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Sunscreen counterindications

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Sunscreen protects against two common forms of skin cancer, squamous cell carcinoma (SCC) and basal cell carcinoma (BCC), and several sunscreen ingredients protect against tumor development in photocarcinogenicity tests in mice. However, there is some evidence, largely arising from correlational studies and in vitro experiments, that particular sunscreen ingredients (such as oxybenzone, benzophenone, octocrylene, or octyl methoxycinnamate) may be linked to increased risks of malignant melanoma, a rarer but more deadly form of skin cancer. It has also been linked to Vitamin D deficiency.[1] The broad areas of concern are:

  • potentially carcinogenic properties of some sunscreen ingredients
  • Vitamin D deficiency caused by reduced exposure to ultraviolet light
  • incomplete protection against the full ultraviolet spectrum combined with increased time spent in the sun

This has led to a sunscreen controversy within the academic community. It is known that some sunscreens only protect against UVB radiation, and not against the more dangerous UVA component of the spectrum. In 2006, a number of class-action lawsuits alleged that sunscreen manufacturers misled consumers into believing that these products provided full sun protection. The lawsuits were settled in 2009.[2] The vitamin D hypothesis is not as widely accepted but continues to generate scholarly debate. Most health authorities and medical associations have concluded that on the whole, sunscreen use is beneficial, but there is not yet a thorough consensus.

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Studies of melanoma rates

Malignant Wikipedia:melanoma has been found more frequently in sunscreen users compared to non-users in some studies.[3] Other studies found fair skinned people used more suncreen and had more skin cancer, but did not address cause and effect.[4][5][6][7][8][9] A meta-analysis of 9067 patients from 11 case–control studies found no association between sunscreen use and development of malignant melanoma. It was suggested that sunscreens block the natural warnings and adaptations mediated by UVB, but allow damage from UVA to go unchecked.[10]

However, these claims could not be supported in three Wikipedia:meta-analyses.[11][12] (Huncharek and Kupelnick, 2000, Annals Epidemiol. vol. 10, p. 467.)

The only evidence suggesting a relationship between sunscreen and melanoma is correlational, and thus cannot be used to establish a Wikipedia:causal relationship.

Even though it is rare, malignant melanoma is responsible for 75 % of all skin cancer-related death cases, making it the most lethal form of skin cancer.[13][14] Many scientists argue that the sun-avoiding health message does increase some forms of skin cancer.[15]

There is a Wikipedia:correlation between high UV exposure, especially during childhood, and the risk to develop melanoma,[16][17][18] resulting in a WHO recommendation for persons under 18 to avoid Wikipedia:sunbeds.[19]

Alternative view

Authors who claim that sunscreen use causes melanoma have speculated that this occurs by one of the following mechanisms:

  • the absence of UVA filters combined with a longer exposure time of the sunscreen user[4][20][21][22]
  • less vitamin D generation in sunscreen users.
  • By reducing the exposure of the skin to UVB radiation, sunscreen suppresses the skin's production of the natural photoprotectant, melanin,[23] and the lack of melanin leads to an increased risk of melanoma.[4]
  • free radical generation by sunscreen chemicals that have penetrated into the skin.[24][25][26][27][28]
  • pathogenic cytotoxicity and carcinogenicity of micronized titanium[29] or zinc oxide nanoparticles.
  • Retinyl palmitate, a form of Vitamin A that is an ingredient in some sunscreens, may encourage tumor growth in animals [4]

Sunscreen ingredients can damage DNA

Some sunscreen ingredients may damage cells when illuminated.[30][31][32][33] PABA causes DNA damage in human cells.[34] PABA was banned as a sunscreen ingredient several years after these findings were published. Phenylbenzimidazole (PBI) causes DNA photodamage when illuminated while in contact with bacteria or human Wikipedia:keratinocytes.[28][35][36]

Some sunscreen ingredients generate Wikipedia:reactive oxygen species (ROS) when exposed to UVA,[37] which can increase carbonyl formation in albumin[38] and damage DNA. It is also well-known that DNA alterations are necessary for Wikipedia:cancer to occur.

Many sunscreen ingredients generate Wikipedia:singlet oxygen under illumination.[39] Several popular UV-filters have been demonstrated to generate free radicals.[38]

Kerry Hanson, et al. have shown for the three sunscreen ingredients Wikipedia:octocrylene, octylmethoxycinnamate, and Wikipedia:benzophenone-3 that after the sunscreen chemicals had time to absorb into the skin the number of ROS and free radicals is higher for the sunscreen user than for the non-user.[27] Such an increase in ROS might increase the chance of melanoma, but this hypothesis has not been tested.

Studies have found that titanium dioxide nanoparticles cause genetic damage in mice, suggesting that humans may be at risk of cancer or genetic disorders resulting from exposure.[40]

DNA, in particular, is susceptible to damage caused by photo-excited compounds.[35]

Sunscreen ingredients penetrate the skin

Between 1% and 10% of some sunscreen ingredients are absorbed into the body through the skin.[24][26][41][42][43][44][45][46][47]

The absorption of the sunscreen ingredients into the skin does not occur instantaneously, but the sunscreen concentration in the deeper levels of the skin increases over time.[27] For this reason the amount of time between the topical application of sunscreen and the end of the illumination period is an important parameter in experimental studies. Illumination of those sunscreen chromophores which have penetrated the stratum corneum amplifies the generation of ROS.[27]

Animal experiments

All studies except for one [48] have found that sunscreens protect mice against melanoma.[49][50][51]

Clinical study

In 2008, a clinical study showed that the application of sunscreen prevents SCC, BCC and Wikipedia:actinic keratosis. The study included 60 transplant patients who received Wikipedia:immunosuppression, a group of persons with a particularly high risk to develop skin cancer. The patients were very compliant, using sunscreen 5.6 days per week on average. The control group was recruited retrospectively and consisted of 60 transplant patients equally matched for age, skin type and kind of transplant organ. The control group had been instructed to use sunscreen as well, but were not provided with cost-free sunscreen and showed very poor compliance.

After 24 months, the sunscreen group showed a 53% reduction of actinic keratosis, while the control group showed an increase of 38%. The difference in the development of SCC and BCC were also highly significant. Non-significant results included a slight decrease of Wikipedia:herpes and Wikipedia:warts and a slight increase in Wikipedia:acne in the sunscreen group.[52][53]

In 2011, Australian researchers found that the regular application of sunscreen with a sun protection factor of 15 or more during a 5-year treatment period reduced the incidence of new primary melanomas during a subsequent 10-year follow-up period. [54]

Social impact

Lawsuits have been filed against sunscreen manufacturers.[55]

These lawsuits limit themselves to the absence of UV-A filters.

In August 2007, the United States Food and Drug Administration tentatively concluded that "the available evidence fails to show that sunscreen use alone prevents skin cancer[...]"[56]

Sunscreen ingredients are not tested in Europe, Japan or Australia for photocarcinogenic effects before being introduced to the market. Even in the US, most sunscreens sold in 2008 have not passed regulatory testing either, due to a Wikipedia:grandfather clause. Three new sunscreen active ingredients introduced in the US since 1978 have fulfilled new testing requirements.[57]

Sunscreen and vitamin D

The use of sunscreen with a Wikipedia:sun protection factor (SPF) of 8 inhibits more than 95% of Wikipedia:vitamin D production in the skin.[58][59] Recent studies showed that, following the successful "Wikipedia:Slip-Slop-Slap" health campaign encouraging Wikipedia:Australians to cover up when exposed to sunlight to prevent Wikipedia:skin cancer, an increased number of Australians and Wikipedia:New Zealanders became vitamin D deficient.[60] Ironically, there are indications that vitamin D deficiency may lead to skin cancer.[61] To avoid vitamin D deficiency, vitamin supplements can be taken. Adequate amounts of vitamin D3 can be made in the skin after only ten to fifteen minutes of sun exposure at least two times per week to the face, arms, hands, or back without sunscreen. This applies in sunlight when the UV index is greater than 3, which occurs daily within the tropics and during the spring and summer seasons in temperate regions. With sunscreen, the required exposure would be longer: if 95% of vitamin D production is inhibited, then it proceeds at only 5%, or 1/20th, the normal rate, and it would take 20 times as long—200 to 300 minutes (3-1/3 to 5 hours), twice a week—of sun exposure to the face, arms, hands, or back for adequate vitamin D to be made in the skin. Obviously, the required time would decrease with increased body exposure area, as when wearing a swimsuit on a beach, a very common setting where sunscreen is used. By this math, it is apparent that vacationers who spend hours on the beach each day with sunscreen on may make more vitamin D in a week of vacation than they do during a typical week in their lives with no sunscreen, if they spend most of their non-vacationing time inside houses, offices, and other buildings where they get almost no sun exposure. Also, it is worth noting that with longer exposure to UVB rays, an equilibrium is achieved in the skin, and the vitamin simply degrades as fast as it is generated. Vitamin D overdose is nearly impossible from natural sources, including food sources.

See also

References

  1. ↑ [1]
  2. ↑ [2]
  3. ↑ Westerdahl J, Ingvar C, Mâsbäck A, Olsson H, (2000). "Sunscreen use and malignant melanoma," Int. J. Cancer, 87, 145–50.
  4. ↑ 4.0 4.1 4.2 Autier P; Dore J F; Schifflers E; et al., (1995). "Melanoma and use of sunscreens: An EORTC case control study in Germany, Belgium and France," Int. J. Cancer, 61, 749–755.
  5. ↑ Weinstock, M. A., (1999). "Do sunscreens increase or decrease melanoma risk: An epidemiologic evaluation," Journal of Investigative Dermatology Symposium Proceedings, 4, 97–100.
  6. ↑ Vainio, H., Bianchini, F., (2000). "Cancer-preventive effects of sunscreens are uncertain," Scandinavian Journal of Work Environment and Health, 26, 529–31.
  7. ↑ Wolf P, Quehenberger F, Müllegger R, Stranz B, Kerl H., (1998). "Phenotypic markers, sunlight-related factors and sunscreen use in patients with cutaneous melanoma: an Austrian case-control study," Melanoma Res., 8, 370–378.
  8. ↑ Graham S, Marshall J, Haughey B, et al., (1985). "An inquiry into the epidemiology of melanoma," Am. J. Epidemiol., 122, 606–19.
  9. ↑ Beitner H, Norell SE, Ringborg U, Wennersten G, Mattson B., (1990). "Malignant melanoma: aetiological importance of individual pigmentation and sun exposure," Br J Dermatol., 122, 43–51.
  10. ↑ Garland C, Garland F, Gorham E, (1992). "Could sunscreens increase melanoma risk?," Am J Public Health, 82, 614–5.
  11. ↑ Huncharek M, Kupelnick B, (2002). "Use of topical sunscreens and the risk of malignant melanoma: a meta-analysis of 9067 patients from 11 case-control studies," Am J Public Health, 92, 1173–7.
  12. ↑ Dennis LK, Beane Freeman LE, VanBeek MJ, (2003). "Sunscreen use and the risk for melanoma: a quantitative review," Ann. Intern. Med., 139, 966–78.
  13. ↑ Jerant AF, Johnson JT, Sheridan CD, Caffrey TJ, (2000). "Early detection and treatment of skin cancer," Am Fam Physician, 62, 357–68, 375–6, 381–2.
  14. ↑ Boring CC, Squires TS, Tong T, (1991). "Cancer statistics, 1991," CA Cancer J Clin, 41, 19–36.
  15. ↑ Ainsleigh HG, (1993). "Beneficial effects of sun exposure on cancer mortality," Prev Med., 22, 132–40.
  16. ↑ KC, (1996). "Sun exposure, sunscreens, and skin cancer prevention: a year-round concern," Ann Pharmacother, 30, 662–673.
  17. ↑ Oliveria S, Saraiya M, Geller A, Heneghan M, Jorgensen C, (2006). "Sun exposure and risk of melanoma," Arch Dis Child, 91, 131–8.
  18. ↑ Wang S, Setlow R, Berwick M, Polsky D, Marghoob A, Kopf A, Bart R, (2001). "Ultraviolet A and melanoma: a review," J Am Acad Dermatol, 44, 837–46.
  19. ↑ The World Health Organization recommends that no person under 18 should use a sunbed
  20. ↑ Autier P, Boniol M, Doré JF, (2007). "Sunscreen use and increased duration of intentional sun exposure: still a burning issue," Int. J. Cancer, 121, 1–5.
  21. ↑ Gorham ED, Mohr SB, Garland CF, Chaplin G, Garland FC, (2007). "Do sunscreens increase risk of melanoma in populations residing at higher latitudes?," Ann Epidemiol, 17, 956–63.
  22. ↑ Diffey BL, (2005). "Sunscreens and melanoma: the future looks bright," Br. J. Dermatol., 153, 378–81.
  23. ↑ Meredith, Paul; Riesz, Jennifer, (2004). "Radiative Relaxation Quantum Yields for Synthetic Eumelanin," Photochemistry and photobiology, 79, 211–6.
  24. ↑ 24.0 24.1 Hayden, C G J; Roberts, M S; Benson, H A E, (1997). "Systemic absorption of sunscreen after topical application," The Lancet, 350, 863–4.
  25. ↑ Walters, K. A.; Roberts, M. S., (2002). "Percutaneous absorption of sunscreens," Book: Bronaugh, R. L.; Maibach, H.I. Eds. Topical absorption of dermatological products. / New York: Dekker; 2002, , 465–81.
  26. ↑ 26.0 26.1 Treffel P, Gabard B, (1996). "Skin penetration and sun protection factor of ultra-violet filters from two vehicles," Pharm. Res., 13, 770–4.
  27. ↑ 27.0 27.1 27.2 27.3 Hanson KM, Gratton E, Bardeen CJ, (2006). "Sunscreen enhancement of UV-induced reactive oxygen species in the skin," Free Radic. Biol. Med., 41, 1205–12.
  28. ↑ 28.0 28.1 Mosley CN, Wang L, Gilley S, Wang S, Yu H, (2007). "Light-induced cytotoxicity and genotoxicity of a sunscreen agent, 2-phenylbenzimidazole in Salmonella typhimurium TA 102 and HaCaT keratinocytes," Int J Environ Res Public Health, 4, 126–31.
  29. ↑ Churg A, Gilks B, Dai J, (1999). "Induction of fibrogenic mediators by fine and ultrafine titanium dioxide in rat tracheal explants," Am. J. Physiol., 277, L975–82.
  30. ↑ Xu, C.; Green, Adele; Parisi, Alfio; Parsons, Peter G, (2001). "Photosensitization of the Sunscreen Octyl p-Dimethylaminobenzoate b UVA in Human Melanocytes but not in Keratinocytes," Photochemistry and Photobiology, 73, 600–604.
  31. ↑ Knowland, John; McKenzie, Edward A.; McHugh, Peter J.; Cridland, Nigel A., (1993). "Sunlight-induced mutagenicity of a common sunscreen ingredient," FEBS Letters, 324, 309–313.
  32. ↑ Damiani E, Greci L, Parsons R, Knowland J, (1999). "Nitroxide radicals protect DNA from damage when illuminated in vitro in the presence of dibenzoylmethane and a common sunscreen ingredient," Free Radic. Biol. Med., 26, 809–16.
  33. ↑ Long SD, Little JB, (1984). "Sunscreen agents induce DNA repair activity in mouse embryo fibroblasts," J. Environ. Pathol. Toxicol. Oncol., 5, 193–200.
  34. ↑ Taylor CR, Stern RS, Leyden JJ, Gilchrest BA, (1990). "Photoaging/photodamage and photoprotection," J. Am. Acad. Dermatol., 22, 1–15.
  35. ↑ 35.0 35.1 Stevenson, C.; Davies, R. J. H., (1999). "Photosensitization of guanine-specific DNA damage by 2-phenylbenzimidazole and the sunscreen agent 2-phenylbenzimidazole-5-sulfonic acid," Chem. Res. Toxicol., 12, 38–45.
  36. ↑ Inbaraj, J. J.; Bilski, P.; Chignell, C. F., (2002). "Photophysical and photochemical studies of 2-phenylbenzimidazole and UVB sunscreen 2-phenylbenzimidazole-5-sulfonic acid," Photochem. Photobiol., 75, 107–116.
  37. ↑ Elisabetta Damiani, Werner Baschong, Lucedio Greci, (2007). "UV-Filter combinations under UV-A exposure: Concomitant quantification of over-all spectral stability and molecular integrity," Journal of Photochemistry and Photobiology B: Biology, 87, 95–104.
  38. ↑ 38.0 38.1 Damiani E. Carloni P. Biondi C. Greci L., (2000). "Increased oxidative modification of albumin when illuminated in vitro in the presence of a common sunscreen ingredient: protection by nitroxide radicals - fractionated studies," Free Radical Biology and Medicine, 28, 193–201.
  39. ↑ J.M. Allen, C.J. Gosset, A.K. Allen, (1996). "Photochemical formation of singlet molecular oxygen in illuminated aqueous solutions of several commercially available sunscreen ingredients," Chem. Res. Toxicol., 9, 605–609.
  40. ↑ "Nanoparticles Used in Common Household Items Cause Genetic Damage in Mice". 17 November 2009. http://www.sciencedaily.com/releases/2009/11/091116165739.htm. Retrieved 2009-11-17. </li>
  41. ↑ Athanasia Varvaresou, (2006). "Percutaneous absorption of organic sunscreens," Journal of Cosmetic Dermatology, 5, 53–57.
  42. ↑ Sheree E Cross; Ruoying Jiang; Heather A E Benson; Michael S Roberts, (2001). "Can Increasing the Viscosity of Formulations be used to Reduce the Human Skin Penetration of the Sunscreen Oxybenzone?," Journal of Investigative Dermatology, 117, 147–150.
  43. ↑ E.Chatelain; B.Gabarda; C.Surber, (2003). "Skin Penetration and Sun Protection Factor of Five UV Filters: Effect of the Vehicle," Skin Pharmacol Appl Skin Physiol, 16, 28–35.
  44. ↑ Kerry Hanson skin penetration
  45. ↑ R Jiang; M S Roberts; D M Collins; H A E Benson, (1999). "Absorption of sunscreens across human skin: an evaluation of commercial products for children and adults," Br J Clin Pharmacol., 48, 635–7.
  46. ↑ http://www.fda.gov/ohrms/dockets/dailys/00/Sep00/090600/c000573_10_Attachment_F.pdf
  47. ↑ N. J. Lowe, Physician's guide to sunscreen , Kap. 8, 1991.
  48. ↑ Wolf P, Donawho CK, Kripke ML, (1994). "Effect of sunscreens on UV radiation-induced enhancement of melanoma growth in mice," J. Natl. Cancer Inst., 86, 99–105.
  49. ↑ Wulf HC, Poulsen T, Brodthagen H, Hou-Jensen K, (1982). "Sunscreens for delay of ultraviolet induction of skin tumors," J. Am. Acad. Dermatol., 7, 194–202.
  50. ↑ Reeve VE; Greenoak GE; Gallagher CH; Canfield PJ; Wilkinson FJ, (1985). "Effect of immunosuppressive agents and sunscreens on UV carcinogenesis in the hairless mouse," Aust J Exp Biol Med Sci, 63, 655–65.
  51. ↑ Flindt-Hansen, HP; Thune P, Larsen, TE, (1990). "The inhibiting effect of PABA on photocarcinogenesis," Arch Dermatol Res, 282, 38–41.
  52. ↑ C, (2008). "Sunscreens in organ transplant patients," Nephrol Dial Transplant, 23, 1805–1808.
  53. ↑ C, (2008). "Prevention of UV-induced infectious and malignant skin diseases in organ transplant patients by regular use of a liposomal sun screen," {{{journal}}}, {{{volume}}}, .
  54. ↑ [3]
  55. ↑ Lawsuit Filed Against Sunscreen Makers
  56. ↑ FDA proposed changes)(page 49079).
  57. ↑ Lautenschlager, Stephan; Wulf, Hans Christian; Pittelkow, Mark R., (2007). "photoprotection," Lancet, 370, 528–37.
  58. ↑ Holick MF, ({{{year}}}). "Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease," American Journal of Clinical Nutrition Full Text, 80, 1678S–88S.
  59. ↑ Robert M., (2007). "Darkness at Noon: Sunscreens and Vitamin D3," Photochemistry and Photobiology, 83, 459–63.
  60. ↑ Nowson C, Margerison C, (2002). "Vitamin D intake and vitamin D status of Australians," Med J Aust, 177, 149–52.
  61. ↑ Grant WB, (2002). "An estimate of premature cancer mortality in the U.S. due to inadequate doses of solar ultraviolet-B radiation," Cancer, 94, 1867–75.

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