What does sunscreen actually have to do with corals?

When it's time to head to the beach, that means putting on sunscreen for us – and usually more than once. And more and more often, the question comes up of what sunscreen actually has to do with corals. Germany's Federal Office for Radiation Protection says there are indications that substances from sunscreens could be harmful to aquatic organisms such as corals; however, experts see the main cause of coral bleaching in the warming of the oceans (BfS, in German). That tells us nothing about what a single sunscreen does in the sea. So we make no claims about how our sunscreen behaves in the sea. What we can tell you is which filters are in it and why.
Many sunscreens work with organic UV filters, often called “chemical”, such as octocrylene. They are dissolved in the cream and therefore leave no white film. To reduce the white cast of mineral UV filters, the mineral particles are often broken down to nano size. Both approaches are permitted in the EU: every UV filter must be listed in the Cosmetics Regulation with a maximum concentration, and nanomaterials must be labelled “(nano)” in the ingredient list. How organic and mineral filters differ is explained in our article UV filters: chemical or mineral?
Our Naseweiss (Naseweiss means “smarty-pants”), today the Solid Sunscreen SPF50, goes its own way. We rely exclusively on mineral UV filters, and with them on really good UVA & UVB protection from titanium dioxide & zinc oxide in the non-nano* range. Nano forms of these two filters are also approved in the EU; we chose the larger particles. Despite the mineral UV filters, our Naseweiss leaves barely any white cast – only on parts of the body with thicker hair might a slightly visible white film appear, since the cream is harder to spread there. But we think that's a small price to pay for a short list of mineral filters.
It's not just the UV filters we thought hard about with the Naseweiss – otherwise too we rely on few and natural ingredients, and deliberately leave out fragrances as well.

*The non-nano UV filters we use comply with Regulation (EC) No. 1223/2009 of the European Parliament and of the Council of 30 November 2009 on cosmetic products. In this case, nanomaterial means an insoluble or biopersistent and intentionally manufactured material with one or more external dimensions, or an internal structure, on the scale from 1 to 100 nm.