News Feature | July 29, 2016

Corrosive Tap Water Linked To Legionnaires' Outbreaks In Flint

Sara Jerome

By Sara Jerome,

Tainted tap water likely contributed to Legionnaires’ outbreaks in Flint, MI, according to a new study.

Flint has struggled with Legionnaires’ disease, a deadly pneumonia, several years in a row. “There were at least 12 deaths linked with an outbreak of Legionnaires' disease in the Flint area and 91 confirmed cases during a during a 17-month period in 2014 and 2015,” The Detroit Free Press reported.

In research published this month by Environmental Science & Technology Letters, scientists posited that “the interrupted corrosion control and associated release of iron, nutrients, and depleted chlorine residual in the distribution system would lead to high levels of [the bacteria] Legionella.”

The reasoning behind this line of investigation: Corrosive water dissolves the lining in pipes, allowing iron to leach out. Iron helps Legionella thrive while inactivating the chlorine that would otherwise kill bacteria.

Here’s what the team found: “The team reported no measurable iron in the baseline surveys and the control group of buildings using Lake Huron water, but found high levels of 51 ppb in the Flint homes and hospitals. No Legionella were detected in the buildings using Lake Huron water,” according to a report on the study in Chemical & Engineering News.

Janet Stout, director of the Special Pathogens Laboratory Pittsburgh, explained the significance of these findings.

“This paper shows that the water quality disruptions in Flint directly contributed to the presence of Legionella bacteria and the disease cases that subsequently occurred. Water operators need to understand that when water service is disrupted, the risk of Legionnaires’ disease can go up and the community should be notified,” she said, per Chemical & Engineering News.

The research team was led by Marc Edwards, the Virginia Tech scientist who helped expose the lead-contamination crisis and who posts about the crisis on a blog.

Amy Pruden, an environmental microbiologist at Virginia Tech and an author of the study, weighed in: “Lab-scale type studies have illustrated that corrosion in drinking water pipes can stimulate the growth of Legionella,” she said. “Our team recognized that the conditions in Flint — a corrosive new water source in an aging water system — were just right for Legionella.”

Most cases of Legionnaires’ disease in the U.S. occur “in private homes with no common link other than their water supply, underscoring that drinking water distribution systems are the ultimate source of outbreaks,” Chemical & Engineering News reported.