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�鶹��Ѱ�����Boulder scholar highlights what to know about this emerging health��issue

About half of the global population . Disposable products, such as tampons and pads, are some of the used around the globe to manage menstrual flow.

Unfortunately, studies have shown that many personal care products, including shampoo, lotion, nail polish and menstrual products, . Items used in or near the vagina are of particular concern because they are in contact with —the moist tissue lining the inside of the vagina that secretes mucus. These tissues .

People use menstrual products 24 hours a day for multiple days monthly, over the course of many years. Tampons, which are used internally, are surrounded by the permeable vaginal mucous membrane for up to eight hours at a time.

�鶹��Ѱ�����Boulder scientist Jenni Shearston is principal investigator in the Chemicals, Environment, Equity, Public Health, and Periods (CEEP.) Lab.

I am an , and I study chemical exposure, its sources and its health effects. As a person who menstruates, I also must make my own decisions around menstrual products and manage the challenge of finding accurate information about women’s health risks, which than men’s health.

In 2024, I co-authored the first paper that detected , including toxic metals like lead and arsenic. My colleagues and I also wrote a review paper that surveyed the scientific literature and found about two dozen studies .

The various chemicals that these studies detected were typically at concentrations low enough to make their health impact unclear. However, they included chemicals known to , which makes and controls hormones that are essential for bodies to function.

How contaminants get into menstrual products

The first modern tampon in the U.S. was . Nearly a century later, tampons still are made primarily from cotton, rayon or a blend of the two.

Chemicals may get into tampons and other menstrual products in a number of ways. Some chemicals, like heavy metals, are , and may be .

Other chemicals, such as zinc, may be intentionally added to menstrual products to . Still others, such as —synthetic chemicals —may leach into menstrual products from or be .

Research suggests that these chemicals are present in a large proportion of menstrual products – we found lead present in . What we don’t yet know is if these chemicals can get into people’s bodies in a high enough concentration to cause health effects in either the reproductive system or elsewhere in the body.

Limited federal regulations

The U.S. Food and Drug Administration as Class II medical devices, which carry moderate to medium risk. Unscented menstrual pads are Class I medical devices, which are considered low-risk. are based on the risk the device may present to a consumer who uses it in the intended way.

FDA offers only a few general guidelines with respect to chemicals. For menstrual tampons and pads, it recommends—but does not require—that products should not contain two specific dioxin products or “any pesticide and herbicide residues.” Dioxins are a chemical by-product of the bleaching process to whiten cotton, and they are associated with . Using non-chlorine bleaching methods can .

The most stringent regulation of tampons in the U.S. occurred after an illness called became a public concern in the 1970s and 1980s. Menstrual toxic shock syndrome occurs when the bacteria Staphlococcus aureus grows in the vagina on inserted menstrual products and releases a toxin called TSST-1. This substance can be absorbed through the vaginal mucosa and cause a variety of symptoms, including .

During , in which at least 52 cases were recorded and seven people died over a period of eight months, —especially a highly absorbent tampon called Rely, which was pulled from the market.

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The U.S. Food and Drug Administration as Class II medical devices, which carry moderate to medium risk. (Photo: iStock)

In response, the FDA that recommended standardizing the tampon absorbencies and advised consumers to use the lowest absorbency for their flow. This is why tampons in the U.S. now come in a range of absorbencies, from light through regular to super and ultra, so that users can choose the level they need while minimizing risk of toxic shock.

Living in a ‘soup of chemicals’

Just because a chemical is present in a menstrual product doesn’t mean it can get into the body. However, chemicals like and are . So it’s important to study whether harmful chemicals present in menstrual products could contribute to health problems.

Humans in the modern world live in what , former director of the , calls a “.” Simply being present on Earth means being exposed to many chemicals, at different concentrations, all at once. This makes it difficult to unravel the relationship between a single chemical exposure and health.

Nonetheless, science has shown that chemical exposure from at least one menstrual product—vaginal douches—does affect health. is the process of washing or cleaning the inside of the vagina with water or other fluids.

The American College of Obstetricians and Gynecologists , which can harm healthy bacteria in the vagina, increasing the risk of .

In addition, a 2015 study found that women who use vaginal douches have higher concentrations of . Exposure to this substance is associated with , such as reduced fertility and increased pregnancy risk.

Can these chemicals be absorbed?

Scientists are working now to determine what concentrations of metals and other chemicals can leach out of tampons and other menstrual products. One 2025 study estimated that volatile organic compounds, a group of chemicals that vaporize quickly, can be . Volatile organic compounds may be as part of fragrances, adhesives or other product components.

My team and I are now shifting our focus to the relationship between menstrual product use, various chemicals, and menstrual pain and bleeding severity. We want to see whether some chemicals will be elevated in menstrual blood, whether these chemical levels are higher in people who use tampons, and whether the chemicals are associated with greater menstrual pain and bleeding.

States are starting to act on this issue. For example, in 2024, to ban multiple chemicals from disposable menstrual products. California bans PFAS, a widely used group of , . New York adopted a law in December 2025 from menstrual products.

California also that requires manufacturers of disposable tampons and pads to measure concentrations of arsenic, cadmium, lead and zinc in their products, and to share those measurements with the state, which can publish them. More information like this will help support informed choices for millions of consumers who rely on menstrual products every month.

Jenni Shearston is an assistant professor in the Department of Integrative Physiology.

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