GWEN IFILL: Now, major environmental concerns over mercury contamination at extensive gold mining operations in the remote regions of the Peruvian Amazon.

Our report is part of a collaboration with the Pulitzer Center on Crisis Reporting.

It comes from special correspondent Steve Sapienza in Peru.

STEVE SAPIENZA: These miners are part of the biggest gold rush the world has ever seen. Recent spikes in gold prices have lured 10 to 15 million people worldwide into the business of small-scale gold mining.

But rising global demand for gold has also fueled demand for a far less prized metal, mercury. The toxic metal is used by millions of miners every day to separate and collect gold from rocks and soil. Miners say mercury is easy to use, readily available, and cheap.

The United Nations Environment Program estimates that small-scale miners use up to 1,350 tons of mercury each year, making it the single largest use of mercury worldwide. In southeastern Peru, the gold rush has attracted some 20,000 small scale miners to the pristine rain forest and rivers of the Madre de Dios region.

The devastation caused by widespread mining is easy to spot, with huge swathes of the forest turned to barren desert, but the damage caused by the heavy use of mercury is harder to detect. Mercury from small-scale mines travels widely, settling in sediments and moving up the food chain into fish, fish-eating wildlife and humans. Scientists and medical researchers only recently started to measure the impact of mercury here.

This fish is called mota. This is a very popular fish around the region. You will find it on a lot of dinner tables, a lot of restaurant menus. This fish is at the top of its food chain. And what that means is it consumes a lot of smaller fish. And a lot of these small fish have mercury in them. And through a process known as biomagnification, this fish accumulates a lot of mercury.

In fact, if a person consumes two servings of this fish per week, they're getting seven-and-a-half times the safe limit of mercury, according to the World Health Organization.

It takes two ounces of mercury to produce a single ounce of gold. That means 50 tons of mercury are used to extract the 25 metric tons of gold mined here each year. Miners mix the soil with mercury, often using their hands and feet, creating a clump of amalgam that contains gold. And yet most miners are unaware of the dangers posed by mercury to the environment and to their health.

CESAR ASCORRA, biologist (through translator): There are very few studies about the contamination of people due to mercury.

STEVE SAPIENZA: Biologists Cesar Ascorra has closely monitored the dramatic increase of mercury use in the Madre de Dios region.

CESAR ASCORRA (through translator): We recently finished one study made on a sample of 30 people in one mining area, and they were all contaminated with mercury above allowable levels. The people that have the worst levels of contamination are those who are not miners, those not linked to the activity itself. They are the merchants, family members, the people who live near the shops where the gold and the mercury is sold.

STEVE SAPIENZA: Gold shops use stoves to heat the miners' clumps of mercury gold amalgam, releasing the vapors into the shop and then outside, further spreading the toxic threat to towns across the region.

Epidemiologist Dr. Manrique Arada Estrada has worked in Madre de Dios for 20 years collecting data on diseases and health risks like mercury poisoning.

DR. MANRIQUE ARADA ESTRADA, director of regional health, Madre de Dios (through translator): We have been able to find cases of acute intoxication. People arrive with abdominal pain. They arrive with a metallic taste in their mouths or headaches. And all of this is related to the handling of mercury.

But we have not been able to find patients with chronic intoxication because we do not have the equipment to make that type of diagnosis.

STEVE SAPIENZA: Dr. Arada thinks small-scale miners need more education on the dangers of mercury and also alternatives to its use.

DR. MANRIQUE ARADA ESTRADA (through translator): There is good mining carried out in a clean way. Finding acceptable methods for obtaining gold without the use of mercury, for example, that would be a good alternative to avoid all this contamination.

STEVE SAPIENZA: With well over 3,000 mining operations to monitor, the unbridled gold rush is overwhelming Ernesto Montanos and his tiny staff at the region's mineral and gas ministry.

ERNESTO MONTANOS, minister of energy, Madre de Dios (through translator): I currently have over 500 environmental impact studies to evaluate. But I only have two professionals, two people who do evaluations.

STEVE SAPIENZA: In Peru, small-scale mining is often the only means of survival for people in poor rural communities. Past government efforts to rein in illegal and destructive gold mining have often resulted in civil unrest and deadly clashes with miners.

While Montanos acknowledges the government must do more to stem the flow of mercury and enforce environmental laws, he also thinks consumers can help change the way gold is mined.

ERNESTO MONTANOS (through translator): All the countries that are consumers of gold, recipients of gold, what they have to demand is to buy green gold, ecologic gold, gold that adheres to all quality standards, to the point where there is no excuse to buy illegal minerals.

STEVE SAPIENZA: Last year, when the government imposed tough new environmental laws on small-scale miners in Madre de Dios, tens of thousands of miners across Peru launched protests.

I'm in Chala, the small fishing and mining town on Peru's southern coast. Last year, six people died on this highway when police tried to remove a roadblock set by small-scale miners who were protesting government plans to impose stricter environmental controls on them.

But in a nearby mining area known as Relave, a small-scale mining company is changing its practices and going green. The AURELSA mining cooperative is a two-hour drive up desolate canyons from the coast. In the wake of the protest violence in Chala, the government singled out AURELSA as an example of best practices in small-scale mining.

Founded by mine workers in 1997, AURELSA is part of growing trend of South American small-scale mines seeking to produce gold with less impact on the environment and more benefit to the miners.

MAN (through translator): Well, with informal mining, the difference is that more is sacrificed, more is risked. There are days when you get money. There are days when you do not get paid. But, here in AURELSA, it is a business with a secure paycheck.

STEVE SAPIENZA: While area miners still rely heavily on crude tools and mercury to extract gold, AURELSA miners have moved to a safer option. Using a method recently approved by Peru's environmental health board, AURELSA miners use cyanide leaching as an alternative to mercury processing.

DANIEL ENRIQUE VALVERDE, general manager, AURELSA Mining Company (through translator): Cyanide can contaminate if it is dumped to a water source. If there was a river nearby, then it is completely poisonous. But if we see that the cyanide is recycled back into the process, then there is no contamination.

STEVE SAPIENZA: General manager Daniel Enrique Valverde hopes AURELSA will soon become fair trade and fair mine certified. For consumers, this means gold is extracted in a way that limits pollution of harmful chemicals like mercury and cyanide. For miners, it means better income, job security, and 10 percent of profits set aside for the community.

DANIEL ENRIQUE VALVERDE (through translator): There is a percentage of that which goes directly for projects in the community, the local population. We are already seeing projects such as recycling, forestry, that are not just at our company, but projects for the schools and the municipality.

STEVE SAPIENZA: Fair trade and fair mine certified gold is already available in Europe, and shipments are slated for the U.S. market next year.

So far, only a handful of small mining companies in South America are adopting fair mine practices, but mines like these offer a hopeful alternative to the unregulated and destructive mining in places like Madre de Dios.

GWEN IFILL: There are more stories by Steve Sapienza about mining in Peru's rain forest at the Pulitzer Center's Crisis Reporting website. You can find their link on our site.