Key facts
- Microplastics act as a 'Trojan horse' delivering pollutants, pesticides, and bacteria through soil.
- The contamination was found in all 227 agricultural fields tested across 11 European countries.
- Microplastics can create 'plastispheres' that foster interactions between microbes, plastics, and agrochemicals.
- An increase in antibiotic-resistant genes was found within plastispheres, amplified by pesticides.
- Higher microplastic concentrations reduced lettuce leaf area, chlorophyll content, and plant biomass.
- Biodegradable plastics can also degrade into microplastics, causing ecological damage.
A five-year multinational research project, funded by the EU, has revealed that microplastics in agricultural soil across Europe are acting as a "Trojan horse," facilitating the delivery of pollutants, pesticides, and bacteria. The study found microplastics in all 227 agricultural fields tested in 11 European countries, highlighting a persistent global threat to healthy soils, which are crucial for life on Earth. The contamination reflects both current farming practices and historical land use, indicating that plastic pollution can endure for many years.
The research also uncovered that microplastics can interact with other agricultural stressors, such as pesticides and veterinary drugs. In one Swiss study, fields with the highest levels of tyre-wear particles also exhibited the highest concentrations of toxic chemicals and metals. Microplastics create new microbial habitats on their surfaces, known as the plastisphere, which serve as hotspots for interactions between plastics, microbes, and agrochemicals. This environment was found to increase antibiotic-resistant genes, an effect further amplified by pesticides.
Edoardo Puglisi, a project partner and professor of microbiology, explained that smaller microplastics tend to adsorb more pollutants, microbes, and DNA, enhancing the "Trojan horse effect" that can potentially spread pathogens and antibiotic-resistance genes. This phenomenon can disrupt critical soil processes like nutrient cycles, impacting earthworms and other soil organisms vital for soil health. Furthermore, the research indicated that microplastics can negatively affect plant growth, with higher concentrations reducing leaf area, chlorophyll content, photosynthetic efficiency, and plant biomass in lettuce. These effects were amplified when combined with drought conditions.
The findings underscore the need for policy changes, as current environmental assessments often overlook the combined effects of co-occurring pollutants. The researchers advocate for a broader recognition of plastic contamination as part of overall soil degradation. They also noted that biodegradable plastics are not inherently safer, as they can still break down into microplastics and cause ecological harm. Esperanza Huerta Lwanga, a research associate, emphasized the difficulty of removing microplastics once they enter the soil and their role as vectors for agrochemicals, altering soil ecosystems. She called for standardized plastic monitoring, manufacturer transparency, and risk assessments that consider the interaction of microplastics with co-pollutants across different species to protect long-term food production and soil health.