A CBS News investigation of child labor in cobalt mines in the Democratic Republic of Congo has revealed that tens of thousands of children are growing up without a childhood today – two years after a damning Amnesty report about human rights abuses in the cobalt trade was published. The Amnesty report first revealed that cobalt mined by children was ending up in products from prominent tech companies including Apple, Microsoft, Tesla and Samsung.

There's such sensitivity around cobalt mining in the DRC that a CBS News team traveling there recently was stopped every few hundred feet while moving along dirt roads and seeing children digging for cobalt. From as young as 4 years old, children can pick cobalt out of a pile, and even those too young to work spend much of the day breathing in toxic fumes.

So, what exactly is cobalt, and what are the health risks for those who work in the DRC's cobalt mining industry?

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What is cobalt?

Cobalt – a naturally occurring element – is a critical component in lithium-ion, rechargeable batteries. In recent years, the growing global market for portable electronic devices and rechargeable batteries has fueled demand for its extraction, Amnesty said in its 2016 report. In fact, many top electronic and electric vehicle companies need cobalt to help power their products.

The element is found in other products as well.

"Cobalt-containing products include corrosion and heat-resistant alloys, hard metal (cobalt-tungsten-carbide alloy), magnets, grinding and cutting tools, pigments, paints, colored glass, surgical implants, catalysts, batteries, and cobalt-coated metal (from electroplating)," says the U.S. Centers for Disease Control and Prevention.

More than half of the world's supply of cobalt comes from the DRC, and 20 percent of that is mined by hand, according to Darton Commodities Ltd., a London-based research company that specializes in cobalt.

Health risks of chronic exposure

According to the CDC, "chronic exposure to cobalt-containing hard metal (dust or fume) can result in a serious lung disease called 'hard metal lung disease'" – a kind of pneumoconiosis, meaning a lung disease caused by inhaling dust particles. Inhalation of cobalt particles can cause respiratory sensitization, asthma, decreased pulmonary function and shortness of breath, the CDC says.

The health agency says skin contact is also a significant health concern "because dermal exposures to hard metal and cobalt salts can result in significant systemic uptake."

"Sustained exposures can cause skin sensitization, which may result in eruptions of contact dermatitis," a red, itchy skin rash, the CDC says.

Despite the health risks, researchers with Amnesty International found that most cobalt miners in Congo lack basic protective equipment like face masks, work clothing and gloves. Many of the miners the organization spoke with for its 2016 report – 90 people in total who work, or worked, in the mines – complained of frequent coughing or lung problems.

Some women complained about the physical nature of the work, with one describing hauling 110-pound sacks of cobalt ore. "We all have problems with our lungs, and pain all over our bodies," the woman said, according to Amnesty.

Moreover, miners said unsupported mining tunnels frequently give way, and that accidents are common.

Miners know their work is dangerous, Todd C. Frankel wrote late last month in The Washington Post.

"But what's less understood are the environmental health risks posed by the extensive mining," he reported. "Southern Congo holds not only vast deposits of cobalt and copper but also uranium. Scientists have recorded alarming radioactivity levels in some mining regions. Mining waste often pollutes rivers and drinking water. The dust from the pulverized rock is known to cause breathing problems. The mining industry's toxic fallout is only now being studied by researchers, mostly in Lubumbashi, the country's mining capital."

"These job are really desired"

Despite the dangers and risks of working as miners in the cobalt industry, at least of the some miners in the Congo "love their jobs," according to Frankel.

"When I talked to the miners there, none of them want to lose their jobs or give up their jobs. They love their jobs," Frankel said Tuesday, speaking on CBSN. "In a country like Congo, mining is one of the few decently paying jobs to be had there, and so they want to hold onto these jobs."

They also want fair treatment, decent pay, and some safety, "and they would love for their kids to not work in the mines," he said.

"It's a poverty problem," Frankel said. "These parents I talked to – they don't want their kids working in these mines. The problem is that their school fees – schools cost money, and you know, food costs money, and they sort of need their kids to work in there."

Poverty also drives children into the mines instead of school – an estimated 40,000 of them work in brutal conditions starting at very young ages.

The thousands of miners who work in tunnels searching for cobalt in the country "do it because they live in one of the poorest countries in the world, and cobalt is valuable," Frankel wrote in the Washington Post article.

"Not doing enough"

CBS News spoke with some of the companies that use cobalt in their lithium-ion batteries. All of the companies acknowledged problems with the supply chain, but said they require suppliers to follow responsible sourcing guidelines. Apple, an industry leader in the fight for responsible sourcing, said walking away from the DRC "would do nothing to improve conditions for the people or the environment."

Amnesty said in November, however, that "major electronics and electric vehicle companies are still not doing enough to stop human rights abuses entering their cobalt supply chains."

"As demand for rechargeable batteries grows, companies have a responsibility to prove that they are not profiting from the misery of miners working in terrible conditions in the DRC," the organization said. "The energy solutions of the future must not be built on human rights abuses."

An estimated two-thirds of children in the region of the DRC that CBS News visited recently are not in school. They're working in mines instead.

CBS News' Debora Patta spoke with an 11-year-old boy, Ziki Swaze, who has no idea how to read or write but is an expert in washing cobalt. Every evening, he returns home with a dollar or two to provide for his family.

"I have to go and work there," he told Patta, "because my grandma has a bad leg and she can't."

He said he dreams of going to school, but has always had to work instead.

"I feel very bad because I can see my friends going to school, and I am struggling," he said.

Amnesty says "it is widely recognized internationally that the involvement of children in mining constitutes one of the worst forms of child labour, which governments are required to prohibit and eliminate."