In the previous part of the post, which you can read here, I briefly explained the differences between UVB and UVA light, explained the standards for testing UVB light protection, and some basic information on how the skin responds to UVA light. As UV labeling is inconsistent in the field of UVA protection, this leads to consumer confusion and, consequently, a greater chance of manufacturers misleading consumers with incorrect indications on their sunscreens.
Testing standards and labeling of UVA protection
British Boots Star System
The first to introduce their standard of testing and labeling UVA protection were the British. In 1992, they introduced a system whereby manufacturers began labeling sunscreens to let consumers know how much protection sunscreen offers in the UVA spectrum relative to the UVB spectrum. The British marking system is called the Boots star system, which is still used today. The Boots Star system gives sunscreens 3-5 stars and in this way indicates how much protection the sunscreen offers in the UVA spectrum. But it should be noted that the Boots system does not directly measure the strength of protection in the UVA spectrum, like UVA-PF, but only measures whether the sunscreen evenly protects throughout the UV light spectrum. Five stars on the Boots system means that UVA protection achieves more than 90% UVB protection.
Britanski Boots Star Rating system – kako posamezne oznake na embalaži označujejo višino zaščite pred UVA svetlobo
0,60 – 0,79
0,80 – 0,89
0,9 or more
Japanese PA + system
Well, when I mentioned that they didn’t know how to uniquely measure UVA protection, they developed their own system of measuring UVA protection in Asia. The Asian UVA protection evaluation system was developed by the Japanese, who first began measuring PPD and introduced the PA + system. This method of measurement is on human skin and is most similar to in vivo SPF measurement.
Japonski PA sistem – kako posamezne oznake na embalaži označujejo višino zaščite pred UVA svetlobo
2 – 4 (50 – 75 % protection against UVA rays)
4 – 8 (75 – 87,5 % protection against UVA rays)
8 – 16 (87,5 – 93,75 % protection against UVA rays)
16 or more (93,75 % or higher protection against UVA rays)
European UVA-PF system
We Europeans were among the last to introduce certain standards in the field of measuring UVA protection. In Europe, a combination of in vivo and in vitro methods of measuring broad spectrality has been introduced. It is a UVA-protection factor or UVA-PF, which measures protection against UVA rays in vitro (on a glass plate, including certain coefficients to make the calculation as similar as possible to the measurement in vivo on human skin). In Europe, the UVA label in the circle was then introduced, ensuring that UVA protection achieves at least 1/3 of the declared UVB protection (i.e. SPF).
American criterion Critical Wavelength 370nm
Well, as I mentioned above, Americans have also developed their own way of evaluating UVA protection. The Americans introduced the criterion of critical wavelength 370nm or the measurement of critical wavelength at 370nm. This criterion allows sunscreens with very low UVA protection to come through, so in the event that the American manufacturer does not operate according to EU standards and provides UVA protection that achieves at least 1/3 of UVB protection, you better not order these sunscreens.
Are UVA protection tests standardized?
Actually, yes. Notwithstanding the fact that the field is not regulated in the same way in all countries, producers must adhere to certain standards. There is now one in vivo ISO standard used to measure UVA protection, which is used all over the world (with the exception of America), called UVA-PF in vivo (PPD measurement). However, there are two other ISO standards for measuring UVA-PF in vitro. The table below lists the ISO standards used to measure UVA-PF in Europe and across other continents or countries.
So in Europe, manufacturers have to stick to the ISO standards listed in the table. After the manufacturer measures everything necessary according to the standards, he is obliged to indicate the protection against UVB rays, ie SPF to be numerically stated on the packaging, while the protection against UVA is not obliged to state. A sunscreen from a European manufacturer can get the UVA mark in a circle if the sunscreen meets the following conditions:
(1) that the UVA-PF reaches at least 1/3 of the SPF and
(2) that the critical wavelength is greater than or equal to 370 nm.
This second criterion is e.g. for Americans, the only thing a sunscreen has to meet if a manufacturer wants to get a “broad-spectrum” label for it. If it doesn’t meet that either, it can still be sold, just without that label.
What if I have a PPD or UVA-PF number, how do I know from this information what the protection against UVA light is?
We may still clarify very quickly if either of these two methods is better. No. The in vitro UVA-PF method is an equivalent alternative to the in vivo PPD method. The in vitro method was developed in order to replace the in vivo method and thus to avoid tests on human skin. In practice, the UVA-PF numbers obtained by one method or the other are very similar.
So what does PPD actually tell me? For example, if the PPD is 20, this means that skin smeared with sunscreen needs 20 times more time to tan after contact with UVA rays than if it is not lubricated with sunscreen. So similar to SPF, except that with SPF we irradiate the skin with UVB rays.
From the data of UVA-PF or PPD we can calculate what percentage of UVA rays the sun cream protects us from.
Calculation of protection from SPF or UVA-PF (PPD) in% and vice versa
UVA (%) = 100 % – 100 % / UVA-PF
Example: the cream has UVA-PF (PPD) 46. What % of protection is this? Answer: UVA (%) = 100 % – 100 % / 46 = 97.8 %.
UVA-PF = 100 % / (100 % – UVA (%))
Example: the cream offers 90 % protection against UVA rays. How much is UVA-PF? Answer: UVA-PF = 100 % / (100 % – 90 %) = 10. UVA-PF of this cream is 10.
UVB (%) = 100 % – 100 % / SPF
Example: the cream has an SPF of 50+. What % of UVB protection is this? Answer: SPF 50+ means that the actual SPF is 60 or more. UVB (%) = 100 % – 100 % / 60 = 98.3 %. The cream protects against at least 98.3 % of UVB rays, ie it transmits a maximum of 1.7 % of UVB rays.
SPF = 100 % / (100 % – UVB (%))
Example: the cream offers 85 % protection against UVB rays. How much is SPF? Answer: SPF = 100 % / (100 % – 85 %) = 6.7. The cream has an SPF of 6.7.
What to do in case I don’t know the PPD data of sunscreen?
In our at least a month-long hunt for data on the level of UVA protection, we finally collected the desired data with the girls and, in order for you to know what you are buying, combined them into one extensive Google Drive document with SPF and UVA data. protection, price and price-performance according to the level of protection and mileage. The data collected so far on sunscreens and their protection against UVA rays can be viewed here:
The table also collects price performances of various sunscreens. These are converted as price / mL in the table. 1mL is the approximate amount for 1x application to the face. So the price / ml is basically the price you pay to smear your face once.
In case you do not find your chosen sunscreens on our list and consequently do not get information about PPD from the manufacturer, the most sure rule is to buy a sunscreen with SPF50 +, which has the UVA label in the circle. SPF50 + means that the SPF is a minimum of 60, which ensures that the UVA-PF is at least 20 and that the protection (due to (2) criteria) is also covered in that part of the UVA spectrum that is already close to visible light. So that the curve is also stretched after UVA work, not just after UVB (as can happen with American sunscreens).
Attention: manufacturers intentionally state % to make the numbers look higher, and people then think that % is the same as UVA-PF but PPD!
This post has been longer than I expected it to be, but I only started writing this post because of such consumer urges. So when you buy sunscreen make sure it has a UVA label in the circle. As I said before, with SPF50 + you get PPD of at least 20 and thus protection against 95% UVA rays. Because some manufacturers have extremely low PPDs, they often quote percentages instead of specific UVA-PF or PPD data, in order to make the protection look higher.
So if you are interested in what UVA protection is in%, you calculate this using the equation below:
THE CREAM LEAVES 1 / PPD * 100%. IN THE CASE OF PPD 20 THIS MEANS THAT 1/20 * 100% = 5%. SO IT DOES NOT TRANSMIT 95% OF THE RAYS. AND IT IS SAID THAT PROTECTION AGAINST UVA RAYS IS 95%.
If a manufacturer pours water on their mill and tries to mislead consumers by quoting percentages, you can quickly figure out what time it is. Otherwise, such claims stating percentages are contrary to European law, but until no one is punished doing it, some will still evade the law to cover up their poor PPDs. If the manufacturer claims that UVA protection is 90%, how do I know how much PPD is?
100 % / (100 % – 90 %) = 10 – THEREFORE THE PPD OF A GIVEN SUNSCREEN IS 10.
The purpose of this publication is to distinguish that % are not the same as UVA-PF and that UVB protection in % is not the same as SPF. Another example, if the manufacturer says that UVB protection is 85 %, that means SPF between 6 and 7.
Can we achieve 100% protection against UVA rays?
Let me break it to you, unfortunately not. Just as we cannot achieve 100% protection against UVB rays, so we cannot achieve 100% protection against UVA rays. Of all the sunscreen data collected in the Google Drive spreadsheet, the highest is PPD 67, which provides protection against 98.5% of UVA rays. When protecting against UVB and UVA, we never generalize, 90% protection against UVA rays is not almost 100% because it still leaks 10%!
What about an antioxidant supplement? Antioxidants are a wonderful addition to sunscreens as they actually provide a secondary line of defense because they neutralize free radicals that form in the skin after exposure to UV radiation. Antioxidants help reduce the damage caused by those few % UVA rays that sunscreen still lets out. But do antioxidants increase UVA protection? No, antioxidants are not UV filters, nor do they absorb or reflect UV rays, so we cannot attribute the same role to them as UV filters.
At the end of the post, I would like to thank the girls with whom we created the Google document on the level of protection of individual sunscreens against UVA light, and especially thank Špela Bordon for selflessly sharing all her knowledge and broadening my horizons in the field of UVA protection. Big thank you to Gabi Nedič, Tiki Hribar, Daši Peternelj, Nini Stajner and Špela, that you selflessly shared your time and nerves, that we gathered all this information in one place.