Scientists in their new study raised alarms over the presence of toxic forever chemicals — per and polyfluoroalkyl substances (PFAS) — in products used by females during menstruation, which, researchers think, might have been deliberately added, according to an Independent report.

According to researchers, while these products are designed to make people feel comfortable during their periods, their labels do not usually contain a list of the ingredients.

In the study which is awaited for peer-review, researchers analysed more than 100 products for fluorinated compounds — which indicates harmful PFAS.

PFAS are used in household products non-stick cookware, stain repellents, and firefighting foam. They are regarded forever chemicals because they stay in the human bloodstream for a very long time without breaking down.

Earlier studies had already raised concerns about the adverse health impacts of PFAS including the development of cancer cells.

According to the new research, while PFAS are absent from many period products, they might be accidentally or intentionally added to others.

Scientists have identified — without ascertaining how it passes into the human body —these compounds in school uniforms and period underwear.

“[PFAs] have demonstrated environmental persistence, can bioaccumulate, and are known to have human and environmental toxicity,” research lead Graham Peaslee, a professor at the University of Notre Dame, said.

Research revealed that PFAS chemicals were also present in additional period products, such as tampons and pads.

Alyssa Wicks from the University of Notre Dame said: “We determined if these products had organic fluorine as a surrogate for PFAS.”

Wicks, a graduate student in Dr Peaslee’s lab noted: “In general, tampons didn’t seem to contain fluorine. Same with menstrual cups and the layers of pads that come in contact with a person’s skin.”

According to scientists, they were surprised by the presence of total fluorine in the wrappers for numerous pads, some tampons and the outer layers of some period underwear.

Scientists estimated that in some of these products, the highest amounts of these compounds are at 1,000 to several thousand parts per million total fluorine.

Researchers citing the concentration concluded that PFAS might be deliberately used in some of these products to keep moisture out of the wrappers so the items inside remain dry.

They said the rationale behind adding these compounds to the outer layer of the period underwear may be to keep blood from escaping the inner layers and stop it from spreading onto a person’s clothing.

Dr Peaslee concluded: “Feminine products are essential, but the need for a fluorinated wrapper, or the need for a fluorinated layer, doesn’t seem to be, because plenty of them are made without relying on these compounds.”

The full details of the study, including the number of products implicated and the amount of PFAS detected, are expected to be presented Sunday at the American Chemical Society meeting in San Francisco.