Brazil Dam's Failure Flooded Region With Toxic Waste, U.N. Report Says

RIO DE JANEIRO—An avalanche of mud unleashed by a massive dam failure in Brazil earlier this month contained "high levels of toxic heavy metals and other toxic chemicals," a pair of United Nations experts said Wednesday.

Special rapporteurs John Knox and Baskut Tuncak cited new evidence showing the presence of toxic waste in the mud, which swallowed entire communities and polluted hundreds of miles of waterways in southeast Brazil. Their findings contradict repeated statements by the Brazilian government and the mining companies responsible for the dam that the chemicals released by the accident were harmless.

"This is not the time for defensive posturing," Messrs. Knox and Tuncak said in a joint statement published to the website of the United Nations Office of the High Commissioner for Human Rights. "It is not acceptable that it has taken three weeks for information about the toxic risks of the mining disaster to surface."

The failure occurred at an earthen dam operated by Samarco Mineraç ã o SA, a joint venture between global mining giants Vale SA and BHP Billiton PLC. It held back some 55 million cubic meters of tailings, waste from Samarco and Vale's nearby iron-ore mines.

All three companies have said the tailings are harmless and consist mostly of mud and sand. The Brazilian government said on Nov. 19 that samples collected by the Geological Service of Brazil and the National Water Agency "indicated that there was not an increase in the presence of heavy metals in the water and sediments of the Rio Doce," the main river in the region.

Nevertheless, authorities cut off water supplies for hundreds of thousands of people along the river as the mud snaked downstream. Reports of major wildlife die-offs emerged in its wake, with news teams and local residents alike publishing videos of mud-coated fish agonizing in the river's reddened waters.

As many as 12 people died and another 11 were left missing.

The plume arrived at the Atlantic Ocean over the weekend, about 530 miles from Samarco's dam.

Samarco, Vale, BHP Billiton and Brazilian authorities have come under fire for their handling of the incident. Residents of Bento Rodrigues, a village just below the dam system, said the mining companies had no alarm system set up to alert them when the dam failed. Brazilian President Dilma Rousseff didn't visit the scene until a week later, and then it was by helicopter.

"This disaster serves as yet another tragic example of the failure of businesses to adequately conduct human rights due diligence to prevent human rights abuses," the U.N. statement said Wednesday.

Vale and BHP Billiton have denied responsibility for the accident, saying Samarco is an independently run, limited liability firm. The former companies didn't immediately respond to a request for comment on the U.N. statement.

A spokeswoman for Samarco, in an emailed statement, reiterated that the tailings from its dam consist "basically" of water, iron-ore particles and quartz. New analyses that the company has requested, she said, "attest that the material analyzed does present a danger to human health."

"The company respects the U.N.'s right to expression," the Samarco spokeswoman added.

Write to Paul Kiernan at [e-mail]

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November 25, 2015 19:45 ET (00:45 GMT)

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