More charges were announced in the Flint water crisis Friday.

NBC25 reports that six state employees will be charged with misconduct in office, neglect of duty and misinterpreting regulations.

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According to the Detroit Free Press, those charged include Michigan Department of Health and Human Services workers Nancy Peeler, Corinne Miller and Robert Scott, and Michigan Department of Environmental Quality employees Leanne Smith; Adam Rosenthal and Patrick Cook.

Stephen Busch, Mike Prysby, and Mike Glasgow are facing more than 10 felony and misdemeanor counts for their actions which allowed residents to drink and bathe in improperly treated water for some 18 months. (Scroll down to see a timeline of events in Flint.)

What happened?

For years, Flint, which is 60 miles from Detroit, got its tap water via Detroit’s water system which is drawn from Lake Huron. In 2014, Flint officials decided that the cost of using Detroit’s system was growing too expensive and they wanted to establish an independent water system that included their own pipeline to Lake Huron.

It would take a while to fund and build the pipeline, so, wanting to save money, officials decided to leave the Detroit system in April 2014, and use the Flint River as a primary water source until the Lake Huron pipeline was completed.

What was the problem with that?

As it turned out, the water in the Flint River is more corrosive than the water in Lake Huron. The water from the Flint River, left untreated, damaged the city’s pipes causing lead to leach from them and into the city’s tap water.

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Didn’t city officials realize that?

Critics are arguing they had to know due to mounting evidence.

Almost immediately after the city switched water sources in April 2014,  residents complained of  smelly, discolored water coming into their homes. Soon after that, people began to report itchy skin after they took baths in the contaminated water. Within months, a pediatrician in the area said she began to see children with signs of lead poisoning.

At one point, a General Motors plant even stopped using the water, saying it was rusting new car parts.

Despite the complaints, officials made public assurances that the water met federal safety guidelines put into place and monitored by the U.S. Environmental Protection Agency.

What did local and state officials know and when did they know it?

According to the Detroit News, the state Department of Environmental Quality  knew about the lack of corrosion control in the water supply as early as April of 2015.  Email exchanges between EPA Region 5 Administrator Susan Hedman  and former Flint Mayor Dayne Walling showed  a "lack of urgency" over the matter, according to the report.

The city received complaints about the water almost from Day One of the switchover in April 2014. By summer, three boil-water advisories had been issued after tests for coliform bacteria came back positive.

In January 2015, following more complaints about the water, city officials got an evaluation of "improvements" in the water system. After hearing of problems, the city of Detroit offers to reconnect Flint to their water system, Flint officials decline the offer, saying the water is safe.

Virginia Tech researchers performed an independent study whose results began to be made known in February, 2015. The study found the water was highly corrosive and since many service lines in Flint were made of lead, the lines were being compromised and lead was being leached into the city’s water supply.

According to an ABC News timeline of the events surrounding the water issues, in March, the city commited to spending $2.24 million on immediate improvements to its water supply. A week later, they said  the quality of the  water had improved and the water met all state and federal standards for safety.

By September, a group of doctors are urging Flint officials to stop using the Flint River as a water source as they are seeing high levels of lead in children’s blood. State regulators assured the group that the water was safe.

Five days later, Gov. Rick Snyder announced he would investigate the high levels of lead reported in the water and would take action. Three days after that, he said the state would spend $1 million to buy water filters and test the water in Flint public schools. A week later he calls for Flint to return to using the Detroit water system.

By the middle of October, millions of dollars are approved in the Michigan Legislature to help pay for filters, inspections and tests.

At the end of December, Snyder accepts the resignation of Department of Environmental Quality Director Dan Wyant. He apologized for what occurred in Flint and days later declared a state of emergency. On that day, Jan. 5, federal officials announce they are investigating what led to the problem in Flint.

Who was responsible?

Blame is being cast on plenty of people. Starting with town officials and going  all the way to Washington.

The head of the U.S. Environmental Protection Agency Gina McCarthy, on Monday defended the Obama administration's handling of the water issue in Flint, saying, "EPA did its job but clearly the outcome was not what anyone would have wanted. So we're going to work with the state, we're going to work with Flint. We're going to take care of the problem.”

Henry Henderson, Midwest director of the Natural Resources Defense Council, told The Guardian that the EPA has authority  to take emergency actions for cases like the one in Flint.

“It’s become painfully obvious that every level of government, including but not limited to the EPA … have felt no urgency about this matter at all,” Henderson said in the Guardian interview, they “have been shockingly lackadaisical, [and] have made inappropriate statements in public in terms of the safety of the situation, which is wildly unsafe.”

As for state and local officials, protesters called for the arrest of Gov. Rick Snyder, The Associated Press reported. They claimed he is complicit in the cases of lead poisoning because he did not act when he knew there was a problem.

Snyder has apologized for the state’s lapse in action. "The checks and balances that theoretically could have been there didn't work. This is a mess. I mean, I feel terrible about all this happening. And that's why I'm working hard to do everything I can to repair the damage and then actually work to strengthen Flint and the citizens," Snyder told the National Journal.

What could have fixed this?

A chemical additive that keeps water from becoming corrosive could have fixed the problem. The delay in adding that additive grew out of efforts by the EPA to force the Michigan Department of Environmental Quality to force the city of  Flint to use the anti-corrosive chemicals, according to Susan Hedman. Hedman said the EPA delayed action in Flint because they were waiting for a legal opinion that wasn’t completed until November, 2015.

What does lead poisoning do to the body?

Lead is a neurotoxin, meaning it affects the workings of the body’s nerve tissue.  In children, lead poisoning can lead to decreased bone and muscle growth, speech and language problems and developmental delays. Excessive amounts of lead are also shown to affect a developing child's IQ, resulting in learning disabilities.

In adults, lead targets the kidneys and blood vessels. People who survive toxic lead levels, children, in particular, can suffer from permanent brain damage. Even a small amount of exposure to lead can cause long-term health problems.

How toxic was the water in Flint?

Lead found in drinking water is measure in parts per billion or ppb. The EPA says if tested water comes back with more than 15 ppb immediate measures should be taken to lower the level. Those steps could include replacing aging pipes or using anti-corrosives in the water source. The 15 ppb that the EPA uses as a measure is a regulatory level, not a number that means the water’s safe to consume.

The EPA guidelines show that Maximum Contaminant Level Goal (MCLG), or the level of a contaminant in drinking water below which there is no known or expected risk to health, is zero for lead.

In Flint, independent studies of the lead in the city’s water showed 27 ppb of lead, The Washington Post reported.

What are the symptoms of lead poisoning?

Possible symptoms from lead poisoning include:

Abdominal pain and cramping (usually the first sign of a high, toxic dose of lead poison)

Aggressive behavior

Anemia

Constipation

Difficulty getting pregnant

Difficulty sleeping

Headaches

Hearing loss

Irritability

Loss of previous developmental skills (in young children)

Low appetite and energy

Reduced sensations

Any other health problems with lead?

Health officials are reporting an odd spike in reported cases of  Legionnaires’ disease  in the Flint area. There has not been an established link between the water problems and the cases of Legionnaire's, but some studying the water issue predicted a spike in the disease. There were 91 cases of  Legionnaire's disease --  a severe form of  pneumonia -- with 12 reported deaths. If a link is made, some suggest that manslaughter charges may also be on the table.

What’s happening now? 

The city has been under a state of emergency, and people there are using filters and bottled water. Celebrities are joining the effort lead by Cher who donated more than 180,000 bottles of water for area residents.

In January, Attorney General Bill Schuette opened an investigation and appointed a special counsel. According to The AP, the state investigation team has more than 20 outside attorneys and investigators and a budget of $1.5 million.

What’s next?

Additional charges could follow as the investigation continues.

Sources: The Detroit News; The Associated Press; The Guardian; CBS News; EPA; The Washington Post; ABC News