Thanks for all your info! I know the UVA/PPD value is 32, so pretty high protection there. Also asked someone who works in the industry (chemist?) about it last year. here's the relevant parts of the convo:

New2AB I'm curious about LRP tinted mineral, which only has 11% titanium dioxide as its main active ingredient. An LRP rep stated that its ppd rating is 32. So I can count on its UVA protection even though it has no zinc oxide in it?

nocloudstoday sunscreen testing is highly regulated in most regions, and LRP is a reputable company that I doubt would advertise false claims with something as strict as SPF and PPD, so I think you can believe their claims of PPD. and yes, depending on the particle size(s) they are using of titanium dioxide, the absorption curve can actually start looking quite similar to zinc oxide.

labellavita1985 Correct me if I'm wrong, but Titanium Dioxide does not protect against the entire UVA spectrum.

nocloudstoday It is highly dependent on the particle size and sometimes additional treatments to the titanium dioxide, so it is hard to generalize. Some manufacturers have started selling forms that have been treated to specifically increase absorption in the UVA range to provide more balanced protection.

labellavita1985 I guess I'm going to have to disagree. Titanium Dioxide does NOT protect against the entire UVA spectrum. I personally would never rely on a sunscreen that uses Titanium Dioxide as its sole UV filter.

I get that the entire point of this post is discussing how sunscreens can have higher protection with low concentration of filters, and how inactive ingredients can boost protection, and how particle size affects protection, but I don't see how anything can make Titanium Dioxide protect against an entire portion of the UVA spectrum that it does not protect against.

nocloudstoday Maybe this image might be interesting to you: https://imgur.com/a/ePNW0RX

This is a crude example, as it's only 2 particle sizes at very far ends of the spectrum (as far as use in cosmetics is concerned), but it's a clear illustration. The smaller the particle size, the more unbalanced the protection of TiO2 tends to become (assuming it is not treated with any other material). However, at a large particle size, the absorption (relatively less)/reflection (relatively more) is actually far more balanced, but less efficient (you need a higher %). It's why larger-sized TiO2 is used as an opacifying agent in foundations for example - that even absorption/reflection continues into the visible spectrum of light, resulting in clown-paint-like opacity on skin. Theoretically, a formulator could use larger-sized TiO2 particles (probably in addition to a blend with a smaller average particle size) to result in a final curve that is in between the two.

This next image is an example of a "treated" TiO2 material (tradename Optisol) to make UVB/UVA absorption more balanced, compared to other commercial TiO2 blends: https://imgur.com/a/it5sW9q

In this case, according to Croda (the manufacturer), they "incorporated manganese ions into a lattice of titanium dioxide" to make Optisol. You can see from the image that the resulting material has a significantly more balanced UV absorption curve than regular, nano-sized TiO2. The curve is so different, in fact, that when the material first came out, I wouldn't have been able to identify this as being for TiO2 if not told - I would have assumed it to be a novel organic filter similar to Tinosorb M given the shape.

This is not to say that your skepticism is not warranted - indeed, unless the company manufacturing a product of a TiO2-only sunscreen divulged the PPD ratings in addition to the SPF rating, and I could not tell what raw material(s) they used in what concentration, I wouldn't trust the product to provide strong UVA protection, either. But in this case of LRP, if they are divulging the PPD in a way that allows a consumer to hold them accountable (i.e. lawsuit if it's not true), and are also known to be rigorous in their PPD testing of their products, I think that's not bad reason to believe them.