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‘Forever chemical’ in English tap water samples carcinogenic, WHO rules

<span>Photograph: Andy Rain/EPA</span>
Photograph: Andy Rain/EPA

A substance found in hundreds of drinking water samples across England has been categorised as carcinogenic by the World Health Organization (WHO).

The move will increase pressure on the UK government to take action on “forever chemicals”.

Perfluorooctanoic acid (PFOA) is one of 10,000 or so chemicals within the family of per- and polyfluoroalkyl substances (PFAS) that are used in a wide range of products, from cosmetics to clothing and food packaging, as well as in industrial processes and in firefighting foams. PFOA and another member of the family, perfluorooctanesulfonic acid (PFOS), have largely been banned, but remain in the environment because of their persistence. Studies have linked the PFAS family of chemicals to cancers, immunodeficiencies, reproductive harms and developmental effects in children. They are not easily metabolised by the body so build up in humans and animals over time.

PFOA has been linked to cancer for some time but a growing body of evidence means it has now been upgraded to “category one”, which means it is “carcinogenic to humans”, according to the WHO’s International Agency for Research on Cancer (IARC).

A recent report from the Drinking Water Inspectorate (DWI) shows that approximately 12,000 samples taken from drinking water sources contain at least one PFAS of some kind.

The highest concentration of PFOA detected in a drinking water source was 149 nanograms a litre (ng/l), 1.5 times the DWI’s maximum limit for tap water. PFOS, categorised by the IARC as a “possible carcinogen”, was found at levels as high as 1,869ng/l, although these levels will have been diluted before reaching a tap.

Analysis of Environment Agency and water company data by Watershed Investigations showed that PFOA was detected in almost 1,000 drinking water sources sampled between 2006 and 2022. And tap water sampling around England found PFOA in more than half of the 45 samples taken, albeit below 10ng/l, deemed “low risk” by the DWI.

Earlier this year, the Guardian and Watershed Investigations found that effluent from the site of a chemicals company flowing into a protected river in Lancashire contained “extremely high levels” of PFOA.

The government has been accused of dragging its feet over taking action on PFAS compared with the EU, which is considering stricter regulation across all 10,000 or so of the substances.

England is behind the EU on drinking water limits: the DWI allows up to 100ng/l for PFOA and PFOS, while the EU applies a limit of 100ng/l for the sum of 20 PFAS. Denmark has set a limit of just 2ng/l for four individual PFAS, and the US Environmental Protection Agency has proposed dropping limits on some to 4ng/l.

Dr Patrick Byrne from Liverpool John Moores University, said: “Recently the Royal Society of Chemistry called on the government to reduce the maximum allowable level of individual PFAS such as PFOA in drinking water from 100ng/l to 10ng/l. This is to bring the UK more in line with other countries such as the US, who are proposing a maximum allowable concentration for PFOA of 4ng/l.

“UK regulations and environmental standards must keep pace with the scientific and medical evidence to protect our drinking water and us.”

Hannah Evans from the chemicals NGO Fidra said the categorisations were “extremely alarming” and highlighted the urgent need for regulatory action on PFAS. “We must take this opportunity to learn from cases such as PFOS and PFOA, and transition towards a PFAS-free economy as quickly and as effectively as possible.”

Philippe Grandjean, professor and chair of environmental medicine at the University of Southern Denmark, said PFAS chemicals were “transferred from a pregnant mother through her placenta to her foetus, and they are excreted in her milk. Thus, a breastfed infant receives a relatively large dose … so we see abnormalities like elevated cholesterol and poor glucose metabolism in children with elevated PFAS exposures. In addition, the immune system is harmed. This has implications for infectious disease but may also be of importance for cancer development, where immune cells are supposed to remove abnormal cells.”

A Defra spokesperson said: “Drinking water quality in England is of an exceptionally high standard and among the best in the world. Water companies are required to carry out regular risk assessments and sampling for any substance – including PFAS – that they believe may cause the water supply to pose a risk to human health.

“Work is continuing across government to help us assess levels of PFAS occurring in the environment, their sources and potential risks to inform future policy and regulatory approaches.”