You may want to think twice about a picking up Rihanna's 'RiRi Woo' lipstick (which debuts today).

A new preliminary study published in Environmental Health Perspectives found that lipsticks and glosses may contain unsafe levels of certain metals. The study looked at 32 lip products from frequently visited stores in California, measuring levels of cadmium, chromium, titanium, and manganese among other metals.

"We looked at nine heavy metals and found that all of them were present in most of the lipsticks, but not necessarily at really high levels," study author Katharine Hammond told The Huffington Post. Hammond is a professor of environmental health sciences in the University of California Berkeley's School of Public Health.

This is not the first time the safety of lip products has come under fire. In 2007, The Campaign for Safe Cosmetics released a study that found levels of lead in 33 lipstick brands were a "cause of concern." In response, the Food and Drug Administration did its own study and found that "the amount of lead found in lipstick is very low and does not pose safety concerns." In 2010, the FDA followed up with a larger-scale study that looked at 100 lipstick brands and reaffirmed its position that while there were "trace amounts" of lead in many of the products, they were still safe to use.

So don't go throwing out your makeup bag just yet. Even Hammond herself warned of jumping to significant conclusions. "I don't think people should go into panic, or abandon lipstick, but I do think this is a concern," she said.