HUNGARY'S TOXIC SPILL

Hungary says it will cost tens of millions of dollars and take at least a year to clean up the damage caused by a spill of industrial toxic red sludge.

Emergency workers are trying to stop the spill, from an alumina plant, from flowing into major waterways, including the River Danube

A state of emergency has been declared in three western counties after the chemical waste burst from a reservoir. Four people are known to have died, and 120 were injured. Six more are missing.

At least seven villages and towns are affected including Devecser, where the torrent was 2m (6.5ft) deep.

Hungarian disaster management spokesman Dr Attila Nyikos says a large scale clean-up is under way.

Emergency workers are trying to stop the spill, from an alumina plant, from flowing into major waterways, including the River Danube

The sludge - a mixture of water and mining waste containing heavy metals - is considered hazardous, according to Hungary's National Directorate General for Disaster Management (NDGDM).

While the cause of the deaths has not yet been officially established, the victims are thought to have drowned.

Some 600,000-700,000 cubic metres (21m-24m cubic feet) of sludge escaped from the plant, 160km (100 miles) from the capital, Budapest, affecting an area of 40 sq km (15.4 sq miles).

The muddy red sludge is waste from the early stages of aluminium production.

Aluminium-containing ore, bauxite, is washed at high temperatures in sodium hydroxide. This dissolves the aluminium, which can then be processed further, but the red sludge is left behind as a waste product. It is this which has leaked from the Hungarian storage reservoirs.

The sludge waste contains a mixture of metal oxides. According to MAL Hungarian Aluminium - the company which produced the waste - between 40% and 45% is iron oxide. This gives the mud its characteristic red colour. Between 10% and 15% is aluminium oxide, a further 10% to 15% silicon oxide and there are smaller quantities of calcium oxide, titanium dioxide and oxygen-bonded sodium oxide.

The sludge is a strong alkali, meaning it will cause burns when it comes into contact with the skin, and can damage lungs and the digestive system if it is ingested. This may cause death.

One of the rivers affected has been treated with chemicals - calcium and magnesium nitrates - to try to counter the alkaline effects.

(Source:text from www.bbc.co.uk and picture from google images)