Researchers have found high levels of lead in the water supply in Flint, Michigan, after the economically battered city switched its water source from Lake Huron to the Flint River in an attempt to save money. The city issued a lead warning on Friday, ramping up residents' health concerns — and questions about the tradeoffs cash-strapped cities make to revive their economies.

One set of study results, released on Thursday, analyzed the blood lead levels in more than 1,500 children in Flint and said the overall number with elevated levels rose to 4 percent in 2015 after the water source was switched, from 2.1 percent in 2013. In some areas, the levels rose to 6.3 percent from 2.5 percent. The study was led by Mona Hanna-Attisha, director of the Pediatric Residency Program at Hurley Medical Center in Flint.

A separate study, conducted by researchers at Virginia Tech, tested water samples from homes in Flint and concluded that the city “has a very serious lead in water problem.” They announced the results in mid-September, saying the lead levels in several samples of city water exceeded 100 parts per billion — well over the EPA’s allowed level of 15 parts per billion.

Flint, synonymous with a perennially devastated rust belt, has long been a poster child of economic depression. Like nearby Detroit, Flint was put into the hands of a succession of emergency managers appointed by the governor. Flint's switch from Lake Huron water, through the Detroit Water and Sewage Department, to water from the Flint River happened during the administration of emergency manager Darnell Earley. In March 2014, the city council voted on a resolution to do “all things necessary” to stop using the Flint River as the city’s water source. Jerry Ambrose, Earley’s successor, called that decision “incomprehensible,” citing a savings of $12 million a year. Ambrose could not immediately be reached for comment at the time this story was published.

Though Flint River has experienced industrial pollution, some researchers believe the high lead content is actually a result of the water’s corrosive nature. According to Marc Edwards, who led the Virginia Tech study, the Flint River is 19 times more corrosive than Lake Huron. As a result, it’s corroding pipes that leach metals like lead and copper into the water supply. Flint could use a corrosion inhibitor to try and prevent that from happening, but to date that has not happened.

While the switch in water supply has benefited the city financially, it has come at a great cost.

Flint resident Melissa Mays, 37, told Al Jazeera that she started noticing problems in August of 2014. She said she began losing her hair and getting rashes over her face and body. She had an upper respiratory infection for six weeks, and every time she coughed up phlegm, it tasted like cleaner or bleach. She was diagnosed with a thyroid disorder last October and has bone spurs on her skeleton. “Every day was worse and worse,” said Mays, who is now part of an advocacy group called Water You Fighting For? She and her children stopped drinking the water a year ago, and stopped cooking with it in January, but she said their health problems persist.

Bob Bowcock is a water resource consultant and environmental investigator for high-profile environmental activist Erin Brokovich. He went to Flint to advise city officials about their water situation.

Bowcock said that cities cannot simply switch from one water supply to another without treating the water differently.

Emergency manager Ambrose “said ‘Turn that on’ and ‘Turn that off,’ and ‘I’m going to save hundreds of thousands a year doing that,’” Bowcock said. “But he caused millions of dollars worth of problems. And he listened to no one. He was accountable to no one. It was horrific.”

State Sen. Jim Ananich is the chair of the Greater Flint Health Coalition, which recently urged the city to issue an advisory to residents about their water. “The transition was done so quickly that I think it was the best intentions of people trying to provide quality water. But mistakes were made, and potentially the public is having to deal with it,” Ananich said.

Boiling water contaminated with lead does not make it safe to drink — in fact, it can make the effects of the lead worse by concentrating it. The options left to people in Flint are to either buy bottled water, or to get filters for their faucets. Both options are a financial stretch for many residents.

According to census data, Flint’s median household income between 2009 and 2013 was $24,834, compared to Michigan’s median household income of $48,411. Between those same years, 41.5 percent of Flint’s residents were living below the poverty level.

“I started calling people and realized that a lot of people in Flint cannot afford to buy bottled water on a regular basis,” said Anurag Mantha, a Virginia Tech graduate student who was on a research team that tested the city’s water.

“A second option that we give them is to buy a national sanitation foundation certified lead filters,” Mantha said. “These are available in home improvement stores and Amazon. But I realized that people couldn’t afford to buy them as well.”

Mantha helped start a GoFundMe campaign to help residents afford water filters. The campaign hopes to raise $25,000 to buy them for at least 1,000 residents, and has so far raised $3,560 in 15 days.

Back in Flint, Melissa Mays faulted the Michigan Department of Environmental Quality, and the City of Flint.

“They’re saying, ‘Oh, it’s not that bad.’ They’re trying to say it only affects a few people and it’s their own problem. They’re trying to shake off all responsibly,” Mays said. “My tub is green because there’s so much copper leaching into both of my bathtubs in my house … and I’m just furious.”

The City of Flint issued a lead advisory on Friday. In a news conference, Mayor Dayne Walling said that the city was working to control the issue, and that he took responsibility for finding solutions, local news outlet WNEM.com reported. Walling has requested $30 million in state funding for water infrastructure assistance, the report said.