Water contamination in Flint, Mich, — where the city switched water sources, causing pipe corrosion and ultimately filling the city's water supply with high levels of lead — has prompted President Obama to declare a state of emergency.

The move, which was requested by Michigan Gov. Rick Snyder, means FEMA is authorized to provide equipment and resources to the people affected. Federal funding will help cover the cost of providing water, water filters and other items.

A state of emergency has been declared by Flint's own mayor since mid-December.

Pediatrician Dr. Mona Hanna-Attisha, who called attention to the elevated lead levels in Flint's children, explained to NPR's Michel Martin last month how the city's water came to be contaminated:

"The city of Flint under state-appointed emergency management, almost bankrupt ... switched their water source from Detroit, which was fresh Great Lakes water source, which we've been using for over 50 years, to the local Flint River to save money.

"And that local Flint River was innately more corrosive than the Great Lakes water source. And the critical corrosion inhibitor, which is mandatory for all drinking water systems to use ... was not added to that water.

"So you had a more corrosive water source without the corrosion control added to it, going into an aging infrastructure with a lot of lead plumbing. That was a perfect storm for that lead to leach out of the pipes into the drinking water and into the bodies of children."

The switch began nearly two years ago, and Flint has since switched back to Detroit's water supply. But the damage to the pipes has already been done, and the leaching of lead into tap water continues.

The question of who knew about the danger — and when — has led to a political crisis in Flint, with protesters calling for the governor's resignation. Concerns over Flint's water were raised months before the state called a state of emergency or provided bottled water.

"Critics say the state's response — in particular, the governor's handling of the crisis — has been inadequate at best, criminal at worst," Michigan Radio's Steve Carmody reported for NPR earlier this week.

"Flint's mayor estimates the cost of fixing the city's water infrastructure at more than a billion dollars. There's no estimate on the cost of the long-term health effects on Flint residents who drank lead-tainted water for more than a year."

Copyright 2021 NPR. To see more, visit https://www.npr.org.