Summary
We found that the application of biosolids from sewage sludge represents an important source of microplastics (MP) to agricultural soils. Soils that received more biosolid treatments in the past exhibit higher levels of MPs, demonstrating progressively increasing pollution. Soil organisms underpinning important ecological and agricultural functions interact with these MPs experiencing sublethal health effects at realistic environmental concentrations. Soil is a non-renewable resource and soil MP pollution is irreversible. To enable sustainable and circular use of sewage sludge, measures that prevent MPs accumulating in it, or that remove them prior to use are necessary.