7.6 What are the possible adverse effects caused by land application of biosolids?

The land application of biosolids can cause several adverse effects on human health and the environment when proper management practices and adherence to regulations are not respected. The actual occurrence and severity of these effects can vary depending on factors such as biosolids quality, application rates, site-specific conditions, and management practices.

The main problems concern the presence of heavy metals, organic contaminants, and/or pathogens in the sludge. The following aspects are possible to occur in case of disregard of standards and improper management:

Environmental Contamination

• Raising the levels of persistent toxins in the soil, vegetation, and wildlife
• Potentially slow and long-term biodiversity reduction through the fertilizing nutrient pollution operating on the vegetation
• Leaching of nitrogen into subsurface drainage and groundwater
• Contamination of ground and surface water with persistent organic compounds
• Eutrophication of water bodies due to excess phosphorus runoff
• Greenhouse gas emissions (e.g. CH₄ and N₂O)
• Release of odorous compounds

Human Health Risks

• Ingestion of contaminated food crops and animal products
• Exposure to emerging pollutants like pharmaceuticals, personal care products, microplastics, and per- and polyfluoroalkyl substances (PFAS)

The risk of these adverse effects is low and manageable as long as standards and management practices are rigorously followed. Properly managed biosolids can provide significant agricultural benefits while maintaining safety for human health and the environment.