Sewage sludge, a byproduct of domestic and industrial sewage and wastewater treated by Scottish Water and other firms, is given or sold to farmers as a low-cost, nutrient-rich fertilizer to spread on agricultural land for growing grass, grains, and crops. Recent studies, including from Scotland’s James Hutton Institute and Scottish Environment LINK, have highlighted pollutants such as microplastics, forever chemicals, and pharmaceuticals that were not removed by treatment. Once spread, these contaminants enter soil and leach into water, potentially affecting wildlife, livestock, crops, and human health. Applying untreated sewage sludge to Scottish land was banned as part of new legislation brought in last year.
Between 2020 and 2024, nearly a fifth of all sewage sludge spread in Scotland – 111,789 tonnes – was in Perth and Kinross. Other areas with large amounts include Aberdeenshire (97,950 tonnes), Scottish Borders (87,000 tonnes), East Lothian (68,500 tonnes), Midlothian, Highland, Fife, and Dumfries and Galloway. More than a third of all sewage sludge, which is rich in nitrogen, was spread in areas at risk from agricultural nitrate pollution, and large quantities of nitrogen can harm the environment and humans by leaching into groundwater and running off into waterways.
Sewage sludge has been found to include man-made organic compounds such as PFAS 'forever chemicals' and PCBs, which could possibly cause cancer in humans. It can also contain pharmaceuticals and personal care products, which are disposed of down drains and toilets.
Thousands of jars of British honey may be contaminated with prescription medicines, with tests on raw honey from hives revealing it contains potent drugs used to treat cancer, fungal infections, and depression, as well as ibuprofen. Scientists suspect the drugs may be getting into honey through treated sewage sprayed on nearby crops. When a person takes a tablet, some of it leaves the body as waste and enters the sewage system, and treated sewage – known as biosolids – is sprayed on agricultural land as a fertilizer. It is estimated that British farmers use more than three million tonnes of sewage sludge a year, and scientists fear bees are collecting contaminated pollen from treated plants and transporting it back to their hives – where it gets into honey bound for high-street shops.
These findings warrant further investigation. The potential risk to consumers remains largely unexplored.
Researchers from the University of Leeds and the UK Centre for Ecology and Hydrology in Oxfordshire took honey samples from 19 hives from a variety of agricultural locations and found more than 100 'suspect chemicals'. Medicines accounted for almost two-thirds of the contamination in honey samples, and hives are also being tainted by industrial chemicals and plastics present in sewage sludge.
Regulations state that all honey must be free of organic or inorganic matter that is 'foreign to its composition', but there are no routine checks for 'contaminants of emerging concern' such as potent medicines or industrial chemicals in honey. Outdated UK regulations focus only on certain metals, leaving pharmaceutical contamination completely unmonitored.
Sewage sludge is authorized to be stored at 2528 locations across Scotland, although the number of active sites at any one time can be low.
The potential risk to consumers remains largely unexplored, and the effectiveness of current monitoring and inspection programs for sewage sludge spreading in Scotland and the UK is unclear.