The UK is mapping out a path to cut down on chemicals in our environment. Recent monitoring data underscores the importance of controlling sources, leveraging science, and implementing targeted interventions.
The latest insights from the UK water industry’s most extensive chemical monitoring initiative indicate that focused policies, collaborative scientific research, and effective source control can significantly reduce harmful chemicals in our environment, including those notorious forever chemicals.
The Chemical Investigations Programme (CIP), spearheaded by UK Water Industry Research (UKWIR), stands as the most thorough scientific effort from the UK water sector to address chemical substances in our water systems.
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By maintaining consistent monitoring, sharing methodologies, and fostering collaboration, this program is enhancing transparency and enabling quicker, more informed actions. It also embodies the kind of comprehensive, integrated approach emphasized in the Government’s recent white paper on water sector reform.
Trend data reveals a significant drop in chemical concentrations
Findings from the CIP3 Trend Monitoring Project (2020–2025) show a decline in concentrations for nearly all monitored chemicals, with the exception of one, including perfluorooctane sulfonate (PFOS) and lead.
The report clearly demonstrates that both national and international source control measures—like product bans and phase-outs—along with improvements to treatment processes, are effectively reducing hazardous substances in UK water systems.
By bolstering the evidence surrounding chemical pollution and pinpointing the factors that affect different locations, CIP aligns with the white paper’s call for more focused interventions, clearer prioritization, and ongoing progress toward cleaner rivers and seas.
Moreover, by showcasing the success of source control and other targeted actions, the program can guide investments to areas where they will yield the most significant environmental benefits, while also ensuring better value for water customers.
Jenni Hughes, the Strategic Programme Manager at UKWIR, shared her insights: “The water industry isn’t the source of these chemicals, and our data clearly indicates that when we implement strict source control, the environment can recover without relying on carbon-heavy and costly interventions from utilities.”
She went on to say: “This evidence-based strategy is laying the groundwork for how the UK can address emerging compounds without resorting to end-of-pipe solutions that would burden bill-payers with hefty costs.”
Trend monitoring strengthens the case for source control
The latest Trend Monitoring Project, which has compiled four and a half years of data from various sites across England and Wales, offers more proof that limiting harmful substances at their source can be incredibly effective.
Initially launched in 2010 as a collaboration between water companies and regulators, including the Environment Agency, Defra, and Natural Resources Wales, the Chemical Investigations Programme is now in its fourth phase (CIP4).
Mark Craig, the Long Term Asset Strategy Lead at Severn Trent Water and UKWIR Co-Lead for Wastewater, emphasized: “You can’t control what you don’t measure. With this trend monitoring, we have the ability to demonstrate what’s really happening in our environment.”
He added: “It shows that for many substances, if the source control measures are properly implemented and functioning, the concentrations in sewage effluent drop significantly.”
Notable declines observed across most priority substances
An analysis of monitoring data from 2020 to 2025 revealed significant downward trends for 19 out of the 20 substances deemed to be of high regulatory concern.
Some of the most striking examples include:
Tributyltin (TBT)
Once widely used as a highly effective biocidal antifouling paint on ship hulls, TBT is a powerful endocrine disruptor that impacts marine life. Following a global ban in 2008, environmental concentrations have plummeted.
This serves as a key example of effective environmental policy, showing that when international bans are strictly enforced, they can really make a difference in reducing the impact of long-lasting pollutants.
PFOS
Part of the per- and polyfluoroalkyl substances (PFAS) family, PFOS is one of those stubborn “forever chemicals” that was commonly used as a stain repellent in fabrics and in firefighting foams.
Recent data from water monitoring sites in the UK, including those managed by Severn Trent Water, indicate that PFOS levels in wastewater are dropping significantly. However, in some rivers, the concentrations still surpass the EU’s Environmental Quality Standards (EQS).
PFOS is particularly tricky due to its extreme persistence and its tendency to seep into groundwater from sources like old landfill sites.
Mercury remains the main exception
The only substance that hasn’t followed the general downward trend is dissolved mercury, which the CIP3 Trend Monitoring Project has found to be on the rise in the environment over time.
Mercury makes its way into the environment through a mix of natural geological processes and human activities, such as mining, burning fossil fuels, and incinerating waste.
Crucially, the report also highlights substances that could lead to future breaches of the EU’s Environmental Quality Standards (EQS), enabling water companies to focus on specific areas for further investigation or remediation.
A flexible scientific framework for future risks
As UKWIR moves forward with CIP4 (2025–2030) and looks ahead to CIP5 (2030–2035), the program is designed to be flexible and responsive, allowing for the investigation of different chemicals as new scientific and environmental evidence emerges.
Mark Craig mentioned:
“We collaborate closely with the Environment Agency to define the scope and will continue to do so in the upcoming phases of the program.”
He mentioned, “We add chemicals to the list and remove them once we’re confident they no longer present a risk. This program is designed to be adaptable and ready for the future.” By focusing on preventing harmful substances from entering the sewer system right from the start, UKWIR is committed to ensuring that the journey towards a cleaner environment is not only scientifically sound but also environmentally responsible and economically viable.
