New findings from the UK water industry’s most extensive chemical monitoring initiative suggest that targeted policy, collaborative science and effective source control can play a significant role in reducing persistent chemicals in the environment.
The UK Water Industry Research (UKWIR) Chemical Investigations Programme (CIP) represents the water sector’s most comprehensive scientific effort to understand and address chemical substances in the water environment. Through consistent monitoring, shared methodologies and collaboration between industry and regulators, the programme is improving transparency and enabling earlier, better-informed action.
The initiative also reflects the system-wide, coordinated approach outlined in the UK government’s recent white paper on water sector reform.
Evidence of progress
Results from the CIP3 Trend Monitoring Project (2020–2025) show declining concentrations for all but one of the monitored chemicals, including Perfluorooctane sulfonate (PFOS) and lead. The findings provide strong evidence that national and international source-control measures — such as product bans and phased withdrawals — combined with improvements to treatment processes are helping to reduce hazardous substances in water systems.
By strengthening the evidence base on chemical pollution and identifying the factors affecting different locations, the programme supports more targeted interventions and clearer prioritisation in efforts to improve water quality. It also helps direct investment towards measures that deliver the greatest environmental benefit for water company customers.
Jenni Hughes, strategic programme manager at UKWIR, emphasised that controlling pollution at its source is key.
“The water industry is not the source of many of these chemicals, and our data shows that when rigorous source controls are introduced, the environment can recover without the need for carbon-intensive and costly treatment solutions,” she said. “This evidence-based approach offers a blueprint for addressing emerging contaminants without relying solely on end-of-pipe interventions that would place significant costs on bill payers.”
Tracking long-term trends
The Trend Monitoring Project collected four and a half years of data from sites across England and Wales, demonstrating the effectiveness of restrictions on harmful substances at the manufacturing stage.
Launched in 2010 as a collaboration between water companies and regulators — including the Environment Agency, Department for Environment, Food and Rural Affairs and Natural Resources Wales — the Chemical Investigations Programme is currently in its fourth phase (CIP4).
Mark Craig, long-term asset strategy lead at Severn Trent Water and UKWIR co-lead for wastewater, highlighted the importance of monitoring.
“You can’t manage what you don’t measure,” he said. “Trend monitoring allows us to demonstrate what is actually happening in the environment. For many substances, when effective source-control measures are in place, concentrations in wastewater effluent decline significantly.”
Analysis of data from 2020 to 2025 shows clear downward trends for 19 of the 20 substances of major regulatory concern.
One example is tributyltin (TBT), formerly used as a biocidal antifouling coating on ship hulls. Following a global ban in 2008, environmental concentrations have fallen sharply, demonstrating the effectiveness of coordinated international regulation.
PFOS, part of the wider family of per- and polyfluoroalkyl substances (PFAS), has also declined at monitoring sites such as those operated by Severn Trent Water. However, concentrations still exceed the EU’s Environmental Quality Standards in some rivers due to the compound’s persistence and its continued release from historic sources such as landfill sites.
The only substance showing an upward trend was dissolved mercury, which enters the environment through both natural geological processes and human activities such as mining, fossil fuel combustion and waste incineration.
Importantly, the report identifies substances that could lead to future breaches of environmental standards, enabling water companies to prioritise catchments for further investigation or remediation.
A flexible scientific framework
As UKWIR progresses through CIP4 (2025–2030) and plans for CIP5 (2030–2035), the programme is designed to remain adaptable, allowing new chemicals to be investigated as emerging scientific evidence and environmental concerns arise.
“We work closely with the Environment Agency to define the scope of each phase and will continue to do so as the programme evolves,” Craig said. “Substances can be added to or removed from the monitoring list as the evidence changes. The programme is designed to remain flexible and future-ready.”
By prioritising measures that prevent harmful substances from entering sewer systems in the first place, UKWIR aims to ensure that efforts to protect the water environment remain scientifically robust, environmentally responsible and economically sustainable.
