Poisonous Legacy of Search for Gold

The shirtless miner slipped into the muddy river, oblivious to the danger. Like hundreds of others, he had come to the Amazon for gold. To get rich, he risked malaria in a mosquito-ridden jungle. He risked drowning in the swirling current as he maneuvered the vacuum tube that sucked up gold-rich silt to his makeshift barge. He even risked having his airhose cut while he was underwater by another miner eager to steal his stake.

But what began as gold-rush adventure has now become an ecological nightmare for the Amazon River basin. The mercury the miners use in the gold-extraction process has become a virtually permanent poison in the world’s richest biosystem.

I visited Amazonia for the first time in 1982. I was awed by its wealth of animals, plants, insects and fish, all sheltered by a towering forest that seemed to dwarf even the greatest greed of men. Since that visit, one-third of the Madeira River forest region alone has been destroyed. Smoke from the burning Amazon can be seen from spacecraft circling the Earth. But no satellite can track the invisible danger of heavy metals in water.

After miners suck the silt to their boats, they add mercury, which bonds with any gold the silt might contain. When the mercury is burned off, pure gold remains. In the process, the miners inhale toxic mercury vapor or absorb it through their skin. In fact, I met a miner who was addicted to the fumes. The miners indifferently toss all mercury waste, mercury residue in the soil, and mercury ash into the river.

Mercury persists in the environment. It accumulates in human and animals, including fish which are either poisoned outright or eaten by human consumers. Mass poisonings occurred in Minamata, Japan, in the 1950s. There, hundreds of inhabitants developed mysterious headaches, numbness and loss of muscle coordination. Babies were born with congenital birth defects. More than 100 fishermen eventually died and nearly a thousand suffered brain damage. The epidemic was traced to consumption of fish that had been caught near a factory dumping mercury waste into the Minamata River and Bay.

Now Minamata was being re-created in the Amazon. I decided to gather some hard data. I asked Dennis Powers of the Hopkins Marine Station at Stanford University, who was a guest biologist with our expedition at the time, to join me on the Madeira. He collected water and fish samples, as well as hair samples from local residents.

Powers found in general that mercury concentrations in fish from the mining zone were two times higher than in fish sampled elsewhere. Hair from people who regularly ate Madeira fish contained two to five times more mercury than people who rarely ate fish. Although mercury levels in humans were about one-fifth the minimum defined by the World Health Organization as causing visible effects and were therefore considered “subtoxic,” we all knew they would rise as mining continued. We made our findings public and recommended the Brazilian government ban mercury use.

Seven years later, evidence of mercury poisoning is mounting. Dozens of people living near a new river mine at Itaituba have become mysteriously ill. When one victim was tested, his blood showed high concentrations of mercury. Bruce Forsberg, an American biologist working in the Amazon, has recently stated that mercury levels in some fish are now “five times the World Health Organization safety level of mercury.”

This year, the Brazilian government did ban mercury use. But today about 500,000 gold-hunters are working the Amazon’s countless rivers, far from the reach of law enforcement. I have trouble picturing them complacently obeying the mercury ban.

Mining poses ecological problems even in well-regulated settings. In Montana recently more than 1,000 waterfowl were found dead from cyanide poisoning after they landed on a pond filled with gold-mine tailings. According to Jim Jensen of the Montana Environmental Information Center, cyanide is more prevalent than mercury as a bonding agent for low-grade Montana ore.

Such pollution violates the law and mining companies try to control it, Jensen said. So far, there has been no illness to humans. But cyanide and metal contamination have seeped into some area wells and local people have taken their damage claims to court. Meanwhile, some mining companies shoot natural gas cannons or play rock music to keep birds away from poisoned water.