Research reveals that gold miners are exposed to dangerous levels of radioactive gases, reports Eddie Koch
WORKERS in South Africa’s gold mines now have to deal with a new set of underground demons: radon and her “daughters”.
New research shows more than 10 000 miners are exposed to doses of subterranean radioactive gases that exceed international safety limits.
Union and government officials fear that clouds of radioactive gas released during blasting underground are causing higher than normal rates of lung cancer in gold-mine workers.
The industry and organised labour have only recently paid serious attention to the radioactive menace on gold mines, although the presence of radon gases in underground workplaces has been known since the 1940s.
The Council for Nuclear Safety (CNS), a government body that monitors occupational health hazards in the nuclear industry, revealed last week that 9 600 workers in the gold mining industry are exposed to a radioactive dose of between 20 and 50 milliSieverts each year. A safety standard set by the International Commission on Radiological Protection (ICRP) is 20 milliSieverts a year.
Recent CNS statistics show that another 1 100 workers are probably breathing in more than 50 milliSieverts of radioactive dust a year. The statistics are based on regular records of dust underground.
“These kinds of exposures are known to cause cancer in the bronchial area of the lungs,” said CNS researcher Bert Winkler. “This cannot be distinguished from tumours caused by smoking and other types of dust and so it is difficult to identify workers who have been affected by radioactive dust. But it is possible that exposed workers are more vulnerable to cancer and that there has been an increase in the incidence of lung cancers due to the presence of these materials.”
Winkler’s statistics show, however, that most workers are exposed to levels of radioactivity that are not regarded as dangerous. More than 200 000 employees breathe in far less than 20 milliSieverts each year.
Research shows that since the 1930s, eight to 15 out of every 1 000 white and coloured mineworkers have contracted occupational lung diseases, including cancers. No accurate statistics have been kept for black workers but “the rate for them will be higher because they work in more dangerous conditions”, said health and safety researcher Dr Imran Patel.
Sazi Jonas, health and safety officer for the National Union of Mineworkers, says his union had been aware that radon released during mining was a danger to workers’ health. Now it has emerged that the gas combines with other radioactive toxins — the “radon daughters” (polonium, bismuth and lead) and uranium and thorium — which cling to dust particles that can penetrate the lungs’ lining.
Radon and its “daughters” escape from gold-bearing rock and are distributed during blasting, when underground rock is removed and when gold ore is extracted on the surface.
Unlike pure radon gas, which is inhaled and exhaled relatively quickly, the “daughters” and dust particles can remain in workers’ lungs for substantial periods. As a result, exposure to even small doses of radioactive materials can be dangerous if workers breathe in the dust over a long time.
The new details about radioactive threats to mineworkers emerged during the current commission of inquiry into health and safety on gold mines.
Until four years ago, there were no regulations controlling the presence of radioactive gas clouds and inhalation. Since then mines have begun adapting ventilation systems to remove dangerous dust clouds.
“Traditionally, the mining industry has been allowed to regulate itself. But the example of contaminated material discovered last year to be fairly widespread revealed to the CNS that the industry was reluctant to take responsibility for protecting its workers from the effects of radioactivity,” said Dr David Fig, research director of the Group for Environmental Monitoring.
Winkler says the CNS’s statistics are based on measuring radioactive doses in the general environment. These were not necessarily an accurate assessment of the actual amounts of radioactive dust that workers inhale each year.
“We are working closely with the industry to find a simple system of measuring exposure doses of individual workers to radioactivity. Substantial reductions (in radioactive dust underground) can be made by planning and improving ventilation systems at little extra cost,” said Winkler. “But with 250 000 workers underground and the extremely deep levels of our mines we have a unique set of problems to contend with.”
Sources in the gold mining industry said the CNS “got its act together” in terms of monitoring radioactive exposure when high radioactivity levels were discovered at Phalaborwa metal scrapyards where waste material from gold mines is stored.
CNS acknowledges at least 20 mines in the Transvaal and Free State generate radioactive by-products.
Sources in the Anglo American Corporation say the Chamber of Mines is conducting research into the problem.
The West Rand Consolidated mine is repoprted to have high levels of radioactivity which has seeped into ground water that flows into parts of Kagiso township. Randgold is resisting a takeover bid from West Rand’s owners on the grounds that it will inherit liabilities that derive from radioactivity at West Rand.