A five-year multinational research project has revealed that microplastics in soil act as a "Trojan horse," transporting pollutants, pesticides, and bacteria, thereby posing a significant global threat to soil health. The EU-funded study analyzed soil samples from 227 agricultural fields across 11 European countries, finding microplastics present in every location tested. Researchers emphasized the critical importance of healthy soils for sustaining life on Earth and highlighted that plastic contamination reflects both current agricultural practices and historical land use, illustrating the long-lasting nature of plastic pollution.

The research further identified that microplastics can interact with various agricultural stressors, including pesticides and veterinary drugs, potentially amplifying their harmful effects. A study conducted in Switzerland found that fields with the highest concentrations of tyre-wear particles also exhibited elevated levels of toxic chemicals and heavy metals. Microplastics provide surfaces known as the “plastisphere,” which act as microbial habitats and hotspots for complex interactions among plastics, microbes, and agrochemicals.

Edoardo Puglisi, a microbiology professor at the Catholic University of the Sacred Heart in Piacenza, Italy, described how smaller microplastics are particularly effective at adsorbing pollutants, microbes, and DNA, which can facilitate the spread of pathogens and antibiotic-resistant genes. This “Trojan horse effect” may disrupt critical soil processes and affect organisms such as earthworms, which play an essential role in shaping soil microbiomes and maintaining ecological functions.

The project, conducted in collaboration with the Countryside and Community Research Institute at the University of Gloucestershire, also examined the impact of microplastics on plants. One study found that higher microplastic concentrations reduced leaf area, chlorophyll content, photosynthetic efficiency, and overall biomass in lettuce. These negative effects were further intensified when combined with drought stress, leading to poorer plant performance than under either condition alone.

Researchers noted that environmental assessments often evaluate pollutants individually, but their findings suggest that contaminants may interact in complex ways when present together, necessitating a broader approach to soil pollution management. Although biodegradable plastics have been increasingly used to address plastic pollution, the research cautioned that these materials are not inherently safer. Biodegradable plastics can still fragment into microplastics, potentially contributing to ecological damage.

Experts involved in the study called for updated policies to protect long-term soil health and food production. Key recommendations include the establishment of standardized plastic monitoring protocols, greater transparency from manufacturers, and comprehensive risk assessments that consider how microplastics interact with co-pollutants across various species and ecosystems.