Mouse Study Tracks Microplastics Into Liver Immune Cells

A new study in mice suggests that the size of a plastic particle may shape what it does once it reaches the body. Researchers led by the University of Bonn, publishing September 29, 2026 in Nature Metabolism, followed polystyrene particles fed to young male mice and found that bacteria-sized microplastics built up in the liver’s immune cells, while much smaller nanoplastics went elsewhere.

What the researchers did

Mice received polystyrene particles by mouth once a week for 12 weeks. The team compared two sizes:

• Microplastics about 500 nanometres across — roughly the size of a bacterium
• Nanoplastics about 50 nanometres across — ten times smaller

What they found

Liver immune cells were the main reservoir. Kupffer cells, the macrophages that line the liver’s smallest blood vessels, were the main place in the liver where the particles collected.

Microplastics clogged them. The larger particles built up in the cells’ lysosomes — the compartments that normally break down what they engulf — and the cells got worse at clearing other cells from the blood.

A signal to store fat. The Kupffer cells also produced more apolipoproteins, which the researchers describe as a stress signal that, they suggest, prompts surrounding liver cells to store more fat. On a high-fat diet, microplastics made that fat build-up worse.

Nanoplastics acted differently. The smaller particles caused much less clogging and left liver metabolism largely unchanged. Instead they built up in brown fat, activated it, and altered glucose handling in mice on the high-fat diet.

The caveats

This is mouse research, not evidence of effects in people. The study used mainly young male mice and one plastic type (polystyrene); the authors say it is still unknown whether females respond the same way. After a six-month break from exposure, particles were still detected in the liver, but the liver changes had improved.

Do not read this as a diagnosis, an exposure limit, or a claim about human “fatty liver disease.” The finding is about fat storage in mice under controlled lab conditions.

What it means for readers

The study adds detail to an open research question: what ingested micro- and nanoplastics do once they reach organs such as the liver. It does not set any exposure limit or show a health risk for people. More research will be needed.

A note on scope: this post summarises a peer-reviewed animal study and its university news release. It is not medical advice, and Hydrology University was not involved in the research. Illustration credit: NIAID (public domain).

Sources

• Makdissi, N. et al. “Size-dependent plastic exposure disrupts macrophage function and tissue-specific metabolism.” Nature Metabolism (2026). DOI: 10.1038/s42255-026-01615-8
• University of Bonn news release (Sep 2026): uni-bonn.de/en/news/191-2026 — use Bonn for background wording only; do not reuse their headline (“Cause Fatty Liver Disease”).

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