Standards should require solar simulators to be more like sunlight. It is possible to re-filter solar simulators to be more like sunlight. Reasonable solar spectra should pass these standards.

1. Diapositive 1
The Need To Improve Solar
The Need To Improve Solar
Simulators And Defining Standards
Simulators And Defining Standards
Robert M. Sayre and John C. Dowdy
Rapid Precision Testing Laboratories, Cordova TN
Laboratories,
Alain M. Chardon and François J. Christiaens
L´ORÉAL Recherche, Clichy, France
Good Morning,
I appreciate being able to speak to this group. We want to acquaint you with sunlight
and how solar and the solar simulator used to test sunscreen products compare. We
further want to acquaint you with the current most complete European solar simulator
standard (COLIPA) and how it insures that solar simulators used to test sunscreens
will be the same throughout the world. In achieving spectral uniformity between solar
simulators, possible serious differences have arisen compared to the spectrum of
sunlight.
The end result is that product labels may not provide accurate estimate of protection
in sunlight. A number of factors need to be considered as improvements to the
system are proposed.

2. Diapositive 2
SUNLIGHT VARIABILITY
SUNLIGHT VARIABILITY
Irradiance (W/cm²/nm)
10-4
10-5
CIE Standard Sun AM1G
10-6 CIE Standard Sun AM1.5G
TUCSON 02Mar99 8:30-4:30
300 320 340 360 380 400
Wavelength (nm)
This slide shows a series of solar spectra, measured in Tucson Arizona several
weeks ago. The most important feature is that there is not a single ubiquitous solar
spectrum. These spectra were measured at 15 minute intervals over an 8 hour
period. During this period the short wavelength UVB cut-off varied and the total
power through the UVA changed.
Shown with the measured solar spectra is a CIE air mass 1.5 standard sun. The solar
altitude of this sun is just under the 45º sun above which dermatologist suggests
protection needs to be used. This is clearly the case because during at least 8 of the
measurement periods there were more than 3 MEDs/hour according to the Solar
Light Biometer measurements being also made.
The first point I want to make is that anyone outdoors will be exposed to many
different spectra. Note the changing shape and cut-off of the short UVB wavelengths.
The second point is that while the UVA power changes, the shape remains the same.
In the UVA you are always at risk to the same spectrum.

3. Diapositive 3
SOLAR SIMULATORS
SOLAR SIMULATORS
10-2
Irradiance (W/cm²/nm)
10-3 UG-11
UG-5
10-4
10-5
10-6
10-7
10-8
10-9
300 400 500 600 700 800
Wavelength (nm)
The spectra of two typical solar simulators are shown in this slide. The xenon arc
solar simulator uses a xenon arc from 150 watts to possibly more than 1000 watts.
The spectrum is shaped by the incorporation of a dichroic mirror which reflects the
UV portion of the source. A cut-off filter is used to shape the short wavelength cut-off
like sunlight and generally an additional band pass filter is added which shapes the
visible cut-off of the system.
Because solar simulators are operated at a wide range of intensities, a method for
comparing one to another has had to be developed. This method of comparison is
incorporated in the the COLIPA Standard.

4. Diapositive 4
COLIPA Standard
COLIPA Standard
Determine Emission % COLIPA Effective Irradiance
Spectrum <290nm (<1.0% )
Multiply by CIE 290nm - 310nm (46.0% - 67.0% )
Erythemal Action 290nm - 320nm (80.0% - 91.0% )
290nm - 330nm (86.5% - 95.0% )
Spectrum
290nm - 340nm (90.5% - 97.0% )
Compare to Typical 290nm - 350nm (93.5% - 99.0% )
and Limit Values
The COLIPA STANDARD requires that the solar simulator spectrum be measured. It
is recommended that it be measured at least from 280 nm to 400 nm with a
resolution of no less than 2 nm and an increment of no more than 2 nm. The spectra
we showed earlier met these requirements but the wavelength range was 250 to 800
nm.
Once the spectrum is known, it is multiplied by the CIE erythemal action spectrum.
The result is an erythemic effective spectrum for the particular solar simulator. The
COLIPA STANDARD requires that the erythemic risk for a series of spectral intervals
be compared to the total erythemic risk for the solar simulator.
For the solar simulator to meet the standard the values must be within the prescribed
limits for all wavelength intervals ; the goal is to get a spectrum as close as possible
to typical values.

5. Diapositive 5
SUNLIGHT vs SOLAR SIMULATOR
SUNLIGHT vs SOLAR SIMULATOR
10-2
In the UVB, typical 10-4
Simulated (W/cm²/nm)
CIE Suns (W/cm²/nm)
solar simulators have 10-3
greater intensity
relative to sunlight. 10-5
10-4 UG-11
UG-5
In the UVA, they have CIE AM1G
CIE AM1.5G
less intensity relative 10-5
10-6
to sunlight
10-6
300 320 340 360 380 400
Wavelength (nm)
This is the most important slide I will show you today. We have plotted two standard
solar spectra of air mass 1 and 1.5 and the two solar simulators previously shown
you using UG-5 / 2 mm or UG-11 / 1 mm filters.
The heights of the spectra have been adjusted by having two axes with equal
spacing simply shifted vertically so that the peak maximum for the solar simulators
track the peak maximum for the air mass 1.0 sun. The same effect could have been
accomplished by normalizing these three spectra.
First note in the UVB 300 to 320 nm that both solar simulators’ intensity are greater
relative to the standard sun. Because the axis is a log axis and the Erythemal Action
spectrum is high, this seemingly small difference causes a large shift of the erythemal
risk to these wavelengths and could make sunscreen products to appear more
protective than they are in sunlight.
Next note that in the longer UVA the solar simulator with the UG-11 / 1 mm filter has
only 1% of the intensity relative to sunlight at 400 nm. This may make sunscreen
products appear more effective because there is little long UVA protection is required
from products. The solar simulator filtered with the UG-5 / 2 mm appears to track
sunlight quite better.

6. Diapositive 6
SOLAR SIMULATORS vs COLIPA
SOLAR SIMULATORS vs COLIPA
% C OLIP A Effective Irradiance U G -11 U G-5
<290nm (<1.0% ) 0.0 1% 0.02%
290nm - 310nm (46.0% - 67.0% ) 57.8% 49.6%
290nm - 320nm (80.0% - 91.0% ) 88.6% 84.9%
290nm - 330nm (86.5% - 95.0% ) 94.1% 91.7%
290nm - 340nm (90.5% - 97.0% ) 96.1% 94.2%
290nm - 350nm (93.5% - 99.0% ) 97.6% 96.1%
Both solar simulators we have discussed meet the COLIPA standard.
Note: the amount of effectiveness in the sources at wavelengths longer than 350 nm.
The UVA defective UG-11 / 1 mm filtered source has only 2.4% if its erythemally
effective irradiance at wavelengths longer than 350 nm. The UG-5 / 2 mm filtered
source has almost 40% more effectiveness at wavelengths longer than 350 nm or
3.9%. Sunlight has more as I will show you shortly.
The increase in UVA-! Effectiveness of the UG-5 / 2 mm filtered solar simulator is
also seen in the decreased emphasis on short UVB effectiveness in the 290-310 nm
increment: 49.6% for the UG-5 / 2 mm filter versus 57.8% for the UG-11 / 1 mm.

7. Diapositive 7
SUNLIGHT AM1 vs COLIPA
SUNLIGHT AM1 vs COLIPA
Irradiance (W/cm²/nm)
10-4
% COLIPA Effective Irradiance
<290nm (<1.0% ) 0.0%
290-310nm (46.0-67.0% ) 55.1%
10-5 290-320nm (80.0-91.0% ) 84.5%
290-330nm (86.5-95.0% ) 90.9%
290-340nm (90.5-97.0% ) 93.4%
10-6 CIE Standard Sun AM1G 290-350nm (93.5-99.0% ) 95.3%
300 320 340 360 380 400
Wavelength (nm)
Here is the Air Mass 1 standard sun spectrum.
It passes the COLIPA standard.
Note the bottom line 290-350. This sun has 4.7% of its effectiveness at wavelengths
longer than 350 nm compared to 3.9 for the UG-5 / 2 mm filtered solar simulator and
only 2.4% for the UG-11.
Standard UG-11 / 1 mm filtered solar simulator has only half of the long wavelength
effective wavelengths as does noon-day overhead sunlight.

8. Diapositive 8
SUNLIGHT AM1.5 VS COLIPA
SUNLIGHT AM1.5 VS COLIPA
10-4
Irradiance (W/cm²/nm)
% COLIPA Effective Irradiance
<290nm (<1.0% ) 0.0%
290-310nm (46.0-67.0% ) 36.3%
10-5 290-320nm (80.0-91.0% ) 74.5%
290-330nm (86.5-95.0% ) 84.7%
290-340nm (90.5-97.0% ) 88.9%
10-6 CIE Standard Sun AM1.5G 290-350nm (93.5-99.0% ) 92.1%
300 320 340 360 380 400
Wavelength (nm)
Here is the Air Mass 1.5 standard sun. It fails COLIPA.
In the outdoor sunlight measurements shown you earlier the spectra which
corresponded to its spectrum produced more than 3 MEDs per hour. Sunlight with a
20 minute or less MED is not harmless.
Yet today this spectrum cannot be used to test sunscreen products!

9. Diapositive 9
MOST SUNLIGHT FAILS COLIPA
MOST SUNLIGHT FAILS COLIPA
Irradiance (W/cm²/nm)
10-4
10-5
CIE Standard Sun AM1G
10-6 CIE Standard Sun AM1.5G
TUCSON 02Mar99 8:30-4:30
300 320 340 360 380 400
Wavelength (nm)
I want to emphasize to you again. Most sunlight fails colipa. I have only 3 solar
spectra out of the 500 in my computer which meet the COLIPA standard. This
standard needs to be re-examined as the spectrum accepted is so-weighted that it
does not represent enough spectrum on this earth.
It seems reasonably clear that the greatest risk is represented by an over-head sun.
We are told by dermatologists that when are shadows are as long as we are tall, we
have only limited risk. That is a sun with and air mass of less than 1.5.
Clearly serious consideration needs to be given to adopting a standard which limits
the range of spectra to this earth.
It seems clear that by selecting the short wavelength cut-off filters with better care,
we can eliminate some of the excess UVB wavelengths. It also seems equally clear
that most if not all of the long UVA discrepancies can be eliminated by simply using a
UG-5 / 2 mm filter instead of the more common UG-11 / 1 mm filters. About this point,
consideration should be taken of the head load due to visible and IR light.

10. Diapositive 10
SUMMARY
SUMMARY
STANDARDS SHOULD REQUIRE SOLAR
SIMULATORS TO BE MORE LIKE SUNLIGHT
IT IS POSSIBLE TO RE-FILTER SOLAR
RE-
SIMULATORS TO BE MORE LIKE SUNLIGHT
REASONABLE SOLAR SPECTRA SHOULD
PASS THESE STANDARDS
These are the thoughts that I want to leave you with.
In the past standards have been developed so that specific solar simulators would
pass. We ought to consider developing the standard so that the spectrum must look
like the source we desire to achieve protection against.
It is clearly possibly to refilter solar simulators to more closely match sunlight and its
erythemal risk. The fact that the UG-5 / 2 mm filter is used in a few solar simulators
shows us one solution. A slightly thicker WG-320 would remove slightly more UVB.
There are other brands of cut-off filters which have different shaped cut-off. One of
these might be better.
Finally, it seems strange that most sunlight to which we are at risk to injury cannot
meet the standard as a source for testing sunscreens. This needs to be corrected.