The active chemicals of commonly-used sunscreens end up in a wearer’s blood. The U.S. Food and Drug Administration, or FDA, reported recently that the chemicals are present at much higher levels than current government health rules permit. For this reason, the researchers call for more safety studies. Sunscreens were first sold to prevent sunburn and did not have to meet many government regulations. Now they are widely used to block radiation from the sun that can cause skin cancer, the most common kind of cancer in the United States. To test some of the effects of sunscreen, researchers worked with 23 volunteers. They tested four forms of sunscreen by putting it on most of the volunteers’ bodies four times a day over four days. Then, they did blood tests over seven days to find the levels of certain chemicals absorbed into the volunteers’ blood. The study looked for the chemicals from sunscreen in plasma, the watery part of blood that contains blood cells. It found four chemicals to be well above the level at which FDA guidelines call for further safety testing.