Story highlights Children who drank Flint River water 46% more likely to have dangerous blood lead levels, report finds

CDC: No safe blood level in children has been identified; exposure can affect nearly every system in the body

(CNN) The residents of Flint, Michigan, continue to face an unprecedented crisis over lead in water. Today, a new report from the Centers for Disease Control and Prevention makes clear how much damage was done.

"When the source of the water supply was switched to the Flint River, without appropriate corrosion control measures, young children who drank the water had blood lead levels that were significantly higher than when the source of water was the Detroit water system," according to the report. "After the switch back to the Detroit water system, the percentage of children under 6 years with elevated blood lead levels returned to levels seen before the water switch took place."

While the city relied on the Flint River for water, children younger than 6 had a 46% higher chance of testing at or above 5 micrograms of lead per deciliter of blood, the CDC's level of concern . The CDC reviewed blood lead level tests for more than 7,000 children 6 and younger. The tests were done before the water supply was switched from the Detroit water system to the Flint River, after the switch but before a water advisory was issued, after the advisory was issued and after the water supply was switched back.

"This crisis was entirely preventable, and a startling reminder of the critical need to eliminate all sources of lead from our children's environment," Patrick Breysse, director of the CDC's National Center for Environmental Health, said in a news release.

Children under 6 are particularly vulnerable to lead poisoning, according to the Mayo Clinic , and it can severely impact mental and physical development.