BBC News Online: Sci/Tech

Cyanide's deadly hold over gold

The Romanian cyanide spill devastated the River Tisza

Cyanide is a highly toxic chemical - less than one gram can be fatal to humans - and river spills can do enormous damage to wildlife and ecosystems.

The principal application of sodium cyanide is in mining precious metals, especially gold, where it is used to separate the metal from its ore.

But there has been concern for many years over leaks and spills.

In January 2000, waste containing sodium cyanide flowed into the River Tisza, a tributary of the Danube, following a dam burst at a goldmine in Romania.

The accident killed around 80% of the fish in the Tisza, and devastated local populations of birds and other animals.

It sparked a bitter political confrontation over responsibility and compensation, between the multinational company operating the mine and the governments of Romania, Hungary and Serbia.

According to the environmental organisation the Mineral Policy Centre, which monitors the mining industry, cyanide spills are a risk in almost every gold mining area.

As scientists have yet to come up with an alternative process that avoids cyanide and is both technically and economically feasible, the risk of further damaging spills seems almost certain.