Hundreds of pharmaceuticals and banned chemicals detected in British farmland

More than 520 chemical substances, including pharmaceuticals and toxins banned decades ago, have been detected in agricultural soils across England, according to new research that points to the long-term environmental consequences of spreading treated human waste on farmland.

The study, conducted by scientists at the University of Leeds and published as a preprint in the Journal of Hazardous Materials, identified a wide range of contaminants associated with biosolids — the treated organic material derived from human sewage that is commonly applied to fields as fertilizer. Researchers found that 46.4% of the pharmaceutical compounds detected had not previously been reported in global soil monitoring campaigns.

Among the substances identified for the first time in English soils were the anticonvulsant drugs lamotrigine and carbamazepine, both widely prescribed for human use. The findings also included a number of chemicals that have been banned or withdrawn for decades, suggesting they are far more persistent in soils than previously understood.

Laura Carter, professor of environmental chemistry at the University of Leeds and a lead author of the study, said the results indicate that agricultural soils can act as long-term reservoirs for pollutants. “Some of the chemicals were banned for use decades ago and their presence suggests that they are really persistent,” she said. “Soils are a long-term sink of these pollutants.”

Scientists are particularly concerned about so-called emerging contaminants — pharmaceuticals and industrial chemicals whose environmental and health impacts remain poorly studied, especially once they re-enter ecosystems through food production. Carter said there is a risk that such substances could be taken up by crops and eventually ingested by humans, while also potentially damaging soil health and crop productivity.

Water companies treat wastewater to remove many contaminants before producing biosolids, but the research suggests these processes are not sufficient to prevent large numbers of chemicals from reaching farmland. Some compounds appear to remain in soils for many years after application.

To conduct the study, researchers collected soil samples submitted by farmers and carried out on-site sampling at selected farms. Using techniques including mass spectrometry, the team analyzed the samples to create what Carter described as a “chemical fingerprint” of English agricultural soils.

The findings come as the European Union moves to strengthen wastewater treatment standards by mandating so-called quaternary treatment, an advanced process designed to remove micropollutants such as pharmaceutical residues. The UK, however, currently relies on less advanced tertiary treatment systems and has no plans to introduce quaternary treatment requirements.

“Wastewater treatment processes can remove some contaminants, but we found that the processes are not as efficient as they need to be,” Carter said. “These chemicals aren’t regulated for, so there isn’t a strong drive to develop technologies that can remove them.”

Soil contamination has received far less attention than pollution of rivers and wastewater systems, despite its importance for food production and ecosystem health, the researchers said. Carter cited technical challenges in detecting trace-level chemicals in complex soil environments, as well as limited awareness of how contaminants move through agricultural systems.

While remediation is possible, options are limited. One approach involves growing plants that absorb contaminants from the soil, though this then creates the challenge of safely disposing of polluted biomass.

Carter said she was particularly surprised by the presence of long-banned substances and certain anti-cancer drugs, which have rarely been detected in soil before. She stressed that farmers are not to blame, noting that the use of biosolids has been promoted as a sustainable practice.

“We need proper regulation and better education so everyone understands what is being applied to land and the potential risks associated with it,” she said.