Researchers say tampons made by many brands contain toxic metals, including lead and arsenic.

In a first-of-its-kind study, researchers at the University of California Berkeley measured 16 metals in tampons, evaluating 14 unidentified brands from the U.S. and Europe. They found “measurable concentrations” of metals — including mercury, copper and iron — in all the tampons they tested.

Millions of people use tampons monthly.

“Tampons are safe,” said Dr. Tamika Auguste, an OB-GYN and chair of women’s and infants’ services at MedStar Washington Hospital Center. “It is OK to still use tampons.”

Just make sure you use tampons correctly and change them frequently. Dr. Auguste said the study is interesting, but not concerning.

“Most likely, these are at levels that are inconsequential to people using tampons, but we need to make sure of that,” she said. “We have not seen any big swells or increase of incidence of bad outcomes,” either in women using tampons or in children that are born to women using tampons.

Auguste added that more research is needed “to see how these metals got there, where they may come from, and what it actually means,” she said. “I don’t think there is any health emergency at this time surrounding the use of tampon products.”

The study’s authors said the results are concerning because the skin of the vagina has a higher potential for chemical absorption, but noted it’s unclear if the metals contribute to any negative health effects.

They said tampon manufacturers should test their products for metals or better label menstrual products.

The FDA is now reviewing the findings.