Integrating experimental data and mechanistic modeling to assess potential lead exposure from tampon use

Trace levels of lead (Pb) have been reported in tampons, prompting concerns about potential exposure during menstrual product use. However, the presence of a chemical in a product does not necessarily translate to biologically relevant exposure. In this study, we characterized the distribution and binding of Pb in menstrual fluid and developed a deterministic, compartmental mass-balance model to evaluate the release and fate of Pb that may be present as an inadvertent trace impurity in tampons. Our experimental measurements demonstrated that Pb preferentially partitions to the red blood cell (RBC) fraction of menstrual fluid. The remaining Pb was distributed in the plasma fraction, where the majority was protein-bound. These distribution and binding characteristics were broadly comparable to those reported for systemic blood. Utilizing these data, a mechanistic model was parameterized to describe the release of Pb from a tampon into menstrual fluid, partitioning between menstrual fluid compartments, reabsorption into the tampon during fluid uptake, and potential permeation across vaginal tissue. Under the conservative assumptions evaluated here, model simulations for a 4-h tampon wear scenario predicted that the majority of theoretically released Pb is reabsorbed into the tampon, with only a very small fraction (<1 ng; <0.3%) available for potential absorption into vaginal tissue. Sensitivity and alternative release scenario analyses demonstrated that predicted tissue uptake remained minimal across various plausible conditions. Collectively, these findings underscore the importance of integrating chemical presence data with physiological context and mechanistic modeling to inform exposure assessment and support science-based evaluation of product safety.