Possible ultraviolet A-induced lentigines: a side effect of chronic tanning salon usage

Association of sunbed use with skin cancer risk factors in Europe: an investigation within the Euromelanoma skin cancer prevention campaign

INTRODUCTION

Sunbed use has been significantly associated with increased risk of melanoma and non-melanoma skin cancer (NMSC), but its relationship with melanoma's risk factors such as high nevus count, atypical nevi and lentigines is poorly studied. Euromelanoma is a skin cancer prevention campaign conducted all over Europe. It offers a once-a-year screening during which participants' data, including sunbed use and phenotype, are collected via questionnaires.

OBJECTIVES

To investigate the association of sunbed use with nevus count, atypical nevi, lentigines and suspicion of skin cancer.

METHODS

To ensure reliability of the data, we defined inclusion and exclusion criteria for countries' eligibility for the risk analysis. Multivariate logistic regression models (including age, gender, education, skin type, family history of melanoma, personal history of skin cancer, any sun exposure and any sunscreen use) were used to calculate summary odds ratios (SORs) of each clinical endpoint for ever sunbed use.

RESULTS

Overall, 227 888 individuals from 30 countries completed the Euromelanoma questionnaire. After the data quality check, 16 countries were eligible for the multivariate analysis, for a total of 145 980 participants (64.8% females; median age 43 years; 62.3% highly educated; 28.5% skin type I-II; 11.0% ever sunbed use). Ever sunbed use was independently associated with nevus count >50 [SOR = 1.05 (1.01-1.10)], atypical nevi [SOR = 1.04 (1.00-1.09)], lentigines [SOR = 1.16 (1.04-1.29)] and suspicion of melanoma [SOR = 1.13 (1.00-1.27)]. Conversely, no significant association was found between ever sunbed use and suspicion of NMSC [SOR = 1.00 (0.91-1.10)].

CONCLUSIONS

Indoor tanning is significantly associated with well-recognized risk factors for melanoma (including high nevus count, presence of atypical nevi and lentigines) as well as suspicion of melanoma within the Euromelanoma screenees. In order to reduce the prevalence of melanoma risk factors, avoidance/discontinuation of sunbed use should always be encouraged, especially but not exclusively for individuals with high-risk phenotypes.

[Clinical aspects and pathogenesis of UV-induced pigmentary disorders]

Solar and ultraviolet (UV) radiation, respectively, are the strongest stimuli for the induction of pigmentation in human skin. UV radiation induces pigmentation by exerting direct and indirect effects on melanocytes. Melanogenesis is a very complex process whose molecular mechanisms are not yet completely understood. Acute UV exposure induces the non-protective immediate pigment darkening as well as delayed tanning which exerts photoprotective effects. Chronic UV exposure causes permanent pigmentary changes by inducing solar lentigines and pigmented actinic keratoses as well hypopigmentated areas. Artificial UV irradiation (UVA, PUVA) can also induce pigmentary disorders, including lentigines. Since the therapeutic options for UV-induced pigmentary changes are limited consequent protection as a prophylactic measure is recommended.

Ultraviolet A and melanoma: a review

The incidence and mortality rates of melanoma have risen for many decades in the United States. Increased exposure to ultraviolet (UV) radiation is generally considered to be responsible. Sunburns, a measure of excess sun exposure, have been identified as a risk factor for the development of melanoma. Because sunburns are primarily due to UVB (280-320 nm) radiation, UVB has been implicated as a potential contributing factor to the pathogenesis of melanoma. The adverse role of UVA (320-400 nm) in this regard is less well studied, and currently there is a great deal of controversy regarding the relationship between UVA exposure and the development of melanoma. This article reviews evidence in the English-language literature that surrounds the controversy concerning a possible role for UVA in the origin of melanoma. Our search found that UVA causes DNA damage via photosensitized reactions that result in the production of oxygen radical species. UVA can induce mutations in various cultured cell lines. Furthermore, in two animal models, the hybrid Xiphophorus fish and the opossum (Mondelphis domestica), melanomas and melanoma precursors can be induced with UVA. UVA radiation has been reported to produce immunosuppression in laboratory animals and in humans. Some epidemiologic studies have reported an increase in melanomas in users of sunbeds and sunscreens and in patients exposed to psoralen and UVA (PUVA) therapy. There is basic scientific evidence of the harmful effects of UVA on DNA, cells and animals. Collectively, these data suggest a potential role for UVA in the pathogenesis of melanoma. To date evidence from epidemiologic studies and clinical observations are inconclusive but seem to be consistent with this hypothesis. Additional research on the possible role of UVA in the pathogenesis of melanoma is required.

Delayed induction of pigmented spots on UVB-irradiated hairless mice

Human skin exposed to solar radiation for a long time subsequently develops pigmented spots, which are named solar lentigines. Since no animal model of this process is currently available, we attempted to induce similar spots in pigmented hairless mice. The mice were irradiated at 38 or 94 mJ/cm(2) three times/week for various periods of time (1-8 weeks) under an ultraviolet light source (Toshiba FL-SE; UVB). Skin pigmentation of irradiated mice was visually observed and skin color was determined with a colorimeter for 78 weeks. Uniform pigmentation was induced, but persisted only during exposure, disappearing completely within 2 weeks after cessation of exposure. At about 28 weeks after the first exposure, pigmented spots suddenly began to appear. These pigmented spots were less than 2 mm in diameter and light brown in color. The length of the latent period until appearance and the extent of development of these spots were dependent on the exposure period. Histological examination revealed increased numbers of active melanocytes and melanin granules in the affected epidermis. These pigmented spots closely resemble solar lentigines in humans, and the mice should be useful as an animal model of solar lentigines.

Indoor tanning: risks, benefits, and future trends

The indoor tanning industry is a $1 billion-a-year business in the United States, and use of these high-intensity UVA tanning devices continues to grow. Many members of the medical community are concerned about the safety of these largely unregulated devices, but tanning salon operators state such concerns are unfounded and unproved. A comprehensive review of current knowledge of the operation and effects of indoor tanning is presented. The effects of UV radiation (especially UVA) on experimental animals and human beings are examined. Both acute and chronic effects are delineated from experimental sources as well as from epidemiologic studies and clinical observations. Existing safety regulations are described. Information on operator knowledge and compliance with existing safety regulations is reviewed.

Mutation spectra in Salmonella of sunlight, white fluorescent light, and light from tanning salon beds: induction of tandem mutations and role of DNA repair

We evaluated the mutagenicity of sunlight (SUN), uncovered coolwhite fluorescent light (FLR), and light from a tanning salon bed (TAN) at the base-substitution allele hisG46 of Salmonella in four DNA repair backgrounds (wild type, uvrB, pKM101, and uvrB + pKM101). Approximately 80% of the radiation emitted by TAN was within the ultraviolet (UV) range, whereas only approximately 10% of the SUN and approximately 1% of the FLR radiation was UV. TAN emitted similar amounts of UVA and UVB, whereas SUN emitted 50-60x and FLR emitted 5-10x more UVA relative to UVB. Based on total dose (UV + visible), the mutagenic potency ranking was TAN > FLR > SUN. Using colony probe hybridization and PCR/DNA sequence analysis, approximately 3000 revertants were analyzed to determine the mutational specificity of the three light sources. The mutation spectra and those induced by 254-nm UV had common features. The uvrB mutation enhanced the mutagenicity of the environmental UV sources more (20-216x) than did the pKM101 plasmid (approximately 20x) relative to wild type DNA repair. All light sources induced equal proportions of transitions and transversions in excision repair-proficient strains, but they induced more transitions relative to transversions in uvrB-containing strains. The majority of the mutations were G.C-->A.T transitions that were induced equally frequently at the first or second position of the CCC codon of the hisG46 allele in all strains except TA1535 (uvrB), where SUN and FLR induced transitions preferentially at the first position, and TAN induced them preferentially at the second position. Identified or presumptive multiple mutations, which constituted the only mutational class enhanced by all three light sources in the presence of uvrB and pKM101 either alone or together, accounted for 3-5% of the induced mutations in the plasmid-containing strains, and their increases (38-82-fold) in TA100 (uvrB, pKM101) were the highest of any mutational class. Of the TAN-induced multiple mutations, 83% (19/23) were CC-->TT tandem transitions. These results show that exposures to the nonsolar environmental UV sources FLR and TAN produce mutations similar to those produced by SUN, a known carcinogen.

North Carolina tanning operators: hazard on the horizon?

BACKGROUND

Previous small studies have demonstrated that operators of commercial tanning equipment may not be adequately trained. Most states have no training requirements for tanning operators. This study was designed to assess the medically relevant knowledge of cosmetic tanning salon operators and relate these to demographic variables.

METHODS

A written, anonymous questionnaire was distributed to 984 attendees of the first required operator training seminars conducted in North Carolina. Between July 1990 and June 1991, proprietors and their employees of the commercial tanning industry who attended these seminars were surveyed. No conference attendee refused to complete the questionnaire. Demographic information and responses to the medical information section of the questionnaire were scored by computer.

RESULTS

Important findings included that 71% of surveyed operators had never received any training for their current position. Operators of cosmetic tanning equipment were often unaware of contraindications to tanning such as photosensitizing drugs and specific medical conditions. Few operators recognized methoxsalen (26%) or trisoralen (34%) or their respective proprietary names as contraindications to tanning. Operator knowledge was not related to their educational achievement, previous tanning salon experience, or prior tanning industry-sponsored training. Children younger than 10 years old were tanned by 2.6% of the operators.

CONCLUSION

These data suggest that the public may be at risk for UV light-induced diseases and burns because of operator lack of knowledge.