Some feminine hygiene products, such as tampons and pads, are privately tested through their manufacturers before they receive the Food and Drug Administration (FDA) approval necessary for market entry. Others, like vaginal wipes and douches, require no specific safety testing at all. In both cases, critics say the process locks the public out of health risk information needed to make informed decisions about products they are using internally on a regular basis.

That’s why Rep. Carolyn Maloney (D-NY) has reintroduced the Robin Danielson Act, a bill named for a woman who died of Toxic Shock Syndrome (TSS) in 1998.

“We need more dedicated and substantial research to address unanswered health concerns regarding the safety of feminine hygiene products,” Maloney told Rewire. “American women spend well over $2 billion per year on feminine hygiene products, and the average woman will use over 16,800 tampons and pads over the course of her lifetime. Despite this large investment and high usage, there has been limited research on the potential health risks these products may pose to women.”

The legislation would require the National Institutes of Health (NIH) to allocate resources for independent research into the potential hazards posed by synthetic fibers and chemicals currently present in many of the feminine hygiene products on the market. It would also mandate research to confirm data submitted to the FDA by manufacturers. The results of all future independent studies would be submitted to Congress, the Environmental Protection Agency (EPA), and the Consumer Product Safety Commission as well as the FDA. These findings would also be available to the public.

Maloney first introduced the Tampon Safety and Research Act in 1997, the year before Danielson died. The bill was re-named and has been brought before Congress a staggering nine times in total. Each time Maloney reintroduces the bill, it’s killed before it can get near a vote. It is currently in the Committee on Energy and Commerce.

A spokesperson for Maloney wasn’t able to comment on why the bill has been shot down so many times, but Chris Bobel, president of the Society for Menstrual Cycle Research, wrote in her 2010 book New Blood: Third-Wave Feminism and the Politics of Menstruation that the bill’s repeated failure could be “a result of activist inattention.” In Bobel’s interviews with feminine hygiene safety activists, she wrote, few seemed to set their sights on legislative action and instead focused on pressuring manufacturers through boycotts and other methods. With increasing public attention being paid to the policies surrounding hygiene products and alternatives to them, that may change—as might any congressional reluctance to engage with reproductive medical issues.

Regardless of activists’ strategy for approaching the topic, Bobel notes they are largely concerned about the health effects of feminine hygiene and menstrual products—especially because so few studies have been done using human subjects. According to everyone interviewed for this story, almost no independent research has investigated potential health impacts of long-term feminine hygiene product use, aside from the many studies on TSS. Bobel says anthropologists and other social scientists have frequently examined the culture around menstruation, but most medical research has centered on reacting to ongoing outbreaks of TSS rather than examining unknown outcomes.

And, health advocates point out, the research that has been done has taken place through product manufacturers. Part of the problem is that tampons and pads are considered “medical devices,” which means companies test them before submitting the results to the FDA as part of their pre-market approval (PMA) documents. PMAs—including testing results—are not readily available to consumers. Furthermore, the FDA does not require companies to list the ingredients on these products.

According to the FDA’s 2005 guidance, a tampon manufacturer submitting a PMA should test for potential health risks including adverse tissue reaction, vaginal injury, vaginal infection, and TSS. Preclinical toxicology and microbiology are “recommended” as well. Those submitting PMAs for pads should address adverse tissue reaction as well. Because so much of the testing data is kept secret, it’s unclear how strictly the FDA enforces the guidelines, much less what the actual results are.

“What’s clear is that there is so little data,” Bobel told Rewire. “We don’t have access to industry data that’s reported to the FDA because they aren’t obligated to release the results of their studies to the consumer. And that’s standard, but it means that consumers can’t make authentically informed choices. So there’s no transparency or accessibility.”

The FDA guidance also says nothing about long-term health effects relating to chemical leakage, which some scientists see as a potential problem concerning tampons in particular.

Philip Tierno, a microbiologist at New York University and author of The Secret Life of Germs, has been conducting independent research on TSS for years. TSS, caused by the bacteria Staphylococcus aureus, became epidemic around 1980. The health crisis was traced to the use of Proctor & Gamble’s Rely tampon, which was comprised of a synthetic blend encased in polyester. Tierno explained that the ingredient carboxymethylcellulose was primarily responsible for encouraging bacterial growth because of the way it “gelled” the liquids inside the vagina.

But toxic shock isn’t the only harm women face when it comes to feminine hygiene products, Tierno argues; it’s just the only disease that has been proven to be linked to them.

“There are many other leachables that come from fibers, and they leach out chemicals whether [the fibers are] organic or inorganic, and [they] clog the liver,” said Tierno. “If you have a woman who has no or low antibodies, not only are the leachables being absorbed, but other chemicals that come into play when the liver is clearing toxins.”

Many of the most toxic tampon ingredients—like the carboxymethylcellulose in Rely tampons—were banned in the 1980s after testing showed a direct connection between them and TSS. But Tierno says many products still include viscose rayon: the bleached wood pulp derivative that produces dioxins, the “leachable” about which he is most concerned. He believes that rayon and synthetics in general are responsible for ongoing cases of TSS, and that the disease can only be avoided by using all-cotton tampons or shunning their use altogether in favor of pads.

According to the EPA, most people have trace amounts (low parts per trillion) of dioxins in their systems. Dioxins are normally absorbed in these tiny amounts through food and water, and enters the environment through things like industrial waste processes and forest fires.

The EPA notes, however, that dioxins can be potentially harmful at moderately increased doses. “At body burden levels 10 times or less above those attributed to average background exposure, adverse non-cancer health effects have been observed both in animals and, to a more limited extent, in humans,” reads a posting about dioxin on the agency’s website. “In animals these effects include changes in hormone systems, alterations in fetal development, reduced reproductive capacity, and immunosuppression. Effects specifically observed in humans include changes in markers of early development and hormone levels. At much higher doses, dioxins can cause a serious skin disease in humans called chloracne.”

In a patient alert from 2013, the FDA stated that “trace amounts” of dioxins had been found in tampons on the market; manufacturers must also provide the FDA with test results of the dioxin levels in their products from independent laboratories. Though the FDA pointed out that the dioxin levels in these tampons were very low, Tierno told Rewire that no studies have ever examined the impacts of dioxin accumulation in the body over a lifetime.

“You have to do some research. There is no research taking place on things like dioxin except at the hands of the manufacturers [during the FDA’s pre-market approval requirements], which is like the fox taking care of the henhouse,” Tierno said. “They aren’t looking at long-term effects. We need data to be able to glean information that can serve as the basis for predicting what can occur.”

The overall lack of a push for research on these issues becomes more glaring when one compares the way feminine product safety is assessed to other products used regularly and internally, such as toothpaste.

For example, in December 2013, concerns about the presence of a chemical called triclosan in Colgate Toothpaste prompted the FDA to begin an ongoing review of its safety risks. The agency hasn’t concluded its study, but in the meantime the governor of Minnesota enacted a law banning triclosan, which has been shown to mimic hormones in animal testing, from all products sold in the state beginning in January 2017. Last year, the European Union voted to ban triclosan from three industrial product groups and is assessing its safety in hygiene products.

In the wake of the controversy, toothpaste manufacturers, such as Proctor & Gamble, which makes Crest, began labeling their oral care products as “100 percent triclosan free.” However, according to a 2013 research study from Women’s Voices for the Earth, several non-toothpaste products on the market—especially feminine wipes, washes, and sprays—could contain either triclosan or similar endocrine disruptors, as well as other ingredients that have been linked to endocrine disruption or other health problems. Yet there has been little focus on feminine hygiene products as sources of these chemicals, especially when contrasted with the widespread reaction to triclosan in toothpaste.

What’s more, because the FDA regards feminine wipes, washes, and douches as “cosmetics,” each product does not require specific testing to get the agency’s approval.

By mandating that the NIH support and fund research into any health risks stemming from all feminine hygiene products—including links between those products and common health conditions—the Robin Danielson Act seeks to close this research gap. It would also require studies examining products’ effect on reproduction: fetal and childhood development as impacted by regular feminine hygiene product use.

“The reality is menstrual health has been considered a taboo subject for far too long,” Maloney said. “It’s time that feminine hygiene products are researched so that we can ensure that complete and accurate information is being collected and made readily accessible. My legislation will give women the ability to make more informed decisions as they seek to lead healthy lives.”

CORRECTION: This article has been updated to clarify the confirmed ingredients found in feminine hygiene products.