Updated 1/12/18 5:20 p.m. The City of Milwaukee health department is under fire -- amid a management shake-up. It became public Friday afternoon that the department failed to properly notify thousands of families, whose children tested positive for elevated blood lead levels. It also became public that health commissioner Bevan Baker has left his post. But well before the news broke about the department not sharing lead testing results, Baker had been facing growing criticism. Advocacy groups have blasted him for how the city has been handling the risk of lead in drinking water. For the last two years, lead in drinking water has been one of the most serious issues the Milwaukee health department has been tasked with addressing. The problem is in older homes that are served by so-called "lateral" pipes that connect the homes to the city's water mains. The laterals in older homes are made of lead, which can flake off as the pipes age -- and flow into the water that people drink. Advocacy groups argued the health department wasn't aggressive enough in spreading the word about the risk of ingesting lead flakes -- or the importance of installing filters on faucets. They also criticized the content of the health department's public education campaign. Health Commissioner Bevan Baker consistently maintained the department was doing everything it could. But it became public Friday afternoon that at the same time, Baker's department was failing to alert thousands of families that their children tested positive for elevated lead levels. Milwaukee Mayor Tom Barrett says he found out about the problems earlier this week. “I am angry, disappointed and I am actively working with department staff to fix it right now,” Barrett says. Barrett says that every year, around 25,000 kids in Milwaukee are tested for lead. Typically, around 3,000 test positive for elevated levels. The health department receives those results and is one of the parties tasked with notifying families and following up with them. Barrett says it's not clear whether the health department consistently followed the procedure. He says he'll make sure the families affected get word about the test results. The Mayor adds, in light of the problem, he and Bevan Baker agreed -- it was time for the health commissioner to leave his post. Members of the Milwaukee Common Council say they'll hold the mayor's administration responsible for the -- quote -- "egregious public health failure." All fifteen aldermen released a statement, expressing their displeasure with the situation. Ald. Tony Zielinski calls it "very distressing." We're talking about the most vulnerable population in our community. We as a city have a responsibility to look out for their welfare and obviously that hasn't happened in this particular situation so there's going to be some serious consequences. Aldermen say they'll begin an investigation next week, to determine what processes and procedures were ignored. Meanwhile, the groups that were critical of former health commissioner Baker say they're pleased to see him go. Sherrie Tussler is executive director of the Hunger Task Force. It's been fighting lead poisoning on a number of fronts -- including pushing for a resolution to require the health department to change the language in its informational campaign. Tussler says the commissioner had been hindering the progress: “Hunger Taskforce has been advocating for full explanations on the causes of blood poisoning in Milwaukee since last February. And the Commissioner Bevan baker has not been forthcoming to try to share information,” Tussler says. Tussler says Baker's departure indicates to her that there's recognition from the mayor's office that the city must be more proactive in educating people about lead -- specifically -- the risk of lead in water.