Exposure to plastic particles alters sex hormones and promotes inflammation in rats, a new study shows. Estrogen levels in female rats that inhaled tiny particles of polyamide – commonly known as nylon – decreased and inflammatory cytokines increased.

Researchers exposed female rats in heat to aerosolized polyamide particles for an average of 4.5 hours. Then they assessed the animals' overall health and measured their cytokine and reproductive hormone levels. They found that after a single exposure to the polyamide particles, the animals' blood pressure increased, estradiol (a form of estrogen) decreased, and pro-inflammatory cytokine interleukin-6 increased.

Small plastic particles, often referred to as microplastics (ranging between 5 millimeters and 100 nanometers) or nanoplastics (less than 100 nanometers), are ubiquitous environmental pollutants. They have been identified in food (especially seafood), soil, drinking water, fresh- and saltwater bodies, and air.

Exposure to microplastics is associated with a wide range of negative health outcomes in humans. For example, a comprehensive review of the effects of microplastics revealed that the pollutants induce oxidative stress and increase the risk for metabolic dysfunction, neurotoxicity, and some cancers. Some of these effects may be due to compounds commonly associated with plastic manufacturing, such as bisphenol A, or BPA, phthalates, and heavy metals, that are present in and on microplastics.

This study demonstrates that even brief exposure to plastic particles is sufficient to alter sex hormones and promote inflammation in female rats.

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