Well, benzene is a known carcinogen. No level of exposure is considered safe. That said, the levels found in sunscreens were relatively low. So by themselves, they don't pose a big risk. That's according to Dr. Daniel Teitelbaum of the Colorado School of Public Health. He spent decades studying benzene exposure. But he says the problem is that we are exposed to low levels of benzene from various sources all the time, in the air we breathe from things like petrochemical refining and vehicle exhaust. “And that, of course, adds up. And that's why low levels of any single product used repeatedly combined with all of our background exposures increases the rates of cancer in the population.”