An analysis of damaged Lead water pipelines supplying drinking water to the residents of Flint by a conducted by a team of scientists from the University of Michigan has revealed a perforated interior surface with holes akin to Swiss cheese where there used to be lead.

The results of the study, which was recently published in the scientific journal, Environmental Science and Technology Letters, supports the widely accepted view that lack of preventative corrosion treatment measures caused lead to leach into the water supply system. The findings contradict a statement made by a regulator earlier in the year who claimed that the water crisis would not have been prevented even if chemicals to control corrosion had been added to the system.

According to the researchers, these findings highlight the importance of continuous anti-corrosion treatment for America's aging water supply network that provides millions of Americans with drinking water.

For the study, the researchers used a scanning electron microscope to closely scrutinize the metal scale, or rust, that encrusts the inside of water service line pipes. They analyzed samples from 10 lead service lines supplying drinking water to Flint, looking at both the texture and chemical composition of the rust scale. They estimated that on average each lead service pipeline released 18 grams of lead into the water over the course of 17 months when Flint river water was used as a drinking water source without any anti-corrosion additives.

"This is the amount of lead that would have entered a single home," said Terese Olson, associate professor of civil and environmental engineering at the University of Michigan, and lead author of the study. "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."

That lead ended up in various places. According to Olson, some of it was ingested, some of it flowed out with wastewater, and some lead may still be lingering in household plumbing, where it continues to pose a potential risk to human health even if the lead service line has since been removed.

According to co-author, Brian Ellis, assistant professor of civil and environmental engineering at U-M, when a lead service line supplies a home fitted with galvanized steel water pipes, those water pipes can absorb the lead and later release it back into the water. So even if the lead service line is replaced with a non-toxic alternative, any lead clinging onto the galvanized steel pipes within the home still poses a health threat.

The researchers also pulverized the service pipe linings to determine what material they were made of. After comparing the composition to that of lead service pipes of twenty-six other water suppliers, they found that Flint lead service pipes had a higher ratio of magnesium and aluminum to lead than normal.

"We estimated how much lead was 'missing' in order to bring the Flint lead scale into line with the amount of aluminum 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."

Over the years, the inner surface of lead pipes become corroded due to oxidization or reactions with other chemicals, causing a layer of rust to develop. Adequate corrosion treatment doesn't prevent the pipes from being corroded, but rather prevents the rust layer from breaking down.

"It's like when you put an old penny in a glass of Coke and watch it get shiny again," Ellis said. "The acid in the Coke dissolves the copper corrosion product. This is similar to what happened in Flint's lines. You can have a stable corrosion product, but when you change the water chemistry the oxidized lead compounds on the surface may become unstable and readily dissolve."

Water supplies that have corrosive water flowing through lead service pipes typically add orthophosphates — a chemical that prevents the layer of rust from breaking down. When Flint's water utility switched their water source from Lake Huron to the more cost effective, yet more corrosive, Flint River, they failed to implement the necessary treatment measures — i.e. they failed to add 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 hope to take their findings one step further by verifying their estimate of how much lead each home was exposed to. To do this they hope to analyze a lead service pipe supplying a home that has been standing vacant since 2014 and thus was never supplied with water originating from the corrosive Flint River.

Journal Reference

Teresa M. Olson, et al. Forensic Estimates of Lead Release from Lead Service Lines during the Water Crisis in Flint, Michigan. Environ. Sci. Technol. Lett., (Web): July 19, 2017, DOI: 10.1021/acs.estlett.7b00226