Tiana Lankford's two-year-old daughter was poisoned by the lead-tainted water that flowed from the taps in their home, causing the toddler to develop appetite and behavioral problems.

The contamination, ignored and then hushed up by government officials, will be in the national spotlight on Sunday as Democratic White House hopefuls come to this poor, predominantly black Rust Belt city for their next debate.

"I'm furious, of course," said Lankford, 33, who has two other daughters. "No one in the world should have to deal with that."

It's not just little Carlina and her sisters who are affected by lead poisoning, which can have devastating impacts on young children by irreversibly harming brain development.

More than 8,000 children in the Michigan city of Flint, economically devastated by the closure of General Motors factories, were exposed to lead for more than a year before the tap water contamination was uncovered by citizen activists.

"It affects your behavior, it affects them eating. I can't tell you how many meals I put over there for them to eat and they don't touch it," Lankford said in an interview with AFP in their sparsely furnished home.

The mother said she boiled water for Carlina's bottles without knowing it was toxic -- and tests now show the girl's blood contains seven micrograms of lead per deciliter of blood, when health experts say anything higher than five micrograms indicates an unsafe level.

"We almost feel like people almost trample on this city on purpose. We can't understand why," Lankford said.

- Clinton and Sanders -

The tainted water, which Lankford said had a rotten egg smell and sometimes ran brown from the taps, is sure to be a major topic of discussion when Hillary Clinton and Bernie Sanders meet for their debate. Lankford is planning to attend.

Republican Governor Rick Snyder has apologized for the state's series of failures but a top Michigan Democrat has called for his resignation, saying emails released by the governor's office in recent weeks showed "negligence and indifference" in his handling of the crisis.

Filmmaker Michael Moore, who is from Flint, has called for Snyder's arrest, while the US Justice Department is investigating why it took until October 2015 for officials to tell residents to stop drinking the water despite months of tests showing dangerous levels of lead.

Flint's drinking water came from Lake Huron, through Detroit, until April 2014 when it was switched to the polluted Flint River.

It is estimated that $100 a day in corrosion controls would have made the water safe.

Instead, they weren't put into place to save money. The polluted water corroded pipes, which then began leaching lead.

It is estimated that the cost of replacing all the pipes will be more than a billion dollars, an amount that only the federal government could afford.

On Friday Flint began its first official replacement of pipes, which service a house belonging to a husband and wife who is pregnant.

One-third of Flint's 100,000 residents are impoverished. The closure of the General Motors plants caused an exodus from the city, and entire streets are abandoned, with houses boarded up.

"It's really hard for a lot of us to make a living. And it's really hard to move out," said Kevin Larsen, a 26-year-old unemployed landscaper. "Right now Flint is really the cheapest place you can live. Houses have gone downhill drastically, to $10,000 or $12,000."

Speaking to AFP on the porch of his tumbledown home, wearing a gun in his belt as permitted by local law, the father of three said the water is a constant worry because of its longterm health impacts.

- Confidence broken -

Lankford had trusted the announcements from various government departments that the water in Flint was safe.

But evidence shows authorities put off issuing warnings about the risks until a persistent mother, a local doctor and researchers from Virginia Tech University broke the news of the contamination in 2014.

In October, Flint reverted to the Detroit water supply, but it's not known how long it will take for tap water to be safe again.

Some ask whether dirty water is to blame for pregnancy miscarriages and a spike in cases of Legionnaires' disease.

Snyder declared a state of emergency in January, which allowed for the release of aid for Flint residents.

More than 2,200 volunteers as well as soldiers from the National Guard have been handing out free bottled water and distributing thousands of water testing kits, often door-to-door.

"When we find out that there are folks with young children or the elderly or the handicapped, they get a priority definitely because they have less of an ability to get the supplies that they need," said American Red Cross volunteer Franklin Dickerson, walking in the snow with an armful of bottled water.