Best friends Arti and Arti, aged 10, worked together as rag pickers – the lowest of the low in Indian society.
They are Dalits, formerly known as Untouchables, whose families migrated to New Delhi from a small village in Uttar Pradesh.
"In the morning we used to go and collect bottles and plastic, then we would go begging. We'd get about 10 to 20 rupees (approximately 30c) a day," the taller girl tells me.
"We would give that money to our mum and she would run the household with it," her friend says, with a shrug of resignation.
We are at the Delhi Child Restoration Project near a sprawling slum which houses hundreds of people.
From the age of four they spend 12 hours a day collecting waste to sell to scrap dealers, who supply a growing number of recycling centres. With a burgeoning middle class in a population of 1.2 billion, India generates 55 million tonnes of solid waste each year.
In this city alone there are an estimated 300,000 rag pickers living on the margins of society.
"When we first came in it was very difficult to digest the lives these children live," says centre manager Raifiel Jos.
"(They) are facing all sorts of abuse: physical, sexual, emotional. They have nothing. Anything you can name that a child should have, they have none of it."
A young woman with a kind face, Raifiel's brow furrows as she describes the relationship between the children and their parents.
"There's an absence of a loving environment; their parents treat them like employees," she says.
Suddenly Madhu, one of the volunteers, speaks up."The mothers need to take better care of their children," she says, angrily.
Some parents, however, are forced into rag picking through what she calls "sheer desperation".
Lajja married young and moved to the city hoping to find domestic work. But because she was born in a rural area she didn't have an identity card.
Her husband turned to drink; she and the kids to rag picking.
"Starvation kicked in," Lajja says. "There were days when we went without food. We would have a small amount of watered rice every day."