Municipal sewage sludge spread on farmland as fertilizer deposits hundreds of microplastic particles per kilogram of soil, contaminating food crops and accumulating irreversibly over decades

Roughly 50% of sewage sludge (biosolids) produced by wastewater treatment plants in the United States and Europe is applied to agricultural land as fertilizer. This sludge concentrates microplastics from household laundry, personal care products, and industrial discharge — all the plastic particles that wastewater treatment successfully removes from the water end up in the sludge, which is then spread on fields. A 2025 study published in a 25-year longitudinal analysis found that soils receiving annual sludge applications at 30 tonnes per hectare contained 545.9 microplastic items per kilogram, compared to 87.6 items per kilogram at half the application rate. Even untreated control fields contained 664 particles per kilogram, suggesting atmospheric deposition and irrigation add additional contamination. This creates a slow-motion agricultural crisis. Microplastics in soil alter soil structure, reduce water retention, and disrupt the microbial communities that drive nutrient cycling. Research shows that microplastic contamination reduces earthworm survival and burrowing activity — earthworms being essential for soil aeration and organic matter decomposition. Crops grown in microplastic-contaminated soil can uptake nanoplastics through their root systems, meaning the contamination enters the food supply even for consumers who avoid plastic packaging. A farmer who has been applying biosolids for 20 years has been unknowingly loading their topsoil with synthetic polymers that do not biodegrade, and there is no remediation technology that can remove microplastics from millions of acres of agricultural soil. The problem persists because banning biosolid application would create two simultaneous crises: a fertilizer shortage for farmers who depend on cheap nutrient-rich sludge, and a waste disposal crisis for wastewater utilities that currently offload millions of tons of sludge to agriculture. Landfilling sludge is expensive and creates its own environmental problems. Incineration destroys the plastics but also destroys the nutrient value and generates air pollution. Wastewater treatment plants were designed to clean water, not to produce plastic-free solid waste. Upgrading them to remove microplastics from sludge before land application would require entirely new treatment processes — and there is no regulatory mandate to do so, because biosolids regulations focus on heavy metals and pathogens, not synthetic polymer particles.