The findings shed light on how tiny plastic particles interact with human cells, but do not show that exposure causes disease or establish the health risks of long-term exposure, the researchers say.

Nanoplastics form when larger plastic items break down. They are thousands of times smaller than the thickness of a human hair and can enter the body through food, water and inhaled air before reaching the bloodstream. Their presence has been confirmed in human tissues, but scientists still do not know the consequences of long-term exposure.

“We know more about how nanoplastics affect human cells, yet we still cannot assess the actual risk posed by daily exposure. Answering this question requires long-term studies that combine laboratory observations with population-based research,” says study co-author Professor Marek Jutel of the Department of Clinical Immunology at Wroclaw Medical University, quoted in a university press release.

The researchers, including scientists from Wroclaw Medical University, examined the effects of polystyrene nanoplastics on human peripheral blood mononuclear cells (PBMCs). These include T cells, B cells and monocytes, which play important roles in the immune response.

They used several methods to track the interaction between nanoplastics and the cells, from the particles entering the cells and triggering structural and metabolic changes to changes in gene activity within individual cells.

The observations showed that nanoplastics penetrated the immune cells and remained in their cytoplasm. One of the key findings was a change in mitochondrial function.

Mitochondria generate the energy required by cells and also play roles in regulating cell activity, survival and immune responses. The scientists observed a decline in mitochondrial respiration and the production of ATP, the cell’s primary energy carrier. The cells also became less able to respond to increased energy demands.

At the same time, the mitochondria changed structurally, becoming smaller and more compact, which indicated severe cellular stress.

“After just one hour of exposure, we observed mitochondrial dysfunction and the activation of cellular stress mechanisms. This demonstrates that even brief contact with nanoplastics can affect fundamental processes within immune cells,” Jutel says.

Gene activity analysis revealed another change. The researchers identified a population of cells that appeared only after exposure to nanoplastics. They called these “stress cells” because they were in a state of severe stress.

These cells increased production of proteins that protect against damage and help repair misfolded proteins. At the same time, the activity of genes associated with normal mitochondrial function decreased.

According to the researchers, this suggests that some cells respond to nanoplastics by shifting away from their primary functions and activating mechanisms that help them survive under adverse conditions.

The scientists also examined whether nanoplastics affected basophils, cells involved in allergic reactions and other immune processes. They found no increase in basophil activation, suggesting that nanoplastics do not affect all components of the immune system in the same way.

“Our results show that nanoplastics can penetrate immune cells and disrupt their metabolism. While this does not yet establish a link to specific diseases, it reveals a biological mechanism worthy of further research,” says Magdalena Zemelka-Wiącek, PhD, a professor at the Department of Clinical Immunology at Wroclaw Medical University.

The study was conducted on cells under laboratory conditions. It therefore cannot determine the health effects of daily, long-term exposure to nanoplastics in humans. However, the findings reveal processes occurring inside cells exposed to the particles and point to areas for further research.

The authors draw on the One Health concept, which views human, animal and environmental health as interconnected.

“The problem of plastic pollution no longer concerns only the environment. Our study shows that its effects can also be observed at the level of human cells, which is why research combining medicine, toxicology and environmental sciences is needed,” Zemelka-Wiącek adds.

The researchers say completely avoiding microplastics and nanoplastics is no longer possible, but some sources of daily exposure can be limited. They recommend not heating food in plastic containers, as high temperatures may increase the release of tiny plastic particles; storing hot or sour food in glass or stainless steel; limiting the use of single-use plastic bottles and packaging where possible; regularly vacuuming and airing the home, as microplastics can accumulate in household dust; and choosing clothes made from natural fibres where possible to reduce the release of synthetic microfibres during washing. (PAP)

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