Cleaning up UK drinking water

Per- and polyfluoroalkyl substances (PFAS) – or ‘forever chemicals’ – are a large, complex group of more than thousands of synthetic chemicals that are valued for a range of benefits such as durability and non-stick, water-repellent and anti-grease properties. They are found in thousands of products, from skin creams and cosmetics to frying pans, outdoor clothing and shoes, firefighting foam, medical devices and batteries.

PFAS molecules have a chain of linked carbon and fluorine atoms. The carbon-flourine bond is considered one of the strongest bonds in organic chemisty, which means these chemicals break down slowly – some take over 1,000 years to do so. They therefore stay present in the environment for a very long time.

The extent to which PFAS are used varies globally. However, they are used and found everywhere – they have even been detected in polar ice caps. Analysis of blood and urine samples suggests that human exposure to PFAS is widespread.

PFAS leak into the soil, water, and air from sources such as industry, firefighting foams and waste infrastructure. Because they break down slowly, if at all, they can build up in the environment, leading to the greater likelihood of them passing into drinking water and the food chain. If people and wildlife consume more PFAS than they excrete, these chemicals can build up in their bodies.

PFAS been linked to a range of adverse impacts on human health, including increasing the risk of testicular and kidney cancer, thyroid disease, high cholesterol, liver damage and the development of unborn children.

People are most likely exposed to these chemicals by consuming PFAS-contaminated water or food, using products made with PFAS, or breathing air containing PFAS.

Water companies in England and Wales are required to measure and manage the levels of 48 varieties of PFAS – though there are thousands of different types, some are never checked.
Concentration levels of each of these individual PFAS in drinking water must not exceed 100 nanograms per litre (ng/L). This is 10 times the recommended ‘low risk’ limit according to the Drinking Water Inspectorate’s own guidance, which states that levels exceeding 10 ng/L are medium or high risk.
In August 2024, the DWI also imposed a new total limit on PFAS which means the sum of the 48 measured PFAS should be no higher than 100 ng/L. The Government, however, has not yet put any of this guidance into legislation, as of October 2024.

In August 2024, the Drinking Water Inspectorate imposed a new total limit on PFAS which means the sum of the 48 measured PFAS should be no higher than 100 ng/L in England and Wales as of 1 January 2025. This goes beyond EU regulations but we are still pushing for those limits to be adopted by the UK Government in legislation.

For comparison, the US has implemented a limit of 4 ng/L for each of PFOS and PFOA, two of the most common PFAS[i] and the EU’s Drinking Water Directive states that 20 widespread PFAS must collectively not exceed 100 ng/L. Scotland has adopted the EU guidance of a total limit of 100 ng/L.

Currently, the most common treatment method for PFAS is water blending (combining water sources to dilute the concentration of PFAS). Water treatment plants can also remove PFAS using a range of methods, with blending water from different sources and granulated carbon filtration being the most commonly used. However, if waste generated during filtration is not dealt with properly, PFAS can be re-released into the environment, where the chemicals can continue to cycle through and pose health risks.

Destructive technologies can break down PFAS once and for all and remove them from the environment for good. However, current options are limited in the scale at which they can be deployed. There are also a range of challenges in monitoring PFAS, including cost, the sheer (and growing number) of these chemicals and a lack of analytical standards for many PFAS. Investment is needed in research, development and innovation (RD&I) to address these challenges – and chemical scientists have an important role to play.

It is important to note that the levels on our interactive map show PFAS concentrations in the water courses themselves – not the drinking water that comes from your tap. Water companies are required to remediate water when a PFAS is found at levels more than 100 ng/L but we are calling for this limit to be reduced.

Scientists are still investigating how these chemicals may impact health. Given this, it is sensible to take a proactive and precautionary approach for the sake of public health. This is why recommended limits are set at a low level.

However, it is important to bear in mind that the links between exposure to a given chemical and the risk of negative impacts on health is complex. Higher levels of PFAS in your local water courses do not mean that you as an individual are necessarily at a high risk of developing health issues as a result.

Household water filtration systems, fitted at the tap or using a jug with a filter, could be useful for removing PFAS from drinking water. However, some technologies are more effective than others, and more research is needed. Most household water filtration jugs use granulated carbon filters, but it is unknown how effective these household versions are at removing PFAS.

Fidra, an environmental charity working to reduce chemical and plastic pollution in the environment, has created a website offering consumers advice on PFAS-free products.