When organisms in the environment are exposed to microplastics, it may weaken their ability to handle other threats—such as infections or toxic chemicals. This study explored that idea using Porcellio scaber, a small land-dwelling crustacean (commonly called a woodlouse), to see whether tire-derived microplastic particles in soil affect their immune system, especially when faced with a second stressor.
The woodlice were first exposed for 14 days to tire particles mixed into soil, at levels that could occur in the environment. After this, they were injected with a bacterial substance called lipopolysaccharide (LPS), which simulates an infection and triggers an immune response. For comparison, another group of woodlice was exposed to a known insecticide, chlorpyrifos, which served as a positive control. Researchers then measured survival and immune responses, such as blood cell counts and cell activity.
Exposure to tire particles or chlorpyrifos alone did not affect the woodlice’s survival. However, chlorpyrifos caused a strong immune reaction, while tire particles had a weaker effect. After the simulated infection, there were no changes in survival in any group, but the immune system showed noticeable changes—especially in animals that had first been exposed to chlorpyrifos.
These results suggest that while tire particles do not appear to increase the risk of death from a second stressor, they may subtly alter how the immune system responds. The study supports the idea of using a “stress-on-stress” testing method, where organisms are first exposed to a pollutant like microplastics and then to a second challenge, to better understand the real-world impacts of low-toxicity substances.
Read the full study here: https://www.sciencedirect.com/science/article/pii/S0048969724018400?via%3Dihub