A UK chemical monitoring water programme examining hazardous substances in wastewater has found declining concentrations of several regulated chemicals across England and Wales.
The findings come from the Chemical Investigations Programme (CIP), coordinated by UK Water Industry Research (UKWIR), which monitors chemical substances entering rivers and seas through wastewater systems.
Mike Rose associated with the UK water industry’s Chemical Investigations Programme research.
Analysis of monitoring data collected between 2020 and 2025 shows downward trends in concentrations for 19 of the 20 substances studied.
The programme was launched as a collaboration between water companies and regulators including the Environment Agency, Defra and Natural Resources Wales.
UK chemical monitoring water programme highlights role of source control
The UK chemical monitoring water programme suggests that regulatory controls targeting chemicals at the manufacturing stage can play a significant role in reducing pollution in water systems.
Among the substances showing declining concentrations is tributyltin (TBT), once widely used in antifouling paint on ship hulls. Following a global ban introduced in 2008, environmental concentrations have fallen significantly.
Monitoring data also shows reductions in perfluorooctane sulfonate (PFOS), a member of the PFAS family of persistent “forever chemicals”. PFOS was previously used in products such as stain-resistant textiles and firefighting foams.
Despite the decline, PFOS remains detectable in some water environments due to its persistence and the continued release of residues from historic sources such as landfill sites.
Evidence supports targeted environmental policy
Researchers involved in the programme say the data demonstrates how regulatory bans and restrictions can reduce environmental contamination over time.
Jenni Hughes, strategic programme manager at UKWIR, said evidence gathered through the programme helps guide policy decisions and environmental investment.
“Our data shows that when there is rigorous source control, the environment heals without the need for carbon-heavy, expensive interventions from utilities.”
The programme also highlights the importance of long-term monitoring to understand trends in environmental contaminants.
Mark Craig, Severn Trent Water’s long-term asset strategy lead and UKWIR co-lead for wastewater, said systematic monitoring allows researchers to track environmental progress.
“With this trend monitoring, we have the power to show what is actually happening in our environment.”
Monitoring emerging contaminants
While most chemicals studied showed declining concentrations, dissolved mercury was the only substance identified as increasing in the monitoring data.
Mercury can enter the environment through natural geological processes as well as industrial activities including mining, fossil fuel combustion and waste incineration.
The Chemical Investigations Programme is currently entering its fourth phase (CIP4), which will run from 2025 to 2030.
Future research will investigate emerging contaminants including antimicrobial resistance, microplastic degradation and the behaviour of PFAS compounds in wastewater sludge.
Further reporting on water quality and environmental monitoring can be found in the Water & Ocean section of Climate Global News.
