The mining company contracted to provide metal for the London 2012 Olympic medals is facing a lawsuit in Utah accused of violating the country's clean air laws.
Reported by Al Jazeera, the findings undermine the London Olympic Organising Committee's (LOCOG) claim that London 2012 will be the "greenest games ever".
Rio Tinto, the company who owns the Kennecott Utah Bingham Copper Mine where the metal for the 4,700 medals was mined, has been accused of placing millions of residents at risk through its practices.
Residents, doctors and environmental watchdogs in the state allege that the mine is responsible for more than 30% of the particulate matter and gases emitted into the atmosphere, making it a major source of industrial pollution in the state.
Only last year, residents of Utah's state capital, Salt Lake City, filed a lawsuit accusing Rio Tinto, a sponsor of the Games, of violating environmental protection agency limits on emissions. The contract for providing the metal was awarded after the lawsuit was filed.
One local doctor, Cris Cowley, told the broadcaster "there's no safe level of particulate matter you can breathe," amid fears that pollution from the Kennecott mine is turning residents into the equivalent of heavy smokers.
On the Rio Tinto website, the company claims: "We are right behind London 2012's commitment to delivering the most sustainable Games".
In a stement, Rio Tinto said: "Kennecott continues to operate within the parameters of its air permits and is consistently in compliance with the US, EPA and Utah Division of Air Quality regulations, which are based on strict standards for protecting human health."
However, speaking earlier this year, Cherise Udell, founder of Utah Moms for Clean Air, said: "In Utah, Rio Tinto are the number one emitter of toxins known to cause harm to human health. Every year, between 1,000 and 2,000 Utahans die prematurely due to chronic air pollution and Rio Tinto's Bingham mine is responsible for about 30 per cent of this."
When asked about the lawsuit, the LOCOG told Al-Jazeera: "We have received no complaints and no representation has been made to us, so there is nothing to investigate. We are completely satisfied with Rio Tinto."
The Rio Tinto case is not the first environmental controversy to blight the London Olympics. The sponsorship of BP and Dow Chemicals sparked criticism, with Meredith Alexander, the ex Olympics 'ethics tsar', quitting her post in January over the fallout from Dow Chemical's endorsement of the stadium wrap.
Watch The Great Olympic Greenwash on Al-Jazeera English on Wednesday, 20 June at 23:30.