Sunscreen controversy

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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 sunscreen use 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 lead 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 spectrum. A number of class-action lawsuits allege that sunscreen manufacturers misled consumers into believing that these products provided full sun protection. 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.

Contents

[edit] Studies of melanoma rates

Malignant melanoma has been found more frequently in sunscreen users compared to non-users by several studies. They have found an increase of malignant melanoma cases associated with sunscreen use.[1] [2][3][4][5][6][7] See also[8].

However, these claims could not be supported in three meta-analyses.[9][10] (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 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.[11][12]Many scientists argue that the sun-avoiding health message does increase some forms of skin cancer.[13]

A correlation exists between the number of sunburns a person sustains and his or her risk to develop melanoma.

[edit] 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[2][14][15][16]
  • 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,[17] and the lack of melanin leads to an increased risk of melanoma.[2]
  • free radical generation by sunscreen chemicals that have penetrated into the skin.[18][19][20][21] [22]
  • pathogenic cytotoxicity and carcinogenicity of micronized titanium or zinc oxide nanoparticles.[23]

[edit] Sunscreen ingredients can damage DNA

Some sunscreen ingredients may damage cells when illuminated. [24] [25][26][27] PABA causes DNA damage in human cells.[28] 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 keratinocytes.[22][29][30]

Some sunscreen ingredients generate Reactive oxygen species when exposed to UV-A,[31] which can increase carbonyl formation in albumin[32] and damage DNA. It is also well-known that DNA alterations are necessary for cancer to occur.

Many sunscreen ingredients generate singlet oxygen under illumination.[33] Several popular UV-filters have been demonstrated to generate free radicals.[32]

Kerry Hanson et al. have shown for the three sunscreen ingredients octocrylene, octylmethoxycinnamate, and 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.[21] Such an increase in ROS might increase the chance of melanoma, but this hypothesis has not been tested.

DNA, in particular, is susceptible to damage caused by photo-excited compounds.[29]

[edit] Sunscreen ingredients penetrate the skin

Between 1% and 10% of some sunscreen ingredients are absorbed into the body through the skin.[34][35][18][36] [37][38][20][18][39] See[40] , [41]

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.[21] 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.[21]

[edit] Animal experiments

All studies except for one [42] have found that sunscreens protect mice against melanoma. [43] [44][45]

[edit] Clinical study

In 2008, a clinical study showed that the application of sunscreen prevents SCC, BCC and actinic keratosis. The study included 60 transplant patients who received 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 herpes and warts and a slight increase in acne in the sunscreen group.[46][47]

[edit] Societal impacts

Lawsuits have been filed against sunscreen manufacturers.Lawsuit Filed Against Sunscreen Makers

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[...]"[48]

Sunscreen ingredients are not tested in Europe, Japan or Australia for photocarcinogenic effects before being introduced to the market. Even the US, most sunscreens sold in 2008 have not passed regulatory testing either, due to a grandfather clause. Three new sunscreen active ingredients introduced in the US since 1978 have fulfilled new testing requirements.[49]

[edit] Sunscreen and Vitamin D

The use of sunscreen with a sun protection factor (SPF) of 8 inhibits more than 95% of Vitamin D production in the skin.[50][51] Recent studies showed that, following the successful "Slip-Slop-Slap" health campaign encouraging Australians to cover up when exposed to sunlight to prevent skin cancer, an increased number of Australians and New Zealanders became vitamin D deficient.[52] Ironically, there are indications that vitamin D deficiency may lead to skin cancer.[53] To avoid vitamin D deficiency, vitamin supplements can be taken.

[edit] See also

[edit] References

  1. ^ Westerdahl J, Ingvar C, Mâsbäck A, Olsson H (July 2000). "Sunscreen use and malignant melanoma". Int. J. Cancer 87 (1): 145–50. doi:10.1002/1097-0215(20000701)87:1<145::AID-IJC22>3.0.CO;2-3. PMID 10861466. 
  2. ^ a b c 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. doi:10.1002/ijc.2910610602. 
  3. ^ Weinstock, M. A. (1999). "Do sunscreens increase or decrease melanoma risk: An epidemiologic evaluation". Journal of Investigative Dermatology Symposium Proceedings 4: 97–100. doi:10.1038/sj.jidsp.. 
  4. ^ Vainio, H., Bianchini, F. (2000). "Cancer-preventive effects of sunscreens are uncertain". Scandinavian Journal of Work Environment and Health 26: 529–31. 
  5. ^ 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 (4): 370–378. doi:10.1097/00008390-199808000-00012. PMID 9764814. 
  6. ^ Graham S, Marshall J, Haughey B, et al (October 1985). "An inquiry into the epidemiology of melanoma". Am. J. Epidemiol. 122 (4): 606–19. PMID 4025303. http://aje.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=4025303. 
  7. ^ 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 (1): 43–51. doi:10.1111/j.1365-2133.1990.tb08238.x. PMID 2297503. 
  8. ^ Garland C, Garland F, Gorham E (1992). "Could sunscreens increase melanoma risk?". Am J Public Health 82 (4): 614–5. doi:10.2105/AJPH.82.4.614. PMID 1546792. http://www.ajph.org/cgi/reprint/82/4/614. 
  9. ^ Huncharek M, Kupelnick B (July 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 (7): 1173–7. doi:10.2105/AJPH.92.7.1173. PMID 12084704. PMC: 1447210. http://www.ajph.org/cgi/pmidlookup?view=long&pmid=12084704. 
  10. ^ Dennis LK, Beane Freeman LE, VanBeek MJ (December 2003). "Sunscreen use and the risk for melanoma: a quantitative review". Ann. Intern. Med. 139 (12): 966–78. PMID 14678916. 
  11. ^ Jerant AF, Johnson JT, Sheridan CD, Caffrey TJ (July 2000). "Early detection and treatment of skin cancer". Am Fam Physician 62 (2): 357–68, 375–6, 381–2. PMID 10929700. http://www.aafp.org/afp/20000715/357.html. 
  12. ^ Boring CC, Squires TS, Tong T (1991). "Cancer statistics, 1991". CA Cancer J Clin 41 (1): 19–36. doi:10.3322/canjclin.41.1.19. PMID 1984806. http://caonline.amcancersoc.org/cgi/pmidlookup?view=long&pmid=1984806. 
  13. ^ Ainsleigh HG (1993). "Beneficial effects of sun exposure on cancer mortality". Prev Med. 22 (1): 132–40. doi:10.1006/pmed.1993.1010. PMID 8475009. 
  14. ^ Autier P, Boniol M, Doré JF (July 2007). "Sunscreen use and increased duration of intentional sun exposure: still a burning issue". Int. J. Cancer 121 (1): 1–5. doi:10.1002/ijc.22745. PMID 17415716. 
  15. ^ Gorham ED, Mohr SB, Garland CF, Chaplin G, Garland FC (December 2007). "Do sunscreens increase risk of melanoma in populations residing at higher latitudes?". Ann Epidemiol 17 (12): 956–63. doi:10.1016/j.annepidem.2007.06.008. PMID 18022535. 
  16. ^ Diffey BL (August 2005). "Sunscreens and melanoma: the future looks bright". Br. J. Dermatol. 153 (2): 378–81. doi:10.1111/j.1365-2133.2005.06729.x. PMID 16086753. 
  17. ^ Meredith, Paul; Riesz, Jennifer (2004). "Radiative Relaxation Quantum Yields for Synthetic Eumelanin". Photochemistry and photobiology 79 (2): 211–6. doi:10.1562/0031-8655(2004)079<0211:RCRQYF>2.0.CO;2. 
  18. ^ a b c Hayden, C G J; Roberts, M S; Benson, H A E (1997). "Systemic absorption of sunscreen after topical application". The Lancet 350 (9081): 863–4. doi:10.1016/S0140-6736(05)62032-6. 
  19. ^ 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. 
  20. ^ a b Treffel P, Gabard B (May 1996). "Skin penetration and sun protection factor of ultra-violet filters from two vehicles". Pharm. Res. 13 (5): 770–4. doi:10.1023/A:1016012019483. PMID 8860435. http://www.kluweronline.com/art.pdf?issn=0724-8741&volume=13&page=770. 
  21. ^ a b c d Hanson KM, Gratton E, Bardeen CJ (October 2006). "Sunscreen enhancement of UV-induced reactive oxygen species in the skin". Free Radic. Biol. Med. 41 (8): 1205–12. doi:10.1016/j.freeradbiomed.2006.06.011. PMID 17015167. 
  22. ^ a b Mosley CN, Wang L, Gilley S, Wang S, Yu H (June 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 (2): 126–31. doi:10.3390/ijerph2007040006. PMID 17617675. 
  23. ^ Churg A, Gilks B, Dai J (November 1999). "Induction of fibrogenic mediators by fine and ultrafine titanium dioxide in rat tracheal explants". Am. J. Physiol. 277 (5 Pt 1): L975–82. PMID 10564183. http://ajplung.physiology.org/cgi/pmidlookup?view=long&pmid=10564183. 
  24. ^ 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 (6): 600–604. doi:10.1562/0031-8655(2001)073<0600:POTSOP>2.0.CO;2. 
  25. ^ Knowland, John; McKenzie, Edward A.; McHugh, Peter J.; Cridland, Nigel A. (1993). "Sunlight-induced mutagenicity of a common sunscreen ingredient". FEBS Letters 324(3): 309–313. doi:10.1016/0014-5793(93)80141-G. 
  26. ^ Damiani E, Greci L, Parsons R, Knowland J (April 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 (7-8): 809–16. doi:10.1016/S0891-5849(98)00292-5. PMID 10232823. http://linkinghub.elsevier.com/retrieve/pii/S0891-5849(98)00292-5. 
  27. ^ Long SD, Little JB (July 1984). "Sunscreen agents induce DNA repair activity in mouse embryo fibroblasts". J. Environ. Pathol. Toxicol. Oncol. 5 (4-5): 193–200. PMID 6520725. 
  28. ^ Taylor CR, Stern RS, Leyden JJ, Gilchrest BA (January 1990). "Photoaging/photodamage and photoprotection". J. Am. Acad. Dermatol. 22 (1): 1–15. doi:10.1016/0190-9622(90)70001-X. PMID 2405022. 
  29. ^ a b 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. doi:10.1021/tx980158l. 
  30. ^ 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. doi:10.1562/0031-8655(2002)075<0107:PAPSOP>2.0.CO;2. 
  31. ^ 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 (2): 95–104. doi:10.1016/j.jphotobiol.2007.03.003. 
  32. ^ a b 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 (2): 193–201. doi:10.1016/S0891-5849(99)00221-X. 
  33. ^ 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. doi:10.1021/tx950197m. 
  34. ^ Athanasia Varvaresou (2006). "Percutaneous absorption of organic sunscreens". Journal of Cosmetic Dermatology 5 (1): 53–57. doi:10.1111/j.1473-2165.2006.00223.x. http://www.blackwell-synergy.com/doi/abs/10.1111/j.1473-2165.2006.00223.x. 
  35. ^ 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. doi:10.1046/j.1523-1747.2001.01398.x. http://www.nature.com/jid/journal/v117/n1/full/5601129a.html. 
  36. ^ Skin Penetration and Sun Protection Factor of Five UV Filters: Effect of the Vehicle
  37. ^ E.Chatelain; B.Gabarda; C.Surber (2003). "Skin Penetration and Sun Protection Factor of Five UV Filters: Effect of the Vehicle" (PDF). Skin Pharmacol Appl Skin Physiol 16: 28–35. doi:10.1159/000068291. http://content.karger.com/ProdukteDB/produkte.asp?Aktion=ShowPDF&ArtikelNr=68291&ProduktNr=224219&Ausgabe=228903&filename=68291.pdf. 
  38. ^ Kerry Hanson skin penetration
  39. ^ R Jiang; M S Roberts; D M Collins; H A E Benson (October 1999). "Absorption of sunscreens across human skin: an evaluation of commercial products for children and adults". Br J Clin Pharmacol. 48 (4): 635–7. doi:10.1046/j.1365-2125.1999.00056.x. PMID 10583038. 
  40. ^ http://www.fda.gov/ohrms/dockets/dailys/00/Sep00/090600/c000573_10_Attachment_F.pdf
  41. ^ N. J. Lowe, Physician's guide to sunscreen , Kap. 8, 1991.
  42. ^ Wolf P, Donawho CK, Kripke ML (January 1994). "Effect of sunscreens on UV radiation-induced enhancement of melanoma growth in mice". J. Natl. Cancer Inst. 86 (2): 99–105. doi:10.1093/jnci/86.2.99. PMID 8271307. http://jnci.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=8271307. 
  43. ^ Wulf HC, Poulsen T, Brodthagen H, Hou-Jensen K (August 1982). "Sunscreens for delay of ultraviolet induction of skin tumors". J. Am. Acad. Dermatol. 7 (2): 194–202. doi:10.1016/S0190-9622(82)70108-2. PMID 6982289. 
  44. ^ Reeve VE; Greenoak GE; Gallagher CH; Canfield PJ; Wilkinson FJ (December 1985). "Effect of immunosuppressive agents and sunscreens on UV carcinogenesis in the hairless mouse". Aust J Exp Biol Med Sci 63: 655. doi:10.1038/icb.1985.69. PMID 3879583. 
  45. ^ Flindt-Hansen, HP; Thune P, Larsen, TE (1990). "The inhibiting effect of PABA on photocarcinogenesis". Arch Dermatol Res 282: 38–41. doi:10.1007/BF00505643. PMID 2317082. 
  46. ^ Ulrich, C; Degen, A, Patel, MJ, Stockfleth, E (2008). "Sunscreens in organ transplant patients". Nephrol Dial Transplant 23: 1805–1808. doi:10.1093/ndt/gfn292. 
  47. ^ Ulrich, C; Hackethal, M, Ulrich, M, Forschner, T, Sterry, W, Stockfleth, E (2008), Prevention of UV-induced infectious and malignant skin diseases in organ transplant patients by regular use of a liposomal sun screen, Berlin 
  48. ^ FDA proposed changes)(page 49079).
  49. ^ Lautenschlager, Stephan; Wulf, Hans Christian; Pittelkow, Mark R. (2007). "photoprotection". Lancet 370: 528–37. doi:10.1016/S0140-6736(07)60638-2. PMID 17693182. 
  50. ^ Holick MF (01 Dec 2004). "Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease". American Journal of Clinical Nutrition Full Text 80 (6): 1678S–88S. PMID 15585788. http://www.ajcn.org/cgi/content/full/80/6/1678S. 
  51. ^ Sayre, Robert M.; John C. Dowdy (2007). "Darkness at Noon: Sunscreens and Vitamin D3". Photochemistry and Photobiology 83 (2): 459. doi:10.1562/2006-06-29-RC-956 (inactive 2008-09-05). http://www.blackwell-synergy.com/doi/abs/10.1562/2006-06-29-RC-956. 
  52. ^ Nowson C, Margerison C (2002). "Vitamin D intake and vitamin D status of Australians". Med J Aust 177 (3): 149–52. PMID 12149085. http://www.mja.com.au/public/issues/177_03_050802/now10763_fm.html. 
  53. ^ Grant WB (2002). "An estimate of premature cancer mortality in the U.S. due to inadequate doses of solar ultraviolet-B radiation". Cancer 94 (6): 1867–75. doi:10.1002/cncr.10427. PMID 11920550. 
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