Workers at ERA's controversial Ranger uranium mine drank water containing 400 times the normal limit of uranium, the mine's supervising scientist said.
The Australian Democrats have called for the mine, in Kakadu National Park, to remain closed until the investigation into the contamination was finished, and the regulation of Australia's uranium mines was overhauled.
ERA on Wednesday closed the Northern Territory mine after elevated levels of uranium were discovered in the water supply.
The Commonwealth's Supervising Scientist for the mine, Dr Arthur Johnston, said 20 workers had been exposed to the contaminated water.
"It (the uranium content) is quite high," Dr Johnston told ABC radio.
"The concentration that has been reported to me has been about 400 times the drinking water limit.
"It is of concern."
ERA said three people had reported mild symptoms following the water contamination, discovered early on Wednesday morning.
"So far there have been no medically-treated cases," the spokeswoman said.
"The company is continuing to monitor thhealth issue carefully."
ERA said the incident occurred at 10.30 (CST) on Tuesday night in the processing plant.
"It appears that an erroneous connection was made between the portable water line (for drinking and washing) and the process line," the spokeswoman said.
ERA was working with regulations to re-open the mine, possibly by the weekend.
Supervising scientist Dr Johnston said the concentration of uranium the workers had been exposed to would likely be "quite small".
"These limits are set for people consuming water continuously throughout their lives from an individual source.
A WORKER at an Australian mine is considering legal action after falling ill from drinking water mistakenly contaminated with uranium.
Twelve workers at Energy Resources of Australia's Ranger mine in Kakadu National Park reported suffering nausea, headaches and stomach cramps after drinking the contaminated water.
The Ranger mine - Australia's biggest uranium mine - was shut down for eight days after the contamination was discovered on March 24. The mine's uranium ore processing plant, where the contamination originated from, remains closed.
The water supply became polluted with uranium and other chemicals after processed water was mistakenly connected to the drinking water supply.
Federal Environment Minister David Kemp today said the incident was unacceptable, and he had asked for a full report.
"This event should not have happened - it's very hard to see standing from outside the mine how it did happen," Dr Kemp told ABC radio.
"There's obviously management issues that need to be addressed within the mine ... (and) we will make sure those steps are taken."
Worker Paul McDonald said he was sacked by his contractor after returning home from the Northern Territory to Perth to seek further medical treatment.
Mr McDonald, a casual fitter, said he had only been at Ranger a couple of days when the contamination occurred.
He said he was now considering legal action after falling ill.
Mr McDonald said he only found out about the extent of the contamination by reading about it "on a newspaper billboard".
"We actually read it in the newspaper ... (that) it was contaminated with uranium 400 times above the accepted level and obviously we all went into a panic then," Mr McDonald told ABC radio.
"I was just very annoyed that nobody had been and told me exactly how serious it was - I just thought the contamination had been just probably a little too much sulphur or chloride or whatever.
"I was mortified when I was found out it was uranium and another cocktail of acids."
ERA had paid all of his medical bills, he said.
"You feel okay and then all of a sudden you go into this sick feeling for three or four hours, and then you come out and you feel okay again.
"The doctors ... really have not got a lot of idea how to deal with this, because not many people go around drinking uranium."
A spokeswoman for ERA said the company was working with the NT government and the Office of the Supervising Scientist to fully investigate the incident.
"It's hoped that preliminary investigations may soon be completed," the spokeswoman said.
"Some affected persons on site were employees of contractors based in Perth and we understand that some people have have sought legal advice.
"ERA has implemented a program of providing information, support and counselling, including specialist medical advice for those who might have been affected by the incident."
Effects on Humans: Metallic uranium and insoluble uranium compounds may produce both chemical poisoning and radiation injury [Clayton and Clayton 1981, p. 1996]. The insoluble uranium compounds are less toxic chemically than the soluble compounds, but uranium and all uranium compounds have the potential to cause radiation damage [Clayton and Clayton 1981, p. 2000; Klaassen, Amdur, and Doull 1986, p. 695]. Exposure to the dusts of uranium or to an insoluble uranium compound may cause respiratory irritation, cough, and shortness of breath [Genium MSDS 1988, No. 238]. Dermatitis has also been reported, and prolonged skin contact causes radiation injury to the basal cells [Proctor, Hughes, and Fischman 1988, p. 502]. Studies have shown that uranium workers are at increased risk of death from respiratory, lymphatic, and hematopoietic cancers; these deaths are presumed to be caused by radiation injury from radon gas, a byproduct of uranium decay [Rom 1983, p. 688]. A study of the risk of respiratory deaths among uranium miners in the United States showed the following dose-response: miners exposed occupationally for 5 to 9.9 years had a 2-fold increase in risk; miners exposed for 10 to 24.9 years had a 3.6-fold increase in risk; and those exposed for greater than 24.9 years had a 3.75-fold increase in risk. Smoking was shown both to increase the risk of death from respiratory disease and to shorten the neoplastic latency period [Clayton and Clayton 1981, pp. 2010-2011].
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