Hazardous metals used in oil production in war-torn South Sudan have polluted drinking water sources as 180,000 people are under health risks, a right group reported on Friday.
Previous tests have shown "direct links" between oil drilling and drinking water pollution.
Klaus Stieglitz, from the German-based Sign of Hope organisation said they were "highly intoxicated with pollutants such as lead and barium," after conducting dangerous tests carried out on hair samples from 96 volunteers living around the Thar Jath oil processing plant in South Sudan’s northern Unity region.
"There is a direct link between the contamination of the people and the activities of the petroleum industry working in this area," he said, adding that the research built on six years of hydrological tests by the group in the region.
Klaus-Dietrich Runow, from Germany's Institute for Functional Medicine and Environmental Health, one of two separate independent toxicologists who assessed the samples and said, "the total toxic stress -- as found in the hair samples -- of the human population of the area is life-threatening."
Several tests in the past have shown "direct links" between oil drilling and drinking water contamination.
Despite small number of samples analysed, the final results of the test suggests they apply to "large sections" of the surrounding population, about 180,000 people.
"There is a concern for health effects in the localities of Koch, Leer, and Nyal," Professor Fritz Pragst, from Berlin's Charite hospital said.
The regions which have experienced a series of violence in more than two-years of civil war, lie in the watershed of the White Nile river and the swamplands of the Sudd, one of the world's largest wetlands.
The UN has said that the regions are at dire risk of famine.
South Sudan is estimated to produce around 150,000 barrels down from 350,000 at independence in 2011.
Many oil fields have stopped operating since war broke out in December 2013 between President Salva Kiir and rebel leader Riek Machar.
South Sudan is currently negotiating a new oil pipelines deal with north Sudan, following a fall in global prices as Juba effectively pay to export crude.
According to the UN figures, tens of thousands have died in the war, more than 2.3 million people have been driven from their homes and 3.9 million South Sudanese face severe food shortages.