In a field outside Piacenza in northern Italy, something invisible is happening in the dirt beneath the lettuce rows. Microplastics — fragments small enough to pass through cell membranes — are accumulating in the soil, and they are not arriving alone. A landmark five-year EU-funded research project, the Minagris initiative, has now confirmed what many soil scientists feared: every single one of the 227 agricultural fields it sampled across 11 European countries contained microplastic contamination. The scale of what those particles are carrying is what makes the findings alarming.

The research, which has produced 22 peer-reviewed studies, found that microplastics function as vectors for pesticides, toxic metals and antibiotic-resistant bacteria. Smaller particles are particularly dangerous because their greater surface area allows them to adsorb — chemically bind — far more pollutants and microbial DNA than larger fragments. Edoardo Puglisi, professor of microbiology at the Catholic University of the Sacred Heart in Piacenza and a lead partner on the project, described the mechanism plainly: "The smaller the microplastics, the more they tend to adsorb pollutants, microbes and DNA, leading to a Trojan horse effect that can potentially increase the diffusion of pathogens and antibiotic-resistance genes." A separate study in Switzerland reinforced the point, finding that fields with the highest concentrations of tyre-wear particles also recorded the highest levels of other toxic chemicals and heavy metals.

The consequences extend up through the food chain. Earthworms, which are architects of soil structure and nutrient cycling, showed disrupted biological processes when exposed to contaminated plastisphere surfaces — the microbial communities that colonise plastic fragments. In controlled experiments, lettuce plants grown in higher microplastic concentrations produced smaller leaves, less chlorophyll and lower biomass.