A new study has revealed “the first direct evidence” that the Flint water crisis was caused by a lack of corrosion control chemicals.
University of Michigan researchers studied the service lines in Flint’s damaged drinking water system to confirm the cause of the crisis. Their findings support the generally accepted view that lead leeched into the system because the water wasn’t treated to prevent corrosion.
Earlier this year, a regulator claimed that corrosion control chemicals would not have prevented the water crisis.
The researchers focused on the layer of metal scale – lead rust – inside ten lead service line samples from around Flint. They analysed both the texture of the rust layer, as well as its chemical composition. Based on their analysis, they estimated that the average lead service line released 18 grams of lead during the 17 months that Flint river water (without corrosion control) flowed through the system.
"This is the amount of lead that would have entered a single home," said Terese Olson, a U-M associate professor of civil and environmental engineering and lead author of a study in Environmental Science and Technology Letters. "If we average that release over the entire period the city received Flint River water, it would suggest that on average, the lead concentration would be at least twice the EPA action level of 15 parts per billion."
The lead ended up in several places. “Some was consumed,” Olson said. “Some washed down the drain. Some might still be stored in the homes’ plumbing. In other words, there is a chance that some of that lead is still a potential health risk even after the lead service line is removed.”
As well as examining pipe samples under an electron microscope, the team also pulverised pipe linings to analyse what they’re made of. They discovered that in the Flint pipes there was a greater ratio of aluminium and magnesium to lead than is typical with other lead service lines. (The data was compared with 26 other water utilities.)
"We estimated how much lead was 'missing' in order to bring the Flint lead scale into line with the amount of aluminium and magnesium that was reported in other communities," Olson said. "That missing lead represents what was leached from the pipes during the Flint corrosion episode."
Adequate water treatment on lead piping doesn’t prevent the creation of rust as the pipes age, but it does prevent the breakdown of the rust layer and its dissolution into water.
Water utilities that handle corrosive water and use lead service lines in their systems add compounds called orthophosphates to prevent their breakdown. When Flint switched Lake Huron water for the more corrosive Flint River to save money, the utility didn’t adjust its treatment process to include orthophosphates.
"Beyond implications for Flint, we demonstrated that small changes in water chemistry can release what was stable lead in a fairly quick pulse," Ellis said. "This is a known condition. So while we weren't surprised, being able to show it underscores the importance of maintaining uninterrupted lead corrosion control."
The researchers say the findings underscore how important uninterrupted anti-corrosion treatment is for the aging water systems that serve millions of American homes. The study is titled Forensic Estimates of Lead Release from Lead Service Lines during the Water Crisis in Flint, Michigan.