Background
Chemical use and emissions
Chemicals are essential to a functioning society. There are many chemical substances in use, including food production, health care, manufacturing, and transport. Environmental contamination of our water, soil and air can result from a diverse range of sources and pathways of release to air, soil and water, including direct industrial discharges, agricultural emissions, vehicles, roads, municipal wastewater systems (pharmaceuticals, personal care products), waste sites and abandoned metal mines.
Once introduced, depending on their properties, chemicals will degrade and transform to different substances. How quickly a chemical degrades (breaks down) will determine how long it remains in the environment. Some substances are persistent, meaning they degrade very slowly and concentrations in the environment may increase over time. Chemicals partition into and move between environmental compartments—air, soil, surface water, groundwater, and animals—a dynamic process which influences exposure and consequently risk. Some chemicals can bioaccumulate in organisms and this may result in biomagnification, where concentrations increase progressively up the food chain. Substances that are identified as persistent (slow to break down), bioaccumulative (accumulating in animal tissues), and toxic are targeted for regulatory risk management actions.
Chemical regulation in the UK
In the UK, the Environment Agency (England), Scottish Environmental Protection Agency (SEPA), Natural Resources Wales (Wales) and the Northern Ireland Environment Agency (Ireland) are environmental regulators responsible for managing environmental pollution from chemicals. Legislation to manage chemical pollution includes a wide range of regulations and actions across the life cycle of chemicals, from manufacture, through use to disposal.
The mere presence of a chemical does not indicate a risk; rather, the potential for harm is determined by its concentration (exposure) and its specific toxicological properties (effects). Protecting and managing chemical risks in the water environment relies on monitoring a suite of priority chemicals, with the results compared against established safety thresholds. Environmental Quality Standards (EQSs) are used to define contaminant concentrations considered safe for ecological health and human health via environmental exposure in water. In England, the Environment Agency also operate the Prioritisation and Early Warning System (PEWS) to identify unregulated chemicals of potential concern that may require further action.
Monitoring data for surface waters in England indicates that concentrations of most established contaminants remain below their defined EQS thresholds. Moreover, long-term monitoring shows successful reductions in some pollutants; for example, concentrations of metals, including cadmium, lead, nickel, copper, and zinc, have substantially decreased in English rivers since 1990, reflecting the success of historical pollution control and regulatory measures. Several ubiquitous, persistent, bioaccumulative and toxic contaminants (uPBT) including mercury, PFOS and PBDEs have widespread exceedances of their EQS despite restrictions on their use many years ago. Their concentrations are declining over time, but their environmental persistence remains a challenge.
Regulatory challenges
Groundwater contamination by chemicals remains a challenge because remediation and natural recovery can take decades. Furthermore, the understanding of chemical presence in soils is less comprehensive than in water, due to less frequent monitoring.
Despite good progress, several significant challenges persist. The ability to detect more and lower concentrations of chemicals in environmental waters means greater awareness of chemical contaminants – known as contaminants of emerging concern, examples include human and veterinary pharmaceuticals (e.g., carbamazepine, imidacloprid). Not all will be harmful, understanding which substances are of greatest concern to target effective risk management is important. Additionally, per- and polyfluoroalkyl substances (PFAS), so called ‘forever’ chemicals, continually challenge regulatory frameworks because of the vast number and complexity of substances, their pervasive use and extreme environmental persistence.
Recorded Lecture
Emma Pemberton who is an environmental chemist and water quality sciencist in the Chief Scientist's Group at the Environment Agency talks about some of the issues around chemicals in the environment in England.
Key reading
Environment Agency(2021) Chemicals: challenges for the water environment.
Environment Agency/Natural England (2025) State of the water environment: long-term trends in river quality in England: 2024
Environment Agency (2018) The state of the environment: water quality.
Environment Agency (2019) The state of the environment: soil.
Environment Agency (2014) Water quality monitoring data GC-MS and LC-MS semi-quantitative screen.
Other Reading Materials
Environment Agency (2018) State of the environment report.
Environment Agency (2019) Polybrominated diphenyl ethers (PBDEs): sources, pathways and environmental data.
Environment Agency (2019) Cypermethrin: Sources, pathways and environmental data.
Environment Agency (2019) Polycyclic aromatic hydrocarbons (PAHs): sources, pathways and environmental data.
Environment Agency (2021) Poly- and perfluoroalkyl substances (PFAS): sources, pathways and environmental data.