Melanoma is the most dangerous type of skin cancer, which accounts for the majority of deaths despite being the least common of the major skin cancers. Despite increased use of sunscreens among the public, the incidence of melanoma has consistently increased. What does this mean? We look at an important study that delves into the question of why both melanoma and sunscreen use are both on the increase.
What is Melanoma?
Melanoma is cancer that develops in the melanocytes, the pigment that produces color in the skin. It is known to be a very aggressive cancer that can metastasize (spread) quickly and has a poor prognosis once it has spread past its original site.1 The dermatologist rarely deals with life and death. However, melanoma is a notable exception, and it’s with good reason that patients are advised to scan their bodies regularly for possible signs of melanoma. For more information on melanoma, see our melanoma FAQ.
Melanoma is relatively rare compared to other skin cancers like basal cell carcinoma and squamous cell carcinoma, which are less dangerous. The concern is that melanoma incidence has consistently been on the increase worldwide, and Canada is no exception.2 In the United States, melanoma has been increasing at a rate of 3% a year.3 Another statistic – sunscreens use – although the data here is weak, it has also been increasing, thanks largely to education about the damage that UV radiation has on the skin. Furthermore, the evidence doesn’t show how sunscreen use is particularly useful in preventing the incidence of melanoma, and in some cases, it may increase it.
Taken together, one might reasonably wonder, does sunscreen use cause cancer? Those that are more inclined towards conspiracies may take the next step and wonder if there is a big pharma/sunscreen manufacturer agenda at play. This view, explicitly stated or implied, is not that uncommon, with various blogs taking the view that “unnatural” products are to blame.4
The Study
This brings us to the study and discussion titled Sunscreen and Melanoma: Is Our Prevention Message Correct? Published in the Journal of the American Board of Family Medicine, the author questions whether the current sunscreen advice is appropriate, given the data on melanoma and sunscreen use.
The cited facts:
- Cutaneous malignant melanoma has increased by 81% from 1973 to 2003 and continues to increase by about 3% per year.
- Studies suggest that sunscreen use either has no effect or increases the incidence of melanoma.
- Cumulative sun exposure may not be a significant factor in developing melanoma*.
- Sunburns are hypothesized as being a more important factor in melanoma.
- Many of the studies are based solely on UVB protection that sunscreen provides before understanding the damaging effects of UVA.
- An Australian study shows evidence that consistent, practiced, and regular use of sunscreen which protects from UVA and UVB, reduces melanoma, but intermittent use (as is common in public) does not.
*It’s worth noting here that there is overwhelming evidence that cumulative sun exposure is the primary factor in causing non-melanoma skin cancers.
Discussion
Several modifications to messaging were considered (as the article is designed to be read by family doctors).
- Sunscreen use is probably not intrinsically related to harm – that is, sunscreens are unlikely to be causing melanoma.
- The dangers of sunburns should be emphasized more.
- Sunscreens can be “abused.” They may promote overconfidence in the user, encouraging longer sun exposure, under the assumption that it provides them immunity.
- UVA radiation may also play an essential role in skin cancer, and patients should be encouraged to use sunscreens that protect against UVA.
- Sunscreen use is not the end-all; simply seeking the shade and wearing protective clothing like long sleeves and hats are just as important.
As the discussion is designed for family practitioners, the focus is on the message to patients, given the available evidence from the studies. The general takeaway is that the effect of sunscreens on melanoma specifically is weak. Possible reasons for this are speculated to be UVA being a more causative agent than UVB,5 or that sunscreen use encourages users to stay in the sun longer than they usually would, and are being sunburnt more (in areas where they failed to apply sunscreen correctly).
Going further: Other Factors
Since the study assumes an audience of mostly family practitioners, the advice is focused on accurate and practical advice. One area it doesn’t delve into is the fear that many people have – and fear can often overwhelm reason. Most people understand that correlation doesn’t imply causation. Perfectly reasonable people can, however, still feel uneasy about something like this. As a blogger who is promoting lifestyle and health puts it:
“Of course, correlation does NOT equal causation, but still. Common sense has got to tell you that slathering on dangerous chemicals is probably not good for your health.”6
Science is the process of repeatedly questioning. Sunscreens, like anything else, should be put under the microscope – and it is. The part that often gets mistranslated by the “chemicals are bad” crowd is that their appeal to nature is always defined vaguely. Water, for example, is a chemical; many polysyllabic chemicals are perfectly safe, while very simple natural ones can be harmful.
Probably the most important factor in the melanoma and sunscreen paradox is that many factors are pointing towards a likely increase in melanoma outside of sunscreen use (sunscreen use is still notoriously low in North America).
We’re getting better at diagnosing and detecting melanoma. The public is far more aware of melanoma.
Almost everyone feels that more people are dying of cancer today than in the past. Back then, people died of vague illnesses like “lung disease,” not to mention that many didn’t live long enough to die of cancer.
Tanning Beds
Tanning beds started becoming popular in the 80s and exploded in the 90s. We can still see the residual effects of this, as melanoma (and cancers in general) don’t form immediately after exposure to a carcinogen. Although on the decline thanks to education, sun tanning is far from gone.
Demographics
Everywhere in the world, the population is aging. Cancer risk goes up as we age as our cells become more damaged over time. About 90% of people who are diagnosed with cancer are 50 or older.7
Climate Change
Ozone depletion is only a part of climate change, but CFCs (chlorofluorocarbons) being released into the air break down the ozone layer, which helps protect us from UV radiation.8 We can expect to see a higher incidence of skin cancer in the future as more UV light is coming through.
1 It’s worth noting, however, that if discovered in its early stages, it has an excellent cure rate. This is why checking your skin is so important and saves lives.
2 http://www.cancer.ca/en/about-us/for-media/media-releases/national/2014/2014-canadian-cancer-statistics/?region=on
3 http://www.jabfm.org/content/24/6/735.full
4 https://www.thankyourbody.com/sunscreen-safe/
5 While UVA protection is provided in most sunscreens today, many sunscreens in the past only protected from UVB.
6 https://www.thankyourbody.com/sunscreen-safe/
7 https://www.cancerresearchuk.org/about-cancer/causes-of-cancer/age-and-cancer
8 https://www.nationalgeographic.com/environment/global-warming/ozone-depletion/
