Writer and National Geographic Fellow Paul Salopek’s Out of Eden Walk is a storytelling odyssey across the world in the footsteps of our human forebears. This is his latest dispatch from India.

The ABC Brick Company, located near the steamy banks of Brahmaputra River in the northeastern state of Assam, is much like any of the estimated 200,000 other brickmaking kilns operating in India. And contract laborer Shazima Kathum, 24, shares the same fate as roughly 12 million other workers toiling in such dusty brickyards.

View Images A recent survey found that nearly half the nation's brick workers were underweight, and more than half, anemic.

Photograph by Paul Salopek

A small, thin, sharp-featured woman, Kathum looks older than her years.

Her parents, also brickmakers, were forced to sell their tiny plot of farmland because their fields could no longer feed the family. They also needed cash to build a house to accommodate six daughters. So Kathum abandoned school at age 14. And she has toiled ever since under the smokestacks of various brick companies. For five months of dry weather each year, jogging beneath a molten white sun, she lugs about 40 pounds—or about eight to 10 unfired bricks—atop her head. A human forklift, she covers several miles a day racing to and from the firing pits. Her sweat turns the thick coating of dust on her face into mud. (See and hear kiln workers on the move in this video by Paul Salopek.)

“I make 136 rupees per 1,000 bricks,” she says, citing daily earnings that add up to less than two dollars. “At first my back really hurt. But you just get used to it.”

View Images India is the second-biggest brick producer in the world, after China. Photograph by Paul Salopek

India is the world’s second largest brick producer after China. To feed a decade-long construction boom in its exploding megacities, multiplying call centers, and new industrial parks, it bakes a staggering 250 billion bricks a year.

But for a much longer time, an immense army of Indian brickmakers have served as global poster children for exploitative labor practices.

Protected in theory by minimum wage laws, anti-child labor rules, and regulations prohibiting bonded labor, millions of men, women, and children still endure conditions that one human rights group calls “systematic slavery.” Many laborers are locked into their backbreaking work by debts to dodgy labor brokers, who charge exorbitant fees to secure the jobs. A recent medical survey found that nearly half the nation’s brick workers were underweight. More than half were anemic.

At the brickyard outside Dhubri, most of the loaders carting raw bricks to the kilns were women. They sang as they balanced their heavy burdens down wooden gangways into the earthen furnaces. (Read more: Tea plantation workers in India face poverty—and dangers.)

"I'm paying my sister's school fees," Kathum said of a younger sibling in the sixth grade. "I don't ever want her to do this."

Then she hustled off for another payload of bricks.

