Medical researchers acknowledged for decades the unsettling observation that the rising popularity of sunscreen coincides with an increase in skin cancer rates. Skin cancer is the most common cancer in the world and melanoma is the deadliest form accounting for 75% of all skin cancer deaths. One in 1,500 Americans born in 1935 was likely to develop melanoma while one in 105 persons born in 1993 is statistically slated to be stricken (Koh H). The Annals of Epidemiology reports that melanoma rates began to rise sharply during the mid-1970s when sunscreens with high sun protection factors became popular (Garland C). An update published in a 2007 issue of the same journal concluded that sunscreens increase melanoma risk in people living in latitudes >40° (Gorman E). The National Cancer Institute reports that in spite of nearly ubiquitous sunscreen use, melanoma incidence continues to rise 2.91 percent every year since 1981.
|Graph of melanoma rates from 1975 to 2006. APC stands for annual percent change and AAPC stands for average annual percent change.Source: National Cancer Institute|
Frequent sunscreen use associated with higher melanoma risk
To investigate the correlation further, numerous studies were undertaken during the 1990s and many report a higher incidence of malignant melanoma among frequent sunscreen users (Beitner 1990 and Autier 1998 and Wolf 1998 and Westerdahl 2000). Studies showing a positive correlation between sunscreen use and skin cancer reported on the incidence of squamous cell carcinoma (SCC), but not other types. SCC is a slow-growing, treatable disease estimated to account for just 16% of all skin cancers annually. Of the remaining cancers, 80% are basal-cell carcinoma and four percent are malignant melanoma (Greenlee 2001). The International Agency for Research on Cancer (IARC) concludes that:
- Sunscreen use may decrease the occurrence of squamous cell carcinoma.
- Sunscreen use has no demonstrated influence on basal cell carcinoma.
- Sunscreen use may increase the risk of melanoma (IARC 2001).
Recently IARC researchers looked more closely at the connection between squamous cell carcinoma and sunscreen use. They report that experiments showing a protective effect were performed on rats and used cancer cells that were similar too, but not the same as human squamous cell carcinoma. Unable to find comparable animal models exploring sunscreen’s effects on human melanoma cells, they reviewed human observational studies comparing rates of skin cancer incidence to human sunscreen use. They report that people who frequently use sunscreen run a higher risk of developing melanoma and basal cell carcinoma. Furthermore, the more sunscreen people use, the higher their risk of developing skin cancer (Autier 2009).
FDA sun alert modifed
Citing the conflicting studies regarding sunscreen use and skin cancer, the FDA decided to withdraw its endorsement that sunscreen could prevent cancer. In an official amendment released in 2007, the Agency modified its sun alert statement to warn consumers that UV exposure could cause cancer, and not that sunscreen could prevent cancer. Under the new rules, Broad Spectrum SPF products may claim “if used as directed with other sun protection measures (see directions), decreases the risk of skin cancer and early skin aging caused by the sun.” Non-Broad Spectrum products, however, may only claim to prevent sunburn. Below is an image of a label approved for a Broad Spectrum SPF product.
Sunscreen may not protect against sunburn damage
Note the approved FDA label above reads its use is to “help prevent sunburn.” This caution reflects studies demonstrating sunscreen can be ineffective in frequent users. One of the first such studies was published in 1995 and it evaluated the correlation between sunscreen use and melanoma rates. The researchers interviewed 418 melanoma patients and 438 healthy in Germany, France and Belgium. They found that regular sunscreen use raised melanoma risk and hypothesized sunscreens delay skin reddening rather than prevent sunburn damage. They also observed that frequent sunscreen users have a higher density of pigmented skin lesions. (Autier 1995).
A report published in 1997 reviewed studies performed on sunbathers at beaches in the vicinity of Copenhagen, Denmark. On a typical sunny day, 65% of sunbathers used a sunscreen and of these, 46% applied it to all exposed skin. The median SPF used was a sun protection factor of five to six. Of the sunscreen users, 43% applied it after arriving at the beach and reapplied it after swimming. The time sunbathers spent in the sun was almost identical among sunscreen users and non-users. The day after sunbathing, more sunscreen users than non-users reported to be sunburn, 42 and 34%, respectively (Wulf 1997).
Researchers reporting in a 2007 review of sunscreen use published in the International Journal of Cancer were surprised to discover that frequent sunscreen users suffer more sunburns than non-users. They were attempting to shed light on why sunscreen use is associated with higher melanoma risk. Hypothesizing that the reason is because sunscreen users stay out in the sun longer than non-users, they reviewed observational studies and randomized trials. The observational studies reported the same finding: sunburns tend to be more frequent among sunscreen users (Autier 2007).
Why sunscreens are associated with more rather than less skin damage
A simple explanation for why sunscreens are associated with more rather than less skin damage is that the sunscreen chemicals generate more free radicals than what they absorb. There are two categories of sun protection ingredients approved by the FDA: chemical sunscreens and physical sunblocks. Chemical sunscreens absorb UV energy but they can’t destroy it, so they must convert UV to some other energy form or release it. Studies prove that most; if not all, approved UV chemical sunscreens generate free radicals. Sunscreen makers commonly add antioxidants to help neutralize the damage the sunscreen chemicals cause, however depending on the type of antioxidant derivative used, this often makes matter worse.
Physical sunblocks lie on the surface of the skin and deflect UV light preventing the energy from being absorbed. For the most part, sunblocks don’t become problematic until they’re made nano-sized enabling them to penetrate and create damage.
Much of the research dealing with sunscreen ingredient safety is published in toxicity journals. Manufacturers rarely perform comprehensive toxicity studies on ingredients prior to making them available in consumer products. When products become as popular as sunscreens and public health is in question, medical researchers often identify the need and step up to the plate.
One particularly worrisome study published in 2006 examined the free radical generating capacity of three widely used chemical sunscreens:
The researchers found that the quantity of free radicals generated by the chemicals is a function of how long the chemical remains on the surface of the skin. After 20 minutes, free radical generation increases although it remains lower than what is generated in unprotected skin. However after 60 minutes, the chemical sunscreens generate more free radicals than are generated on unprotected skin (Hanson 2006).
In addition to octocrylene, the Neutrogena product featured above also contains avobenzone. Avobenzone is one of the most heavily documented free radical generators and defines the basic problem with any UV absorber. Energy cannot be destroyed, thus the absorbing chemical must convert UV energy into some other chemical energy which is typically released as free radicals in the body (Allen 1996 and Hanson 2006 and Serpone 2002).
Not only are chemical sunscreens potent free radical generators, but also notorious for their photoinstability. UVA blockers are particularly instable, a fact prompting medical professionals to urge the FDA to go further in its regulation of sunscreens. They insist manufacturers also alert consumers to how long their products remain stable before degrading. Furthermore, once these chemicals breakdown, they degenerate into cytotoxic by-products that directly kill skin cells (Damiani 2010). The sad truth of the matter is that after an hour in the sun using most commercial chemical sunscreens, your skin is at least twice as compromised as it would have been had you applied no sunscreen. Is it any wonder sunscreen use is associated with more rather than less skin damage?
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