A major scientific study has uncovered a startling chemical cocktail within English agricultural soils, raising significant concerns about the long-term practice of using treated human waste as fertiliser.
A Chemical Fingerprint in the Soil
Research led by scientists at the University of Leeds has detected more than 520 different chemicals in soil samples taken from arable land across England. The findings, published as a preprint in the Journal of Hazardous Materials, highlight a worrying array of substances, from modern pharmaceuticals to toxins banned decades ago.
The source of this contamination is linked to the widespread agricultural use of treated biosolids. Water companies process human waste, removing some contaminants to create this organic material, which is then spread on fields as a sustainable fertiliser. However, the study indicates that current treatment processes are insufficient, allowing hundreds of chemicals to leach into and persist in the soil.
Professor Laura Carter, an environmental chemistry expert at the University of Leeds and one of the study's authors, stated: "Some of the chemicals were banned for use decades ago and their presence suggests that they are really persistent … so soils are a long-term sink of these pollutants."
Banned Substances and New Discoveries
The research team employed advanced techniques like mass spectrometry to create a detailed "chemical fingerprint" of the soil. Alarmingly, close to half (46.4%) of the pharmaceutical substances they found had never been reported in previous global soil monitoring campaigns.
Among the human-use medicines detected for the first time in English soils were the anticonvulsants lamotrigine and carbamazepine. The study also revealed the presence of several anti-cancer drugs, a discovery that surprised researchers due to the lack of existing data in this area.
Of particular concern are "emerging contaminants"—pharmaceuticals and other chemicals whose environmental and health impacts are not yet fully understood, especially as they potentially re-enter the food chain through crops.
Regulatory Gap and Environmental Risk
The persistence of these pollutants presents a dual threat. Firstly, they could be taken up by crops and eventually ingested by humans. Secondly, they may harm soil health and farm productivity by inhibiting plant growth or disrupting nutrient cycles.
Professor Carter explained the regulatory challenge: "These chemicals aren’t regulated for so there isn’t a drive to develop or to focus on technologies that can remove them." While the European Union is moving to implement advanced "quaternary treatment" to remove such micropollutants from wastewater, the UK currently has no plans to upgrade beyond its less precise tertiary treatment systems.
The researchers emphasise that farmers are not at fault, as they follow guidance to use biosolids as a sustainable practice. The solution, they argue, lies in better regulation, investment in advanced treatment technology, and greater awareness of the risks. "We need to regulate for them properly and we need education," Carter concluded, highlighting the complex journey from soil to consumption that requires urgent further study.
