A boy carries a bag used to transport cobalt-laden dirt and rock at a mineral market near Kolwezi, Congo. (Michael Robinson Chavez/The Washington Post)

The effort to learn what Congo’s miners think about their jobs began with a simple text message.

It was something of a surprise.

Americans might be accustomed to online surveys and telemarketing calls. But that’s less true in developing countries, where people are harder to reach, with limited access to the Internet and few landlines. They do have mobile phones. Lots of them.

Eighty percent of Africans, for example, have access to mobile phones, according to the International Telecommunication Union, despite the continent having by far the world’s lowest penetration rates for home computers and online access.

A text message is often the best way to reach someone there. And that’s where a company like GeoPoll comes in.

The Denver-based company specializes in polling on mobile phones, mostly in Africa and Asia. The firm conducts market research for clients such as Procter & Gamble and the World Food Program. GeoPoll has deals with mobile service providers in different countries that supply them with phone numbers, sometimes included with data about the user's age and gender, said Samir Goswami, a product consultant with GeoPoll. Other times, the company gets this information by conducting surveys that provide information for future use.

In the past, GeoPoll has used its mobile polling service to ask West African residents about the economic impact of the 2014 Ebola outbreak there and to ask residents along Kenya's coast about child labor law violations in the country's fishing industry.

The effort to poll Congo’s miners, GeoPoll said, was motivated in part by The Post’s investigation this year of Congo’s cobalt trade, which found dangerous, at times deadly, work conditions and the presence of child workers.

On Oct. 26, a month after The Post’s story, GeoPoll sent a text message to thousands of mobile phones in some of Congo's mining provinces to ask if the recipients worked in mining and would be willing to answer some questions. More than 1,500 people fit the bill. And 159 of them completed the entire survey — enough to provide a rough sense of how these miners felt about their jobs. They were paid the equivalent of 50 cents for their time and texting charges.

While the survey was limited and did not reach the level of a representative sampling, it does appear to provide additional evidence of widespread safety hazards in mines. GeoPoll hopes to do more polling in the future as a way for companies to learn more about the workers in the farthest reaches of their supply chains.

Among the findings:

  • 93 miners (58 percent) said they had seen children working in mines.
  • 95 miners (60 percent) said they had seen a child hurt working in the mines.
  • 87 miners (55 percent) said they had seen a death in the mines.
  • 54 miners (64 percent) who reported seeing accidents said the most common cause was a mine cave-in.
  • 84 miners (53 percent) said there was no safety equipment.

Nearly half of the respondents said they worked in artisanal mines, where digging is done by hand, often in the most risky circumstances.

Most worked in diamond or gold mines, followed by tin and copper. Only a few worked in cobalt mines, but the poll results showed how problems are prevalent no matter the mineral.

The miners were also asked to answer the question, “What do you think should be done to make sure children don’t have to work in the mines?”

The answers showed how the problem of child labor is not just one of regulation — after all, child labor is illegal in the Congo. The problem is poverty. Among the most common answers from miners included guaranteeing access to free education — many children in Congo pay school fees — and providing parents a living wage.

As one miner explained via text message, “Free education, work and living wage for parents. Mining is dangerous for children.”