THE massive conflagration at the Buncefield oil depot has had no impact whatsoever on the environment and public health, an in-depth investigation has concluded.

Although the fire, which started with a massive explosion on December 11 and was still attended by firefighters at Christmas, was the biggest ever in peace-time Europe, detailed tests by the Health Protection Agency have found no evidence of harmful pollution, either as ground deposits or in the air.

The agency's report says: "This investigation has not found any credible evidence of contamination of soil and grasses.

"Pollutant levels in the vast majority of surface soil and grasses are unexceptional and do not present a risk to human health.

While localised smoke plume grounding can not be discounted, this investigation supports the view that prolonged plume grounding downwind of the fire did not occur."

Samples of soil and grass, together with wipes of dust, were taken from 33 locations roughly south south-east of Buncefield, the wind direction at the time, including two in Chiswell Green and one in Napsbury.

The samples were tested for five categories of potential pollutants: polycylic aromatic carbons (PAH), dioxins and furans, heavy metals such as nickel and vanadium, fluorides, and PFOS (a harmful substance used in firefighting foam).

Comparison with a control sample taken elsewhere showed no sign that any of the substances were present at increased levels, with two exceptions - traces of PFOS in two samples and unusually high PAHs at a site in south Watford.

The Agency says the PFOS traces were well below official safety guidelines, and the high PAH results are probably due to some pollution problem completely unrelated to the fire.

The investigation also analysed records of people seeking medical help and concluded the health impact was relatively small.

Several people went to hospital complaining of breathing problems associated with the fire, but the great majority were either employed at Buncefield or attended the site as emergency workers.

Press reports that harmful levels of PFOS could enter the local water supply via the River Ver have been denied by Three Valley Water.

A statement coinciding with the Health Protection Agency report reads: "Sampling for perfluorooctane sulfonate (PFOS), a major constituent of the fire-fighting foam used at Buncefield, is being carried out at observation boreholes close to Buncefield and those of the company's boreholes which have been identified as being at possible risk.

"All the company's water resources in this area are from groundwater, not rivers and streams.

"The results from the groundwater sources have been reassuring. The majority have not had any PFOS present.

"Occasionally there has been a trace found in a small number of samples, which includes a sample from our groundwater source at Mud Lane borehole, which had a result of 5.9 microgrammes per litre the official maximum safe level in drinking water is three microgrammes per litre.

"This result has been subject to review and repeat analysis of the same sample and a duplicate sample did not corroborate the figure, showing results of 0.9 and 0.2 respectively.

"Results of samples of treated drinking water supplied to our customers have shown no PFOS to be present.

"As well as being used in fire-fighting foams, PFOS has seen wide application in a range of other materials, including Scotchguard dirt repellent for fabrics.

"Our aim has been to try to avoid using raw water sources which might carry any PFOS risk, but those sources which are downstream of Buncefield do have treatment processes in place which we believe would be likely to remove most, if not all, of any PFOS that might be present."