photodermatol Photoimmunol Photomed. 2000; 16: 134-38.

19. Moerhle M, Koehle W, Dietz K, Lischka G. Reduction of minimal erythema dose by sweating. Photodermatol Photoimmunol Photomed. 2000; 16: 260-62.

20. Gambichler T, Hatch KL, Avermaete A, Altmeyer P, Hoffman K. Influence of wetness on the ultraviolet protection factor (UPF) of textiles: in vitro and in vivo measurements. Photodermatol Photoimmunol Photomed. 2002; 18: 29-35.

Matthew J. Meier, MD, Resident in Dermatology, University of Cincinnati, College of Medicine, Department of Dermatology, Cincinnati, Ohio

Brian B. Adams, MD, MPH, Associate Professor, University of Cincinnati, College of Medicine, Department of Dermatology; Chief of Dermatology, Veterans Administration Medical Center, Cincinnati, Ohio

Address correspondence and reprint requests to:

Brian B. Adams, MD, MPH, University of Cincinnati, College of Medicine, Department of Dermatology, P.O. Box 670592, Cincinnati, OH 45267-0592; [e-mail]

Table 1 Factors Affecting UPF

Increase UPF   Decrease UPF

Polyester      Stretch
Tight weave    Wetness
Dyed clothing
UVR absorbers
Laundering