New framework quantifies metal exposure risks from tampon use

Metals such as lead, arsenic, cadmium, and mercury have been detected in tampons in recent years, triggering widespread public alarm and headlines about “toxic metals” in menstrual products. But a new study argues that detection is not the same as danger. For the first time, researchers have moved beyond simply measuring what is inside a tampon and instead asked the question that actually determines health risk: how much of those metals can leach out under real-world conditions, cross vaginal tissue, and enter the bloodstream? The answer, according to a rigorous new risk assessment, is vanishingly little — so little, in fact, that even exposure scenarios 10,000 times worse than anything physiologically plausible still leave enormous safety margins.

The study, published in the journal Environmental Advances, was conducted by a team of toxicologists led by Aryatara Shakya of TRC Environmental, working in collaboration with Charles River Laboratories in Edinburgh, United Kingdom. Rather than relying on bulk content measurements alone — the approach that dominated earlier research, including a widely publicized 2024 study that found metal(loid)s in every tampon tested — the team built an experimental framework designed to translate trace metal content into an estimate of actual absorbed dose. That distinction matters because, as critics of the earlier work pointed out, finding lead at nanogram-per-gram levels in a product tells you nothing about whether the body ever takes it up.

The researchers focused on six elements chosen for their toxicological relevance and their routine appearance in regulatory biocompatibility evaluations: arsenic, cadmium, cobalt, chromium, lead, and mercury. Trace amounts of these metals are ubiquitous in plant-derived textiles like cotton and rayon, introduced through uptake from soil, atmospheric deposition, agrochemicals, and industrial processing — not intentional addition. The team confirmed this baseline, detecting all six metals in dry tampon material at low nanogram-per-gram concentrations, with lead the only element reliably quantifiable, at a mean of about 88.7 ng/g — consistent with the geometric mean of 120 ng/g reported across 30 tampons from 14 brands in the 2024 study.

The first experimental phase simulated actual use. Whole commercial tampons were incubated in 12 milliliters of artificial menstrual fluid for 12 hours at 37 degrees Celsius — deliberately longer than the average wear time of roughly 4.4 to 4.6 hours and even the labeled maximum of 8 hours, to maximize per-tampon metal release. The artificial menses fluid was formulated to be physiologically realistic, containing hemoglobin, albumin with sulfhydryl groups, and ferrous iron at a slightly alkaline pH of 7.4, mimicking the chemistry of real menstrual blood. The results were striking: metal release into the fluid was minimal across all six elements, with most concentrations falling at or below the limits of quantification. Lead was again the only metal quantifiable, peaking at 3.4 ng/mL — a mass-transfer figure directionally consistent with the modest drop in lead measured in the soaked tampon material itself.

The second phase addressed the critical unknown: whether metals that do leach out can penetrate vaginal tissue. The team used the EpiVaginal full-thickness model, a three-dimensional reconstructed human vaginal-ectocervical tissue built from primary human epithelial cells and fibroblasts cultured at an air-liquid interface. The model, in use since 2003, forms stratified, multilayered tissue with tight junctions and desmosomes that closely mimics the non-keratinized, highly vascularized vaginal mucosa — the only commercially available model of its kind. Tissues were exposed for 12 hours to the raw leachate and to two surrogate solutions prepared at 1,000-fold and 10,000-fold the measured leachate concentrations, deliberately creating worst-case bounding scenarios.

After exposure, the researchers measured metal distribution across three compartments: a rinse fluid capturing surface-associated material, the tissue itself, and a receptor fluid representing the bloodstream side of the epithelial barrier. The pattern was unambiguous. For every metal at both surrogate concentrations, the vast majority of recovered mass — between 50 and 95 percent — stayed in the rinse, meaning it remained surface-bound and would simply drain away with menstrual flow. Tissue-associated fractions were modest, and transfer into the receptor fluid was nearly absent: detectable only for arsenic, chromium, and lead, and even then representing just fractions of a percent to a few percent of the applied dose. Transepithelial electrical resistance measurements confirmed the tissue barrier remained intact throughout, with no exposure-related impairment.

The final step was quantitative risk characterization using the margin of safety (MoS) approach codified in ISO 10993-17, the international standard for toxicological risk assessment of medical device constituents — a framework particularly apt here because the U.S. FDA classifies tampons as medical devices. The team calculated estimated daily exposure doses, combining the maximal single-tampon release with an aggressive assumption of six tampons per day, and compared those doses against permitted daily exposure values from the ICH Q3D guidance on elemental impurities. Parenteral PDEs were deliberately chosen as conservative benchmarks, since they assume direct delivery into systemic circulation without any reduction from incomplete absorption.

Under the measured leachate conditions, the results were emphatic. Margin of safety values — where a value of at least 1 indicates acceptable risk — ranged from approximately 97,000 for cobalt to roughly 64.5 million for chromium. Even under the deliberately extreme 10,000-fold surrogate scenario, which has no plausible physiological basis, all margins remained above unity, from about 24 for cadmium to nearly 4,000 for chromium. A sensitivity analysis that assumed six tampons used every single day of the year — an obviously impossible scenario — still left all margins above the acceptance threshold, with cadmium, the most conservative case, at approximately 3.9.

The implications for lead, the metal that generated the most public concern following the 2024 findings, are particularly significant. Because no threshold exists for lead neurotoxicity, the team evaluated absorbed dose rather than product content. They estimated systemic lead exposure of roughly 0.00001 micrograms per day under real leachate conditions — thousands of times below the FDA’s interim reference level of 8.8 micrograms per day for females of childbearing age. The predicted contribution to blood lead would be well below 0.01 micrograms per deciliter, analytically indistinguishable from background. Blood lead levels, the authors conclude, are unlikely to differ measurably between tampon users and non-users. Their findings also align with independent mechanistic modeling published in Toxicological Sciences in 2026, which predicted that less than 1 percent of lead released from a tampon would be taken up by vaginal tissue, and that lead naturally present in menstrual fluid exceeds the amount absorbed from the product itself.

For chromium, the team addressed the speciation question by attributing measured total chromium to Cr(III), the form that predominates in plant-derived materials and is actively generated by the reductant-rich chemistry of menstrual fluid, which converts any Cr(VI) to Cr(III) at physiological pH. Even under a precautionary assumption that all chromium were the more hazardous Cr(VI), the margin of safety would still be roughly 6,030 under actual use conditions.

The authors are careful to situate their findings in a broader risk-communication context. Ultra-trace detection at nanogram levels, they note, reflects the extraordinary sensitivity of modern analytical instrumentation, not evidence of harm. Professional toxicology organizations, including the American College of Medical Toxicology, have already cautioned that detection-only messaging can foster undue alarm — and in some cases dangerous responses such as unnecessary chelation therapy. Tampons, they emphasize, serve an important public health function, supporting education, employment, and daily life for hundreds of millions of people worldwide.

The study does have limitations: it evaluated a single commercial product, did not analytically determine chromium speciation, and, like all in vitro systems, cannot fully replicate living vaginal physiology with its hormonal cycling, mucus turnover, and microbiome activity. But the researchers argue these factors cut toward conservatism — the static design likely overestimates contact time, and the tissue model may be more permeable than native mucosa. The regulatory timing is notable: the FDA has initiated bench studies of metal release from tampons, and the International Organization for Standardization’s technical committee TC 338 is developing global safety standards for menstrual products. The framework established here — leaching under physiological conditions, direct measurement of epithelial permeation, and absorbed-dose-based risk characterization — offers regulators a reproducible template. The arithmetic, the authors note, is ultimately constraining: a tampon containing a metal at even one part per million holds only a few micrograms in total, and only a fraction leaches, and only a fraction of that crosses tissue. Realistic worst cases simply cannot approach toxicological thresholds — and now, for the first time, that conclusion rests on direct experimental evidence rather than assumption.