Overview
Ellison et al. measured endogenous and experimentally spiked lead (Pb) in menstrual fluid fractions and used those data in a deterministic mass-balance model for tampon use. The source is exposure and bioavailability evidence for the menstrual-tampon category, not product-occurrence evidence: product Pb content was taken from a prior total-digestion tampon study and then modeled through menstrual-fluid partitioning, tampon reabsorption, and potential vaginal-tissue uptake.
Key numbers
The study measured endogenous Pb in whole menstrual fluid, menstrual-fluid-derived plasma, and menstrual-fluid-derived red blood cells. Across the donor-to-donor comparison, whole menstrual-fluid Pb ranged from 0.98 to 4.81 ppb, with a group average of 2.98 +/- 1.28 ppb. The corresponding averages were 0.47 +/- 0.31 ppb in menstrual plasma and 1.46 +/- 0.55 ppb in menstrual red blood cells.
For exogenous Pb added to day-2 menstrual fluid, Table 5 reports 60-minute incubations at 1, 10, and 25 ng/mL. At the 10 ng/mL dose, whole menstrual-fluid Pb averaged 13.44 +/- 3.28 ng/mL for donor RP54 and 11.16 +/- 4.76 ng/mL for donor RP83. Menstrual-plasma Pb at that dose averaged 0.38 +/- 0.23 ng/mL for RP54 and 5.69 +/- 3.54 ng/mL for RP83, while menstrual-RBC Pb averaged 11.03 +/- 2.73 ng/mL for RP54 and 4.93 +/- 2.18 ng/mL for RP83. Six additional donors dosed at 10 ng/mL had whole menstrual-fluid averages from 10.21 to 15.17 ng/mL.
Table 6 reports partition coefficients for Pb distribution in menstrual fluid. With exogenous 10 ng/mL Pb, the menstrual-RBC:menstrual-plasma partition coefficient averaged 14.1 across all eight donors and 2.6 when the high-partitioning RP54 donor was excluded. The corresponding whole-menstrual-fluid:menstrual-plasma coefficient averaged 4.3 across all donors and 1.4 without RP54.
Table 7 reports the unbound Pb fraction in plasma. In menstrual-fluid-derived plasma dosed with 10 ng/mL Pb, the four-donor pool had 12.2 +/- 1.5% unbound Pb. Dose-response values ranged from 1.2% to 3.6% for donor RP54 and from 3.2% to 10.3% for donor RP83. In systemic plasma, the unbound fraction was 21.4 +/- 10.9% at 1 ng/mL, 6.3 +/- 0.5% at 10 ng/mL, and 7.5 +/- 0.8% at 25 ng/mL.
The baseline mass-balance simulation assumed 264 ng Pb in a 2.2 g tampon, derived from Shearston et al.’s reported geometric mean of 120 ng/g under total-digestion conditions. The model released that 264 ng continuously over a 4-hour wear period at 66 ng/hour. At the end of the baseline 4-hour scenario, the model predicted 87.39% of released Pb reabsorbed into the tampon, 9% associated with menstrual-fluid red blood cells, 3.4% in menstrual plasma, and 0.22% or 0.58 ng potentially permeated into vaginal tissue. In two alternative release scenarios, potential tissue absorption remained about 0.25% of released Pb.
Methods (brief)
Participants collected menstrual fluid with menstrual cups over 24-hour periods. The authors separated whole menstrual fluid into plasma and red-blood-cell fractions by centrifugation, measured hematocrit, and quantified Pb by microwave digestion and ICP-MS using an Agilent 7900 instrument. Exogenous Pb experiments used lead(II) acetate trihydrate added to menstrual fluid at 1, 10, or 25 ng/mL, with incubation times of 10, 60, or 240 minutes depending on the experiment.
The model represented four compartments: menstrual-fluid-derived plasma, menstrual-fluid-derived red blood cells, vaginal tissue as cumulative uptake, and tampon reabsorption as cumulative mass. It used a release rate of 66 ng/hour, menstrual-fluid absorption into the tampon of 1 mL/hour, free menstrual-fluid volume of 0.5 mL, exposed vaginal-tissue area of 21 cm2, a conservative apparent permeability coefficient of 1 x 10^-6 cm/s, an unbound fraction of 0.12 in menstrual plasma, and an RBC:plasma partition coefficient of 2.6.
Implications
Microbiome: Not applicable.
Related evidence
Update history
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