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Microplastics infiltrate global farmland and food supply
Tiny plastic fragments, now pervasive in soil and water, are entering crops and raising concerns about long-term health risks, researchers warn.
Widespread contamination
Microplastics have been detected in nearly every ecosystem-from Antarctic ice to deep-sea trenches and drinking water. A 2021 study estimated 24.4 trillion microplastic fragments float in the world's oceans. On land, European farmland may hold the largest reservoir, with 31,000 to 42,000 tonnes of microplastics added annually through sewage sludge used as fertilizer.
Researchers at Cardiff University found one UK wastewater treatment plant alone released 650 million microplastic particles daily into sewage sludge, which later spread on fields. Catherine Wilson, a co-author of the study, called the figures "probably an underestimation," noting many particles are too small to detect.
From soil to supper
Microplastics persist in soil for decades. A German study found plastic fragments 90cm underground 34 years after sludge application. Ploughing further disperses particles, while rain washes them into rivers and oceans. A Canadian study revealed 99% of microplastics eventually enter aquatic environments.
Plants absorb the smallest particles-nanoplastics measuring 1-100 nanometers-through root cracks. Willie Peijnenburg of Leiden University found most plastics accumulate in roots, with minimal amounts reaching leaves. Root vegetables like carrots showed the highest contamination in a 2020 Italian study, while apples topped the list among fruits.
"Concentrations in leaves are well below 1%, but root vegetables pose a greater risk," Peijnenburg said.
Toxic legacy
Microplastics leach harmful chemicals into soil, including PFAS-"forever chemicals" linked to cancer and developmental issues. A UK Environment Agency report found sewage sludge destined for farmland contained dioxins and polycyclic aromatic hydrocarbons at levels posing potential health risks.
Plastics also disrupt soil ecosystems. Earthworms exposed to microplastics lost weight and grew more slowly, likely due to digestive blockages. Kansas University research showed plastic increased cadmium uptake in wheat, a toxic heavy metal.
Health risks emerge
While human health impacts remain unclear, studies suggest cause for concern. University of Hull researchers found microplastic ingestion approaches levels that damage human cells, triggering inflammation, allergic reactions, and oxidative stress.
"We know microplastics can cross cell barriers and break them," said Evangelos Danopoulos, the study's lead author. "Irregularly shaped particles were most likely to cause cell death."
Chemicals in plastics may disrupt hormones, with links to heart disease and poor fetal development. Danopoulos questioned whether sludge should be used as fertilizer given the risks: "If plants extract microplastics from soil, should we keep spreading contaminated sludge?"
Policy responses vary
The Netherlands banned sludge fertilizer in 1995, while Switzerland followed in 2003, citing harmful substances. Maine became the first US state to prohibit the practice in 2022 after PFAS contamination forced farm closures. The law bans sludge-based compost but allows exports.
Wilson argued against total bans, warning they could push farmers toward synthetic fertilizers made from fossil fuels. Instead, she proposed incinerating high-microplastic sludge for energy or extracting fats and oils-major plastic carriers-for biofuel.
Call for urgent action
Researchers agree more data is needed on microplastic levels in soil and their health effects. Danopoulos warned microplastics could shift from "contaminant" to "pollutant" if proven harmful, requiring stricter regulations.
"It will take decades to remove plastics from the environment," Peijnenburg said. "Even if risks are low now, persistent chemicals will accumulate."
Without intervention, the problem will worsen, underscoring the need for global strategies to curb plastic pollution at its source.
