If Dr. Scott Fosko had his way, truckers would slather on sunscreen as routinely as they log their miles. As National Skin Cancer Awareness month rolls by and the sun's rays get stronger, Fosko, chairman of dermatology at St. Louis University Medical School, wants people to know that driving increases the risk for skin cancer on the left side of the body.
For some time, he and colleagues in his department had been noticing that skin cancer was showing up more on the left side of their patients' faces and bodies than on the right side, especially on male patients.
To see if there was anything to their observations, they analyzed the medical records of all patients with non-midline skin cancer who had been referred for Mohs micrographic surgery at St. Louis University in 2004.
Of 890 patients, 468 (52.6 percent) had skin cancer on the left side of their face or body. That number was even higher when they looked at just men: 301 out of 557 (54 percent) had it on their left side.
"As we say in the research world, it was statistically significant for men to have left-side predominant skin cancer," Fosko said. "If women were 50 or younger, they had a left-side predominance as well."
He can only speculate, but Fosko thinks this statistic is rooted in the way women's driving habits have changed. Women age 50 and older rode in the passenger seat more often than driving. About 25 years ago, two-car homes became common, and a lot of women began driving as much as men.
Angie Laird had a basal cell carcinoma removed from her face recently and a malignant melanoma removed from her leg three years ago. Both were on her left side, and she's pretty sure that's no coincidence.
As director of marketing and admissions for a nursing home, Laird, 43, of Jerseyville, spends at least 25 hours a week in her car, driving to hospitals to do medical screenings and check on residents.
"Plus, my parents have a pool, I love to golf and we go to Mexico and on cruises a lot," she said. "What's odd about all this is that my grandfather had skin cancer on his hands. He sold insurance for years and would drive to Springfield once a week. He always drove with both hands on top of the steering wheel."
Joseph H. Mueller, 75, of Webster Groves, had already come to the conclusion that the basal cell carcinomas removed from his left ear and the left side of his nose were probably from driving.
"Of course in the winter time it shouldn't make a difference with the windows up," he said.
Not so, said the American Academy of Dermatology. Windshields now block UVA and UVB rays, but side and rear windows usually block only UVB rays.
UVB rays burn the skin and cause basal cell carcinoma and squamous cell carcinoma which are in the top layer of skin and not usually fatal. UVA rays penetrate the top layer of skin and are thought to cause melanoma, which can be more serious and even deadly. Experts also believe they might increase the carcinogenic affect of UVB rays.
Mueller was surprised by this nugget of information.
"I thought you could sit next to a window in a house and have sunlight streaming through and feel the warmth but not have the ultraviolet rays coming through," he said. "Apparently I'm mistaken."
Fosko recommends tinting or using UV filters on side windows and wearing broad-spectrum sunscreen and protective clothing while driving.
"If you're going to be in the car a lot and you have a lot of the risk factors for skin cancer, you probably want to protect yourself as best you can," said Fosko.
His study, which will appear in an upcoming issue of the Journal of the American Academy of Dermatology, also turned up a rather surprising finding: that 75 percent of one particular kind of skin cancer -- malignant melanoma in situ -- was on the left side of the body.
"It goes into the photo biology, or the pattern of ultraviolet exposure," he said. "Different types of exposure cause different types of damage to the cells of the skin. The thinking with malignant melanoma in situ is that it's chronic, long-term and cumulative exposure to the sun."
Malignant melanoma in situ affects only the top layer of skin. Fosko said it's nearly 99 percent curable if caught early, and is cut out of the skin during an outpatient procedure. It usually does not recur.
Fosko notes how professional drivers -- truck drivers, delivery drivers, postal carriers -- often wear safety equipment such as gloves, steel-toed boots and safety glasses. He strongly recommends they wear sunscreen, too.
SKIN CANCER TYPES IN SLU STUDY
In 2004, the department of dermatology at St. Louis University saw 890 patients with non-midline skin cancer, where the cancer was clearly on one side of the body.
The patients' average age was 68; 557 of them (62.5 percent) were men.
Dr. Scott Fosko, chairman of the department of dermatology, breaks down their skin cancer diagnoses.
608 (68.3 percent) had basal cell carcinoma -- It is nonfatal but can be disfiguring if not treated promptly. It appears as an open sore, reddish patch, shiny bump, pink growth or scar-like area.
178 (20 percent) had squamous cell carcinoma -- It is curable but can become disfiguring if it penetrates underlying tissues. A small percentage metastasize to distant tissues and organs, and can be fatal. It can also recur after removal. It looks like a thick, scaly patch that can bleed if bumped.
42 (4.7 percent) had malignant melanoma in situ -- It is confined to the top layer of skin and is nearly 100 percent curable. It appears as an irregularly shaped mole that's brown, asymmetrical and grows.
38 (4.2 percent) had squamous cell carcinoma in situ -- It is on the top layer of skin. It's highly curable because it hasn't penetrated skin layers or spread to other tissues and organs.
23 (2.5 percent) had invasive malignant melanoma -- It can quickly spread to lymph nodes and organs. It causes 75 percent of all skin cancer deaths. People who start using tanning beds before age 30 are 75 percent more likely to develop melanoma.
Explore further: Rising skin cancer rates are more likely to affect wealthy people, says 12-year review
Visit skincancer.org for more information.