Several drinking water wells in the highly populated Red River delta area of Vietnam contain dangerous levels of arsenic. This can lead to several health problems such as cancer, neurological problems and hypertension, researchers informed on Tuesday.

They also said in a paper published in a journal Proceedings of the National Academy of Sciences that 44 percent of the wells in the delta contain levels of manganese that go beyond World Health Organization guidelines.

Around 7 million people are at huge risk of chronic arsenic poisoning. In an email written to Reuters, main author Michael Berg explained that this is certainly disturbing since groundwater is the main source of drinking water in the entire delta.

The delta is home to 16.6 million people. It includes eight provinces and two municipalities which are the capital Hanoi and Hai Phong port. About eleven million residents have no access to the public water supply and only rely to other sources such as the tube wells.

The researchers collected samples from 512 private wells throughout the delta and examined them for presence of arsenic, manganese, as well as other toxins such as selenium and barium.

They found out that sixty-five percent of the groundwater wells in Red River delta contain levels of naturally-occurring toxic elements that exceed the safety standards from World Health Organization, Berg, a senior scientist at the Swiss Federal Institute of Aquatic Science and Technology, wrote in the journal.

He also informed that the most health threatening are arsenic and manganese. Arsenic is above WHO guidelines at 27 percent of the wells and manganese at 44 percent.

Berg and his colleagues alleged that the extensive contamination is owed to a long history of groundwater exploitation around the delta.