Microplastics from human waste are being spread on UK farmland in fertiliser, remaining in the food chain and continuing the cycle of pollution and poor human health.
A by-product of sewage treatment in the form of dry solids (AKA sludge) is used in the UK as agricultural fertiliser. In 2023, 819,000 tonnes of these solids were applied to over 375,000 acres of land in England, and similar practices take place in the UK’s other regions of Scotland, Wales, and Northern Ireland, according to environmental consultancy, EcoCognito.
However, the company says that under current legislation, microplastics pollution from human waste is not counted as a harmful substance, and that testing at present of dry solids only checks for heavy metals such as lead and zinc. The legislative gap means microplastics end up back in the food chain, and are re-ingested.
EcoCognito is calling for tighter regulations, “to protect human health and our environment from this harmful and avoidable pollution,” a spokesperson said. “Research also reveals that microplastics damage and disrupt ecosystems, damage soils and aquatic environments, and harm wildlife and other biota, so urgent action is needed to stop microplastics entering our environment in sewage sludge.” EcoCognito accessed UK government data from 2023 which is drawn from reports filed by UK water companies.
The European Commission’s recent re-evaluation of its legislation governing the sector, the Sewage Sludge Directive, noted that “the set of pollutants which [the Sewage Sludge Directive] regulates needs review, notably considering organic compounds, pathogens, pharmaceuticals, and microplastics which are present in sewage sludge.”
While spreading sewerage works’ by-products onto agricultural land is less costly than incineration (the commonly-cited alternative method of disposal), both the EU and the UK’s oversight of the practice seem to be in need of a significant overhaul.
The UK’s private water companies have come under increased scrutiny in the last few years, with incidents of waterway pollution by sewerage plants the focus of outcry by the British public. Lack of legislative force to regulate water companies’ activities has been blamed on the Environmental Bill, approved by Parliament in November 2021, which critics claim is too lenient on water companies that pollute the UK’s waterways, and that sets ‘acceptable levels’ of pollution too high.
Evidence for the potentially-harmful effects of microplastics on humans has begun to emerge, so curbing their presence in products applied to agricultural land seems sensible. But any stronger oversight of the contents of dry solids from sewerage processing seems unlikely in the present legislative environment.
Rather than the UK government overseeing the activities of the private water companies, a YouGov poll in 2024 showed that 82% of the public thought water companies should be brought back into the public sector. According to the Guardian, the governing Labour Party used “‘economically illiterate’ analysis paid for by water companies” to argue against the re-nationalisation of the sector in England.
(Image source: “Microplastics in sediments” by Martin Wagner et al. is licensed under CC BY 4.0.)
