EWG came out with new version of sunscreen guide http://www.ewg.org/2013sunscreen/
Sunscreens are not effective at preventing skin cancer and ageing
"Broad spectrum protection – Almost every sunscreen meets the FDA’s new rules for “broad spectrum protection,” meaning, protection against both ultraviolet A and B rays. The catch is, the FDA’s criteria are the weakest in the modern world. Half of the U.S. sunscreens that meet the FDA rules would not make it to store shelves in Europe, where, since 2006, sunscreen makers have voluntarily complied with stricter European Union standards (European Commission 2006).
High SPF – Sky-high SPF numbers are no measure of product effectiveness. A sunscreen’s sun protection factor, or SPF, measures its ability to screen skin burning UV rays, primarily UVB rays. The SPF value does not reflect the product’s ability to filter out UVA rays that, according to a growing body of evidence, cause skin damage, immune suppression and possibly melanoma. Studies show that high-SPF users are exposed to as many or more ultraviolet rays than those who use lower-SPF products. Experts believe that people get a false sense of security from those big numbers, don’t apply enough sunscreen, wait to long before reapplying and spend too much time in bright sun."