By Paul Kiernan 

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 contradicted 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 Mineração SA, a joint venture between global mining giants Vale SA and BHP Billiton Ltd. The dam held back some 55 million cubic meters of tailings, waste from Samarco and Vale's nearby iron-ore mines.

As many as 12 people died when the sludge inundated towns in the area. At least 11 people are still missing.

All three companies have said the tailings are harmless and consist mostly of mud and sand.

Based on the available data, the tailings released by the dam were "chemically stable" and would behave like normal soils in the area, BHP said in a statement late Wednesday.

"The tailings that entered the Rio Doce were comprised of clay and silt material from the washing and processing of earth containing iron ore, which is naturally abundant in the region," BHP said.

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 requested, she said, "attest that the material analyzed does not present a danger to human health."

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

A Vale spokeswoman deferred to Samarco for comment.

The U.N. special rapporteurs received their information from the town of Baixo Guandu's water department, which hired local laboratory Tommasi to analyze samples taken at three points along the Rio Doce, the main river in the region.

One of the samples, taken in the industrial city of Governador Valadares, showed levels of arsenic, manganese and other metals at several thousand times the acceptable maximums.

"I find it difficult to imagine that you would see such high, elevated levels normally--in a region where people are eating fish and drinking the water--and not have major impacts on human health or the environment, " Mr. Tuncak said in a phone interview.

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."

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.

The plume arrived at the Atlantic Ocean over the weekend, roughly 500 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.

"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.

Rhiannon Hoyle in Sydney contributed to this article.

Write to Paul Kiernan at paul.kiernan@wsj.com

 

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(END) Dow Jones Newswires

November 25, 2015 22:22 ET (03:22 GMT)

Copyright (c) 2015 Dow Jones & Company, Inc.
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