US-based researcher Jacob Bogle, who has created a comprehensive map of the country from satellite images, made the alarming discovery while looking at pictures of Pyongsan uranium mine dating back to 2003.
Mr Bogle noticed that a waste pipe built to carry toxic water from the facility - which processes coal into uranium - to a nearby reservoir appears to be leaking into a river.
That tributary runs into the Ryesong River, which in turn empties into the Yellow Sea - an area between mainland China and the Korean Peninsula around which some 600 million people live.
Mr Bogle said: 'I was able to review high-resolution historical satellite imagery for multiple years going back to 2003.
'Each of the images shows an ever-growing pile of leaked material on either end of the pipe that takes waste material from the plant to an unlined reservoir.
'Some of the images also show fluids being actively spilled directly into the river.
'The plant is one of two declared uranium milling facilities in the country. It takes low-quality coal and processes it to create yellowcake, which contains around 80 per cent uranium.
'The extraction and milling requires multiple chemical processes and leaves behind a very toxic mix of waste materials.
'That toxic waste is then sent to the nearby reservoir, leaking and travelling into the Ryesong River in the process.'
The plant lies roughly 60 miles south of the North Korean capital, Pyongyang. Mr Bogle estimates that, within just nine miles of the Ryesong, there could be as many as 400,000 people consuming the river water or the crops fed by it.
The Daily Mail
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