Two out of nine groundwater samples contained dangerously high levels of Perfluorooctane Sulphonate (PFOS), a bio-accumulative chemical with strong links to bladder cancer also thought to cause reproductive problems.

The chemical may have originated in the fire fighting foam used in the aftermath of the blast. The latest tests, carried out as part of the EA’s regular monitoring programme, found two water samples to contain 4.8 and 5.9 micrograms of PFOS per litre – well above the safe limit of 3 micrograms set by the Drinking Water Inspectorate.

But further measurements at one of the sites showed lower values, prompting the EA to declare the results “inconsistent” and needing further study.

Robert Runcie, the EA’s Thames Region director, said: “Following an incident like Buncefield, where 680,000 litres of fire-fighting foam – some of which contained PFOS – was released to control the blaze and protect the community, we would expect to see elevated levels of PFOS in the environment.

“However, these results are variable and inconsistent and therefore may be unreliable. We are investigating further.”

Groundwater contamination does not necessarily mean the same PFOS levels in drinking water, the agency pointed out.

Mr Runcie said: “I stress that these are not samples of drinking water and these results do not mean there is PFOS above the DWI limit in the public water supply or in people’s taps.

“We have immediately passed this information onto Three Valleys Water Company and the Drinking Water Inspectorate for their information and action.”

PFOS contamination has never been routinely monitored before, and the EA is about to begin a wider study into background levels in England and Wales.

The chemical has long raised health concerns because of its tendency to bio-accumulate in human and animal tissue and links to cancer. It is widely used as a grease repellent, in chrome plating, photographic equipment and aeroplane hydraulic fluids as well as fire fighting foam. Previous tests have found it to be widely present in the environment and in human blood.

The largest global producer of PFOS, 3M, decided to phase out the chemical in 2000. The UK first made moves to ban it in October 2004 (see related story). Europe recently proposed an EU-wide, although only partial, ban. Fire fighting foams would be one of several uses exempted from the EU ban under current proposals.

Goska Romanowicz

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