Chemicals in Water

Clean water under threat from multiple sources of pollution

Access to clean water is a fundamental human right and a critical pillar of the UK’s health, food security, environmental integrity, and economic resilience. 

However, our water is increasingly under threat due to a growing burden of chemical and plastic contamination in the UK, this pollution comes from a complex mix of regulated and unregulated sources.  Not a single river in England has reached ‘good’ chemical status​, with only 16% of water bodies achieving ‘good’ status in Scotland​1,2 – this means our rivers are suffering from high levels of toxic chemical pollution. Chemical and plastic contaminants can enter our waterways from multiple sources including via agricultural runoff, road runoff, industrial activities and sewage overflows. These contaminants accumulate in rivers, lakes, and even drinking water supplies, posing risks to aquatic life, ecosystem function, and potentially human health. The prevalence of these pollutants underscore the urgent need for enhanced monitoring that informs regulation on source controls, better treatment infrastructure, and a more robust legislative framework to prevent pollution.

What contaminants are in our waterways?

UK water bodies contain a complex mixture of chemical pollutants with widespread and concerning impacts, here are just a few:

Pharmaceuticals have been found in 96% of monitored river locations in England’s National Parks3, with antidepressants, antibiotics, and hormones disrupting fish reproduction4 and contributing to antimicrobial resistance5.

PFAS (forever chemicals) appear in 96% of surface water samples across England6, with 81 of 105 rivers exceeding proposed EU standards, some by over 20 times6. These ‘forever chemicals’ include over 10,000 individual substances, for example trifluoroacetic acid (TFA), a highly mobile and persistent ultrashort-chain PFAS linked to potential harm to aquatic life, which has recently been detected in 98% of rivers tested across the UK.

Pesticides from agricultural runoff, including herbicides, insecticides, and fungicides, continue contaminating waterways and often form metabolites more toxic than the original compounds.

Flame retardants, both legacy PBDEs (which persist despite being phased out, with all assessed sites exceeding safety standards) and newer OPFRs, enter water through wastewater and product leaching.

Microplastics, found in major UK rivers and even in 33% of Thames roach fish7, act as carriers for other harmful chemicals and have been detected in human blood, lungs, and breast milk 8-11. Even when removed from wastewater at 99.9% efficiency 12, they concentrate in sewage sludge used as fertiliser, with 99% eventually returning to aquatic environments 13, illustrating the cyclical nature of water contamination.

Chemical complexity

The fate of chemicals within water depends on their physical and chemical properties, how they interact with other substances, and the surrounding environmental conditions.

  • Some chemicals can degrade into other substances, breaking down to be more or less harmful
  • Others can be highly stable, like PFAS, and resist the breakdown process, allowing these substances to persist in water for extended periods of time and travel long distances from the original source
  • Shifts in environmental conditions, particularly increased water temperature and light conditions, can influence natural degradation processes
  • Chemicals can also bind to sediments or organic matter, leading to ‘pollution reservoirs’, for example hydrophobic pesticides 14
  • Unfortunately the fate of some chemicals is that they will bioaccumulate in aquatic organisms, moving their way up the food chain which leads to high concentrations in predators, as seen with mercury and PCB’s in Orca 15

Chemicals in waterways with source examples

Chemical cocktails

And of course it’s important to note that rivers, lakes, and even drinking water sources are being contaminated by combinations of chemical contaminants. Many of these substances are unregulated, and even those that are rarely account for how they interact when combined. This poses a significant risk as chemical mixtures can have synergistic effects, meaning their combined impact on wildlife and human health may be far greater than the sum of their parts. The true danger lies in these unknowns. The lack of comprehensive monitoring, data, and regulation around these mixtures leaves critical gaps in our understanding and undermines our ability to protect ecosystems and public health effectively.  

Impacted wildlife and the cocktail effect

Failures to address chemical and plastic pollution in policy and regulation

Water pollution across the UK is governed by a complex framework of legislation that varies by nation. Much of this regulation originates from EU directives that have remained largely unchanged since Brexit, with each UK nation implementing these historic regulations through different means. For example, the Water Framework Directive and the Urban Wastewater Treatment Directive exist in all nations under separate legislation, alongside regulations relating to drinking water quality. However, alarmingly, the level of chemical and plastic pollutants allowed in water remains unregulated or unmonitored for many pollutants under current UK law across all four nations. There is also a lack of source control to prevent these pollutants reaching our water, through restricting use or setting effective permits for emissions. For example, most PFAS in use today face no restrictions to limit their use or prevent water contamination. From pesticides running off a field, or forever chemicals PFAS washing off a school uniform, there are many different ways chemicals and plastic can get into our environment, but there is a common solution – robust regulation that takes into account the whole lifestyle of products including potential routes into the environment. Using regulations (such as REACH), we can consider which/how substances are used in the first place to stop this pollution before it happens.

A new vision for water in England?

UK water policy in England is currently undergoing major structural reform following the publication of the Water White Paper in January 2026. The reforms respond to the Independent Water Commission’s report The Cunliffe Review) published in summer 2025, which called for a “fundamental reset” of the sector to address pollution, infrastructure decay, and falling public trust. While the White Paper claims to set out policies and plans to deliver clean rivers, lakes and seas, there is little new detail on tackling wider pollution pressure, beyond the water industry, and it fails to address sources of sources of chemical pollution. With a Water Reform Bill on the way and key regulations such as the Water Framework Directive earmarked for review, we look at what the Government can to do to get chemicals under control and deliver the transformation our water systems need in our recent blog.

Fidra’s asks of UK water policy to prevent chemical and microplastic pollution 

Effective regulatory frameworks for the water environment 

  • Prevent chemical pollution of water by stopping contamination at source through alignment with the EU on chemical regulation 

Align GB chemical regulations to the EU, including REACH to address the use of harmful chemicals such as bisphenols, chemical flame retardants and the proposed universal PFAS restriction.  Alignment should also include CLP, biocidal product regulations as well as pesticide regulations to ensure health and environmental protections are harmonised across the UK (see our chemical alignment page)

  • Improve monitoring and factor in mixtures to get a true picture of pollution and its impacts to inform regulation 

Update Water Framework Directive’s priority substances and watchlist in line with EU, develop more Environmental Quality Standards (EQS), and improve use of modelling and mixture assessment factors to better account for chemical mixtures. Monitor more sites, more often, including during drought, flood and high flow events. Ensure data is transparent, accessible, and supports precautionary regulatory action such as restrictions on chemicals. 

  • Protect water from chemical pollution at every stage 

Manage chemicals across their lifecycle and require chemical data transparency and accessibility throughout product supply chains. This must be supported by robust regulations and effective enforcement by resourced and coordinated regulators.

 

Pollution Prevention in Practice  

  • Phase out agricultural use of contaminated sewage sludge to prevent contaminants entering water bodies 

The review of the sludge use in agriculture regulations needs to update the regulated contaminants to include chemicals of concern and microplastic, bring sludge regulation into the environmental permitting regulations, and develop plans to phase out sludge application to land (see our sewage free soils project).

  •  Stop microplastics getting into water 

We need regulation to prevent microplastic entering our waterways from artificial pitches and from the plastic pellets made and used by the plastic industry. The government must introduce extended producer responsibility schemes and robust regulations for safe and sustainable product design to prevent plastic loss and fund water treatment. 

  • Prevent all sources of PFAS pollution from entering the water environment   

The UK must commit to phasing out all sources of PFAS pollution including pesticides, biocides, pharmaceuticals, and veterinary products (in addition to aligning with proposed EU PFAS universal restriction). Further details on our PFAS free website.

 

Water News

Our rivers, lakes and seas are in crisis, suffocated by decades of pollution and inaction. The way we treat our waters is no longer something the public, or the environment, is going to tolerate.

Clean water can’t wait: the Government must take action now for nature and people

Our rivers, lakes and seas are in crisis, suffocated by decades of pollution and inaction. The way we treat our waters is no longer something the public, or the environment, is going to tolerate.

Read more
Stopping chemical and plastic pollution at source is needed to deliver clean rivers, lakes and seas.

A new vision for water? How the UK Government’s Water White Paper falls short on chemical pollution

Stopping chemical and plastic pollution at source is needed to deliver clean rivers, lakes and seas.

Read more
person touching water on kayak

Cunliffe’s Water Commission highlights need for regulation to tackle chemical and plastic pollution

Independent Water Commission’s Review recommends regulation to tackle chemical and plastic pollution from polluting products and sewage sludge

Read more

References 

  1. Environment Agency. State of the water environment indicator B3: supporting evidence. https://www.gov.uk/government/publications/state-of-the-water-environment-indicator-b3-supporting-evidence/state-of-the-water-environment-indicator-b3-supporting-evidence#:~:text=This%20evidence%20summary%20supports%20the,are%20at%20good%20ecological%20status. (2019).
  2. Scottish Environment Protection Agency. State of Scotland’s Water Environment, Summary Report 2024. https://www.sepa.org.uk/environment/water/aquatic-classification/. (2024)
  3. Boxall, A. B. A. et al. Pharmaceutical Pollution of the English National Parks. Environ Toxicol Chem 43, 2422–2435 (2024).
  4. The Environment Agency (Lange, A. , P. G. C. and T. C. R. ). Long-Term Exposure to Environmentally Relevant Concentrations of Ethinyloestradiol Affects Sexual Differentiation and Development in Roach, Rutilus Rutilus. https://assets.publishing.service.gov.uk/media/5a7c5c3040f0b660183b6d82/scho0408bnzh-e-e.pdf (2008).
  5. Samreen, Ahmad, I., Malak, H. A. & Abulreesh, H. H. Environmental antimicrobial resistance and its drivers: a potential threat to public health. J Glob Antimicrob Resist 27, 101–111 (2021).
  6. Wildlife and Countryside Link. UK falling behind in the fight against toxic ‘forever chemical’ cocktail in our rivers. https://www.wcl.org.uk/uk-falling-behind-in-fight-against-toxic-forever-chemicals.asp (2023).
  7. Horton, A. A., Jürgens, M. D., Lahive, E., van Bodegom, P. M. & Vijver, M. G. The influence of exposure and physiology on microplastic ingestion by the freshwater fish Rutilus rutilus (roach) in the River Thames, UK. Environmental Pollution 236, 188–194 (2018).
  8. Leslie, H. A. et al. Discovery and quantification of plastic particle pollution in human blood. Environ Int 163, 107199 (2022).
  9. Jenner, L. C. et al. Detection of microplastics in human lung tissue using μFTIR spectroscopy. Science of The Total Environment 831, 154907 (2022).
  10. Ragusa, A. et al. Plasticenta: First evidence of microplastics in human placenta. Environ Int 146, 106274 (2021).
  11. Saraluck, A. et al. Detection of Microplastics in Human Breast Milk and Its Association with Changes in Human Milk Bacterial Microbiota. J Clin Med 13, 4029 (2024).
  12. W. Magnusson, C. “Screening of Microplastic Particles in and Down- Stream of a Wastewater Treatment Plant.” . (2014).
  13. Crossman, J., Hurley, R. R., Futter, M. & Nizzetto, L. Transfer and transport of microplastics from biosolids to agricultural soils and the wider environment. Science of The Total Environment 724, 138334 (2020).
  14. Ramage, C. I., Lopes dos Santos, R. A., Yon, L., Johnson, M. F. & Vane, C. H. Widespread pesticide pollution in two English river catchments of contrasting land-use: from sediments to fish. Environmental Pollution 375, 126371 (2025).
  15. Alava, J. J., Cisneros-Montemayor, A. M., Sumaila, U. R. & Cheung, W. W. L. Projected amplification of food web bioaccumulation of MeHg and PCBs under climate change in the Northeastern Pacific. Sci Rep 8, 13460 (2018).