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Change of Ultraviolet Absorbance of Sunscreens by Exposure to Solar-Simulated Radiation

2001; Elsevier BV; Volume: 117; Issue: 2 Linguagem: Inglês

10.1046/j.0022-202x.2001.01425.x

1523-1747

Harald Maier, Herbert Hönigsmann, Günther Schauberger, K. Brunnhofer,

Dermatologic Treatments and Research

Regarding the outdoor behavior of the Caucasian population, modern sunscreens should provide high and broad-spectrum ultraviolet protection in the ultraviolet B as well as in the ultraviolet A range and should be photochemically stable for ultraviolet doses, which can be expected in solar radiation. At present an assessment of the photostability of suncare products is not a general requirement before marketing. In order to evaluate the photostability of suncare products we conducted an in vitro test and measured the spectral absorbance of 16 sunscreens before, and after exposure to increasing biologically weighted standard erythema doses (5, 12.5, 25, 50) of solar-simulated radiation. Seven of 16 suncare products showed a significant dose- and wavelength-dependent decrease of the ultraviolet A protective capacity, whereas the ability to absorb ultraviolet B was not affected. In the ultraviolet A range, the decrease of absorbance (photoinactivation), respectively, the increase of transmission was 12–48% for an ultraviolet exposure of 25 standard erythema dose. Photoinactivation started in the wavelength range between 320 and 335 nm with a maximum above 350 nm. Furthermore, our analysis showed that the behavior of suncare products was not predictable from its individual ingredients. Neither complex combinations of organic filters nor addition of inorganic filters could absolutely prevent photoinactivation. The inclusion of a single photounstable filter did not mean photoinstability of the complete suncare product. Photoinactivation of sunscreens appears to be an underestimated hazard to the skin, first, by formation of free radicals, second, by increased ultraviolet A transmission. Regarding the outdoor behavior of the Caucasian population, modern sunscreens should provide high and broad-spectrum ultraviolet protection in the ultraviolet B as well as in the ultraviolet A range and should be photochemically stable for ultraviolet doses, which can be expected in solar radiation. At present an assessment of the photostability of suncare products is not a general requirement before marketing. In order to evaluate the photostability of suncare products we conducted an in vitro test and measured the spectral absorbance of 16 sunscreens before, and after exposure to increasing biologically weighted standard erythema doses (5, 12.5, 25, 50) of solar-simulated radiation. Seven of 16 suncare products showed a significant dose- and wavelength-dependent decrease of the ultraviolet A protective capacity, whereas the ability to absorb ultraviolet B was not affected. In the ultraviolet A range, the decrease of absorbance (photoinactivation), respectively, the increase of transmission was 12–48% for an ultraviolet exposure of 25 standard erythema dose. Photoinactivation started in the wavelength range between 320 and 335 nm with a maximum above 350 nm. Furthermore, our analysis showed that the behavior of suncare products was not predictable from its individual ingredients. Neither complex combinations of organic filters nor addition of inorganic filters could absolutely prevent photoinactivation. The inclusion of a single photounstable filter did not mean photoinstability of the complete suncare product. Photoinactivation of sunscreens appears to be an underestimated hazard to the skin, first, by formation of free radicals, second, by increased ultraviolet A transmission. International Agency for Research on Cancer reactive oxygen species standard erythema dose = 100 J per m2 of erythemally weighted UV radiation ultraviolet A = wavelength 320–380 nm ultraviolet B = wavelength 280–320 nm Recent studies show that regular use of sunscreens reduces the carcinogenic risk (Thompson et al., 1993Thompson S.C. Jolley D. Marks R. Reduction of solar keratoses by regular sunscreen use.N Engl J Med. 1993; 329: 1147-1151Crossref PubMed Scopus (630) Google Scholar;Fourtanier, 1996Fourtanier A. Mexoryl SX protects against solar-simulated UVR-induced photocarcinogenesis in mice.Photochem Photobiol. 1996; 64: 688-693Crossref PubMed Scopus (39) Google Scholar), provides protection against immune suppression (Wolf et al., 1993Wolf P. Donawho C.K. Kripke M.L. Analysis of the protective effect of different sunscreens on ultraviolet radiation-induced local and systemic suppression of contact hypersensitivity and inflammatory responses in mice.J Invest Dermatol. 1993; 100: 254-259Abstract Full Text PDF PubMed Google Scholar;Krien and Moyal, 1994Krien P.M. Moyal D. Sunscreens with broad-spectrum absorption decrease the trans to cis photoisomerization of urocanic acid in the human stratum corneum after multiple UV light exposures.Photochem Photobiol. 1994; 60: 280-287Crossref PubMed Scopus (37) Google Scholar;Damian et al., 1997Damian D.L. Halliday G.M. Barnetson R.S. Broad-spectrum sunscreens provide greater protection against ultraviolet-radiation induced suppression of contact hypersensitivity to recall antigen in humans.J Invest Dermatol. 1997; 109: 146-151Crossref PubMed Scopus (118) Google Scholar;Serre et al., 1997Serre I. Cano J.P. Picot M.C. Meynadier J. Meunier L. Immunosuppression induced by acute solar-simulated ultraviolet exposure in humans: prevention by a sunscreen with a sun protection factor of 15 and high UVA protection.J Am Acad Dermatol. 1997; 37: 187-194Abstract Full Text Full Text PDF PubMed Scopus (73) Google Scholar) and prevents photoaging (Harrison et al., 1991Harrison J.A. Walker S.L. Plastow S.R. Batt M.D. Hawk J.L.M. Young A.R. Sunscreens with low sun protection factor inhibit ultraviolet B and A photoaging in the skin of hairless albino mouse.Photodermatol Photoimmunol Photomed. 1991; 8: 12-20PubMed Google Scholar;Bernstein et al., 1997Bernstein E.F. Brown D.B. Takeuchi T. Kong S.K. Uitto J. Evaluation of sunscreens with various sun protection factors in a new transgenic mouse model of cutaneous photoaging that measures elastin promoter activation.J Am Acad Dermatol. 1997; 31: 725-729Abstract Full Text Full Text PDF Scopus (21) Google Scholar). It has been pointed out repeatedly that ultraviolet (UV) A radiation (320–380 nm) contributes to skin photodamage (Parrish et al., 1978Parrish J.A. Anderson R.R. Urbach F. Pitts D. UVA Biological Effects of Ultraviolet Radiation with Emphasis on Human Responses to Longwave Ultraviolet. Plenum Press, New York1978: 1-6Google Scholar). Photodamage is predicted to become a major threat to public health in the coming decades (Kaminer, 1995Kaminer M.S. Photodamage: magnitude of the problem.in: Gilchrest B.A. Photodamage. 1st edn. Blackwell Science, Cambridge1995: 1-11Google Scholar); therefore, in addition to a high protection in the UVB range (280–320 nm) also protection against UVA radiation appears to be mandatory (Young and Walker, 1999Young A.R. Walker S.L. Sunscreens: Photoprotection of non-erythema endpoints relevant to skin cancer.Photodermatol Photoimmunol Photomed. 1999; 15: 221-225Crossref PubMed Scopus (15) Google Scholar). A new generation of broad-spectrum sunscreens provides high protective capacity in both, the UVA and UVB range. The major advantage of these suncare products should be a more effective protection of acute and chronic adverse effects of solar UV radiation to skin areas usually exposed to sunlight (face, hands, lower legs) and areas exposed under special conditions (outdoor work, outdoor sport). The misleading advertising of a "safe tan" by sunscreen producers, however, encourages people to (mis)use modern sunscreens in order to stay much longer in the sun (Boldeman et al., 1996Boldeman C. Breitner H. Jansson B. Nilsson B. Ullen H. Sunbed use in relation to phenotype, erythema, sunscreen use and skin disease. A questionnaire survey among Swedish adolescents.Br J Dermatol. 1996; 135: 712-716Crossref PubMed Scopus (63) Google Scholar;Autier et al., 1998Autier P. Dore J.F. Cattaruzza M.S. et al.Sunscreen use, wearing clothes, and number of nevi in 6- to 7-year-old European children. European Organization for Research and Treatment of Cancer Melanoma Cooperative Group.J Natl Cancer Inst. 1998; 90: 1873-1880Crossref PubMed Google Scholar). Prolonged exposure time together with a wrong self-assessment of the personal burning capacity (Stender et al., 1996Stender I.M. Lock-Andersen J. Wulf H.C. Sun-protection behaviour and self-assessed burning tendency among sunbathers.Photodermatol Photoimmunol Photomed. 1996; 12: 162-165Crossref PubMed Scopus (15) Google Scholar) and incorrect mode of application (Azurdia et al., 1999Azurdia R.M. Pagliaro J.A. Diffey B.L. Rhodes L.E. Sunscreen application by photosensitive patients is inadequate for protection.Br J Dermatol. 1999; 140: 255-258https://doi.org/10.1046/j.1365-2133.1999.02658.xCrossref PubMed Scopus (115) Google Scholar;Pruim et al., 1999Pruim B. Wright L. Green A. Do people who apply sunscreens, re-apply them?.Australas J Dermatol. 1999; 40: 79-82https://doi.org/10.1046/j.1440-0960.1999.00325.xCrossref PubMed Scopus (31) Google Scholar) reduces the benefits of high protective factors and broad-spectrum protection. At present, it appears that in public opinion sunscreens are regarded as first-line photoprotective modality. This is the reason why an International Working Group of experts convened by the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) concluded that sunscreens should be only one part of a comprehensive sun avoidance strategy (IARC (International Agency for Research on Cancer), 2000aIARC (International Agency for Research on Cancer) Do sunscreens prevent skin.cancer? IARC, Lyon2000http://www.iarc.frGoogle Scholar). The most important recommendations on sun behavior forwarded by the IARC are, moving into the shade, wearing UV protective clothing (IARC (International Agency for Research on Cancer), 2000bIARC (International Agency for Research on Cancer) Cancer-preventive effect of sunscreens. IARC, Lyon2000http://www.iarc.frGoogle Scholar) and that advertising should avoid promoting sunscreens for intentional sun exposure (IARC (International Agency for Research on Cancer), 2000bIARC (International Agency for Research on Cancer) Cancer-preventive effect of sunscreens. IARC, Lyon2000http://www.iarc.frGoogle Scholar). Furthermore, evidence is increasing that sunscreens may not be as harmless as they have been supposed to be (Knowland et al., 1997Knowland J. McHugh P.J. Dunford R. The photochemical potential of some sunscreens to damage DNA.in: Gasparro F.P. Sunscreen Photobiology.Molecular, Cellular and Physiological Aspects. 1st edn. Springer-Verlag, Berlin1997: 47-68Crossref Google Scholar). Suncare products are a mixture of many different ingredients, all of them should resist UV doses relevant for a sunny day. It was shown, however, that certain organic UV filters are inactivated by UV radiation (Chignell et al., 1980Chignell C.F. Kalyanaraman B. Mason R.P. Sik R.H. Spectroscopic studies of cutaneous photosensitizing agents-I. Spin trapping of photolysis products from sulfanilamide, 4-aminobenzoic acid and related compounds.Photochem Photobiol. 1980; 32: 563-571Crossref Scopus (69) Google Scholar;Gasparro, 1985Gasparro F.P. UV-induced photoproducts of para-aminobenzoic acid.Photodermatology. 1985; 2: 151-157PubMed Google Scholar;Knowland et al., 1993Knowland J. McKenzie E.A. McHugh P.J. Cridland N.A. Sunlight-induced mutagenicity of a common sunscreen ingredient.FEBS Lett. 1993; 324: 309-313Abstract Full Text PDF PubMed Scopus (79) Google Scholar;Schwack and Rudolph, 1995Schwack W. Rudolph T. : Photochemistry of dibenzoylmethane UVA, filters Part I.J Photochem Photobiol B. 1995; 28: 229-234Crossref Scopus (137) Google Scholar;Allen et al., 1996Allen J.M. Gossett C.J. Allen A.K. Photochemical formation of singlet molecular oxygen in illuminated aqueous solutions of several commercially available sunscreen ingredients.Chem Res Toxicol. 1996; 9: 605-609Crossref PubMed Scopus (89) Google Scholar;Berset et al., 1996Berset G. Gonzenbach H. Christ R. et al.Proposed protocol for determination of photostability Part I. cosmetic UV filters.Int J Cosmet Sci. 1996; 18: 167-177Crossref PubMed Scopus (59) Google Scholar;Schallreuter et al., 1996Schallreuter K.U. Wood J.M. Farwell D.W. Moore J. Edwards H.G.M. Oxybenzone oxidation following solar irradiation of skin: Photoprotection versus antioxidant inactivation.J Invest Dermatol. 1996; 106: 583-586Crossref PubMed Scopus (49) Google Scholar;Tarras-Wahlberg et al., 1999Tarras-Wahlberg N. Stenhagen G. Larkö O. Rosen A. Wennberg A. Wennerström O. Changes in ultraviolet absorption of sunscreens after ultraviolet irradiation.J Invest Dermatol. 1999; 113: 547-553https://doi.org/10.1046/j.1523-1747.1999.00721.xCrossref PubMed Scopus (149) Google Scholar;Vanquerp et al., 1999Vanquerp V. Rodriguez C. Coiffard C. Coiffard L.J.M. De Roeck-Holtzhauser Y. High-performance liquid chromatographic method for the comparison of the photostability of five sunscreen agents.J Chromatogr. 1999; 832: 273-277Crossref PubMed Scopus (66) Google Scholar), lose their UV protective capacity (Diffey et al., 1997Diffey B.L. Stokes R.P. Forestier S. Mazilier C. Rougier A. Suncare product photostability: a key parrmeter for a more realistic in vitro efficacy evaluation.Eur J Dermatol. 1997; 7: 226-228Google Scholar) and may behave as photo-oxidants (Allen et al., 1996Allen J.M. Gossett C.J. Allen A.K. Photochemical formation of singlet molecular oxygen in illuminated aqueous solutions of several commercially available sunscreen ingredients.Chem Res Toxicol. 1996; 9: 605-609Crossref PubMed Scopus (89) Google Scholar;Schallreuter et al., 1996Schallreuter K.U. Wood J.M. Farwell D.W. Moore J. Edwards H.G.M. Oxybenzone oxidation following solar irradiation of skin: Photoprotection versus antioxidant inactivation.J Invest Dermatol. 1996; 106: 583-586Crossref PubMed Scopus (49) Google Scholar;McHugh and Knowland, 1997McHugh P.J. Knowland J. Characterization of DNA damage inflicted by free radicals from a mutagenic sunscreen ingredient and its location using an in vitro genetic reversion assay.Photochem Photobiol. 1997; 66: 276-281Crossref PubMed Scopus (47) Google Scholar). This is of utmost significance because filter molecules penetrate through the epidermis (Kenney et al., 1995Kenney G.E. Sakr A. Lichtin J.L. Chou H. Bronaugh R.L. In vitro skin absorption and metabolism of Padimate-O and nitrosamine formed in Padimate-O-containing cosmetic products.J Soc Cosmet Chem. 1995; 46: 117-127Google Scholar;Hayden et al., 1997Hayden C.G.J. Roberts M.S. Benson H.A.E. Systemic absorption of sunscreen after topical application.Lancet. 1997; 350: 863-864Abstract Full Text Full Text PDF PubMed Scopus (183) Google Scholar;Jiang et al., 1999Jiang R. Roberts M.S. Collins D.M. Benson H.A.E. Absorption of sunscreens across human skin: An evaluation of commercial products for children and adults.Br J Clin Pharmacol. 1999; 48: 635-637https://doi.org/10.1046/j.1365-2125.1999.00056.xCrossref PubMed Scopus (132) Google Scholar) and highly reactive intermediates of photounstable filter substances get in direct contact with epidermal and dermal structures (Schallreuter et al., 1996Schallreuter K.U. Wood J.M. Farwell D.W. Moore J. Edwards H.G.M. Oxybenzone oxidation following solar irradiation of skin: Photoprotection versus antioxidant inactivation.J Invest Dermatol. 1996; 106: 583-586Crossref PubMed Scopus (49) Google Scholar;Gulston and Knowland, 1999Gulston M. Knowland J. Illumination of human keratinocytes in the presence of the sunscreen ingredient Padimate-O and through an SPF-15 sunscreen reduces direct photodamage to DNA but increases strand breaks.Mutat Res. 1999; 444: 49-60Crossref PubMed Scopus (30) Google Scholar). Furthermore,Hayden et al., 1997Hayden C.G.J. Roberts M.S. Benson H.A.E. Systemic absorption of sunscreen after topical application.Lancet. 1997; 350: 863-864Abstract Full Text Full Text PDF PubMed Scopus (183) Google Scholar recovered oxybenzone as unchanged oxybenzone and metabolites in the urine after topical application. From this point of view it is surprising that at present standardized photostability tests of finished suncare products are not required before marketing, although this has been recommended repeatedly (Berset et al., 1996Berset G. Gonzenbach H. Christ R. et al.Proposed protocol for determination of photostability Part I. cosmetic UV filters.Int J Cosmet Sci. 1996; 18: 167-177Crossref PubMed Scopus (59) Google Scholar;Vanquerp et al, 1998;Sayre and Dowdy, 1999Sayre R.M. Dowdy J.C. Photostability testing of avobenzone.Cosmet Toil. 1999; 114: 85-91Google Scholar;IARC (International Agency for Research on Cancer), 2000bIARC (International Agency for Research on Cancer) Cancer-preventive effect of sunscreens. IARC, Lyon2000http://www.iarc.frGoogle Scholar). We purchased 16 commercially available sunscreens (products A–Q) with declared UVA and UVB protection Table I. Nine creams/lotions (products H-Q) were recommended by the producer for use in infancy and childhood. The samples were stored at room temperature and in the dark and opened immediately before our test procedure. By circular movements of a gloved finger quartz glass slides were covered with a layer of 1.5 ± 0.15 mg per cm2 for the standard products (A-G) 1Maier H, Brunnhofer K, Schauberger G, Hönigsmann H: Photoinactivation of sun protection products. Arch Dermatol Res 290:34, 1998 (abstr.) according to the guidelines for the evaluation of sunscreen products DIN 67501 (Deutsches Institut für Normung) and 2.0 ± 0.2 mg per cm2 for child products (H-Q) according to the COLIPA (European Cosmetic, Toiletry and Perfumery Association) guidelines to measure the sun protection factor (SPF) of sunscreens. The correct quantity was checked immediately after application by a laboratory balance. The samples were dried for 30 min at constant temperature (26°C) and constant relative humidity (50%). Thereafter, the slides were irradiated with a solar simulator (COLIPA Dermasun Dr Hönle 400F/5, Planegg, Germany) at a radiometrically (Solar Light SL 5D, Solar Light, Philadelphia, PA) defined, homogeneous field of irradiance. By using the standard erythema dose (SED) (CIE (International Commission on Illumination), 1998CIE (International Commission on Illumination) CIE Standard: CIE S007/E-1998.Erythema Reference Action Spectrum and Standard Erythema Dose. CIE, Vienna1998Google Scholar), the mean biologically effective irradiance was 12.75 SED per h, corresponding to solar radiation at midsummer noon and cloudless sky in central Europe. The variability of the radiation field was 5.3%, which is significantly below the limit of the COLIPA guidelines. During the entire irradiation time the temperature and humidity were kept constant at 26°C and 50%, respectively. The spectral irradiance of the solar simulator was measured by using a spectroradiometer with a double monochromator (Bentham, DTM 300, Bentham, Reading, U.K.) and a photomultiplier (Bentham, DH-1 (Bi), Bentham, Reading, UK) fulfilling the requirements of the COLIPA guidelines Figure 1. The first series of suncare products (A–G) was exposed up to 50 SED, the second series recommended for children (H–Q) was exposed up to 25 SED.Table ISunscreen active ingredients and declaration of photobiologically relevant data on packageFilter substances (chemical filters according to CTFAaCosmetic Toiletry and Fragrance Association./INCIbInternational Nomenclature Cosmetic Ingredient.)Sunscreen producthSunscreen producers: A Ambre Solaire Intensivschutz Sonnenmilch (Laboratoires Garnier, Paris, France); B AS SUN Sonnenmilch (E. Kiessling & Cie GmbH & Co., Georgensgmünd, Germany); C delial Sensitive Sonnen Balm (Bayer AG, Leverkusen, Germany); D Anthelios Sonnenmilch (La Roche-Posay Laboratoire Pharmaceutique, La Roche – Posay, France); E Nivea Sun Sonnenmilch (Beiersdorf AG, Hamburg, Germany); F Nivea Sun Sonnen Balsam (Beiersdorf AG, Hamburg, Germany); G Tiroler Nussöl Sensitiv Sonnen Milch (Tiroler Nussöl Sonnenkosmetik, München, Germany); H AS Sonnenmilch für Kinder (E. Kiessling & Cie GmbH. & Co Georgensgmünd, Germany); I Ellen Betrix Sun Care Sonnenmilch für Kinder (P & G, Weybridge, UK); K Nivea Sun Sonnenmilch für Kinder (Beiersdorf AG, Hamburg, Germany; L Ambre Solaire Kinder Intensivschutz Sonnenmilch (Laboratoires Garnier, Paris, France); M Delial Sonnenmilch für Kinder (Sara Lee, Düsseldorf, Germany); N Vichy Capital Soleil Sunblocker-Milch speziell für Kinderhaut (Vichy Laboratoires, Vichy, France); O pH5-Eucerin Sun Sensitive Kinder Lotio (Beiersdorf AG, Hamburg, Germany); P Bübchen Sonnen Milk (Bübchen Werk Ewald Hermes Pharmazeutische Fabrik GmbH, Soest, Germany); Q Penaten Baby Sonnenmilch (Johnson & Johnson GmbH, Düsseldorf, Germany).ABCDEFGHIKLMNOPQZinc oxidexTitanium dioxidexxxxxxxxxxxxxOctocrylenexxxxBenzophenone-3xPhenyldibenzimidazole sulfonic acidxxTerephthalylidene dicamphor sulfonic acidxxxButyl methoxydibenzoylmethanexxxxxxxxxxxxxxMexoryl SXxIsoamyl p-methoxycinnamatexxxOctyl methoxycinnamatexxxxxxxxxxxMethylbenzylidene camphorxxxxxxxxxxxxOctyl triazonexxxxxBroad spectrum protection made evidentxxxxxxxxxxxxxxxxSPFcSun Protection Factor.201820202016182024182526gIn all other European countries only available with SPF = 25.25251818UVA protection factor/method of assessmentAUSdAustralian Standard.7PPDePermanent Pigment Darkening. 18 IPDfImmediate Pigment Darkening.AUSAUSAUSAUS10 PPDAUSAUSPhotostability made evidentxxa Cosmetic Toiletry and Fragrance Association.b International Nomenclature Cosmetic Ingredient.c Sun Protection Factor.d Australian Standard.e Permanent Pigment Darkening.f Immediate Pigment Darkening.g In all other European countries only available with SPF = 25.h Sunscreen producers: A Ambre Solaire Intensivschutz Sonnenmilch (Laboratoires Garnier, Paris, France); B AS SUN Sonnenmilch (E. Kiessling & Cie GmbH & Co., Georgensgmünd, Germany); C delial Sensitive Sonnen Balm (Bayer AG, Leverkusen, Germany); D Anthelios Sonnenmilch (La Roche-Posay Laboratoire Pharmaceutique, La Roche – Posay, France); E Nivea Sun Sonnenmilch (Beiersdorf AG, Hamburg, Germany); F Nivea Sun Sonnen Balsam (Beiersdorf AG, Hamburg, Germany); G Tiroler Nussöl Sensitiv Sonnen Milch (Tiroler Nussöl Sonnenkosmetik, München, Germany); H AS Sonnenmilch für Kinder (E. Kiessling & Cie GmbH. & Co Georgensgmünd, Germany); I Ellen Betrix Sun Care Sonnenmilch für Kinder (P & G, Weybridge, UK); K Nivea Sun Sonnenmilch für Kinder (Beiersdorf AG, Hamburg, Germany; L Ambre Solaire Kinder Intensivschutz Sonnenmilch (Laboratoires Garnier, Paris, France); M Delial Sonnenmilch für Kinder (Sara Lee, Düsseldorf, Germany); N Vichy Capital Soleil Sunblocker-Milch speziell für Kinderhaut (Vichy Laboratoires, Vichy, France); O pH5-Eucerin Sun Sensitive Kinder Lotio (Beiersdorf AG, Hamburg, Germany); P Bübchen Sonnen Milk (Bübchen Werk Ewald Hermes Pharmazeutische Fabrik GmbH, Soest, Germany); Q Penaten Baby Sonnenmilch (Johnson & Johnson GmbH, Düsseldorf, Germany). Open table in a new tab We measured the spectral absorbance (ratio of the absorbed radiant flux to the incident flux according to the CIE International Lighting Vocabulary;CIE (International Commission on Illumination), 1987CIE (International Commission on Illumination) A reference action spectrum for ultraviolet induced erythema in human skin. CIE Research Note.CIE J. 1987; 6: 17-22Google Scholar) (in percentage) for the 16 sunscreens in both, the UVA (320–380 nm) and UVB (280–320 nm) range before, after 5 SED (products A, C, E, H–Q), 12.5 and 25 SED (all products), and 50 SED (products A–G) of solar-simulated UV radiation with a resolution of 1 nm by a spectrophotometer (Varian Cary 3E, Varian Australia PTY Ltd, Mulgrave, Victoria, Australia) connected with a sphere (Labsphere DRA-CA-30, Labsphere, North Sutton, NH) (Marginean et al., 1995Marginean G. Fructus A.E. Marty J.P. Arnaud-Battandier J. New ex-vivo method for evaluating the photoprotective efficacy of sunscreens.Int J Cosmet Sci. 1995; 17: 233-243Crossref PubMed Scopus (11) Google Scholar). This instrument is a double-beam, ratio-recording spectrophotometer that automatically performs a baseline correction. To cut off fluorescent effects the sphere was armed with a Schott UG 11 filter (Schott, Mainz, Germany) according to theAustralian/New Zealand Standard, 1996Australian/New Zealand Standard Sun protective clothing 3/4 Evaluation and classification AS/NZS.in: 4399. Standards Australia/Standards New Zealand, Homebush/Wellington1996Google Scholar. In order to keep the samples in an identical position during consecutive measurements we added a steel frame (inner measurements 25 × 80 mm) to the provided transmittance sample holder. The quartz glass slides were put into the tight fitting frame and fixed by a shutter. An aperture faded out the lateral portions of the sample and allowed transmission only in a central field of approximately 6 cm2. The sample holder was screwed up in the transmittance sample port. Two samples of each suncare product of the same lot are stored under standardized conditions. In order to describe the effect of photoinstability we used the spectral photoinactivation, ΔAë, due to the UV exposure, calculated by the difference between the spectral absorbance, Aë,D, for a UV dose, D, and the spectral absorption before the UV exposure, Aë,0:ΔAλ,D=Aλ,0−Aλ,D(1) The mean difference of the absorbance, ΔA, was calculated for both, the UVA (320–380 nm) and UVB (280–320 nm) range, called as photoinactivation. The results are presented in Table II showing the absorbance before UV exposure, A0, the photoinactivation for UVB and UVA, ΔA, as the difference between the absorption before and after UV exposure for following UV doses, D, of 5 SED (products A, C, E, H–Q), 12.5 SED and 25 SED (all products), and 50 SED (products A–G), respectively.Table IIAbsorbanceaData presented as mean values for the UVB (280–320 nm) and UVA (320–380 nm) range.of the suncare products (A–Q)bPhotounstable products are highlighted bold.before UV exposure and photoinactivationcData presented as mean values for the UVB (280–320 nm) and UVA (320–380 nm) range. The photoinactivation is defined as the change of absorbance due to UV exposure according to Eqn 1.after increasing UV exposuredUV exposure is given in standard erythema dose (SED).Photoinactivation, ΔA (%), by biologically effective UV-exposure (SED)ProductAbsorbance A (%)512.52550UVB A99.60.10.20.20.2 B100.00.00.00.0 C98.60.60.70.81.8 D99.60.00.20.2 E99.60.20.20.20.4 F71.34.0-5.1-1.0 G99.90.00.00.0 H99.90.00.00.0 I99.80.20.10.1 K99.90.00.00.0 L99.90.00.00.0 M99.90.00.00.0 N99.70.10.10.1 O99.90.00.00.0 P99.90.00.00.0 Q99.70.30.20.4UVA A98.50.30.60.31.6 B99.415.728.129.7 C92.613.036.348.452.0 D99.60.00.20.3 E97.75.313.826.532.7 F57.211.712.327.4 G70.9-1.6-2.0-3.0 H97.20.00.00.2 I98.47.713.224.3 K99.90.10.00.0 L99.90.00.00.0 M99.90.00.10.5 N99.60.10.10.2 O99.90.00.10.6 P96.017.623.622.6 Q95.58.318.231.8a Data presented as mean values for the UVB (280–320 nm) and UVA (320–380 nm) range.b Photounstable products are highlighted bold.c Data presented as mean values for the UVB (280–320 nm) and UVA (320–380 nm) range. The photoinactivation is defined as the change of absorbance due to UV exposure according to Eqn 1.d UV exposure is given in standard erythema dose (SED). Open table in a new tab Table I shows the detailed photobiologically relevant data of the selected suncare products. The product information printed on the packages of the respective sunscreens promised broad-spectrum UV protection. For all suncare products the SPF (median 20, 16–26) was declared, whereas a quantification of the protective capacity in the UVA range was given for only two (D, N). The term "photostability" was mentioned in the product information of only two sunscreens (A, L) produced by the same company. A detailed list of active ingredients was available for all sunscreens. Table I shows that the UV broad spectrum protective capacity of the 16 examined sunscreens was due to a total of different filter combinations. None of the examined suncare products contained p-aminobenzoic acid (PABA) or PABA derivatives, e.g., octyl dimethyl PABA (padimate-O), or isopropyldibenzoylmethane. Benzophenone-3 (oxybenzone), however, was included in one (product G) and butyl methoxydibenzoylmethane in 14 (A–F, I–Q) of the 16 sunscreens. In all sunscreens except product C and F organic UV filters were combined with one inorganic UV filter, zinc oxide (ZnO) in product H or titanium dioxide (TiO2) in suncare products A, B, D–G, and I–Q. The photoinactivation, ΔA, for all measured doses, D, are presented for the UVA and UVB range Table II. In the UVB range the absorbance before UV exposure, A0, for all products except product F showed values above 98% Table II. Sunscreen F had a high water content. Owing to the rapid and significant water loss during application it was difficult to achieve a homogeneous layer. This seems to be the reason why the absorbance before UV exposure, A0, for product F was only 71%. In the UVB range, the values of the decrease of absorbance (photoinactivation), ΔA, for all sunscreens and UV doses were below 5%. In the UVA range 14 of 16 products showed an absorbance before UV exposure, A0, of more than 90% Table II. Only for two products we measured an absorbance before UV exposure of less than 90% (product F 57%, product G 71%). Contrary to the behavior in the UVB range seven of 16 products were significantly photounstable in the UVA range, which resulted in a decrease of the absorbance (photoinactivation), ΔA, between 12% (F) and 48% (C) at 25 SED Table II. The photoinactivation for the nine photostable products, however, was negligible (< 1%). Figure 2 shows the spect