Toxic chemicals have been found in drinking water which could increase the risk of chronic diseases.
Exposure to the poisons could spark a range of serious health conditions such as high cholestoral, type 2 diabetes and other conditions such as obesity which can lead to heart disease,.
Those living in one particular county, south Cambridgeshire, are most at risk and the county is supplied by utility firm Cambridge Water.
The company last June cut off a supply containing four times the 'legal limit' of perfluorooctane sulphonate (PFOS).
But the firm has not revealed how long people had been piped water before it was cut.
The contaminated water, it assures customers "never reached taps" and was instead "blended with other sources".
Those living in the area say they were never informed about the discovery last summer, The Guardian reported.
An estimated 1,000 people in the supply area are understood to have been affected.
Residents of Stapleford and Great Shelford, where around 7,000 live, have heard “nothing at all” from Cambridge Water.
And the title reports that while investigations happened, it “had not told the community”.
The Drinking Water Inspectorate limits PFOS to 100 nanograms per litre (ng/l).
Elinor Cordiner, head of drinking water quality and compliance at Cambridge Water, said sample surveys had happened to determine if there was any risk to customers after January 2021.
But it claomed all of the locations, apart from one, fell within tier 1, which the company says is the 'lowest risk' category.
A site at Duxford Airfield was in the tier 3 category, and tier 4 was the highest.
Affected houses were supplied by an acquifer which had PFOS levels at almost 400ng/l - four times the legal limit.
Ms Cordiner said in a statement "water supplies from this source have always been blended with other sources before reaching our customers".
She added: "This means that levels of PFAS at customer taps were at, or around, the tier 1 (lowest risk) level."
The site was removed from supply as a "precautionary measure" and Cambridge Water is "in the process of installing additional treatment at the site".
It said: "We confirm that we have not breeched any legal limit... We can assure customers that all drinking water in our supply region was, and remains to be, in line with expected safe levels."
The Guardian reports that Cambridge Water said it was “unable to guarantee a blend below 100ng/l for our customers at all times”.
But Tony Fletcher, associate professor at the London School of Hygiene and Tropical Medicine, described levels in Duxford as “grossly exceeding" recommended drinking water limits.
PFOS, he said accumulate in the body and it takes a long time to remove them.
The aquifer sits close to Duxford airfield. and these sort of locations are known to be potentially significant sources of PFOS according to the Sun.
Duxford airfield said no banned substances “are knowingly used anywhere across our estate”
PFOS has gradually phased out since the early 2000s after harm to the environment and human health.
However, it is persistent in the environment. Due to its design, it never breaks down, dubbed a “forever chemical”.
Humans only come into contact with PFOS through contaminated food and water.
A report from Public health England states:“studies with animals fed PFOS or PFOA for a long period showed effects on the stomach, liver and thyroid hormones”, but there is sparse information from human studies.
At very high levels, animals exposed for prolonged periods were at risk of cancer.
Jamie DeWitt, a professor of pharmacology and toxicology at East Carolina University in the US, saiid people who had drank water over a sustained period have increased risk of certain types of diseases.
These she said included cholestorol changes and lower vaccine antibody responses.
Andy Willicott, managing director at Cambridge Water, said: "I can reassure customers that their water supply is safe.
"Upon receipt of the new guidance our teams proactively carried out a series of tests across our water network, including tests at customer taps, to make sure that the water we supplied was safe and followed the new guidelines.
"Our approach and all test results were shared with the DWI and Health Security Agency. Water from Duxford does contain low levels of PFAS, however is blended with other groundwater sources resulting in PFAS levels, which in line with the recent guidance does not require any further action, due to such low levels.
"However, to ensure we fully mitigated all risks we took that source out of supply until we have installed an additional level of treatment.
"Totally removing the risk of PFAS for our customers.
"Ensuring our water is safe for our customers is our highest priority.
"The PFAS levels within the water that supplies our customers has remained within the guidance levels set out by the independent water quality regulator, and our customers can therefore be confident that their supply has been, and continues to be safe.”
