What does "UVA-protection has to be at least 1/3 of UVB-protection" actually mean?

EU has renewed its legislation about sunscreen claims. I read that "UVA-protection has to be at least 1/3 of UVB-protection. This will be informed with UVA-logo on sunscreen products." But what does this actually mean? I thought spf is not reversible to measure protection from UVA-radiation? What is this converted to PA/PPD? If I have spf 30, the UVA protection should be "10". Does this mean spf 10 = 90% of UVA-rays are blocked or what? I've also seen many sunscreens carrying the UVA-logo and "broad spectrum" written on them, but only active ingredient is titanium dioxide. I've been under an impression that titanium dioxide blocks only UVB and UVA2, and doesn't offer any protection from UVA1. How can this be "broad spectrum"? I am confused.


  • I don't know but to be safe I would check with the manufacturer of your sunscreen product.
  • I see. I don't think this revision is really thought through and in favor of a consumer. I mean, it's one step forward to take also UVA-protection in consideration, but there should be some clear measure for it. This is just confusing and potentially gives false sense of protection, like those ridiculously high spf rates. Thank you for replying, anyway!
  • edited May 2017
    The amount of UVA protection is actually measured in a lab, according some pretty strict rules. The UK has a boot rating system, Asia the PA rating system, US the critical wavelength and Europe the 1/3 rule (which has been used for quite some years already). They all give information about the amount of UVA protection, just like the SPF value does for UVB radiaton. The 1/3 rule means that an SPF30 needs to have at least an UVAPF of 10, so about 90% of the UVA radiation are blocked. In addition to that, EU sunscreens must also pass the critical wavelength test (the broadspectrum claim in the USA). This article discusses some of the techniques. By adding spf boosters and adjusting the particle size it is possible to obtain reasonable good uva protection with titanium dioxide alone.
  • Thank you for the clarification, it helps a lot. I'm gonna read the link thoroughly. All these different terms are so confusing. Nice to know I'll be likely well protected even if only titanium dioxide is used, this has bothered me a lot. Think I'll still stick with zinc-titanium combo just to be sure :)
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