The list of ingredients on a box of tampons is typically brief, including a shortlist of materials the product “may contain.” And menstrual pads often don’t come with any ingredient disclosures on the package.

Now, advocates concerned about exposure to potentially toxic pesticide residues or other additives or byproducts are pushing for greater transparency and safety testing of components that make up feminine care products.

Rep. Grace Meng (D-N.Y.) has introduced the Menstrual Products Right to Know Act, which would require companies to provide a detailed list of ingredients on menstrual products. And a bill reintroduced by Rep Carolyn B. Maloney (D-N.Y.) would direct the National Institutes of Health to conduct research to determine whether chemicals used in feminine hygiene products present health risks, including links to cancer or infertility.

“We want to make sure that women know what is in these products, which actually have the closest contact with our bodies,” Meng said in an interview.

The vast majority of women in the United States wear pads or tampons every month for decades of their lives. The vagina contains some of the most sensitive and absorbent tissue in the body and has a dense concentration of blood vessels that can enable transfer of chemicals into the circulatory system, properties that advocates say bolster the need for higher safety precautions and disclosure requirements for menstrual care products.

Meng’s bill is part of a larger wave of activism around decreasing the stigma of menstruation, making menstrual products more affordable and accessible to poor or vulnerable women, and improving women’s health and safety.

In recent years, two dozen states or jurisdictions have introduced bills to eliminate the sales tax on menstrual products, and four states and the District of Columbia have approved them. Campaigns to provide menstrual products free to women in public schools or homeless shelters or detention facilities are taking off in cities around the country.

The bill also reflects a generation of more critical consumers, according to Ashley Orgain, director of mission advocacy and engagement for Seventh Generation, a company that produces menstrual products made from organic cotton.

“We are seeing the rise of the conscious consumer, the millennial consumer that has grown up more aware of the environmental impacts we are facing as a society,” Orgain said.

The U.S. Food and Drug Administration classifies tampons and pads as medical devices. Unlike with food and drugs, the regulator does not require manufacturers to list individual ingredients.

Angela Stark, an FDA spokeswoman, said that companies seeking to market tampons must provide testing to support the safety and effectiveness of the product, including tests that assess the material safety of the products and microbiological tests to evaluate whether the tampon enhances the growth of the bacteria that causes toxic shock syndrome, a rare but potentially fatal illness.

Maria Burquest, associate director for communications overseeing Tampax and Always brand feminine care products for Procter & Gamble, which comprise 52 percent of the U.S. market for tampons and pads, said the company takes its responsibility to provide information to women seriously. P&G shares more detailed information about the components in pads and tampons on its websites, an approach some other companies, including Kimberly-Clark Corporation which produces Kotex brand products, are also now taking as activists have begun to call for more information.

Burquest said the company shares safety assessments with independent experts and health-care providers to assure they can be used safely before they are brought to market.

But since industry reports are not published, and without detailed ingredient lists readily available, it’s still too hard for women to answer the question: “How do I know my tampons are safe?” said Erin Switalski, executive director of Women’s Voices for the Earth, which published a report in 2013 about the potential health effects of toxic chemicals in feminine care products.

Tampons are typically made from cotton or rayon or pulp fiber, but advocates are concerned about potential contamination with toxic dioxins that could occur when the fibers are bleached with chlorine compounds. P&G says on its website that its cotton and rayon purification process involves an “elemental chlorine-free process that does not cause the production of dioxin.”

Advocates are also concerned about pesticide residues that can be found in nonorganic cotton in pads or tampons, as well as adhesive chemicals used in pads or other additives used to improve absorbency. Other unknown chemicals come from products that contain fragrances, which can be composed of a large range of chemical combinations that are not required to be disclosed.

The FDA recommends that tampons be free from dioxins and pesticide or herbicide residue and requests that companies provide assurances, including test plans, for monitoring them.

In addition to pads and tampons, advocates are scrutinizing feminine hygiene products including douches, sprays, washes and wipes. These products are regulated as cosmetics, and manufacturers are required to print more detailed ingredients, but many of the products contain undisclosed added fragrances. The American Congress of Obstetricians and Gynecologists recommends against using douches, because they are considered medically unnecessary and could increase the chance of bacterial infections or other problems.

Some gynecologists and women’s health advocates recommend that women avoid scented products, including sprays, douches, and wipes. Such products encourage “body shaming and they make women feel like the vagina is dirty,” Switalski said. “I encourage women to ask, ‘Do I really need this?’”