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.

1. Diapositive 1
8th Congress of the European Society for Photobiology
Granada, Spain, 3-8 September, 1999
L’ORÉAL
R E C H E R C H E
SUNSCREEN EFFICACY CAN VARY WITHSUNSCREEN EFFICACY CAN VARY WITH
THE UV SOLAR SPECTRUM AND THETHE UV SOLAR SPECTRUM AND THE
STANDARD FOR UV SOLAR SIMULATORSSTANDARD FOR UV SOLAR SIMULATORS
A. Chardon, F. Christiaens,
L'Oréal Recherche, Clichy (France)
&
J. Dowdy, R. Sayre
Rapid Precision Testing Laboratory, Cordova TN (USA)
Ladies and Gentlemen, good afternoon!

2. 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’ORÉAL
R E C H E R C H E
INTRODUCTION
The Sun Protection Factor (SPF) labelled on the sunscreen products to quantify their
efficacy to protect the skin against sunburn is evaluated in human skin using a solar
simulator as an artificial source of ultraviolet rays.
The characteristics of the emission spectrum of this solar simulator are particularly
specified in the European Colipa SPF test method, in comparison with that of a
standard 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 with
appropriated short and long cut-off filters to only retain the desired ultraviolet
wavelengths in the right proportion.
This proportion is checked using as a criterion the spectral distribution of the
erythemal efficacy of the source.

3. 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 source
L’ORÉAL
R E C H E R C H E
AIM
The aim of this modelling study is to point out the potential variation of the SPF value
of sunscreen products with the quality of the standard sun spectrum retained, as this
quality varies with the sun altitude above the horizon, that is to say with the air mass
crossed by the sun rays.
This was performed in relation with the type of sunscreen to be tested, characterised
by the UVB to UVA ratio of their absorption profile.
The effect of variation of practical cut-off optical filters used the UV source will also
be examined.

4. Diapositive 4
• Skin erythema action spectrum E(λ)
• UV source emission spectrum S(λ)
• Sunscreen absorption spectrum mPF(λ)
L’ORÉAL
R E C H E R C H E
MEANS
∑
∑
∆
∆
= nm
nm
nm
nm
mPFSE
SE
spf 400
290
400
290
)(/*)(*)(
*)(*)(
λλλλ
λλλ
For this modelling study we used as a response this expression of the SPF, used in
in-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 400
nanometers.

5. Diapositive 5
• CIE (1987) Erythema Action Spectrum E(λ)
L’ORÉAL
R E C H E R C H E
1E-04
1E-03
1E-02
1E-01
1E+00
1E+01
280 300 320 340 360 380 400
Wavelength (nm)
Relat.Response(1/MED)
E(λ) = 1
E(λ) = 0.094 * (298 - λ)
E(λ) = 0.015 * (139 - λ)
The CIE erythema standard action spectrum with the 3 corresponding formulae.

6. Diapositive 6
• UV Source Emission Spectrum S(λ)
L’ORÉAL
R E C H E R C H E
1.0E-05
2.0E-01
4.0E-01
6.0E-01
8.0E-01
1.0E+00
1.2E+00
1.4E+00
1.6E+00
290 300 310 320 330 340 350 360 370 380 390 400
Wavelength (nm)
Relat.Irrad.(norm.350nm)
UG5 / 2mm
UG11 / 1mm
Colipa standard sun
WG320 /
1mm
1.5mm
2mm
Filtered xenon
Here are some examples of emission spectra of the UV source tested in the study.

7. Diapositive 7
• UV source emission spectrum characterised by the
UVB (290-320nm) Relative Cumulative Erythemal
Efficacy (UVB-RCEE%)
L’ORÉAL
R E C H E R C H E
100*
*)(*)(
*)(*)(
% 400
290
320
290
∑
∑
∆
∆
=− nm
nm
nm
nm
SE
SE
RCEEUVB
λλλ
λλλ
The emission spectrum of the UV source, either sun or UV solar simulator, is usually
characterised by using:
the Relative Cumulative Erythemal Efficacy or RCEE percentage at various
wavelengths.
Thus, the RCEE value calculated at 320nm, giving the UVB ratio in the total
erythemal effectiveness of the UV source, is particularly significant.

8. 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’ORÉAL
R E C H E R C H E
91.0 %
The UVB-RCEE value of the Colipa standard sun is 84%, while the lower acceptance
limit of the current method for the UV solar simulator is 80 % and the upper limit is
91 %.
This upper limit corresponds in fact to a sun spectrum of more than five thousand
meter 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%.

9. Diapositive 9
P4
SPF 15
• 4 Typical SPF15 Sunscreens: mPF Curves
L’ORÉAL
R E C H E R C H E
1
6
11
16
21
26
31
36
280 290 300 310 320 330 340 350 360 370 380 390 400
Wavelength (nm)
mPF P1 : B
P2 : B + a
P2 : B + A
P4 : B = A
P1
P2
P3
UVB UVA
The absorption profiles of the four products tested, based on actual filtering systems,
are represented on this graph in term of monochromatic protection factors (mPF), all
four spectra resulting in the same SPF 15 value, as calculated with the Colipa
standard 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.

10. Diapositive 10
8th Congress of the European Society for Photobiology
Granada, Spain, 3-8 September, 1999
• Global potential effect of the UVB RCEE of the
UV source on SPF values of 4 typical sunscreens
• Variation between the Colipa acceptance limits
• Variation of actual possible UV source filtering
systems
L’ORÉAL
R E C H E R C H E
RESULTS
Let us now examine the results:
- the global potential effect of the UVB RCEE of the UV source on the SPF values of
each sunscreen
- the variation in the Colipa acceptance limits of source
- the effect of variation on the optical filtering system of the UV source.

11. Diapositive 11
L’ORÉAL
R E C H E R C H E
Potential effect of UV source variation on SPF of Product P1
1
6
11
16
21
26
0 10 20 30 40 50 60 70 80 90 100
UVB %RCEE
of the UV SOURCE
SPF
P1: SPF15
B
75
AM1AM 2 AM 1.5
6726
AM 5.6
SPF 15
84
The blue curve of this graph represents the overall potential variation of the
calculated SPF value of Product P1 (with no UVA protection added) in relation with
the UVB erythemal effectiveness of the source, ranging from high altitude sun (I
mean 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 value
15), the more intense the sun, the higher the calculated SPF value.
Using a UV source more effective than the standard sun would induce a significant
overestimation of the SPF value, as compared with the nominal value of 15.

12. Diapositive 12
L’ORÉAL
R E C H E R C H E
Potential effect of UV source variation on SPF of Product P2
1
6
11
16
21
26
0 10 20 30 40 50 60 70 80 90 100
UVB %RCEE
of the UV SOURCE
SPF
P1: SPF15
B
P2: SPF15
B + a
75
AM1AM 2 AM 1.5
6726
AM 5.6
SPF 15
84
Results (ctd.) (Option 1 - Three slides)
With product P2, including a minimal UVA protection added, the overall variation of
the SPF, as shown by the green curve, is already strongly reduced, as compared
with Product P1. The SPF then ranges from 8 to 20.

13. Diapositive 13
L’ORÉAL
R E C H E R C H E
Potential effect of UV source variation on SPF of Product P3
1
6
11
16
21
26
0 10 20 30 40 50 60 70 80 90 100
UVB %RCEE
of the UV SOURCE
SPF
P1: SPF15
B
P2: SPF15
B + a
P3: SPF15
B + A
75
AM1AM 2 AM 1.5
6726
AM 5.6
SPF 15
84
With product P3, including a significant UVA protection added, the variation of the
SPF, as shown by the pink curve, the calculated SPF ranges from 11 to 17.

14. Diapositive 14
L’ORÉAL
R E C H E R C H E
Potential effect of UV source variation on SPF of Product P4
1
6
11
16
21
26
0 10 20 30 40 50 60 70 80 90 100
UVB %RCEE
of the UV SOURCE
SPF
P1: SPF15
B
P2: SPF15
B + a
P3: SPF15
B + A
P4: SPF15
B ~ A
75
AM1AM 2 AM 1.5
6726
AM 5.6
SPF 15
84
Finally, with product P4 in red, with high UVA protection and presenting a rather flat
absorption profile, the SPF value no longer varies with the quality of the emission
spectrum of the UV source. The SPF remains constant at nominal SPF15 value.

15. Diapositive 15
L’ORÉAL
R E C H E R C H E
Potential effect of UV source variation on SPF of Products P1-P4
1
6
11
16
21
26
0 10 20 30 40 50 60 70 80 90 100
UVB %RCEE
of the UV SOURCE
SPF
P1: SPF15
B
P2: SPF15
B + a
P3: SPF15
B + A
P4: SPF15
B ~ A
75
AM1AM 2 AM 1.5
6726
AM 5.6
SPF 15
84
Results (Ctd.) (Option 2 - One slide)
With product P2, including a minimal UVA protection added, the overall variation of
the SPF, as shown by the green curve, is already strongly reduced, as compared
with Product P1. The SPF then ranges from 8 to 20.
With product P3, including a significant UVA protection added, the variation of the
SPF, 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 flat
absorption profile, the SPF value no longer varies with the quality of the emission
spectrum of the UV source. The SPF remains constant at nominal SPF15 value,
whatever the source.

16. Diapositive 16
L’ORÉAL
R E C H E R C H E
Current Colipa UV solar simulator standard
1
6
11
16
21
26
0 10 20 30 40 50 60 70 80 90 100
UVB %RCEE
of the UV SOURCE
SPF
P1: SPF 15
B
P2 : SPF 15
B+a
P3 : SPF 15
B + A
P4 : SPF 15
B ~A
756726 84
Current COLIPA
acceptance limits :
80% - 91%
AM 2 AM 1.5AM 5.6
Colipa Std Sun
SPF 14
SPF 21
SPF 15
AM 1
Now 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 on
this 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 like
24 with when the solar simulators exceed the Colipa standard upper limit, which may
lead to a significant overestimation of the product actual protection.
It must be noticed here that the current acceptance limits of the current Colipa
standard, though its merits, appear still too wide, with the upper limit already
exceeding the characteristics of the zenithal sun at sea level.

17. Diapositive 17
L’ORÉAL
R E C H E R C H E
Proposed new acceptance limits for UV solar simulators
1
6
11
16
21
26
0 10 20 30 40 50 60 70 80 90 100
UVB %RCEE
of the UV SOURCE
SPF
P1: SPF 15
B
P2 : SPF 15
B+a
P3 : SPF 15
B + A
P4 : SPF 15
b+A
756726 84
PROPOSED
solar simulator
acceptance limits:
75 - 84%
AM 2 AM 1.5AM 5.6 AM 1
SPF 15
SPF 13
SPF 17
For 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 sun
characteristics (with 84% UVB RCEE), and the lower limit down to 75%, these limits
representing sun variation from zenith to 42° altitude above the horizon, that’s to say
from 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 relation
with the artificial UV source spectrum.

18. Diapositive 18
L’ORÉAL
R E C H E R C H E
Potential effect of short cut-off filter characteristics
1
6
11
16
21
26
31
0 10 20 30 40 50 60 70 80 90 100
UVB %RCEE
of the UV SOURCE
SPF
P1: SPF15
B
WG320 / 1mm
8475
AM 1AM 2 AM 1.5
6726
AM 5.6
+5nm +2.5nm NOM. -2.5 -5 -7nm
Now, let us speak in terms of practical filtration.
According to Schott catalogue, the cut-off wavelength at 50% transmission of WG320
filter (used for mimicking the ozone layer) may vary from - 6 to + 6nm and these
specifications 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 carefully
checked and the thickness of the filter adapted accordingly, following the procedure
recommended by the Colipa SPF test method.

19. Diapositive 19
L’ORÉAL
R E C H E R C H E
Potential effect of long w.l. filtration: UG5 / 2mm - UG11 / 1mm
1
6
11
16
21
26
0 10 20 30 40 50 60 70 80 90 100
UVB %RCEE
of the UV SOURCE
SPF
P1: SPF15
B
P4 : SPF15
B = A
UG11 / 1mm
UG5 / 2mm
UG11 / 1mm
UG5 / 2mm
8475
AM 1AM 2 AM 1.5
6726
AM 5.6
As far as the long cut-off filtration is concerned, this graph shows the potential SPF
variation obtained when changing from a Schott UG5 2mm filter to a UG11 - 1 mm
thick.
The change would be minor for the flat product P4.
For product P1, the change could be more significant, inducing a difference of about
1 SPF unit and the nominal value would be better approached with the UG5 filter.

20. Diapositive 20
CONCLUSION: Sunscreen SPF can vary
with the UV source spectrum
• SPF increases when the source spectrum shows:
– more short UVB
– less long UVA
• Colipa SPF test method should recommend
spectrum limits leading to more accurate SPF
values
• SPF of highly UVA protective sunscreens do not
depend on UV source conditions
L’ORÉAL
R E C H E R C H E
Conclusion (option 1)
As a conclusion, this modelling study shows that:
- the sunscreen SPF increases when the UV source spectrum contains more UVB
energy
- or less long UVA energy than the standard sun.
The UV solar simulator acceptance limits of the current Colipa SPF test method
should be tightened and lowered so that the conditions of the zenithal standard sun
could 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 UV
source spectrum.
Thank you very much for your attention.

21. Diapositive 21
• SPF tends to increase when more short UVB are
present in source spectrum (increasing UVB-
RCEE%)
• SPF tends to slightly increase when less long
UVA are present (with UG11 filter)
• Higher UVA protection in product leads to:
– lower SPF variation with short (WG320) or long (UG)
wavelength variation
L’ORÉAL
R E C H E R C H E
CONCLUSION 1
Conclusion (option 2):
In conclusion, this study showed that:
-The SPF of the products tends increasing when relatively more UVB are present in
the 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 source
spectrum, (I mean with UG11 filter instead of UG5.)
-Increasing the UVA protection in the products allows reducing all these effects on
the SPF values.

22. 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 1.5
L’ORÉAL
R E C H E R C H E
CONCLUSION 2
Because 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 should
be tightened and lowered so that the conditions of the zenithal sun (AM 1) could not
be exceeded.
Standardising the long cut-off filtration by recommending the UG11 filter would allow
to reduce the heat load on the skin and on the products, while further reducing the
SPF variation.

23. 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 sources
available
L’ORÉAL
R E C H E R C H E
CONCLUSION 3
On a practical point of view and as a consequence, reducing the UVB RCEE of the
UV source would likely reduce its global erythemal effectiveness, while increasing the
UV exposures accordingly.
But this can be compensated with the more powerful UV sources available.
Tank you very much for your attention !

24. Diapositive 24
L’ORÉAL
R E C H E R C H E
8th Congress of the European Society for Photobiology
Granada, Spain, 3-8 September, 1999
Photo A.Chardon