Indoor Tanning: The Link To Melanoma Is No Longer Deniable

Elena B. Hawryluk, MD, PhD
Dermatology Program, Boston Children’s
Hospital, Harvard Medical School
Department of Dermatology
Massachusetts General Hospital
Harvard Medical School, Boston, MA

Alan C. Geller
School of Public Health
Harvard Medical School, Boston, MA

David E. Fisher, MD, PhD
Department of Dermatology
Massachusetts General Hospital
Harvard Medical School, Boston, MA


Indoor tanning devices such as sun lamps, tanning beds, and tanning booths expose the skin to concentrated amounts of ultraviolet radiation (UVR), and a growing body of research now links this exposure more convincingly than ever to an increased risk of melanoma and other skin cancers. While some early studies pointing to the carcinogenic effects of indoor tanning started emerging as early as the 1990s, in the past few years, with advances in scientific scrutiny and the results of multiple investigations, the weight of evidence has become virtually irrefutable.

The Source of the Damage

We now know that tanning beds darken the skin through a process that requires UV-induced DNA damage; this damage activates transcription of cellular repair signals that ultimately increase skin pigmentation as a partial barrier against further damage. Unfortunately, some damage has already been done, and the repairs are probably never complete; the remaining damage is what produces genetic mutations that can lead to skin cancers.

Figure 1: Molecular Mechanism of Skin Pigmentation Induced by UV Radiation: Ultraviolet light triggers DNA damage in the nucleus of keratinocytes, resulting in the activation of p53, which transcriptionally up-regulates the expression of the gene encoding proopiomelanocortin (POMC ). POMC is post-translationally processed to produce melanocyte-stimulating hormone (MSH) and β-endorphin. After secretion, MSH acts on its receptor, the melanocortin 1 receptor, located on melanocytes at the basal layer of the epidermis, thereby inducing the production of pigment, which is subsequently transported out of melanocytes to overlying keratinocytes, where the pigment vesicles coalesce over the UV-exposed side of the nucleus, resulting in tanning.

As its name suggests, artificial tanning (tanning machines, not to be confused with sunless tanning) essentially mimics or reproduces natural UVR from the sun. Natural sunlight produces UVR of different wavelengths – UVA, UVB, and UVC – but UVC rays are largely filtered out by stratospheric ozone before reaching the earth. While older tanning lamps (before the late 1970s) also produced a broad spectrum of radiation including UVA, UVB, and UVC, more recent tanning lamps primarily emit UVA, the most effective wavelength for inducing a tan without incurring sunburn.

When tanning machines were altered in this way, it was widely believed that because UVB caused sunburn and UVA didn’t, UVB was far more dangerous. We now know differently. UVA has longer wavelengths than UVB (320-400 nm vs. 290-320 nm), penetrates the skin more deeply, and unlike UVB, which causes direct DNA damage and mutation, UVA inflicts DNA damage indirectly, by producing free radicals that cause oxidative damage and stress. In short, both UVA and UVB cause skin damage and skin cancer. [Figure 1.]

In 2009, the World Health Organization’s International Agency for Research on Cancer classified UV radiation, from both the sun and artificial UV tanning devices, as carcinogenic to humans.1 Both old and newer tanning lamps have been shown to increase risk of skin cancer, 2,3 and a recent report linked indoor tanning to 170,000 nonmelanoma skin cancer cases per year in the US.4 The impact of indoor tanning on an individual’s total UV exposure can be substantial: in fact, the UV emission spectra of sunbeds exceed the UV index of the noontime summer sun at intermediate latitudes.5 While the sunbed emission spectra of UVB are similar to those of the sun, the UVA emission spectra of sunbeds are 10-15 times that of solar emission.5 Frequent tanners (with 100 or more sessions in their lifetime) who use modern high-pressure sunlamps may have up to 12 times the annual UV exposure of suntanners.6

The Problem is Widespread

The amount of damage caused by indoor tanning is especially alarming in light of its popularity. The U.S. Food and Drug Administration (FDA) estimates that more than 30 million Americans use tanning devices annually. These machines can be found not just at tanning salons, but increasingly at spas, health clubs, and hair salons as a service for patrons. A 2008 cross-sectional, interview-based survey of 29,394 individuals examined the prevalence of indoor tanning and found the rates highest among those who were young, white, and female.7 The highest prevalence (20.4 percent) was among individuals 18 to 29 years of age.7 More recently, according to the 2010 National Health Interview Survey, 32 percent of non-Hispanic white women aged 18-21 reported indoor tanning, with the tanners reporting an average of 28 sessions per year.8

The practice unfortunately is very common among adolescents as well: the 2011 national Youth Risk Behavior Surveillance System found that 13 percent of high school students engaged in indoor tanning, including 29 percent of white high school girls, and 32 percent of girls in the 12th grade.8 Guy and colleagues further noted that 16.7 percent of these girls had tanned during the preceding year.9 And including even younger teens, a 2011 cross-sectional interview-based study of 6,125 adolescents (ages 14-17) in the 100 most populated American cities found that over the preceding year, indoor tanning was utilized by 17.1 percent of girls and 3.2 percent of boys.10 Greater use of tanning beds is associated not just with being white and female, but also with having a parent who practices indoor tanning, having a greater allowance, and living within two miles of a tanning facility.

From Westerdahl On: The Link to Melanoma Starts To Crystallize

The belief that tanning devices cause melanoma and other skin cancers started gaining credence as early as 1994, with a Swedish study by Westerdahl et al. linking sunbed or sunlamp use (independent of sun exposure) to an increased risk of the disease, especially among patients younger than 30 years of age.11 Among this population, for those with more than 10 sessions per year, only melanomas on the trunk were significantly associated with tanning. In 1998, however, Swerdlow and Weinstock came to the conclusion that while there were “several reasons for concern” that tanning beds cause melanoma, new meta-analyses and more precise data were required before arriving at that conclusion.12

In 2002, Karagas and colleagues took a notable stride, publishing a wellrespected study showing that tanning bed users were 2.5 times more likely to develop squamous cell carcinoma (SCC) and 1.5 times more likely to develop basal cell carcinoma (BCC), but the study looked only at these nonmelanoma skin cancers.13

In the past few years, finally, the metaanalyses and more precise data Swerdlow and Weinstock were looking for have come to light, along with striking increases in melanoma incidence among young people that appear to parallel the increases in indoor tanning. In 2010, a US analysis by the Surveillance, Epidemiology, and End Results (SEER) Program showed that melanoma incidence has risen preferentially among young American women, prevalently on body sites naturally photoprotected by clothing, such as the trunk;14 as an aside, the researchers observed that this sizable melanoma increase in young women happened to coincide with the massive increase in indoor tanning in the US. SEER data was also analyzed by Purdue and colleagues, who similarly reported that the annual incidence of melanoma among young women increased from the 1990s onward, for thinner and thicker melanomas, regional and distant tumors alike.15 Again, these increases took place concurrently with the rise in young women’s tanning bed usage.16

The Evidence Mounts

Other large, convincing studies have continued amassing the evidence, further explicating and quantifying the increase in risk of melanoma and other skin cancers due to tanning.

  • In 2010, Lazovich and colleagues conducted a population-based case-control study comparing 1,167 cases of invasive cutaneous melanoma to age- and gender-matched controls in Minnesota, finding that 63 percent of the melanoma patients and 51 percent of the controls had indoor tanning exposure.3 The authors demonstrated that melanoma risk increased with indoor tanning years (P <0.006), hours (P<0.0001), and sessions (P=0.0002).These increased risks were found across device types and regardless of the age when tanning initiated.
  • In 2011, a case-control-family study by Cust and colleagues examined 604 melanoma cases in Australia and determined that 76 percent ofthe melanomas were attributable to sunbed use.17 This risk was increased with earlier age at first exposure as well as increased frequency of use, and was associated with earlier onset melanoma. Similarly, a year later, Wehner et al. found that the risk of developing melanoma was especially increased for individuals who started indoor tanning before age 25.18
  • In 2012, Boniol and colleagues provided a systematic review and meta-analysis of 27 case-control, cohort, and cross-sectional studies that demonstrated an association between tanning bed use and melanoma risk among individuals who had ever used indoor tanning. As with Cust et al. and Wehner et al., this risk increased with both number of tanning sessions and initial usage at a young age (<35 years).19 A 1.8 percent increase in melanoma risk occurred for each additional sunbed session per year, and the authors calculated an estimated 3,438 melanoma cases attributed annually to sunbed use in European countries.
  • Also in 2012, Zhang and colleagues utilized a large, well-characterized cohort (73,494 female nurses from 1989-2009) to identify a dose-response relationship between the use of tanning beds and the risk of skin cancers, with 11 percent increased risk of melanoma among participants who used tanning beds four times per year, in addition to a 15 percent increased risk of both SCC and BCC.2 With SCC comprising over 20 percent of all skin cancer deaths and melanoma the vast majority of skin cancer deaths, the elevated risk of both cancers caused by indoor tanning is of major public health importance. Also of note were the researchers’ findings that the increased risk of skin cancer due to tanning bed use was similar among participants of different natural pigmentation (both fair skin and darker skin) — a clear indication that public health messages about the dangers of tanning need to be emphasized across all populations.

These and many other significant studies have appeared in just the past few years. With each new bit of research showing a dose-dependent relationship between tanning, melanoma, and other skin cancers, and special vulnerability in those who start young, the certainty of the link becomes more solidified, as well as the urgency for imparting this message to people everywhere as early in life as possible.

Regulation of Tanning

The increased appreciation of skin cancer risks associated with indoor tanning has brought increased restrictions to tanning access worldwide. In 2003, only France and Brazil had any nationwide tanning laws, but just nine years later, a 2012 review of international legislation found 11 countries with legislation that restricts indoor tanning for individuals under age 18.20

In the US, the FDA device classification of tanning beds is Class I, indicating that they present minimal potential to cause harm (offering no more danger than a tongue depressor), and they are subject only to general controls to ensure safety and efficacy; however, given the mounting evidence, in 2010 the General and Plastic Surgery Devices Panel made the recommendation to change this classification. In May 2013, the FDA proposed raising the classification for tanning devices to a Class II level, which would require special controls including labeling requirements, performance standards, surveillance, patient registries, and guidance documents. A final rule on this proposed administrative order is pending.

In 2011, California became the first state to ban indoor tanning for anyone under age 18. Next came Vermont in 2012, followed closely by a succession of other states. In 2013 alone, Illinois, Nevada, Texas, and Oregon (where under-18s are prohibited unless they provide a prescription) have all banned indoor tanning for people under age 18. Connecticut, New York, and New Jersey have bans for young people under age 17, and Wisconsin for those under age 16. Many other states have enacted bans for those under age 14, or require a prescription, parental accompaniment, and/or parental consent along with various age limitations. Currently at the state level, 35 states and the District of Columbia now have tanning restrictions in place for minors of varying ages, and an additional 11 states have introduced legislation.21

The efficacy of these developments, however, was called into question by a 2011 study of adolescent tanning by Mayer and colleagues, who found that residence in a state with youth accesslimiting legislation was not significantly associated with effective reduction of tanning usage among adolescents in the most populated US cities.10 Existing legislation is often difficult to enforce, and some states’ regulations are so lax that children under age 14 can legally tan with parental permission or accompaniment.22 Given the significant prevalence of indoor tanning among high school students9 and their proven vulnerability to UV damage, it is important that minors under age 18 be banned altogether from tanning. [The current restrictions against tanning access for a 17-year-old adolescent on a state-by-state basis are depicted in Figure 2.21, 22]

The problem is, federal oversight of the tanning industry is lacking. While the FDA has provided recommended exposure limits, a 2003 community-based survey study in North Carolina showed that the FDA-recommended exposure limits for tanning were exceeded by 95 percent of users.23

Now that the melanoma risk associated with indoor tanning is more firmly established than ever, the practice is being strongly discouraged by most prominent health organizations, including the World Health Organization, the American Medical Association, the American Academy of Dermatology, and the American Academy of Pediatrics, as well as The Skin Cancer Foundation. All have issued strong statements about the dangers of tanning. It is time for the FDA to revisit the safety data, and to move forward with raising the classification of tanning devices to ClassII, requiring increased regulation. It is time, in fact, to pass nationwide laws banning all minors under age 18 from indoor tanning.

Figure 2: Indoor Tanning Restrictions for Minors, effective October 1, 201321,22: States with tanning bans for 17-year-olds in place or approved are highlighted in red; states requiring parental accompaniment or consent for adolescents at age 17 are shaded yellow; states without restrictions for 17-year-olds are shaded in green. Map courtesy of DIYMaps.net.

References

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