Published online: 12 December 2005; | doi:10.1038/news051212-2 Burning oil depot plagues England's skies What are the consequences of the explosions near London? Mark Peplow A series of explosions at an oil depot just north of London has created one of the biggest industrial fires ever seen in Europe and injured 43 people. Starting at about 6:00 GMT on 11 December, a thick pall of black smoke has spread from the Buncefield oil depot in Hemel Hempstead, Hertfordshire, for more than 120 kilometres across southern England. As the fire rages on, Nature investigates efforts to damp the blaze, and asks about the environmental and health effects of the smoke.
How did it start?
No one knows for sure, but police say they have no reason to suspect foul play.
How serious is it?
Flames and smoke rise from the Buncefield oil depot near Hemel Hempstead, England. © AP Photo/Hertfordshire Police "Any incident that you can see from space is not your average garden bonfire," says Zäl Rustom, who works for Hi-Bar UK, a pollution-response company in West Sussex. "It's major."
But he adds that the fire now seems to be under control, and pipelines supplying the facility were shut off immediately after the explosions.
Firefighters have 250,000 litres of foam concentrate at their disposal. This is added to water to make a thick blanket that starves a fire of oxygen. "The main problem now is the logistics of getting foam on top of the tanks," says Rustom.
Roy Wilsher, Hertfordshire's chief fire officer, told a press conference on 12 December that it was impossible to say how long the blaze might burn. "We are in uncharted territory," he said. "This is the largest fire of its kind that we in the UK, and in Europe, have dealt with."
What is burning?
Up to 270 million litres of kerosene, diesel and gasoline, held in 20 storage tanks on the site. Half of those tanks' fires have now been extinguished.
The facility is co-owned by Total and Texaco, but also used by oil companies such as BP and Shell. Much of the fuel at Buncefield is transported by train and pipeline to the nearby airports at Luton and Heathrow.
What pollution is it producing?
Smoke, mostly. And a research aircraft is now trying to find out more.
"We're flying around the extremities of the plume as far as we can," says Steve Ball, who heads the Facility for Airborne Atmospheric Measurements, based at Cranfield University in Bedfordshire. The plane is normally used to monitor urban pollution, part of a joint project between the Met Office and the Natural Environment Research Council (NERC).
Today it is tracking the speed and shape of the cloud. The Met Office hopes this will help its researchers to forecast the plume's path. The cloud is currently being blown southwest.
Researchers hope that the plane will return tomorrow with additional equipment that can sample the gases and particles in the smoke. Carbon monoxide, carbon dioxide, sulphur dioxide and oxides of nitrogen are all pouring from the fire, along with tiny flecks of soot.
"There will be hundreds of different molecules in there," says Met Office meteorologist Wayne Elliott. "And the smoke may continue even after the fire is out," he adds.
What are the health effects?
Health Protection Agency officials are advising that the smoke is likely to affect only those with existing respiratory problems, such as asthma. For those bothered by the smoke, staying indoors is the best precaution, they say. Colbeck adds that unless a person's exposure is exceedingly high, a one-off incident such as this shouldn't trigger any long-term health problems.
Once the fire is out, local air quality should return to normal levels within a few days, says Ian Colbeck, an expert on the role of aerosols in the environment at the University of Essex, Colchester.
What are the environmental effects?
The cloud will contain pollutants known as polyaromatic hydrocarbons (PAHs), but it is unlikely that they could accumulate to a high enough concentration to cause severe environmental effects, says Dan Osborn of NERC's Centre for Ecology and Hydrology in Lancaster.
"There's nothing in the cloud that isn't already in the environment," adds Osborn. The plume is also too small to have any direct effects on climate.
England's rainy weather may also help to disperse the pollutants, spreading material over a wider area at lower concentration, so that toxic effects are less likely to build up. "If it does rain out, it should be less of a problem," says Osborn. England's rainy weather may also help to disperse the pollutants, spreading material over a wider area at lower concentration, so that toxic effects are less likely to build up. "If it does rain out, it should be less of a problem," says Osborn.
The biggest potential difficulties could be caused by attempts to put the fire out, he adds. "When a mass of water goes into the ground, it can flush older contaminants out," Osborn says. "There has also been concern in recent years about the materials in fire-fighting foam." So the run-off mixture of foam, water and fuel will be contained within temporary reservoirs to avoid contaminations of water supplies.
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Location of Hemel Hempstead within the UK
A shot of the fire taken near the depot

A series of large explosions have occurred close to Hemel Hempstead  Hertfordshire, UK. The source of the explosions has been confirmed as the Hertfordshire Oil Storage Terminal (HOSL), Hemel Hempstead, known locally as the Buncefield complex. Up to  150 fire fighters are reported to be at the scene with 10 fire appliances and 1 specialist foamer.

The first 'blast' was heard near Hemel Hempstead on Sunday 11 Dec at 6 am. Further smaller explosions followed at 6:24am , 6:26am, 6:30am. BBC News 24 reported an additional, fourth large explosion.  Hertfordshire Police Constabulary are currently treating the explosion as an accident.  

Reports say the explosion, which registered 2.4 on the Richter scale, was heard as far away as Oxford, and Whitehall, Central London which is 60km (38 miles) away. Eyewitness statements report that the explosion was heard from at least 160km (100 miles) away and as far away as France and The Netherlands. Pilots reported noticing the blast from the North Sea and the West Country area of the UK.  The M1 motorway which runs close by has been closed in both directions near the blast which is causing travel chaos as other roads become congested.

Malcom Stewart, a BBC News24 eyewitness who is a tanker driver for the site has reported that the site supplies several oil companies and is a joint operation between Total UK and Texaco, it is also used by BP, Shell and the British Pipeline association. The complex is not a refinery but a storage facility for refined petroleum awaiting distribution to airports and filling stations. The eyewitness reports that the depot has approximately 20 tanks which can hold about 3 million gallons (11 million litres or 70,000 barrels) each.  Another News24 eyewitness has just reported that he has seen at least 5 of these tanks on fire.

Satellite image of Hemel Hempstead fuel explosion showing black smoke from the explosion near London

The depot operates on a 24 hour basis and is split into 2 parts - aviation fuel and domestic fuel.  A number of eyewitnesses have reported on UK news that the aviation fuel side appears to be the part of the site that has been affected.

Local authorities were not immediately available for comment but there have been reports of casualties.

Some reports on live television state that, "Several other neighbours said they did see a plane go into the depot."  BBC News 24 were also discussing the idea a possible plane crash as the cause of the explosions.  Hertfordshire police have now gone on the record to say that there is no plane involved (BBC News24).

The police have issued a contact number 0800 096 0095 and asked that people do not call the emergency services in Hertfordshire directly unless it is an emergency. 
Buncefield Fire, taken from Dunsmore, Bucks - about 20miles away.

In addition to being an oil storage depot, it is a major hub on the UK oil pipeline network with pipelines to Killingholme Lindsey Oil Refinery (LOR), Humberside (10 inch), Merseyside (10 and 12 inch), Coryton on the Thames Estuary (14 inch) and Heathrow (6 and 8 inch) and Gatwick airports radiating from it.

The disaster is believed to be the worst explosion at a petrochemical plant in the UK since the Flixborough disaster of 1974.
Hertfordshire's Chief Fire Officer Roy Wilsher said: "This is possibly the largest incident of its kind in peacetime Europe." 

A firefighting press officer said that they are stock piling foam from neighboring regions for a prolonged attach which they hope will stop the spread of the fire, however, the inferno itself will have to burn out which could take between 24 hours and a few days.

Despite the authorities saying that there is no need to panic buy petrol, filling stations have had above average queues since this morning and some small garages have ran out.

Deputy Prime Minister John Prescott has visited the scene.

Smoke Viewed from St Albans