The lead-poisoned water that flowed into Flint homes at the peak of the crisis three years ago carried another deadly threat: Legionella bacteria that triggered an outbreak, sickening 90 people and killing at least 12 over two years.
In the months after Flint’s noxious water drew national attention, Michigan public health officials said that it would be impossible to know if the bacterial outbreak — which happened during the same months the city switched its water supply to the Flint River — had been caused by the water itself.
But a new study published in the Proceedings of the National Academy of Sciences makes the strongest case yet that Flint River water was the source of at least 80% of the Legionnaires’ cases that occurred in 2014 and 2015.
“There was a suspicion that the outbreak was governed by the failure of the water system, but it wasn’t properly quantified,” study leader Sammy Zahran, associate professor of demography at Colorado State University, told BuzzFeed News.
The team found that, for the months that Flint River water ran through their taps, Flint residents were seven times more likely to get Legionnaires’ than were people in other counties.
“This is a big deal,” Janet Stout, research associate professor of civil and environmental engineering at the University of Pittsburgh, who was not involved with the PNAS study, told BuzzFeed News. “The link to the impact of the water quality on the outbreak has been something that has never been seen before or explored in the level of depth as this investigation.”
In a release published Monday, the Michigan Department of Health and Human Services said the work had "numerous flaws" and announced that the state’s relationship with the research group would be terminated.
MDHHS had asked a Dutch research group, KWR Watercycle Research Institute, to review the study ahead of publication. Among its criticisms, MDHHS said that the study did not take into account the correct timeframe of cases, and focused on the wrong strain of bacteria.
The state health agency offered to continue the relationship with the US academics if they would agree to oversight by KWR, according to the release. But the US scientists did not agree to these terms.
“By publishing these inaccurate, incomplete studies at this point, FACHEP has done nothing to help the citizens of Flint and has only added to the public confusion on this issue,” the release stated.
The Flint Legionnaires’ cases made up the second-largest outbreak in recent history, just behind a 2015 outbreak in the Bronx, in which at least 10 people died and more than 100 fell ill, Stout told BuzzFeed News.
Legionnaires’ disease is a form of pneumonia and can be fatal in 10% of cases. The Legionella bacteria find a comfy home in the cooling towers of air-conditioning units, and poorly cleaned pipes, showers, or faucets. If inhaled, the bacteria infect the lungs.
Chlorine, used by water utilities as a disinfectant, typically keeps bacteria like Legionella at bay. Zahran and his team show that the switch in water supply to the Flint river was followed by major fluctuations in chlorine levels across neighborhoods.
But because authorities failed to add necessary anti-corrosion chemicals after switching to Flint River water, it ate through the pipes, releasing lead and flakes of iron. This brew laid waste to the city’s water infrastructure, but it also reacted with and reduced the chlorine, creating an environment in which Legionella bugs are known to thrive.
“This is really an extraordinary piece of research,” Lynn Goldman, dean of the Milken Institute School of Public Health at George Washington University, told BuzzFeed News by email, adding that such an approach will help “pin down causality.”
Following the reports of bacterial disease, some public health officials blamed the outbreak on seasonal fluctuations. Stout of the University of Pittsburgh told BuzzFeed News that she contacted representatives from the EPA, the Genesee County Health Department, and the Michigan Department of Health and Human Services, and offered to test Flint water for Legionella. But she did not get a response from any of them.
Then in 2016, the Flint Journal reported that the Centers for Disease Control and Prevention had genetically matched three cases of Legionnaires' to the McLaren Flint hospital. This appeared to point to the hospital, not the water, as the source for the outbreak, and state officials intensified their focus on the facility.
Even so, many scientists had their doubts — the sharp rise in the number of cases began very soon after the water crisis, and tapered off weeks after the water returned to a clean source.
“This was clearly a systemic problem throughout the Flint community and it was triggered by a change in the water supply and the chemistry,” Amy Pruden, a professor of civil and environmental engineering at Virginia Tech, who was not affiliated with the new study, told BuzzFeed News.
Pruden and her colleague, water scientist Marc Edwards, collected their own samples from Flint residents' homes and published two studies showing that the biochemistry of Flint River water presented a comfortable home for the bacteria.
The new study took a more comprehensive approach. The researchers included every case of Legionnaires’ recorded by the Michigan Department of Health and Human Services between 2010 and 2016 in Flint’s Genesee County and two neighboring counties. They then analyzed those against water chlorine measurements obtained weekly from eight sites in Flint over three years.
Zahran’s team showed that, in the first four months of the crisis, Flint residents were 10 times more likely to contract Legionnaires’ than were those in other counties.
Then in September 2014, Flint began issuing “boil water advisories,” instructing residents to consume tap water only after it was heated. The Legionnaires’ risk dipped slightly after these announcements, possibly because some people began turning to bottled water and avoiding taps, Zahran said.
Finally, after the city stopped running Flint River water and returned to Lake Huron water, the risk for Legionnaires’ returned to the levels seen before the lead crisis.
Still, researchers were puzzled by a few cases of Legionnaires’ that showed up in communities that weren’t affected by the water switch. To explain this, the team looked at commuter data, and showed that the likelihood of Legionnaires’ increased in a community if there were residents commuting to Flint during the time the water was bad.
Ultimately, Zahran and team ascribed 80% of the Legionnaires’ cases to the change in Flint’s water.
“There’s this growing of chorus of scientific voices, mine included, that in many respects disagree with some of the public health officials,” Stout said. “The voices are getting louder.”
This article was updated to include a response from the Michigan Department of Health and Human Services.