Truth Behind Chemicals in Sunscreens

Chemicals are tested on single cells, then animals and then humans. With increasing frequency, the animal testing is minimized or skipped. Data from humans trumps data from animals which trumps data from cell cultures. So, if in a cell culture, a chemical is shown to be harmful, but in humans, it is shown to be safe, then the human data is what matters. 

Why the difference between single cells and whole humans? There are dozens of reasons why this may be true, but one reason is the levels of the chemical that the cell culture cells see is often exaggerated. This is the case with sunscreens. The real-world level of most sunscreens is well below that which showed some laboratory effects on sea life. The exception is the benzophenones which were toxic and have been pretty much eliminated from commercial sunscreens and will probably be completely gone in the near future. 

As above, toxicologists must also consider real world conditions. Using the sunscreen example, a highly water resistant sunscreen maintains its protection for at least 80 minutes in the water. This means the sunscreens, for the most part, stay on you and don’t dissolve into the water. If you want to respect the ocean, use a highly water resistant sunscreen if you’re going into the water. This also brings up another dimension of toxicology and that's the cost benefit. If the benefit is marginal, then any cost is too much. Sticking with sunscreens, if they are not doing you any good, then why use them at all. But, sunscreens are doing you a great deal of good in helping to prevent skin cancer and certainly in limiting photoaging, the majority of skin changes we see as we age. So, pick the best one: one that works, one that stays on and one that is elegant enough that you will actually use as it was meant to be used. A really effective but horrible feeling skin care product is pretty much useless because no one will use it.