FLINT, MI -- A study by professors and students at Virginia Tech University concludes that the use of the Flint River for drinking water was "a likely trigger contributing to the increase in Legionnaires' disease incidence" here in parts of 2014 and 2015.
Although the study, released Tuesday, Aug. 29, says there remains a lack of data directly linking drinking water to the disease, it presents evidence that city water was conducive to the growth of Legionella bacteria.
"This study demonstrates ... water quality also deteriorated in a manner that produced conditions known to be conducive to Legionella proliferation," the manuscript says.
"These include: increased water main breaks, instability of chlorine residual in the distribution system, elevated water temperatures during summer months, and elevated iron concentrations."
The peer-reviewed paper was published by the American Chemical Society's publication Environmental Science & Technology, and its authors include Marc Edwards, a key figure in exposing high lead levels in Flint water in 2015, and Amy Pruden, who authored a 2016 study that found Legionella levels up to 1,000 times higher than normal tap water in Flint.
Flint's Legionnaires' outbreak in coincided with a change in water source in the city from April 2014 until October 2015.
While state-appointed emergency managers ran the city, Flint's water source changed to the Flint River in April 2014, but the river water was never treated to make it less corrosive to pipes and plumbing in the water system.
Testing by Edwards and the state of Michigan showed lead levels spiked after the switch and 88 cases of Legionnaires were also documented from June 2014 until November 2015, just after use of the Flint River ended.
By comparison, the VT study says just 16 cases of Legionnaires' were reported in 2016 and only four were reported this year from Jan. 1 until July 24.
MLive-The Flint Journal reported in February that the Centers for Disease Control and Prevention had discovered the first genetic links between city water and patients diagnosed with Legionnaires' -- something researchers have sought throughout the Flint water crisis.
But the meaning of the molecular matches has been questioned by the state Department of Health and Human Services, which has focused on a large number of Legionnaires' cases tied to McLaren-Flint hospital.
The new study says 70 percent of the Legionnaires' cases during the water crisis had a known exposure to Flint drinking water in a healthcare setting.
The experimental and field data the study says was used to compose the report includes:
- Monthly water quality reports from 2010 until 2016, which shows levels of chloride, phosphate and free chlorine in water.
- Results from four separate water surveys of 156 homes in Flint, which were scanned for inorganic material including iron, chloride and phosphrus, "which serve as indicators of unlined iron pipe corrosion, corrosivity of the drinking water and level of corrosion control ..."
- Water quality testing that measured total iron, phosphate and chloride and separate testing to measure chlorine stability in water.
The paper says it highlights the "important role for water utilities in preventing Legionnaires' disease through distribution system management and infrastrucure.
"Even in the absence of federal regulations, increased awareness of this responsibility and improved communication among diverse stakeholders ... will be vital for preventing future disease," the report says.