AN EXPLOSION at an oil distribution terminal in southern England ignited Europe鈥檚 largest peacetime fire on Sunday. But the cold weather and the ferocity of the blaze have kept health risks to people across southern England surprisingly low.
The explosion at the Buncefield depot in Hemel Hempstead, 40 kilometres north-west of London, which supplies fuel to the capital鈥檚 airports, occurred just after 6 am, injuring 43 people and damaging local property. It created a plume of smoke more than 3 kilometres high, which soon spread over a large part of southern England.
While the cause is still unknown, eyewitnesses reported seeing vapour and smelling petrol just before the explosion, leading to speculation that there may have been a fuel spillage or leak that was eventually ignited by a stray spark.
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As New Scientist went to press, firefighters were trying to extinguish fires in the last three of the 20 fuel tanks that exploded. The inferno is being contained by blanketing the tanks with synthetic foam sprayed at a rate of 32,000 litres per minute.
Though the burning fuel was meant for cars and aircraft, the explosion鈥檚 plume differs from typical vehicle exhaust. 鈥淎 car is designed to minimise the amount of smoke, but this is generating as much smoke as it can,鈥� says Ian Colbeck of the aerosol science group at the University of Essex in Colchester. The uncontrolled burning leads to stickier and much higher-density particles, which could trap toxic gases and bring them back to ground level. The plume probably contains sulphur dioxide, nitrogen oxides, polycyclic aromatic hydrocarbons and volatile organic compounds such as benzene.
However, the dry, cold weather saved people by creating a temperature inversion 鈥� a layer of warm air above the colder air near the ground. The powerful plume burst through this layer, which then acted as a barrier against any particles and gas settling back down. 鈥淗ad this been a hot summer鈥檚 day, much more material would have made it down to the surface,鈥� says Derrick Ryall at the UK鈥檚 Met Office in Exeter.
Any pollutants that do reach the ground are unlikely to cause severe health effects, although the nitrogen oxides could affect people with asthma and other breathing problems. 鈥淧eople are going to be coughing up black sputum and having black handkerchiefs for some time,鈥� says John Henry of St Mary鈥檚 Hospital in London.
鈥淧eople are going to be coughing up black sputum and having black handkerchiefs for some time鈥�
Any toxic run-off from the firefighting should be caught by concrete walls surrounding the fuel tanks. Each one can hold 10 per cent more than the volume of the tank it protects.
The blaze will not have affected global warming significantly. 鈥淭his is clearly undesirable, but not a big increment on total CO2 emissions,鈥� says Roy Harrison, an environmental health specialist at the University of Birmingham.
