Variation of sunscreen efficacy using solar spectrum and solar simulators.
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Variation of sunscreen efficacy using solar spectrum and solar simulators.

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Sunscreen SPF can vary with the UV source spectrum: SPF tends to increase when more short UVB and/or less long UVA radiation is present in the source spectrum. Higher UVA protection in sunscreen ...

Sunscreen SPF can vary with the UV source spectrum: SPF tends to increase when more short UVB and/or less long UVA radiation is present in the source spectrum. Higher UVA protection in sunscreen products leads to lower SPF variation due to the source spectrum. With increasing labelled SPF values, there is a need for more realistic simulated UV spectra and tightened compliance limits.

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Variation of sunscreen efficacy using solar spectrum and solar simulators. Variation of sunscreen efficacy using solar spectrum and solar simulators. Document Transcript

  • Diapositive 18th Congress of the European Society for PhotobiologyGranada, Spain, 3-8 September, 1999L’ORÉALR E C H E R C H ESUNSCREEN EFFICACY CAN VARY WITHSUNSCREEN EFFICACY CAN VARY WITHTHE UV SOLAR SPECTRUM AND THETHE UV SOLAR SPECTRUM AND THESTANDARD FOR UV SOLAR SIMULATORSSTANDARD FOR UV SOLAR SIMULATORSA. Chardon, F. Christiaens,LOréal Recherche, Clichy (France)&J. Dowdy, R. SayreRapid Precision Testing Laboratory, Cordova TN (USA)Ladies and Gentlemen, good afternoon!
  • Diapositive 2• Sunscreen efficacy: Sun Protection Factor (SPF)• European Standard: Colipa SPF test method• Standard sun: quasi-zenithal spectrum• UV solar simulator:– Xenon + optical filters– Criterion: spectral erythemal efficacy (RCEE)L’ORÉALR E C H E R C H EINTRODUCTIONThe Sun Protection Factor (SPF) labelled on the sunscreen products to quantify theirefficacy to protect the skin against sunburn is evaluated in human skin using a solarsimulator as an artificial source of ultraviolet rays.The characteristics of the emission spectrum of this solar simulator are particularlyspecified in the European Colipa SPF test method, in comparison with that of astandard quasi-zenithal sun spectrum defined in the method for low earth altitude.The solar simulator is made of a xenon source whose spectrum is modified withappropriated short and long cut-off filters to only retain the desired ultravioletwavelengths in the right proportion.This proportion is checked using as a criterion the spectral distribution of theerythemal efficacy of the source.
  • Diapositive 3• Potential variation of the SPF value, with:– Sun altitude (Air Mass)– Type of sunscreen (absorption profile, UVB / UVA)– Cut-off filters of the UV sourceL’ORÉALR E C H E R C H EAIMThe aim of this modelling study is to point out the potential variation of the SPF valueof sunscreen products with the quality of the standard sun spectrum retained, as thisquality varies with the sun altitude above the horizon, that is to say with the air masscrossed by the sun rays.This was performed in relation with the type of sunscreen to be tested, characterisedby the UVB to UVA ratio of their absorption profile.The effect of variation of practical cut-off optical filters used the UV source will alsobe examined.
  • Diapositive 4• Skin erythema action spectrum E(λ)• UV source emission spectrum S(λ)• Sunscreen absorption spectrum mPF(λ)L’ORÉALR E C H E R C H EMEANS∑∑∆∆= nmnmnmnmmPFSESEspf 400290400290)(/*)(*)(*)(*)(λλλλλλλFor this modelling study we used as a response this expression of the SPF, used inin-vitro SPF determination and which includes:- the CIE 1987 erythema action spectrum E(λ)- the spectral irradiance of the UV source E(λ)- and the monochromatic protection factor of the product mPF(λ)The sums are integrated, nanometer by nanometer between 290 and 400nanometers.
  • Diapositive 5• CIE (1987) Erythema Action Spectrum E(λ)L’ORÉALR E C H E R C H E1E-041E-031E-021E-011E+001E+01280 300 320 340 360 380 400Wavelength (nm)Relat.Response(1/MED)E(λ) = 1E(λ) = 0.094 * (298 - λ)E(λ) = 0.015 * (139 - λ)The CIE erythema standard action spectrum with the 3 corresponding formulae.
  • Diapositive 6• UV Source Emission Spectrum S(λ)L’ORÉALR E C H E R C H E1.0E-052.0E-014.0E-016.0E-018.0E-011.0E+001.2E+001.4E+001.6E+00290 300 310 320 330 340 350 360 370 380 390 400Wavelength (nm)Relat.Irrad.(norm.350nm)UG5 / 2mmUG11 / 1mmColipa standard sunWG320 /1mm1.5mm2mmFiltered xenonHere are some examples of emission spectra of the UV source tested in the study.
  • Diapositive 7• UV source emission spectrum characterised by theUVB (290-320nm) Relative Cumulative ErythemalEfficacy (UVB-RCEE%)L’ORÉALR E C H E R C H E100**)(*)(*)(*)(% 400290320290∑∑∆∆=− nmnmnmnmSESERCEEUVBλλλλλλThe emission spectrum of the UV source, either sun or UV solar simulator, is usuallycharacterised by using:the Relative Cumulative Erythemal Efficacy or RCEE percentage at variouswavelengths.Thus, the RCEE value calculated at 320nm, giving the UVB ratio in the totalerythemal effectiveness of the UV source, is particularly significant.
  • Diapositive 8• Typical UVB-RCEE % values:– Colipa standard sun 84%– Colipa acceptance limits of the UV source:• Upper limit• Lower limit 80.0 %– AM 1 85 %– AM 1.5 75 %– AM 2 67 %L’ORÉALR E C H E R C H E91.0 %The UVB-RCEE value of the Colipa standard sun is 84%, while the lower acceptancelimit of the current method for the UV solar simulator is 80 % and the upper limit is91 %.This upper limit corresponds in fact to a sun spectrum of more than five thousandmeter altitude, which is not very realistic.The UVB RCEE% of AM1.5 corresponding to a sun with 48° zenithal angle is 75%,and that of AM2 corresponding to 60° zenithal angle is 67%.
  • Diapositive 9P4SPF 15• 4 Typical SPF15 Sunscreens: mPF CurvesL’ORÉALR E C H E R C H E16111621263136280 290 300 310 320 330 340 350 360 370 380 390 400Wavelength (nm)mPF P1 : BP2 : B + aP2 : B + AP4 : B = AP1P2P3UVB UVAThe absorption profiles of the four products tested, based on actual filtering systems,are represented on this graph in term of monochromatic protection factors (mPF), allfour spectra resulting in the same SPF 15 value, as calculated with the Colipastandard sun spectrum.Product P1 with no UVA protection added;Product P2 with a low amount of UVA protection added;Product P3 with a medium level of UVA protection;and Product P4 with a rather flat profile, offering similar UVA and UVB protection.
  • Diapositive 108th Congress of the European Society for PhotobiologyGranada, Spain, 3-8 September, 1999• Global potential effect of the UVB RCEE of theUV source on SPF values of 4 typical sunscreens• Variation between the Colipa acceptance limits• Variation of actual possible UV source filteringsystemsL’ORÉALR E C H E R C H ERESULTSLet us now examine the results:- the global potential effect of the UVB RCEE of the UV source on the SPF values ofeach sunscreen- the variation in the Colipa acceptance limits of source- the effect of variation on the optical filtering system of the UV source.
  • Diapositive 11L’ORÉALR E C H E R C H EPotential effect of UV source variation on SPF of Product P116111621260 10 20 30 40 50 60 70 80 90 100UVB %RCEEof the UV SOURCESPFP1: SPF15B75AM1AM 2 AM 1.56726AM 5.6SPF 1584The blue curve of this graph represents the overall potential variation of thecalculated SPF value of Product P1 (with no UVA protection added) in relation withthe UVB erythemal effectiveness of the source, ranging from high altitude sun (Imean in high mountain) to sun at 30° above the horizon at sea level.It is clear that the SPF value may vary considerably (from 6 to 25, for nominal value15), the more intense the sun, the higher the calculated SPF value.Using a UV source more effective than the standard sun would induce a significantoverestimation of the SPF value, as compared with the nominal value of 15.
  • Diapositive 12L’ORÉALR E C H E R C H EPotential effect of UV source variation on SPF of Product P216111621260 10 20 30 40 50 60 70 80 90 100UVB %RCEEof the UV SOURCESPFP1: SPF15BP2: SPF15B + a75AM1AM 2 AM 1.56726AM 5.6SPF 1584Results (ctd.) (Option 1 - Three slides)With product P2, including a minimal UVA protection added, the overall variation ofthe SPF, as shown by the green curve, is already strongly reduced, as comparedwith Product P1. The SPF then ranges from 8 to 20.
  • Diapositive 13L’ORÉALR E C H E R C H EPotential effect of UV source variation on SPF of Product P316111621260 10 20 30 40 50 60 70 80 90 100UVB %RCEEof the UV SOURCESPFP1: SPF15BP2: SPF15B + aP3: SPF15B + A75AM1AM 2 AM 1.56726AM 5.6SPF 1584With product P3, including a significant UVA protection added, the variation of theSPF, as shown by the pink curve, the calculated SPF ranges from 11 to 17.
  • Diapositive 14L’ORÉALR E C H E R C H EPotential effect of UV source variation on SPF of Product P416111621260 10 20 30 40 50 60 70 80 90 100UVB %RCEEof the UV SOURCESPFP1: SPF15BP2: SPF15B + aP3: SPF15B + AP4: SPF15B ~ A75AM1AM 2 AM 1.56726AM 5.6SPF 1584Finally, with product P4 in red, with high UVA protection and presenting a rather flatabsorption profile, the SPF value no longer varies with the quality of the emissionspectrum of the UV source. The SPF remains constant at nominal SPF15 value.
  • Diapositive 15L’ORÉALR E C H E R C H EPotential effect of UV source variation on SPF of Products P1-P416111621260 10 20 30 40 50 60 70 80 90 100UVB %RCEEof the UV SOURCESPFP1: SPF15BP2: SPF15B + aP3: SPF15B + AP4: SPF15B ~ A75AM1AM 2 AM 1.56726AM 5.6SPF 1584Results (Ctd.) (Option 2 - One slide)With product P2, including a minimal UVA protection added, the overall variation ofthe SPF, as shown by the green curve, is already strongly reduced, as comparedwith Product P1. The SPF then ranges from 8 to 20.With product P3, including a significant UVA protection added, the variation of theSPF, as shown by the pink curve, the calculated SPF ranges from 11 to 17.Finally, with product P4 in red, with high UVA protection and presenting a rather flatabsorption profile, the SPF value no longer varies with the quality of the emissionspectrum of the UV source. The SPF remains constant at nominal SPF15 value,whatever the source.
  • Diapositive 16L’ORÉALR E C H E R C H ECurrent Colipa UV solar simulator standard16111621260 10 20 30 40 50 60 70 80 90 100UVB %RCEEof the UV SOURCESPFP1: SPF 15BP2 : SPF 15B+aP3 : SPF 15B + AP4 : SPF 15B ~A756726 84Current COLIPAacceptance limits :80% - 91%AM 2 AM 1.5AM 5.6Colipa Std SunSPF 14SPF 21SPF 15AM 1Now let us be more realistic:Of course, if the artificial UV source, used for the in vivo SPF determination in human,complies with the current specifications of the Colipa SPF test method reported onthis graph, the potential variation of the SPF of Products P1 to P3 are more limited.However, the SPF of product P1 could still vary from 14 to 20, or to higher values like24 with when the solar simulators exceed the Colipa standard upper limit, which maylead to a significant overestimation of the product actual protection.It must be noticed here that the current acceptance limits of the current Colipastandard, though its merits, appear still too wide, with the upper limit alreadyexceeding the characteristics of the zenithal sun at sea level.
  • Diapositive 17L’ORÉALR E C H E R C H EProposed new acceptance limits for UV solar simulators16111621260 10 20 30 40 50 60 70 80 90 100UVB %RCEEof the UV SOURCESPFP1: SPF 15BP2 : SPF 15B+aP3 : SPF 15B + AP4 : SPF 15b+A756726 84PROPOSEDsolar simulatoracceptance limits:75 - 84%AM 2 AM 1.5AM 5.6 AM 1SPF 15SPF 13SPF 17For these reasons, we propose:- firstly, to tighten the acceptance limits of the current Colipa SPF test method;- secondly, to lower the upper acceptance limit down to the standard suncharacteristics (with 84% UVB RCEE), and the lower limit down to 75%, these limitsrepresenting sun variation from zenith to 42° altitude above the horizon, that’s to sayfrom AM1 to AM 1.5, in the range where the shadow rule applies, which says that“the risk is at maximum as long as your shadow is longer than your height” .In these conditions, the SPF of product P1 could only vary from 13 to 17 in relationwith the artificial UV source spectrum.
  • Diapositive 18L’ORÉALR E C H E R C H EPotential effect of short cut-off filter characteristics1611162126310 10 20 30 40 50 60 70 80 90 100UVB %RCEEof the UV SOURCESPFP1: SPF15BWG320 / 1mm8475AM 1AM 2 AM 1.56726AM 5.6+5nm +2.5nm NOM. -2.5 -5 -7nmNow, let us speak in terms of practical filtration.According to Schott catalogue, the cut-off wavelength at 50% transmission of WG320filter (used for mimicking the ozone layer) may vary from - 6 to + 6nm and thesespecifications have been recently changed, adding more uncertainty.Fortunately, the typical actual variation observed is much lower.However, this means that the characteristics of the filter batch must be carefullychecked and the thickness of the filter adapted accordingly, following the procedurerecommended by the Colipa SPF test method.
  • Diapositive 19L’ORÉALR E C H E R C H EPotential effect of long w.l. filtration: UG5 / 2mm - UG11 / 1mm16111621260 10 20 30 40 50 60 70 80 90 100UVB %RCEEof the UV SOURCESPFP1: SPF15BP4 : SPF15B = AUG11 / 1mmUG5 / 2mmUG11 / 1mmUG5 / 2mm8475AM 1AM 2 AM 1.56726AM 5.6As far as the long cut-off filtration is concerned, this graph shows the potential SPFvariation obtained when changing from a Schott UG5 2mm filter to a UG11 - 1 mmthick.The change would be minor for the flat product P4.For product P1, the change could be more significant, inducing a difference of about1 SPF unit and the nominal value would be better approached with the UG5 filter.
  • Diapositive 20CONCLUSION: Sunscreen SPF can varywith the UV source spectrum• SPF increases when the source spectrum shows:– more short UVB– less long UVA• Colipa SPF test method should recommendspectrum limits leading to more accurate SPFvalues• SPF of highly UVA protective sunscreens do notdepend on UV source conditionsL’ORÉALR E C H E R C H EConclusion (option 1)As a conclusion, this modelling study shows that:- the sunscreen SPF increases when the UV source spectrum contains more UVBenergy- or less long UVA energy than the standard sun.The UV solar simulator acceptance limits of the current Colipa SPF test methodshould be tightened and lowered so that the conditions of the zenithal standard suncould not be exceeded in order to yield more realistic SPF values.The SPF of highly UVA protective sunscreens do not depend on the quality of the UVsource spectrum.Thank you very much for your attention.
  • Diapositive 21• SPF tends to increase when more short UVB arepresent in source spectrum (increasing UVB-RCEE%)• SPF tends to slightly increase when less longUVA are present (with UG11 filter)• Higher UVA protection in product leads to:– lower SPF variation with short (WG320) or long (UG)wavelength variationL’ORÉALR E C H E R C H ECONCLUSION 1Conclusion (option 2):In conclusion, this study showed that:-The SPF of the products tends increasing when relatively more UVB are present inthe source spectrum, that’s to say when the UVB RCEE increases.-The SPF tends to slightly increase when less long UVA are present in the sourcespectrum, (I mean with UG11 filter instead of UG5.)-Increasing the UVA protection in the products allows reducing all these effects onthe SPF values.
  • Diapositive 22• Increasing labelled SPF values call for:– Better control of the UV source spectrum– More realistic UV spectrum– Lower and tightened Colipa acceptance limits:• Upper acceptance limit ≤ AM 1 standard sun• Lower acceptance limit ~ AM 1.5L’ORÉALR E C H E R C H ECONCLUSION 2Because of increasing labelled SPF values, there is a need for- a better control of the UV source spectrum- a more realistic UV spectrum, which means that the Colipa acceptance limits shouldbe tightened and lowered so that the conditions of the zenithal sun (AM 1) could notbe exceeded.Standardising the long cut-off filtration by recommending the UG11 filter would allowto reduce the heat load on the skin and on the products, while further reducing theSPF variation.
  • Diapositive 23• Reducing the UVB RCEE% of the source:– would reduce erythemal effectiveness of the UV source– would increase MED irradiation times• Compensated by more powerful UV sourcesavailableL’ORÉALR E C H E R C H ECONCLUSION 3On a practical point of view and as a consequence, reducing the UVB RCEE of theUV source would likely reduce its global erythemal effectiveness, while increasing theUV exposures accordingly.But this can be compensated with the more powerful UV sources available.Tank you very much for your attention !
  • Diapositive 24L’ORÉALR E C H E R C H E8th Congress of the European Society for PhotobiologyGranada, Spain, 3-8 September, 1999Photo A.Chardon