Sewage sludge, also known as biosolids, is a by-product of wastewater treatment that is often used in agriculture to recycle nutrients and organic matter. While this practice has benefits, recent research has raised serious concerns about the potential risks posed by contaminants found in biosolids. The James Hutton Institute, at the request of Fidra, has conducted a comprehensive study to reassess these risks, highlighting the need for a closer look at the substances in sewage sludge and their potential impact on soil health, human wellbeing, and the wider environment.
Treated sewage sludge, though processed to remove pathogens, can still contain a cocktail of harmful and unregulated contaminants. These include microplastics, poly- or per-fluorinated alkyl substances (PFAS), pharmaceuticals and personal care products (PPCPs), and chemical flame retardants. Many of these chemicals are persistent in the environment and do not degrade easily. Alarmingly, they are neither monitored nor removed during treatment, meaning they may end up in the soil when biosolids are used as fertilisers.
The research conducted by the James Hutton Institute highlights the potential risks these contaminants pose to soil biota, including essential organisms like worms, microbes, and insects. These organisms play a vital role in maintaining healthy soils, which are essential for sustainable agriculture. The report also highlights the wider human health risks, including the possibility of harmful substances entering the food chain, as well as their potential to disrupt ecosystems, water quality, and biodiversity.
Following the findings of this research, Fidra has made several critical recommendations to reduce the risks associated with sewage sludge use in agriculture. These recommendations are in line with the broader goals of the One Health Breakthrough Partnership, which seeks to promote the interconnected health of people, animals, and the environment. The objectives of this partnership aim to address environmental and public health challenges through integrated, cross-sector solutions.
- Improved Monitoring and Regulation: Fidra calls for the UK government to significantly improve the monitoring of contaminants in treated sewage sludge and to introduce stronger legislation around its use in agriculture. Until it can be proven safe, the use of biosolids in agriculture should be suspended. This aligns with the One Health approach, which recognises the importance of protecting the health of all ecosystems—human, animal, and environmental.
- Prevention at Source: The research underscores the need for tighter controls on harmful substances such as PFAS, bisphenols, and flame retardants. By addressing the source of contamination—through better regulation of chemicals and plastics—the risk of these substances entering the sewage system and, ultimately, our soils, can be greatly reduced. This is a key component of the One Health framework, which advocates for preventive action to safeguard public health and ecosystems alike.
- Promotion of Safer Fertiliser Alternatives: Fidra advocates for the promotion of cleaner, safer organic fertilisers derived from non-sewage sources. These alternatives would reduce the reliance on biosolids and help mitigate the risks posed by contaminated sewage sludge, supporting more sustainable and health-conscious agricultural practices. This aligns with One Health principles by prioritising long-term ecosystem health while reducing potential human health hazards.
- Investment in Sustainable Sewage Management: The government is encouraged to invest in upgrading sewage treatment systems, including the development of nutrient recovery technologies. This would help future-proof sewage management, reduce the environmental impact of biosolid application, and support a circular economy for waste resources, all of which contribute to a healthier planet. Again, this supports the interconnected objectives of One Health, with a focus on ensuring that systems are sustainable and resilient.
To further engage the public and stakeholders in this crucial conversation, Fidra will be hosting a webinar on Wednesday, 29th January 2025, from 2-3 pm to present the findings of the research and discuss its implications. This will be a valuable opportunity for scientists, policymakers, and the public to explore solutions for reducing the environmental and health risks associated with sewage sludge use.
The findings of this report highlight the urgent need to reassess how we manage biosolids in the UK. The interconnectedness of human health, environmental sustainability, and soil health calls for a coordinated, One Health approach to addressing the risks posed by sewage sludge. Fidra’s recommendations offer a clear path forward, from stricter regulation and monitoring to a greater emphasis on sustainable and cleaner alternatives.
To learn more about the study and access the full report, please visit Fidra’s website: James Hutton Institute Report – Sewage Sludge Risks Research.