Update on water quality findings in historic report

We have been made aware of a historic academic research report into the presence of PFOS compounds in water sources around the UK. The report in question was published in February 2008 and based on research carried out in 2007.

Recent news articles have linked our Duxford Airfield site to PFOS compounds. This site is included as one of 20 locations tested in the 2008 report.

You may recall that we successfully challenged misleading information in some media coverage. With that in mind, we believe this information to be very important in the reading of this document.

As you may know, the water from our Duxford site was never used in its raw form as the supply into your home. It was always blended with other water to ensure it reached necessary guidance thresholds set by the Drinking Water Inspectorate (DWI).

What does the report state?

The 2008 report includes measurement of PFOS in the groundwater which are in line with the known levels.

It has been known for some time that the raw water at our Duxford site contained PFOS compounds at a stable level of between 0.2 micrograms per litre (µg/litre) and 0.4µg/litre – note this is not the drinking water supply. A microgram is one millionth of a gram.

The recorded level of PFOS set out in the report for what its authors term ‘final’ water is 0.13µg/litre. It is not clear if this ‘final’ water was tested at a tap or further back in the distribution system and would have been subject to further blending treatment.

In 2007, when this test was carried out, this sample (0.13µg/litre) was below the DWI threshold of 9.0µg/litre and considered ‘wholesome’ by the DWI’s definition.

Current drinking water quality guidance

The DWI updated its guidance in 2009 and lowered the threshold for the presence of PFOS in drinking water to 1.0µg/litre. It further updated its guidance in January 2021. The new guidance lowered the threshold again to 0.1µg/litre.

We therefore consider it to be unreasonable to measure historic test results against updated, more stringent guidance, which came into effect 15 years after the tests in the report were completed.

The testing framework we operate in is among the strictest in the world. Last year we carried out almost half a million tests against over 200 criteria, achieving a 99.99% compliance rate.

Among these tests were tests at the customer tap for PFOS, which led to the Duxford site being disconnected from the water supply in line with the DWI’s latest, more stringent, guidance.

The water we supply to all our customers is safe to drink.

Where was the groundwater distributed to?

As we have previously confirmed, there are around 6,500 homes in the distribution area which could have possibly received water partially sourced from the Duxford site. It is, however, certain that many homes in this area never received any water from this source or, if they did, it was in very low or untraceable levels.

We have included a map below which identifies these areas of theoretical reach (click to enlarge).

map of Duxford Airfield area of supply

Regular monitoring of water quality at the tap and in line with the introduction of new, lower guidance levels of PFOS, resulted in the Duxford site source being disconnected from the supply in summer 2021.

Key facts

  • The Duxford Airfield groundwater source never formed your water supply in its entirety
  • In line with guidance, it formed part of a blended supply
  • Levels of PFOS measured in the 2008 report samples were below DWI thresholds in use at the time
  • New guidance limits for the presence of PFOS were introduced in 2021
  • The Duxford Airfield site was disconnected from the supply network in 2021
  • Your drinking water is safe as confirmed by independent testing carried out in February 2022
  • Overall, we reach a 99.99% water quality compliance rate measured against some of the strictest standards in the world

Read the DWI PFAS leaflet.
We hope this information is useful to you and please check back for further updates regarding this matter.

Posted: 25 February 2022
Updated: 2 March 2022