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University Study Confirms Flint Corrosion Story

Tuesday, August 1, 2017

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A study headed up by University of Michigan researchers appears to have confirmed what was long suspected about the source of heightened lead levels in the city of Flint’s drinking water: The heavy metal leached from inside service lines, and the release could have been prevented with a commonly used corrosion-inhibiting additive.

The new research, published in Environmental Science and Technology Letters, says scales on the interiors of 10 lead service line samples taken from around the Michigan city after the drinking-water crisis were subject to “selective dissolution” due to corrosive water and insufficient treatment. The university describes the pattern of corrosion and dissolution as “a Swiss cheese pattern.”

Flint pipe crossection
Terese Olson / University of Michigan

According to the new study, scales on the interiors of 10 lead service line samples taken from around the Michigan city after the drinking-water crisis were subject to “selective dissolution” due to corrosive water and insufficient treatment.

According to the researchers, evidence uncovered in the study shows that each lead service line in the city likely leached about 18 grams of lead during the period in which Flint River water was running through the water system, a period of 17 months.

"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," said lead author Terese Olson, professor of civil and environmental engineering at Michigan.

Phosphate Concerns

The study concludes that it was likely the absence of added orthophosphate in the Flint River-derived water that led to the dissolution of lead phosphate in the layer of corrosion scale inside the lead service lines. Diminished lead phosphate and relative increases in aluminum and magnesium silicates in the scale led the researchers to determine that lead that would have been locked into the scale was released during the period when the untreated river water was flowing through the lines, from April 2014 through October 2015.

Back scattered electron images of a cross-section of a layer of metal scale
Brian Ellis / University of Michigan

The university describes the pattern of corrosion and dissolution, shown here in a backscattered electron image of a crosssection of scale, as “a Swiss cheese pattern.”

The lead particles that were released ended up, the researchers say, being consumed by Flint residents, as well as making their way into wastewater and likely, to an extent, adsorbing into galvanized pipes downstream, where they could still pose a health risk.

Virginia Tech Study

The new Michigan study serves as a follow-up to a paper published in February by a team led by Virginia Tech’s Marc Edwards, which concluded that in at least one case, “the immediate cause of the high water lead levels was the destabilization of lead-bearing corrosion rust layers that accumulated over decades on a galvanized iron pipe downstream of a lead pipe.”

The Virginia Tech paper examined the galvanized service line from the home of “Resident Zero,” a Flint resident with two children whose experience with heightened lead levels first brought the Virginia Tech team to study Flint’s service lines.

Regulator’s Take

The authors of the new Michigan study note that their conclusion directly contradicts one former Michigan official, who earlier this year argued that the lack of orthophosphate additives was not to blame for the lead crisis.

In April, at a talk titled “Flint: What Really Happened?” former state Department of Environmental Quality official Bryce Feighner argued that events including a rash of water-main breaks during the harsh 2014 and 2015 winters were likely more to blame for the corrosion and elevated lead levels than the lack of phosphates.

"You can have the most perfect, non-corrosive water in world—however you choose to define that—and if you have water-main breaks, extreme velocities, changes in flow directions; it's going to strip every coating you've created off those pipes over the last several decades," Feighner said, according to MLive.

Feighner served as director of the DEQ’s Drinking Water and Municipal Assistance division from late 2014 through the beginning of July 2017. At the time of the April talk, he had already announced his pending retirement from the agency.

Virginia Tech’s Edwards immediately refuted Feighner’s claim; Olson and her team from Michigan also expressly cite Feighner as having been incorrect, according to their data.


Tagged categories: Corrosion; Lead; potable water

Comment from Fred Salome, (8/1/2017, 3:01 AM)

If you don't have lead pipes in the first place you don't have to entertain arguments about how or why they polluted the water supply. It can't be that difficult to replace them with non-lead pipes. Until that happens there will always be potential for a human or natural "accident" to cause harm to people.

Comment from Michael Breaux, (8/1/2017, 8:56 AM)

Not that I disagree but if you take the stance that until you remove the lead containing lines and by extension lead containing paint exposure will continue to be an issue then this should be done nationwide as a consolidated effort. The costs will be incredibly high while the benefits may take some time to be felt meaning any major effort by any city, state, or other entity will be unlikely. I find the uproar over this ONE town somewhat frustrating as once the Flint crisis is solved the topic of lead service lines and lead paint is going to just fade away until the next city shows up in the news due to children testing at high lead levels followed by the same outrage and disbelief of "How can this be happening? This is the 21st century in the US!" This wasn't directed at the previous comment, somewhat went on a tangent.

Comment from Catherine Brooks of Eco-Strip, (8/1/2017, 3:15 PM)

It is a national crisis that lead is so prolific in old pipes and houses. The paint companies try to avoid responsibility for the damage done by the lead they consciously added to paint hundreds of years ago. The lead poisoning prevention health and education programs have to fight hard to keep their funding from the states and federal sources. The public is still not educated about this crisis. With older homes being renovated and gentrified, middle class families are now being impacted by old lead paint. It's hard to fight the battle when the higher classes don't feel the impact on education, health, social services, prisons, and other costs.

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