The Obama administration has declared a state of emergency in Flint, Michigan, a city of nearly 100,000 people who can't drink their tap water because it's poisonous.
Officials denied the water's danger right up until a local pediatrician documented high lead levels in Flint kids' blood last fall. Lead is a deadly neurotoxin that can cause stunted growth and brain damage in young children.
Here is a list of some of the mistakes that local, state and national officials made.
It all started with a decision to change Flint's water source.
For decades, Flint bought its water from the Detroit Water And Sewerage Department. In 2013, the Flint city council voted to join the Karegnondi Water Authority, a new system that would pump water from Lake Huron. But Flint couldn't connect until 2016, so the city, operating under the control of emergency managers appointed by Michigan Gov. Rick Snyder (R), opted to save money by using the Flint River in the meantime.
Local leaders in Flint, including then-mayor Dayne Walling (D), literally toasted the decision by drinking glasses of the new water at a ceremony in April 2014. “It’s a historic moment for the city of Flint to return to its roots and use our own river as our drinking water supply," Walling said at the time.
Pretty much immediately, Flint residents complained that their water looked and tasted funny. In January 2015, the city warned residents that the water had high levels of disinfection byproducts.
The city wasn't vigilant about its water.
Employees of public water systems are supposed to monitor water lead levels by testing the water in homes that are connected to water mains via lead service lines, but Flint failed to do so, according to an investigation by The Flint Journal. Avoiding high-risk testing sites can mask the extent of a lead problem and delay measures to fix it.
The Michigan Department of Environmental Quality failed to ensure the water was treated for its corrosiveness.
The Flint River water turned out to be more corrosive than the water Flint received from Detroit -- so corrosive, in fact, that in October 2014, General Motors opted to quit using it to avoid corroding parts in its engine plant. Corrosiveness is a problem because Flint, like many American cities, has water pipes that are made from lead, which can leach into the water and poison people who drink it.
Back in 2011, Flint had commissioned an evaluation of Flint River water, the results of which indicated it would need to be treated with phosphates to reduce its corrosiveness. Two years later, according to the Detroit Free Press, a Flint official forwarded that information to the Michigan Department of Environmental Quality, which is responsible for ensuring that Flint follows the federal Safe Drinking Water Act. But the MDEQ didn't do its job.
As Miguel Del Toral, an expert with the Environmental Protection Agency who was investigating local complaints about the water, explained in a June 2015 memo: "Recent drinking water sample results indicate the presence of high lead results in the drinking water, which is to be expected in a public water system that is not providing corrosion control treatment. The lack of any mitigating treatment for lead is of serious concern for residents that live in homes with lead service lines or partial lead service lines, which are common throughout the City of Flint."
In October, the MDEQ admitted it failed to follow the correct protocol for corrosion. In December, the agency's director and spokesman both resigned after a task force appointed by Snyder blamed the MDEQ above all other agencies for failing to ensure the safety of Flint's water.
The EPA stood by as state officials dismissed its investigation.
Facing questions about Del Toral's alarming memo, the EPA's regional administrator, Susan Hedman, told city and state officials that it was a draft report that should not have been released. City and state officials took that assurance and ran with it, telling residents and reporters not to worry, and went as far to say that Del Toral was a "rogue employee."
In a recent interview, Hedman told The Huffington Post that the agency couldn't talk publicly about the memo because it contained identifying information about a private citizen, Lee Ann Walters, whose children were exposed to high lead levels. For much of last year, Walters worked to publicize the problem and even petitioned the EPA to take emergency measures.
The corrosion never got controlled.
Hedman told HuffPost that while the EPA didn't publicize its corrosion concerns, the agency was busy behind the scenes pressuring the MDEQ to get its act together. But even though MDEQ agreed to implement corrosion control in July, an MDEQ spokeswoman told HuffPost that no corrosion control occurred before Flint switched back to Detroit's water system in October.
EPA spokeswoman Monica Lee said that under the Safe Drinking Water Act, it was up to the state of Michigan to make sure its water was safe.
"While EPA worked within the framework of the law to repeatedly and urgently communicate the steps the state needed to take to properly treat its water, those necessary actions were not taken as quickly as they should have been," Lee said in an email, adding that the EPA will consider what it could have done differently.
"The situation in Flint -- of a large system switching from purchasing treated water to untreated water -- is highly unusual," Lee said. "EPA's ability to oversee MDEQ’s management of that situation was impacted by failures and resistance at the state and local levels to work with us in a forthright, transparent and proactive manner consistent with the seriousness of the risks to public health. We must ensure this situation never happens again."
State agencies ignored red flags.
In July, an internal report from the Michigan Department of Health and Human Services warned that blood lead levels "were higher than usual for children under age 16 living in the City of Flint during the months of July, August and September, 2014." But the department convinced itself that the numbers were the result of normal seasonal variation in blood lead levels, a message it also relayed to a top Snyder aide who expressed concern about the water situation in a July email.
Officials also dismissed reports last September that the city's water contained high levels of lead after Virginia Tech civil engineering professor Marc Edwards and his research team sampled water in Flint. Edwards wound up filing Freedom of Information Act requests that exposed the state's knowledge of high lead levels in locals' blood, among other things.
Officials stopped denying the problem at the beginning of October, shortly after Dr. Mona Hanna-Attisha, director of the pediatric residency program at the Hurley Medical Center in Flint, reported that the number of local children with high amounts of lead in their blood had doubled.
"This poisoning of an entire population was entirely preventable," Hanna-Attisha told HuffPost.
Though the city has switched back to Detroit's water system, it's not clear when Flint's water will be safe to drink again. Michigan state police and the members of the National Guard are assisting with door-to-door delivery of bottled water and filters.
This story has been updated to include comment from the Environmental Protection Agency.