Thousands of South African gold miners and their families can pursue a multi-million-dollar class action against mining companies over fatal respiratory diseases contracted at work, a high court judge has ruled.

Key points: Thousands of gold miners contracted fatal respiratory diseases

Thousands of gold miners contracted fatal respiratory diseases Judge rules miners can launch class action against companies

Judge rules miners can launch class action against companies The suits could cost mining companies hundreds of millions

The decision opens the way for the current and former miners to sue about 30 companies for damages, after suffering silicosis and tuberculosis from dangerous underground working conditions dating back decades.

Analysts have said the suits could cost the gold industry hundreds of millions of dollars.

Many miners caught silicosis, which has no known cure, from inhaling silica dust while drilling rock.

The dust lodges in the lungs and causes permanent scars.

Symptoms include persistent coughing and shortness of breath, and the disease often leads to tuberculosis and death.

"We hold the view that in the context of this case, class action is the only realistic option," Judge Phineas Mojapelo told the High Court in Johannesburg.

Judge Mojapelo said workers who had died of the diseases could be included in the suits, with any damages paid to family members, and that each mining company should be held liable separately for any damages.

'We have been struggling for so long'

Some miners walked out of the courthouse triumphantly with fists raised, while activists sang and danced outside.

Sunlight shines from behind a gold mine pithead near Johannesburg. ( Mike Hutchings: Reuters )

"This will make a difference in our lives, because we have been struggling for so long," Vuyani Dwadube, 74, a former rock driller who worked at Harmony Gold and suffers from tuberculosis, said.

In their heyday in the 1980s, South Africa's gold mines employed 500,000 men, and some medical research suggests as many as one in two former gold miners has silicosis.

The defendants in the case include some of the world's biggest bullion producers, who have been hit by a slide in commodities' prices and widespread labour unrest among miners.

In a separate case in South Africa earlier this year, about 4,400 silicosis victims and their families won a $32 million settlement from mining giants Anglo American and AngloGold Ashanti.

South Africa is one of the world's leading gold-producing countries, and lax labour health and labour practices during the apartheid-era contributed to the spread of work-related diseases.

AFP/Reuters