Sun Hazards in Your Car Watch Out for Skin Cancers and Photoaging on the Left Side of Your Body by Susan T. Butler MD When thinking about sun exposure, you might envision yourself on the beach or exercising outdoors. Research increasingly points to ultraviolet A UVA radiation penetrating through car windows. UV radiation from the sun, associated with about 90 percent of all skin cancers, reaches the earth as long- wavelength UVA and shortwave UV B rays. UV exposure is cumulative, and research has proven that skin exposed to sun shining through window glass, even in the office, can over time lead to significant skin damage. In a US study by Singer, et al, the researchers found asymmetric photodamage sun- induced skin damage on the face, with more brown pigment color and deeper wrinkles on the left. This finding is especially pronounced in men, who more consistently spend time driving cars over a lifetime. While younger women have more left-side than right-side skin cancers, at age 50 this trend in them reverses, and right-side skin cancers predominate until age 80. Though we can only speculate, the shift seen around age 50 may indicate that younger women spend more time as car drivers, receiving more exposure on the left side of their bodies, while older women may more often be passengers, thus sustaining more right-side sun damage. However, the number of vehicles per household has nearly doubled in the last 25 years, making it more likely that women today will spend more time as drivers rather than passengers. Our observations suggest that UVA exposure over the years may indeed play an important role in the development of this potentially dangerous skin cancer. Melanoma is linked with intense, intermittent UV exposure; its association with cumulative UV exposure has been unclear. In the US, the left side of the head, neck, arm and hand receive up to six times the dose of UV radiation as the right side in those sitting on the left side of the car. Protecting Yourself There are several ways to protect yourself in a car. The first is to apply a broad-spectrum sunscreen with an SPF sun protection factor of 15 or higher to your face, arms, neck and hands, about half an hour before you go driving. Be sure to reapply after two hours, or after sweating heavily. Hats are particularly important for men who have thinning hair and are at risk for developing skin cancer on top of their heads. Another sun safety strategy in the car is tinting or laminating applying UV-protective film to the window glass. Window tinting is regulated in many states, so be sure to check the laws, but clear window film is available throughout the country. One study noted a 93 percent reduction in skin cell death when UV exposure was filtered through UV-absorbing auto glass. Following all these precautions will help you stay sun-safe both on the road and once you reach your destination. Butler is a dermatologist and fellowship-trained Mohs micrographic surgeon. She is in private practice at the California Skin Institute in San Mateo, CA. Ann Dermatol Venereol 1994;121:721-3. Assessment of cumulative exposure to UVA through the study of asymmetrical facial skin aging. Clin Int in Aging 2010; 5:277-84. Association of asymmetrical facial photodamage with automobile driving. British Med J Clin Res 1986; 293:18. Increased prevalence of left-sided skin cancers. J Am Acad Dermatol 2010; Dec;63 6 :1006-10. Aging cars, aging drivers: important findings from the National Household Travel Survey. Institute of Transportation Engineers 2005; 75 9 :30-37. Indoor tanning and risk of melanoma: a case control study in a highly exposed population. Cancer Epidem Biomar Prev June 2010; 19 6. UV exposure in cars. Photodermatol Photoimmunol Photomed 2003;19:175-181. Measurement of protection afforded by ultraviolet-absorbing window film using an in vitro model of photodamage.
