Tampons, which are used by millions of women, may carry “alarming” amounts of toxic metals including lead, arsenic and cadmium, a study by academics in the United States has warned.

The findings by a team of researchers led by Jenni A Shearston at the University of California at Berkeley (UC Berkeley) are especially concerning because of the vagina’s greater capacity for absorbing chemicals compared with other parts of the body, experts said.

The tampon was invented by Dr Earle Haas in the US in 1929. Five years later, Gertrude Tenderich bought the patent and founded the company Tampax, making the tampon commercially available. In the early days of the business, she would actually hand-sew the tampons herself.

Today, more than half of all women use tampons at some point in their lives, and estimates are as high as 80 percent in Western countries, according to the UC Berkeley School of Public Health.

“Despite this large potential for public health concern, very little research has been done to measure chemicals in tampons,” said Shearston, a postdoctoral scholar at the UC Berkeley School of Public Health and UC Berkeley’s Department of Environmental Science, Policy and Management.

Here is what we know so far about the manufacture of tampons and the findings of this study:

What are tampons made of?

Tampons are usually made from a mix of cotton and rayon (also known as viscose, a semisynthetic fibre made from agricultural products), both of which are highly absorbent and biocompatible. Biocompatibility means the material can be present inside the body without causing a bad reaction.

Some tampons are 100 percent cotton, and some are made from 100 percent “certified organic” cotton.

Until the late 1990s, a chlorinated bleaching process was used during manufacturing to remove any impurities from the raw materials. This was also done to make it easier for women to see the colour and quantity of menstruation.

However, this bleaching process was found to produce dioxins, harmful chemicals that the World Heath Organization considers a “known human carcinogen”.

Since the late 1990s, the manufacture of tampons has not included this chlorinated bleaching process. Instead, hydrogen peroxide, which is more biocompatible, is used to whiten the material.

Is the manufacture of tampons regulated?

Tampons are highly regulated and are classified as a medical device in the United Kingdom under the Medicines and Healthcare products Regulatory Agency, in the US under the Food and Drug Administration; and in the European Union under the General Product Safety Directive.

Regulatory guidelines vary, but in general, each agency requires companies to develop “good practices” around the manufacturing of tampons and provide enough information to the consumer to assess the inherent “risk” of the products.

What has the new study into tampons found?

Overall, the study, which did not name brands and referred only to “generic A”, “generic B”, etc, found traces of a total of 16 types of metal in tampons, including toxic metals such as lead, arsenic and cadmium.

The study investigated the makeup of tampons that were sold in New York City, Athens and London from 2022 to 2023.

The study stated: “We also generally selected products with greater absorbancies to ensure there was enough material for multiple tests. We purchased tampons between September 2022 and March 2023 from brick-and-mortar stores in the US (New York City), the European Union (EU: Athens, Greece), and the United Kingdom (UK: London, England), and from two major online retailers.”

The study examined 30 kinds of tampons across 14 brands with different levels of absorbency.

Although the research detected toxic metals in tampons, the researchers made clear they cannot determine if these are dangerous to the women using them. They called for further studies to determine if these metals can leach from tampons and be absorbed through vaginal tissue.

“Although toxic metals are ubiquitous and we are exposed to low levels at any given time, our study clearly shows that metals are also present in menstrual products and that women might be at higher risk for exposure using these products,” said study co-author Kathrin Schilling, assistant professor at Columbia University’s Mailman School of Public Health in New York.

Were organic tampons found to be safer?

Surprisingly, the researchers found that organic tampons had higher levels of arsenic than nonorganic tampons. The researchers explained that arsenic may be more ever present in organic tampons as a result of the use of natural fertilisers in organic cotton fields.

The study said: “This may increase the bioavailability of As (arsenic) in soil, although more studies are needed to confirm this hypothesis.”

The researchers did not show a marked difference in quantities of arsenic found in tampons made from cotton and those made from viscose.

Are tampons safe to use?

In general, tampons are safe to use, according to health regulatory agencies, but further research is required, the researchers said, due to their findings.

Clarity is needed about how certain metals have come to be contained in tampons and whether this happens during the cultivation process of the materials or the manufacturing process.

“I really hope that manufacturers are required to test their products for metals, especially for toxic metals,” Shearston said.

In another 2022 study of tampons, Mamavation, a consumer watchdog site that conducts “eco-wellness product investigations for moms”, sent 23 kinds of tampons to a certified laboratory to be examined for indications of per- and polyfluoroalkyl substances (PFAS).

PFAS are sometimes referred to as “forever chemicals” by environmental activists and campaigners because they do not biodegrade and can last for thousands of years, according to Clean Water Action, a US-based action group campaigning for tougher laws on clean water. Some PFAS are used in the manufacture of waterproofing sealants. They are found in products that have been made since the 1950s, including umbrellas, nonstick cooking pans, medical equipment, building products and other items that are required to be waterproof, grease-proof, stick-proof or stain-resistant. They can also be found in personal care products, such as dental floss, mascara, makeup and menstrual underwear.

The US Environmental Protection Agency has linked PFAS to a range of health issues that can include reduced fertility in both women and men and high blood pressure in pregnant women. In addition, they have been linked to a higher risk of some cancers, including prostate, kidney and testicular cancers.

The Mamvation study found that 22 percent of tampons had indications of PFAS, including two “organic” tampons.

Mamavation concluded: “We may not be able to tell you if or how much PFAS will leach into the body from exposure in the vagina. But we do know that PFAS exposure is possible based on some studies looking at dermal exposure in animals. Biomonitoring evidence from the Centers for Disease Control (CDC) has found PFAS in most of Americans.”

What are the best alternatives to tampons?

Many women around the world use menstrual pads, which can be placed inside underwear and remain outside the body.

For those who wish to use internal menstrual protection, some obstetricians and gynaecologists recommend a menstrual cup or disc instead of tampons. Similar to tampons, which are inserted into the vagina, menstrual cups or discs are folded and then inserted. Tampons must be disposed of after use while cups and discs can be either disposable or reusable.

It is recommended that women use a medical-grade thermoplastic elastomer or silicone disc or cup.

It is also possible to use “period underwear”, which is highly absorbant, but some may also contain PFAS, so consumer research is required.