2024 AIChE Annual Meeting

Chemical Analysis of Nanoplastics Shed from Tampons

For many people around the world, tampons are an accessible and easy-to-use period product. Researchers have been increasingly focused on synthetic polymers (plastics) fragmenting into micro- and nanoplastics (<1000 nm) and their environmental impact, but not much work has been done on studying toxicity to humans. A 2021 preliminary study found that tampons release up to 17 billion nanoplastic (<1000 mm) particles per use, with currently unknown adverse health effects. Before determining the potential health implications, the chemistry of components and shed nanoparticles from 5 commercially available tampon brands have been analyzed.

To begin, the chemical analysis of tampon components–such as the outer casing, inner core, and string–were recorded via attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR). The peaks for notable functional groups were identified in the infrared spectra of the components to determine the composition. Particles were collected through a process meant to mimic physiological conditions and normal wear. Two different solvents were used to limit background interference during FTIR analysis–phosphate buffered saline (PBS) and deionized water. The solvents were filtered to limit potential particles from the solvents and adjusted to between pH 3.8 and 4.2. Samples were taken from different brands of regular absorbency tampons, placed in the pH-adjusted filtered solvent then in a 37℃ water bath on a shaker table at 100 rpm for 4 hours. Next, any large particles (>1000 nm) were filtered out and the samples’ pHs were adjusted to neutral to prevent excess degradation of the samples. To confirm the presence of nanoparticles in the samples, the concentration and average size of the particles were measured via nanoparticle tracking analysis. Once confirmed, the samples were freeze dried and analyzed via ATR-FTIR.

The FTIR analysis for tampon components was performed by matching peak wavenumbers; this showed that 2 out of 5 brands contain cotton (1030, 1310-1320, 2890-2900, 3330 cm-1), 2 brands contain polyester (721, 872, 1020, 1100, 1240, 1710, 2970 cm-1), 3 brands contain polyethylene (717, 1470, 2850, 2910 cm-1), 1 brand contains polypropylene (1380, 1460, 2840-2950 cm-1), 3 brands contain rayon (1020, 1370, 2890, 3350 cm-1), and 1 brand contains wax paper [believed to be paraffin coated cellulose] (1030, 1320-1460, 2850, 2920, 3340 cm-1). Nanoparticle tracking analysis measured average size between 129.9 and 309.7 nm and average concentration of up to 376 million particles. The FTIR analysis of the particle samples is harder to analyze because of background interference.

The ATR-FTIR analysis performed on the tampon components showed various types of plastics. Furthermore, the nanoparticle tracking analysis confirmed that millions of particles were being shed from tampons. However, future work needs to be done to further investigate the chemical composition of the particles shed.