I am having the same problem verifying the PPD ratings of my sunblock. In my case, I have been using Bioderma Minerale. It claims a PPD of 22, though its active ingredients consist only of zinc oxide and titanium dioxide. I thought it was not possible to reach such a high PPD using only physical sunblocking agents. I have contacted Bioderma, requesting information about the percentage of active ingredients (which is not labeled on the bottle) as well as data supporting the verity of the PPD claims, but they have not responded. It's too bad. I want to like the sunscreen, but I don't know if I can trust the purported protection level.
Happy Lemon, did you have any success confirming the PPD rating of your Anthelios sunscreen?
This info was taken from a post by Eva Victoria (lost the link):
If ZnO is non-micro/nano than the UVB protection is minimal. But UVAI is extremely good (up to 520nm).
Micro ZnO provides better UVB protection and less UVAI protection. Though the UVAI protection is still concidered good (385nm). this is the best broad spectrum protection in one singel filter. Should be combined with organic filters though like OMC or Polysilicone-15 (not permitted in the US) to achieve better UVB protection. (ZnO stabilizes OMC).
Nano-ZnO provides very good UVB protection, just as good as TiO2 but UVAII protection is partial and UVAI is as good as non-existent.
Why ZnO is such a good sunscreen agent alone is because it can really give broad-spectrum protection in one single agent when it is used in high enough concentration (15%+). AND it is inherently photo-stable.
While organic filters provide higher SPF (UVB protection) and UVAII protection pr. percent of active required to achieve the required SPF/PPD (and they are conciderably cheaper when it comes to costs) they tend to provide narrower protection scale and they tend to be extremely photo-unstable. Hence they should be reapplied every 2 hours and combined with each other to provide broader protection.
The only true organic UVAI protection is possible with Tinosorb M. But it is not really an organic filter either. It is a so called organic particle filter. It is also inherently photostable. Its real advantage is that it is water soluble while almost all other filters (inorganic filters included) are oil soluble. The other good thing is that it is very affordable and it gives high UVA II and I protection pr. % active used. The drawback: it is not worldwide approved.
Why organic filters are so popular is because they are cheap to produce. Much less actives are needed to achieve high SPF sunscreens or UVA(II) protection. The profit can be increased much more than using 20% ZnO to achieve a sunscreen with lower SPF (but with the same UVA(II) protection or lower). The cost for this sunscreen is about 7-10 times more than achieving the same UVA(II) protection with organic filters (like AVO).
Organic filters are much more cosmetically elegant as well. So it is easier to sell.
But from the consumers' point they are though elegant (or more elegant) and cheaper, they are photo-unstable and have to be reapplied every 2h.
With todays technology it is possible to produce ZnO containing sunscreens with 15-25% ZnO, combined with OMC (7.5%) to achieve high SPF (50) and adequate UVA protection (PPD20). These sunscreens can be formulated mattish (while organic ones are almost always very oily and shiny). ZnO containing sunscreens with the right formulation can be used as visual skin perfectors (while organics actually make the imperfections of the skin look more pronounced).
The Refractive Index of ZnO can easily be turned into a very nice skin-veil that actually hides imperfections and makes it more dewy.
But the real difference between an organic sunscreen and a ZnO (15%+) containing one is that the UVAI protection from 385nm is usually non-existent for organic sunscreens (even when they contain TiO2*) while the one with 15%+ ZnO has at least PPD 10 at 385nm and about 4-8 at 400nm (depending on the particle size). So it provides lower SPF and PPD (UVAII) but it actually does cover the whole UVA spectrum! And again it is inherently photostable!
(PPD 20 means 95% protection; 15 means 93% protection; 8 means 87% protection!)
So what is better a sunscreen with AVO with an impressive PPD 30 (96% protection**) at 360nm but about 2 (50% protection**) at 390nm and 0 at 400nm, OR a ZnO containing sunscreen with a modest PPD 15 (93% protection at 360nm and PPD 17 -94% protection- at 385nm) and about PPD 8 (87% protection) at 400nm?
End of message
My post:
Take home message here would appear that PPD correlates more to protection between 320-360nm and much less protection from 360-400nm.(more penetrating rays)
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Move over potential hazardous chemical sunscreens that need to be re-applied often or can do more harm than good.. More and more people are realizing the superiority of Zinc Oxide sunscreens such as Burnout, Eco, Devita, Marie Veronique which are both cosmetically elegant and offer a high % of zinc._______________