More than 520 chemicals have been detected in soils across England, including pharmaceutical residues and toxins banned decades ago, according to new research that raises concerns about long-term contamination from treated human waste used as fertiliser. The study, led by scientists at the University of Leeds and published as a preprint in the Journal of Hazardous Materials, suggests that the practice of spreading biosolids on farmland is allowing hundreds of chemicals to enter and persist in agricultural soil.
The researchers found that almost half of the pharmaceutical substances identified in English soils—46.4%—had never been reported in previous global monitoring campaigns. Among the newly detected medicines were the anticonvulsants lamotrigine and carbamazepine, both widely used in human healthcare and now emerging as contaminants in the environment. Scientists warn that these “emerging contaminants” remain poorly understood, especially in terms of how they interact with ecosystems and re-enter the food chain.
Chemicals Persist in Soil for Decades Despite Treatment
Water companies remove contaminants from wastewater during treatment, producing biosolids—organic matter derived from human waste—which are often spread on farmland as a nutrient-rich fertiliser. However, the research shows that many chemicals survive the treatment process and accumulate in soil, including several substances banned long ago. Their persistence highlights a growing environmental challenge.
Lead researcher Professor Laura Carter said the findings show that soils serve as a long-term reservoir for pollutants. She warned that chemicals lingering in the soil may eventually enter the food chain or undermine crop health and agricultural productivity. Previous work by her team already documented the uptake of contaminants in crops and the effects on soil quality.
The study collected soil samples from farms across England, with researchers using mass spectrometry and other techniques to build a “chemical fingerprint” of the soils. The analysis revealed not only persistent legacy chemicals but also traces of anti-cancer drugs—substances rarely monitored and not previously detected in UK farmland soils.
UK Lags Behind EU on Removal of Micropollutants
The findings come as the EU prepares to introduce mandatory “quaternary treatment” for wastewater facilities, an advanced system designed to remove micropollutants such as pharmaceuticals. The UK currently has no plans to adopt this higher standard and continues to rely on older tertiary treatment systems, which researchers say are less effective.
Professor Carter stressed that although some contaminants are removed during treatment, the process is not efficient enough to prevent widespread soil pollution. Because these chemicals are not regulated, there is little incentive for water companies to adopt advanced removal technologies. Soil monitoring also remains limited due to analytical challenges and low awareness of contamination pathways.
Urgent Need for Regulation and Awareness
The study emphasises that farmers are not to blame, as they have been encouraged to use treated biosolids to support sustainable agriculture. Instead, researchers argue that policymakers must create proper regulations and raise awareness about the risks associated with chemical residues in biosolids.
Carter highlighted that contaminants can be removed through techniques such as cropping systems designed to absorb pollutants, though these generate new problems in disposing of the contaminated plants. The persistence of banned chemicals was one of the most surprising findings, underlining the long-lasting impact of legacy pollution on soil health.
The research adds to mounting evidence of widespread environmental contamination in the UK, following recent reports on polluted rivers, sewage discharges, and growing concerns about microplastics and chemical build-up in natural ecosystems.
