14th May 2025

Defra research recommends reducing sewage sludge recycling to land as a cost-effective measure to tackle microplastic pollution.


A new report released by Defra has recommended options to reduce the application of sewage sludge to agricultural land by either 50 or 95 percent by the year 20301. These options are alongside four other recommendations to reduce environmental emissions of intentionally added microplastics in the UK.

Intentionally added microplastics are plastic particles (typically under 5 mm in size) that manufacturers deliberately add to products for a specific performance function (e.g. abrasive texture) or purpose (e.g. as an encapsulating barrier) and are a significant yet overlooked source of pollution in the UK. Despite the 2018 ban on microbeads in rinse-off cosmetics2, many products still contain microplastics that can escape into the environment, and Defra’s report noted that agricultural soils were the biggest source of environmental intentionally added microplastic emissions in the UK1.

One of the main ways microplastics enter agricultural soils is through the widespread use of treated sewage sludge (or biosolids) as a fertiliser.  These microplastics come from the use of cosmetics, cleaning agents and pharmaceuticals as well as inputs from industrial and hospital effluents, landfill leachates and road runoff fed into wastewater treatment plants.  Up to 99% of the intentionally added microplastics that go to wastewater treatment plants become concentrated in sewage sludge. It is important to note that microplastics (and other contaminants found in sludge like PFAS) are not regulated through the current sludge use in agriculture regulations. When biosolids are recycled to farmland, a significant load of microplastics is applied directly onto soils4. These particles are alarmingly persistent, accumulating in terrestrial and aquatic ecosystems and entering the food chain – posing risks to all organisms that ingest them5. In fact, a recent study found a staggering 1,450% increase in microplastic levels in soil samples after just four years of repeated sludge application (4See our blog here). Reviews have projected that soil microplastic contamination is likely to be as high, if not higher, than water microplastic contamination6, 7.

Ingestion of these microplastics is widespread, with particles found in many UK species from fish8, to small mammals9and earthworms – where studies suggest that they can reduce reproduction, impacting soil health and ecosystems10. The ubiquitous nature of these particles extends to human exposure via contaminated food and water consumption; microplastics have been detected in food11, drinking water12 (all tap water and bottled water in this study found microplastics), air13, and even human organs, including blood14 and lungs15. Furthermore, it is important to note that microplastics can act as carriers for chemicals (especially organic chemicals such as PFAS) adsorbed to their surfaces due to their large surface area and hydrophobic nature16

Despite growing awareness, the UK has yet to implement comprehensive regulations addressing all sources of intentionally added microplastics, leaving the UK’s environmental and public health at continued risk of harm.

Defra’s report assesses and recommends the following options to reduce intentionally added microplastic emissions in the UK:

Measures RMO 3A and RMO 3B recognise treated sewage sludge (biosolids) as a huge intentionally added microplastic exposure pathway via down-the-drain wastewater transport and eventual concentration in biosolids and application to soils. These two ‘downstream’ solution options for diverting sludge away from agricultural land were found to be relatively cost-effective measures, with ‘co-benefits of reducing exposure to other contaminants in sewage sludge’, for example PFAS and pharmaceuticals. Although there is increasing evidence of the impacts of microplastics on soil organisms, there are critical gaps in our understanding of the interactions between mixtures of contaminants such as those within treated sewage sludge17. When chemicals adsorb to plastic particles, they can be transported between environmental compartments, moving from terrestrial to aquatic ecosystems and up food chains, enhancing their persistence and potential toxicity in the environment18. They can also impact the bioavailability of adsorbed chemicals when microplastics are ingested by organisms19.

Fidra is keen to understand how these report findings will influence future policies. It would be good to have clarity on what the next steps and timeline are for Defra and the Environment Agency’s Safe and Sustainable Sludge Use in Agriculture Strategy and improvements proposed as part of the new Environmental Permitting Regulations20.

 

Our Asks

  • Fidra calls on the UK Government to further regulatory efforts to mitigate loss of microplastics to the environment.

  • Fidra supports the precautionary approach to safeguard agricultural soils, environmental and public health from harmful microplastics and chemicals found in sewage sludge.

  • Fidra urge the UK Government to take meaningful actions by considering the benefits of reducing exposure to all unregulated chemical contaminants found in sewage sludge, including intentionally added microplastics.

  • Fidra supports the UK government in taking urgent action to match and exceed the provisions that EU REACH have already made in restricting intentionally added microplastics21.

 

References

  1. Defra (2025) Option appraisal for intentionally added microplastics: final report Retrieved online May 14, 2025 from: https://sciencesearch.defra.gov.uk/ProjectDetails?ProjectId=21802.
  2. UK Government (2018) Word-leading microbeads ban takes effect Retrieved online May 13, 2025 from: https://www.gov.uk/government/news/world-leading-microbeads-ban-takes-effect.
  3. UKWIR (2022) The National Chemical Investigations Programme 2020-2022 Volume 2 – Investigations into the fate and behaviour of Microplastics within wastewater treatment works. Retrieved online May 14, 2025 from: Available at: https://UKWIR.org/water-industry-technical-report?object=91d0b63a-a522-4880-9c1e-fa05cdb763a8 (Accessed: 23 May 2024).
  4. Ramage SJFF, Coull M, Cooper P, Campbell CD, Prabhu R, Yates K, Dawson LA, Devalla S, & Pagaling E (2025) Microplastics in agricultural soils following sewage sludge applications: Evidence from a 25-year study Chemosphere 376 144277, https://doi.org/10.1016/j.chemosphere.2025.144277.
  5. Thacharodi A, Meenatchi R, Hassan S, Hussain N, Bhat MA, Arockiaraj J, Ngo HH, Le QH, & Pugazhendhi A (2024) Microplastics in the environment: A critical overview on its fate, toxicity, implications, management, and bioremediation strategies J Environ Manage 349 119433, https://doi.org/10.1016/j.jenvman.2023.119433.
  6. Gavigan J, Kefela T, Macadam-Somer I, Suh S, & Geyer R (2020) Synthetic microfiber emissions to land rival those to waterbodies and are growing PLoS One 15(9) e0237839, https://doi.org/10.1371/journal.pone.0237839.
  7. Nizzetto L, Futter M, & Langaas S (2016) Are Agricultural Soils Dumps for Microplastics of Urban Origin? Environ Sci Technol 50(20) 10777–10779, https://doi.org/10.1021/acs.est.6b04140.
  8. Horton AA, Weerasinghe KDI, Mayor DJ, & Lampitt R (2024) Microplastics in commercial marine fish species in the UK – A case study in the River Thames and the River Stour (East Anglia) estuaries Science of The Total Environment 915 170170, https://doi.org/10.1016/j.scitotenv.2024.170170.
  9. Thrift E, Porter A, Galloway TS, Coomber FG, & Mathews F (2022) Ingestion of plastics by terrestrial small mammals Science of The Total Environment 842 156679, https://doi.org/10.1016/j.scitotenv.2022.156679.
  10. Lahive E, Walton A, Horton AA, Spurgeon DJ, & Svendsen C (2019) Microplastic particles reduce reproduction in the terrestrial worm Enchytraeus crypticus in a soil exposure Environmental Pollution 255 113174, https://doi.org/10.1016/j.envpol.2019.113174.
  11. Mamun A Al, Prasetya TAE, Dewi IR, & Ahmad M (2023) Microplastics in human food chains: Food becoming a threat to health safety Science of The Total Environment 858 159834, https://doi.org/10.1016/j.scitotenv.2022.159834.
  12. Al-Mansoori M, Stephenson M, Harrad S, & Abdallah MA-E (2025) Synthetic Microplastics in UK tap and bottled water; Implications for human exposure Emerg Contam 11(1) 100417, https://doi.org/10.1016/j.emcon.2024.100417.
  13. Li Y, Shao L, Wang W, Zhang M, Feng X, Li W, & Zhang D (2020) Airborne fiber particles: Types, size and concentration observed in Beijing Science of The Total Environment 705 135967, https://doi.org/10.1016/j.scitotenv.2019.135967.
  14. Leslie HA, van Velzen MJM, Brandsma SH, Vethaak AD, Garcia-Vallejo JJ, & Lamoree MH (2022) Discovery and quantification of plastic particle pollution in human blood Environ Int 163 107199, https://doi.org/10.1016/j.envint.2022.107199.
  15. Jenner LC, Rotchell JM, Bennett RT, Cowen M, Tentzeris V, & Sadofsky LR (2022) Detection of microplastics in human lung tissue using μFTIR spectroscopy Science of The Total Environment 831 154907, https://doi.org/10.1016/j.scitotenv.2022.154907.
  16. Costigan E, Collins A, Hatinoglu MD, Bhagat K, MacRae J, Perreault F, & Apul O (2022) Adsorption of organic pollutants by microplastics: Overview of a dissonant literature Journal of Hazardous Materials Advances 6 100091, https://doi.org/10.1016/j.hazadv.2022.100091.
  17. Rupert Hough (2024) Using new contaminants information to re-assess environmental risks from sewage sludge Retrieved online May 14, 2025 from: https://www.fidra.org.uk/download/james-hutton-institute-re-assessment-of-environmental-risks-from-sewage-sludge/.
  18. Andrade H, Glüge J, Herzke D, Ashta NM, Nayagar SM, & Scheringer M (2021) Oceanic long-range transport of organic additives present in plastic products: an overview Environ Sci Eur 33(1) 85, https://doi.org/10.1186/s12302-021-00522-x.
  19. Tanaka K, Takada H, Yamashita R, Mizukawa K, Fukuwaka M, & Watanuki Y (2013) Accumulation of plastic-derived chemicals in tissues of seabirds ingesting marine plastics Mar Pollut Bull 69(1–2) 219–222, https://doi.org/10.1016/j.marpolbul.2012.12.010.
  20. Environment Agency (2023) Environment Agency strategy for safe and sustainable sludge use Retrieved online May 13, 2025 from: https://www.gov.uk/government/publications/environment-agency-strategy-for-safe-and-sustainable-sludge-use/environment-agency-strategy-for-safe-and-sustainable-sludge-use.
  21. European Commission D-G for IMIE and Sme (2023) Commission Regulation (EU) 2023/2055 of 25 September 2023 amending Annex XVII to Regulation (EC) No 1907/2006 of the European Parliament and of the Council concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) as regards synthetic polymer microparticles (Text with EEA relevance) European Union.