Wear Sunscreen: Occupational risks for skin cancer
Dr. Sonja Molin, Chair of the Division of Dermatology, recently invited Dr. Peter Elsner, Professor of Dermatology and Chairman at Friedrich-Schiller-University Jena to speak at our Medical Grand Rounds on skin cancer as an occupational risk. Spoiler alert, the occupational victims are not miners, poisoned by arsenic, radium or some nefarious toxin, it is outdoor workers, poisoned by unprotected exposure to the sun.
Drs. Molin and Elsner
Ladies and Gentlemen of the class of '99, Wear Sunscreen
If I could offer you only one tip for the future, Sunscreen would be it
The long term benefits of sunscreen have been proved by scientists
whereas the rest of my advice has no basis more reliable than my own meandering experience
I will dispense this advice now
...Mary Theresa Schmich(born November 29, 1953)
Ms Schmich is a Pulitzer prize winning Chicago Tribune columnist who penned this amazing bit of life advice for a fictitious convocation. It was popularized in a recording produced by Baz Luhrmann, featuring spoken song by Lee Parry, an Australian voice-over artist. Since the first release of this blog my daughter, Elizabeth, sent me a podcast on the incredible story of Sunscreen's genesis (check it out).
I want to share Dr. Elsner’s simple but important message, in hopes it helps you or someone you care about avoid skin cancer. His message? Certain occupations, notably those requiring prolonged outdoor work, accelerate skin aging and formation of precancerous lesions. Over time, prolonged occupational sun exposure more than doubles the risk of developing the two commonest skin cancers,squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) (Figure below).
Figure 1:Actinic Keratosis (precancerous) Basal cell carcinoma (BCC) squamous cell carcinoma (SCC)
We live on a planet that is bombarded with ultraviolet (UV) radiation, a form of short-wave length light that is invisible to the eye. It is called ultraviolet because its wavelengths are in the range just below that of the lowest wavelengths in the visible light spectrum, that of the colour violet (Figure below).
Originating from the sun, much of the UV radiation is absorbed by our beleaguered ozone layer.This layer is part of Earth’s stratosphere that is enriched in ozone. Ozone is our planet’s sunscreen! It absorbs all of UVC and much of UV A&B.
On the theme of sunscreen, our planet has been losing its celestial sunscreen because of human use of chemicals like freon and numerous chlorofluorocarbons. These chemicals were used as propellants in products like deodorants and refrigerants for air conditioners. With intervention (replacing chemicals like freon with safer alternatives, to be completed by 2020) the ozone hole it has made some recovery (below).
However, because of both a thinning ozone layer and more leisure time for outdoor activity the incidence of skin cancer is increasing. Dr. Elsner is shown here with a graph illustrating the incidence of skin cancer in men (on left) and women on right (top bars on his Figure). Note that skin cancer is the most common malignancy, account for >25% of all cancers in men and women. Skin cancer, while usually treatable, can be disfiguring and on occasion fatal.
When UV light gets through the ozone layer it’s next stop is your skin. The skin’s first line of defense are cells called keratinocytes in the epidermis. Keratinocytes accumulate a protective brown pigment, melanin, which is imported from melanocytes. If the UV light gets past the keratinocyte and its natural melanin sunscreen you’re on a path to sunburn and over time to skin aging and cancer! Absorbed UV radiation is both a mutagen and a non-specific damaging agent and has properties of both a tumor initiator and a tumor promoter. The resulting DNA mutations first damage and age the skin and then lead in a dose-dependent manner to premalignant skin lesions, called actinic keratosis. Ultimately, sufficient UV radiation promotes skin cancer itself (BCC or SCC), Figure 1 above.
It’s a problem for all people but if you lack pigment (albinism) or are fair skinned you are at a disadvantage. Fortunately, prevention exists in the form of barriers to UV absorption by the skin (clothing and sunscreen). There is a a scale to measure your UV sensitivity, the Fitzpatrick Scale. This scale is a semi-quantitative and includes six phototypes that describe skin color by basal complexion, melanin level, inflammatory response to UV radiation and cancer risk. A low Fitzpatrick score means you have less eumelanin, are more sensitive to UV light and thus are more sensitive to sunburns and skin cancer.
The Fitzpatrick scale:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3709783/
If you are of Northern European origin and have blue green eyes and freckles for example you’re a Fitzpatrick 1 and are more likely to burn on sun exposure and are at increased risk of skin cancer. You will definitely want to augment your skin’s natural protective capacity by applying sunscreen and avoiding prolonged sunlight exposure. The opposite end of the scale is a person of African origin with black skin and dark hair (Fitzpatrick 6), who would be much less at risk of skin cancer.
In the image below you can see that UVA and its shorter wavelength cousin UVB penetrate the skin causing damage and malignancy. Fortunately, most UVC does not reach the earth’s surface.
While exposure to UV-irradiation is an established risk factor both SCC and BCC, the relative impact of occupational UV exposurefor SCC and BCC has been more recently recognized. Dr. Elsner reminded us that solar occupational UV exposure is a major risk factor for developing SCC and BCC, over and above the risk a person experiences in their non-working life. Increased prevention efforts are necessary for those employed in outdoor workplaces to reduce the rising incidence of skin cancer.
His research focuses on measuring (and reducing) cancer risk in people who have occupations that require them to work outdoors for long hours, window washers, sanitary engineers, construction workers, farmers and sports instructors. These people are often in the sun whether they wish to be or not, and often at peak UV hours, (10 am to 4 pm). In Germany, any disease which doubles in incidence within member of a profession, is classified as an occupational disease. BCC and SCC meet these criteria.Dr. Elsner has published extensively showing that outdoor workers often fail to protect themselves from UV radiation. Paradoxically many workers fail to use solar protection at work, even if they use protection when exposure to sun occurs during leisure activities. Prevention requires awareness! As a consequence, these workers have marked increases in BCC and SCC. This is avoidable with education and simple preventative measures [use sunscreen (SPF>15), wear protective clothing, use UV sunglasses, minimize skin exposure between 10am and 4 pm and avoid sunburn]! Here are some workers modeling sun safety and others, not so much…you be the judge which outfit reduces the risk of cancer by >2-fold!
Skin cancer is to some extent recognized as an occupational disease in Canada too, although I’m not sure the general public, particularly outdoor workers, have translated the knowledge on this website into action.
This video reminds us that outdoor workers in Canada, as in Germany have a 2.5-3.5 fold increase in the risk of skin cancer. Radespiel-Tröger, M., Meyer, M., Pfahlberg, A., Lausen, B., Uter, W., and Gefeller, O. (2009). Outdoor work and skin cancer incidence: a registry-based study in Bavaria. Int Arch Occup Environ Health, 82, 357–36.
However, unlike Germany compensation for cancer care and large preventative interventions to reduce skin cancer in the work place, have not occurred in Canada. One can make the case, as they have in Germany, that the relationship of work-related solar exposure to skin cancer is no different than the relationship between asbestos exposure and lung cancer and should be targeted by prevention. Prevention should occur both at the level of the employer and employee, with clear standards for workplace protection and support of programs for screening of outdoor workers for skin cancers.
Hopefully, this blog reminds you, whether you are a health care professional, a parent or just someone interested in your own skin health…the sun is powerful source of UV radiation and we can easily reduce our private and work places risks of developing skin cancer by following Mary Schmich’s advice, Trust me on the Sunscreen!