This story was produced in collaboration with the Center for Investigative Reporting.
SANTA BARBARA, Philippines — Romnick Bocejo picked up his blowtorch and blasted a small lump of mercury and gold. A cloud of toxic fumes rose around his head as the heat vaporized the mercury. He covered his mouth and nose with his T-shirt, and kept working.
At 16, Bocejo has worked half his life in the meager family business: looking for gold in the remote mining region of Camarines Norte, about 200 miles southeast of Manila.
One of his jobs is to burn the mercury, and on this occasion, he produced a button-size lump of nearly pure gold. He is uncertain whether to believe the smoke is dangerous.
"I have been doing this since I was 8," he said. "I do it every day now. I don't know if the mercury contains poison. No one has ever told me that."
Bocejo is among the 115 million children ages 5 to 17 who work in hazardous occupations worldwide, the United Nations International Labor Organization estimates. About a million children work in mining, and many are exposed to mercury while their growing brains are most vulnerable.
Mercury's perils are well known. The liquid metal can cause tremors, memory loss, brain damage, and other ailments. It accumulates in the body over time, and its effects are irreversible. It can be absorbed through the skin, ingested in food, or inhaled as a vapor.
Small-scale gold mining is the largest source of mercury emissions caused by humans, accounting for more than 35 percent of the global total, according to the U.N. Environmental Program.
Mercury use is widespread in the Philippines and Indonesia, where child labor is common and small-scale gold miners operate freely.
On the Indonesian island of Sulawesi, thousands of miners hack apart mountains in Poboya-Paneki Grand Forest Park and use mercury to process the ore. On Borneo, miners clear-cut the rain forest and dredge the soil in the hunt for gold, poisoning the environment and themselves with mercury and leaving thousands of acres of wasteland.
The two neighboring Southeast Asian nations, made up of about 25,000 islands, restrict the use of child labor. The burning of mercury is prohibited in the Philippines and in parts of Indonesia, but in both countries, pervasive corruption and weak central governments make it difficult to curb these practices, especially in remote areas.
"That's the problem in developing countries," said Halimah Syafrul, assistant deputy for hazardous substance management in Indonesia's Ministry of Environment. "Our government can be bribed. Money can talk."
In the Philippines, the government estimates there are more than 300,000 small-scale gold miners. Officials acknowledge that laws restricting them are seldom enforced. Some operate under permits issued by local officials.
Much of the gold from here ends up in China. Once it enters the world gold market, there is no way to know how much reaches the United States.
For centuries, miners have used mercury to extract gold and create an amalgam of the two metals. Large gold producers have switched to newer techniques. But small-scale miners' casual use of mercury introduces it into waterways, the air and the food supply--particularly fish--imperiling entire communities.
Julie Hall, World Health Organization representative to the Philippines, said mercury is one of the top 10 chemicals of public health concern worldwide.
Because children's brains "are growing every day," she said, "they are very vulnerable to toxins such as mercury."
While less than a metric ton of mercury was imported legally to Indonesia last year, 300 to 400 tons were smuggled in, said Syafrul, the Indonesian official. "The problem is that the government cannot stop the import of mercury," she said in an interview at her Jakarta office. "The mercury keeps coming into Indonesia and is still widely used in gold mining."
Yuyun Ismawati, cofounder of BaliFokus, an environmental group pushing to reduce mercury use, contends high-level payoffs play a part.
"Gold is the daily allowance of the generals," said Ismawati, who received the 2009 Goldman Environmental Prize for her work. She is the lead representative on small-scale gold mining for IPEN, a global coalition of 700 nonprofit groups working to eliminate pollutants.
This fall, Indonesia, the Philippines, and the United States were among more than 90 nations signing the Minamata Convention, a global pact to phase out mercury mining and reduce emissions. The treaty encourages countries to reduce mercury use in gold mining but does not ban it.
In 2008, a gold rush in central Sulawesi lured thousands of miners to the Poboya-Paneki park. For five years, they have tunneled into a mountain there, breaking it apart rock by rock with hammers and crowbars. Today, the sound of hammering fills the air as miners carry 90-pound sacks of ore down rocky paths.
The miners know of the ban on mining in the park but say police don't enforce it. The tunnels are not always well shored up, and collapses are common.
Some miners soften seams of quartz with a prandel, a five-foot metal rod that shoots out fire. The flame creates a hellish glow in the tunnel.
"It's hot and dangerous," said Errol Arnold, 34, a prandel operator who narrowly escaped a tunnel collapse in October that killed two friends.
Moments after he spoke, part of his tunnel collapsed with a crash. More than 100 miners came rushing out of the warren of tunnels. They waited a half-hour before deciding it was safe to go back.
Ridaeni, who like many Indonesians goes by one name, was living near the mountain when the gold rush began. She claimed four mine shafts and pays miners a share to work them.
She estimates that more than 1,000 miners work on the mountain, 50 to 100 of them children. Many more work at mines elsewhere in the park.
"Most of the kids are dropouts from school," she said as she sat under a tarp near the opening of one of her mines. "Some start at age 5 pounding the rock with hammers, filling the bags and fetching water. It's sad, but the parents come here for work. They travel as a family and work as a family."
Nearby, Yoyo, 10, and his friend, Duku, 8, hammered on rocks, working barefoot in a 20-foot-deep hole with Yoyo's mother, grandmother, and a few other relatives. Duku's parents worked nearby. The boys loaded the broken rocks into bags and carried them to the surface.
Yoyo's mother, Hayati, 29, said of her son, "He loves to work here."
Yoyo, wearing filthy yellow shorts and shirt, can't read and has never been to school. Hayati said she earns less than $5 a day and cannot afford books or shoes for him. But she said she is not concerned about his future.
"It's better to be with his family," she said.
Did Yoyo want to be a miner? The boy shyly hung his head. "I will let my mother decide," he said. "If I can, I would like to be a miner."
From the mountain, the ore is trucked three miles to Poboya, a gold-rush town of wooden shacks, to be processed in hundreds of ball mills, open-sided structures with rotating drums that grind the rock to dust. Workers put pea-size gobs of mercury in the drums with the ore so the gold will stick together.
Later, miners use more mercury as they pan the crushed ore. To form the lump of metal, they often squeeze out excess mercury with a filter made from umbrella fabric.
The final stage is burning off the mercury. On Poboya's main street, gold merchants have converted oil drums into makeshift fireplaces where they and the miners torch bits of metal.
When BaliFokus tested the air there in 2011, it found mercury levels twice the Indonesian safety standard and five times the U.S. danger limit, Ismawati said.
At the main intersection of Poboya, miners come to Upriani's small shop to buy mercury. She is the only dealer in town.
Upriani, 38, said she sells at least 35 kilograms a day for the equivalent of $133 per kilo. She spends some of it buying gold from miners. When business is brisk, she shoves rupiah notes into an overflowing drawer.
After she first opened her shop four years ago, police seized her mercury, she said. But instead of prosecuting her, they introduced her to her current supplier, a well-connected businessman. She said she operates legally because her supplier has a permit. Authorities in Jakarta disagree, but she remains in business.
A mother of three, Upriani acknowledges the health risks. "I know it is dangerous, but distributing mercury supports the economy out here," she said. "The miners need the mercury, and I need the gold."
Environmental groups such as BaliFokus in Indonesia and Ban Toxics in the Philippines want miners to switch to borax, a safe compound that can extract more gold but requires more skill. But in most gold mining areas, mercury remains part of the routine.
In Cisitu on the Indonesian island of Java, where small-scale miners have used mercury for two decades, air sampling in August by BaliFokus found levels far above the safety threshold.
In Diwalwal on the Philippine island of Mindanao, miners have built mills beneath their homes and often burn mercury there. The fumes waft up into the houses.
Most of the 750 families of Santa Barbara make a living from mining. The hillside village was spared by Typhoon Haiyan, which passed more than 260 miles to the south in November, killing more than 6,000 people. The miners halted work--for a day.
A creek runs through the village, and the houses facing it have ball mills instead of patios.
Many boys leave school to work in the mines. The miners cart ore home to the ball mills, load it into the drums and add a bit of mercury, much of which ends up in the creek.
At the Bocejo house, Romnick Bocejo burned the amalgam in an open shed with a thatched roof. The lump of metal sat on a workbench in a clay dish. The teenager held the torch inches away. Within moments the metal glowed red-hot.
Younger children came close to watch as fumes filled the air. "Most of the time when I am burning gold, I smell an odor," Bocejo said. "I cover my mouth with my shirt. As of now, I don't feel any problems."
Journalists Debbie M. Price and Sol Vanzi, in Manila, contributed to this report. Larry C. Price is documenting child labor in developing countries as part of a long-term project funded by grants from the Pulitzer Center. This story was produced in collaboration with the Center for Investigative Reporting and The Philadelphia Inquirer.