Yesterday several news outlets published the results of a study that said “four out of five brand-name sunscreens either provide inadequate sun protection or contain chemicals that may be unsafe.” The report comes from the Environmental Working Group (EWG) and has been heavily criticized by sunblock makers, although their complaints are of the general sort (“they don’t understand sunblock!”) or vaguely hysterical (“they’ll convince people to stop using sunblock!”). We don’t know how valid the study ultimately is, but here are the basics—and regardless of the more sensational claims, their list of the best sunblocks may help you when choosing a product.