(NewsNation) — New research indicates that tampons are a potential source of exposure to 16 metals, some toxic.

Published in Environmental International, the study looked at the concentration of 16 metalloids in 30 tampons across 14 brands, finding “measurable concentrations” of all assessed metals.

The widely accessible brands of tampons were purchased in large U.S. retail chains and online from Greece and the United Kingdom.

The following metals were assessed: arsenic, barium, calcium, cadmium, cobalt, chromium, copper, iron, mercury, manganese, nickel, lead, selenium, strontium, vanadium and zinc.

Toxic metals such as cadmium, lead and arsenic were found in higher concentrations, while mercury and chromium showed up less. Notably, there is no exposure level to lead considered “safe.”

Though the concentration of metals changed depending on organic or non-organic material used, it didn’t matter whether the tampons were name-brand on not or where they were bought: “No category had consistently lower concentrations of all or most metals.”

A majority — 52 to 86% — of people who menstruate use tampons during their periods, meaning that potential toxic exposure could impact a large portion of consumers.

“Future research is necessary to replicate our findings and determine whether metals can leach out of tampons and cross the vaginal epithelium into systemic circulation. Our findings point towards the need for regulations requiring the testing of metals in tampons by manufacturers,” researchers said.