Sunscreen controversy

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. [http://www.direct-ms.org/pdf/VitDNonAuto/HolickAJCN.pdf] 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

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.

tudies 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. cite journal |author=Westerdahl J, Ingvar C, Mâsbäck A, Olsson H |title=Sunscreen use and malignant melanoma |journal=Int. J. Cancer |volume=87 |issue=1 |pages=145–50 |year=2000 |month=Jul |pmid=10861466 |doi=10.1002/1097-0215(20000701)87:1<145::AID-IJC22>3.0.CO;2-3] cite journal |author=Autier P; Dore J F; Schifflers E; et al |title=Melanoma and use of sunscreens: An EORTC case control study in Germany, Belgium and France |url= |journal=Int. J. Cancer |volume=61 |issue= |pages=749–755 |year=1995|doi=10.1002/ijc.2910610602] cite journal |author=Weinstock, M. A. |title=Do sunscreens increase or decrease melanoma risk: An epidemiologic evaluation |url= |journal=Journal of Investigative Dermatology Symposium Proceedings |volume=4 |issue= |pages= 97–100 |year=1999|doi=10.1038/sj.jidsp.] cite journal |author=Vainio, H., Bianchini, F. |title=Cancer-preventive effects of sunscreens are uncertain |url= |journal=Scandinavian Journal of Work Environment and Health |volume=26 |issue= |pages=529–31 |year=2000 |issn=] cite journal |author=Wolf P, Quehenberger F, Müllegger R, Stranz B, Kerl H. |title=Phenotypic markers, sunlight-related factors and sunscreen use in patients with cutaneous melanoma: an Austrian case-control study |url= |journal=Melanoma Res. |volume=8 |issue=4 |pages=370–378 |year=1998 |pmid=9764814|doi=10.1097/00008390-199808000-00012] cite journal |author=Graham S, Marshall J, Haughey B, "et al" |title=An inquiry into the epidemiology of melanoma |journal=Am. J. Epidemiol. |volume=122 |issue=4 |pages=606–19 |year=1985 |month=Oct |pmid=4025303 |doi= |url=http://aje.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=4025303] cite journal |author=Beitner H, Norell SE, Ringborg U, Wennersten G, Mattson B. |title=Malignant melanoma: aetiological importance of individual pigmentation and sun exposure |journal=Br J Dermatol.|volume=122 |issue=1 |pages=43–51 |year=1990 |pmid=2297503|doi=10.1111/j.1365-2133.1990.tb08238.x] See alsocite journal |author=Garland C, Garland F, Gorham E |title=Could sunscreens increase melanoma risk? |url= http://www.ajph.org/cgi/reprint/82/4/614 |journal=Am J Public Health |volume=82 |issue=4 |pages=614–5 |year=1992 |pmid=1546792 |issn=] .

However, these claims could not be supported in three meta-analyses. [cite journal |author=Huncharek M, Kupelnick B |title=Use of topical sunscreens and the risk of malignant melanoma: a meta-analysis of 9067 patients from 11 case-control studies |journal=Am J Public Health |volume=92 |issue=7 |pages=1173–7 |year=2002 |month=July |pmid=12084704 |pmc=1447210 |doi= |url=http://www.ajph.org/cgi/pmidlookup?view=long&pmid=12084704] [cite journal |author=Dennis LK, Beane Freeman LE, VanBeek MJ |title=Sunscreen use and the risk for melanoma: a quantitative review |journal=Ann. Intern. Med. |volume=139 |issue=12 |pages=966–78 |year=2003 |month=Dec |pmid=14678916 |doi= |url=] (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.cite journal |author=Jerant AF, Johnson JT, Sheridan CD, Caffrey TJ |title=Early detection and treatment of skin cancer |journal=Am Fam Physician |volume=62 |issue=2 |pages=357–68, 375–6, 381–2 |year=2000 |month=Jul |pmid=10929700 |doi= |url=http://www.aafp.org/afp/20000715/357.html ] cite journal |author=Boring CC, Squires TS, Tong T |title=Cancer statistics, 1991 |journal=CA Cancer J Clin |volume=41 |issue=1 |pages=19–36 |year=1991 |pmid=1984806 |doi=10.3322/canjclin.41.1.19 |url=http://caonline.amcancersoc.org/cgi/pmidlookup?view=long&pmid=1984806] Many scientists argue that the sun-avoiding health message does increase some forms of skin cancer. cite journal |author=Ainsleigh HG |title=Beneficial effects of sun exposure on cancer mortality |journal=Prev Med. |volume=22 |issue=1 |pages=132–40 |year=1993 |pmid=8475009|doi=10.1006/pmed.1993.1010]

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

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 [cite journal |author=Autier P, Boniol M, Doré JF |title=Sunscreen use and increased duration of intentional sun exposure: still a burning issue |journal=Int. J. Cancer |volume=121 |issue=1 |pages=1–5 |year=2007 |month=Jul |pmid=17415716 |doi=10.1002/ijc.22745 |url=] [cite journal |author=Gorham ED, Mohr SB, Garland CF, Chaplin G, Garland FC |title=Do sunscreens increase risk of melanoma in populations residing at higher latitudes? |journal=Ann Epidemiol |volume=17 |issue=12 |pages=956–63 |year=2007 |month=Dec |pmid=18022535 |doi=10.1016/j.annepidem.2007.06.008 |url=] [cite journal |author=Diffey BL |title=Sunscreens and melanoma: the future looks bright |journal=Br. J. Dermatol. |volume=153 |issue=2 |pages=378–81 |year=2005 |month=Aug |pmid=16086753 |doi=10.1111/j.1365-2133.2005.06729.x |url=]
* 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,cite journal |author=Meredith, Paul; Riesz, Jennifer |title=Radiative Relaxation Quantum Yields for Synthetic Eumelanin |url= |journal= Photochemistry and photobiology |volume=79 |issue=2 |pages=211–6 |year=2004|doi=10.1562/0031-8655(2004)079<0211:RCRQYF>2.0.CO;2] and the lack of melanin leads to an increased risk of melanoma.
* free radical generation by sunscreen chemicals that have penetrated into the skin. cite journal |author=Hayden, C G J; Roberts, M S; Benson, H A E |year= 1997 |month= |title= Systemic absorption of sunscreen after topical application |journal= The Lancet |volume= 350 |issue= 9081 |pages=863–4 |id= |url=|doi= 10.1016/S0140-6736(05)62032-6] cite journal |author=Walters, K. A.; Roberts, M. S. |year= 2002 |month= |title= Percutaneous absorption of sunscreens |journal= Book: Bronaugh, R. L.; Maibach, H.I. Eds. Topical absorption of dermatological products. / New York: Dekker; 2002 |volume= |issue= |pages= 465–81 |id= |url=] cite journal |author=Treffel P, Gabard B |title=Skin penetration and sun protection factor of ultra-violet filters from two vehicles |journal=Pharm. Res. |volume=13 |issue=5 |pages=770–4 |year=1996 |month=May |pmid=8860435 |doi=10.1023/A:1016012019483 |url=http://www.kluweronline.com/art.pdf?issn=0724-8741&volume=13&page=770] cite journal |author=Hanson KM, Gratton E, Bardeen CJ |title=Sunscreen enhancement of UV-induced reactive oxygen species in the skin |journal=Free Radic. Biol. Med. |volume=41 |issue=8 |pages=1205–12 |year=2006 |month=Oct |pmid=17015167 |doi=10.1016/j.freeradbiomed.2006.06.011 |url=] cite journal |author=Mosley CN, Wang L, Gilley S, Wang S, Yu H |title=Light-induced cytotoxicity and genotoxicity of a sunscreen agent, 2-phenylbenzimidazole in Salmonella typhimurium TA 102 and HaCaT keratinocytes |journal=Int J Environ Res Public Health |volume=4 |issue=2 |pages=126–31 |year=2007 |month=Jun |pmid=17617675 |doi= |url=]
* pathogenic cytotoxicity and carcinogenicity of micronized titanium or zinc oxide nanoparticles.cite journal |author=Churg A, Gilks B, Dai J |title=Induction of fibrogenic mediators by fine and ultrafine titanium dioxide in rat tracheal explants |journal=Am. J. Physiol. |volume=277 |issue=5 Pt 1 |pages=L975–82 |year=1999 |month=Nov |pmid=10564183 |doi= |url=http://ajplung.physiology.org/cgi/pmidlookup?view=long&pmid=10564183]

unscreen ingredients can damage DNA

Some sunscreen ingredients may damage cells when illuminated. cite journal |author=Xu, C.; Green, Adele; Parisi, Alfio; Parsons, Peter G |year= 2001 |month= |title= Photosensitization of the Sunscreen Octyl p-Dimethylaminobenzoate b UVA in Human Melanocytes but not in Keratinocytes |journal= Photochemistry and Photobiology |volume= 73 |issue= 6 |pages=600–604 |id= |url=|doi= 10.1562/0031-8655(2001)073<0600:POTSOP>2.0.CO;2] cite journal |author=Knowland, John; McKenzie, Edward A.; McHugh, Peter J.; Cridland, Nigel A. |title= Sunlight-induced mutagenicity of a common sunscreen ingredient | journal= FEBS Letters |volume= 324(3) |pages=309–313 |year=1993 |doi= 10.1016/0014-5793(93)80141-G ] cite journal |author=Damiani E, Greci L, Parsons R, Knowland J |title=Nitroxide radicals protect DNA from damage when illuminated in vitro in the presence of dibenzoylmethane and a common sunscreen ingredient |journal=Free Radic. Biol. Med. |volume=26 |issue=7-8 |pages=809–16 |year=1999 |month=Apr |pmid=10232823 |doi=10.1016/S0891-5849(98)00292-5 |url=http://linkinghub.elsevier.com/retrieve/pii/S0891-5849(98)00292-5] cite journal |author=Long SD, Little JB |title=Sunscreen agents induce DNA repair activity in mouse embryo fibroblasts |journal=J. Environ. Pathol. Toxicol. Oncol. |volume=5 |issue=4-5 |pages=193–200 |year=1984 |month=Jul |pmid=6520725 |doi= |url=] PABA causes DNA damage in human cells.cite journal |author=Taylor CR, Stern RS, Leyden JJ, Gilchrest BA |title=Photoaging/photodamage and photoprotection |journal=J. Am. Acad. Dermatol. |volume=22 |issue=1 |pages=1–15 |year=1990 |month=Jan |pmid=2405022 |doi= |url=] 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.cite journal |author=Mosley, C N; Wang, L; Gilley, S; Wang, S; Yu,H |year= 2007 |month= |title= Light-Induced Cytotoxicity and Genotoxicity of a Sunscreen Agent, 2-Phenylbenzimidazol in Salmonella typhimurium TA 102 and HaCaT Keratinocytes |journal= International Journal of Environmental Research and Public Health |volume= 4 |issue= 2 |pages=126–131 |id= |url=] cite journal |author=Stevenson, C.; Davies, R. J. H. |year= 1999 |month= |title= Photosensitization of guanine-specific DNA damage by 2-phenylbenzimidazole and the sunscreen agent 2-phenylbenzimidazole-5-sulfonic acid |journal= Chem. Res. Toxicol. |volume= 12 |issue= |pages=38–45 |id= |url=|doi= 10.1021/tx980158l] cite journal |author=Inbaraj, J. J.; Bilski, P.; Chignell, C. F. |year= 2002 |month= |title= Photophysical and photochemical studies of 2-phenylbenzimidazole and UVB sunscreen 2-phenylbenzimidazole-5-sulfonic acid |journal= Photochem. Photobiol. |volume= 75 |issue= |pages=107–116 |id= |url=|doi= 10.1562/0031-8655(2002)075<0107:PAPSOP>2.0.CO;2]

Some sunscreen ingredients generate Reactive oxygen species when exposed to UV-A, cite journal |author=Elisabetta Damiani, Werner Baschong, Lucedio Greci |title= UV-Filter combinations under UV-A exposure: Concomitant quantification of over-all spectral stability and molecular integrity |journal= Journal of Photochemistry and Photobiology B: Biology |volume= 87 |issue= 2 |pages=95–104 |year=2007 |doi= 10.1016/j.jphotobiol.2007.03.003 ] which can increase carbonyl formation in albumin cite journal |author=Damiani E. Carloni P. Biondi C. Greci L. |title= Increased oxidative modification of albumin when illuminated in vitro in the presence of a common sunscreen ingredient: protection by nitroxide radicals - fractionated studies | journal= Free Radical Biology and Medicine |volume= 28 |issue=2 |pages=193–201 |year=2000 |doi= 10.1016/S0891-5849(99)00221-X ] 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. cite journal |author= J.M. Allen, C.J. Gosset, A.K. Allen |year= 1996 |month= |title=Photochemical formation of singlet molecular oxygen in illuminated aqueous solutions of several commercially available sunscreen ingredients |journal= Chem. Res. Toxicol. |volume= 9 |issue= |pages=605–609 |id= |url=|doi=10.1021/tx950197m] Several popular UV-filters have been demonstrated to generate free radicals.

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. 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.

unscreen ingredients penetrate the skin

Between 1% and 10% of some sunscreen ingredients are absorbed into the body through the skin. cite journal |author=Athanasia Varvaresou |year= 2006 |month= |title=Percutaneous absorption of organic sunscreens |journal= Journal of Cosmetic Dermatology |volume= 5 |issue=1 |pages=53–57 |id= |doi= 10.1111/j.1473-2165.2006.00223.x |url=http://www.blackwell-synergy.com/doi/abs/10.1111/j.1473-2165.2006.00223.x] cite journal |author=Sheree E Cross; Ruoying Jiang; Heather A E Benson; Michael S Roberts |year= 2001 |month= |title= Can Increasing the Viscosity of Formulations be used to Reduce the Human Skin Penetration of the Sunscreen Oxybenzone? |journal= Journal of Investigative Dermatology |volume= 117 |issue= |pages=147–150 |id= |doi= 10.1046/j.1523-1747.2001.01398.x |url=http://www.nature.com/jid/journal/v117/n1/full/5601129a.html] cite journal |author=Hayden, C G J; Roberts, M S; Benson, H A E |year= 1997 |month= |title= Systemic absorption of sunscreen after topical application |journal= The Lancet |volume= 350 |issue= 9081 |pages=863–864 |id= |url=|doi= 10.1016/S0140-6736(05)62032-6] [ [http://content.karger.com/ProdukteDB/produkte.asp?Aktion=ShowPDF&ArtikelNr=68291&ProduktNr=224219&Ausgabe=228903&filename=68291.pdf Skin Penetration and Sun Protection Factor of Five UV Filters: Effect of the Vehicle ] ] cite journal |author=E.Chatelain; B.Gabarda; C.Surber |year= 2003 |month= |title=Skin Penetration and Sun Protection Factor of Five UV Filters: Effect of the Vehicle |journal= Skin Pharmacol Appl Skin Physiol |volume= 16 |issue= |pages=28–35 |id= |doi= 10.1159/000068291 |url=http://content.karger.com/ProdukteDB/produkte.asp?Aktion=ShowPDF&ArtikelNr=68291&ProduktNr=224219&Ausgabe=228903&filename=68291.pdf] [http://www.sciencedaily.com/releases/2006/08/060828211528.htm Kerry Hanson skin penetration] ] cite journal |author=Treffel, P.; Gabard, B. |year= 1996 |month= |title= Skin penetration and SPF of ultraviolet filters from two vehicles |journal= Pharm. Res. |volume= 13 |issue= |pages=770–4 |pmid=8860435 |doi= 10.1023/A:1016012019483] cite journal |author=Hayden, C G J; Roberts, M S; Benson, H A E |year= 1997 |month= |title= Systemic absorption of sunscreen after topical application |journal= The Lancet |volume= 350 |issue= 9081 |pages=863–4 |pmid=9310609 |doi= 10.1016/S0140-6736(05)62032-6] cite journal |author=R Jiang; M S Roberts; D M Collins; H A E Benson |year= 1999 |month=October |title= Absorption of sunscreens across human skin: an evaluation of commercial products for children and adults |journal= Br J Clin Pharmacol. |volume= 48 |issue=4 |pages=635–7 |pmid=10583038 |pmc=2014387 |doi= 10.1046/j.1365-2125.1999.00056.x] Seehttp://www.fda.gov/ohrms/dockets/dailys/00/Sep00/090600/c000573_10_Attachment_F.pdf] , [N. J. Lowe, "Physician's guide to sunscreen" , Kap. 8, 1991.]

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. 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.

Animal experiments

All studies except for one cite journal |author=Wolf P, Donawho CK, Kripke ML |title=Effect of sunscreens on UV radiation-induced enhancement of melanoma growth in mice |journal=J. Natl. Cancer Inst. |volume=86 |issue=2 |pages=99–105 |year=1994 |month=Jan |pmid=8271307 |doi=10.1093/jnci/86.2.99 |url=http://jnci.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=8271307] have found that sunscreens protect mice against melanoma cite journal |author=Wulf HC, Poulsen T, Brodthagen H, Hou-Jensen K |title=Sunscreens for delay of ultraviolet induction of skin tumors |journal=J. Am. Acad. Dermatol. |volume=7 |issue=2 |pages=194–202 |year=1982 |month=Aug |pmid=6982289 |doi= |url=] cite journal |author=Reeve VE; Greenoak GE; Gallagher CH; Canfield PJ; Wilkinson FJ |title=Effect of immunosuppressive agents and sunscreens on UV carcinogenesis in the hairless mouse |url= |journal=Aust J Exp Biol Med Sci |volume=63 |pages=655 |year=1985 |month=Dec |pmid=3879583 |doi=10.1038/icb.1985.69] cite journal |author=Flindt-Hansen, HP; Thune P, Larsen, TE |title=The inhibiting effect of PABA on photocarcinogenesis |url= |journal=Arch Dermatol Res |volume=282 |pages=38–41 |year=1990 |pmid=2317082 |doi=10.1007/BF00505643]

ocietal impacts

Lawsuits have been filed against sunscreen manufacturers. [http://www.webmd.com/news/20060331/lawsuit-against-sunscreen-makers 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 [...] " [ [http://www.fda.gov/OHRMS/DOCKETS/98fr/07-4131.pdf FDA proposed changes] )(page 49079). ]

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. cite journal |author=Lautenschlager, Stephan; Wulf, Hans Christian; Pittelkow, Mark R. |title= photoprotection | journal= Lancet |volume=370 |pages=528–37 |year=2007 |pmid=17693182 |doi= 10.1016/S0140-6736(07)60638-2 ]

unscreen 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.cite journal | author=Holick MF | title=Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease | journal=American Journal of Clinical Nutrition Full Text | year=2004 | pages=1678S–88S| volume=80 | issue=6 | url=http://www.ajcn.org/cgi/content/full/80/6/1678S | pmid=15585788 ] [cite journal |last=Sayre |first=Robert M. |coauthors=John C. Dowdy |year=2007 |title=Darkness at Noon: Sunscreens and Vitamin D₃ |journal=Photochemistry and Photobiology |volume=83 |issue=2 |pages=459 |doi=10.1562/2006-06-29-RC-956 |url=http://www.blackwell-synergy.com/doi/abs/10.1562/2006-06-29-RC-956 |doi_brokendate=2008-09-05] 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.cite journal |author=Nowson C, Margerison C |title=Vitamin D intake and vitamin D status of Australians |url=http://www.mja.com.au/public/issues/177_03_050802/now10763_fm.html |journal=Med J Aust |volume=177 |issue=3 |pages=149–52 |year=2002 |pmid=12149085] Ironically, there are indications that vitamin D deficiency may lead to skin cancer. [cite journal | author=Grant WB | title=An estimate of premature cancer mortality in the U.S. due to inadequate doses of solar ultraviolet-B radiation | journal=Cancer | year=2002 | pages=1867–75 | volume=94 | issue=6 | pmid=11920550 | doi = 10.1002/cncr.10427 ] To avoid vitamin D deficiency, vitamin supplements can be taken.

ee also

*Melanoma
*tanning activator
*sun protective clothing
*Vitamin D

References