Scientists found the lead reacted with the chlorine to create an environment more hospitable to legionella bacteria
New research published in the Proceedings of the National Academy of Sciences by a team of scientists from the University of Michigan, Colorado State University and Wayne State University revealed low chlorine levels as the cause of the 2014 to 2015 Legionnaires’ disease outbreak in Flint, Mich. The scientists analyzed water and epidemiological data from the six year period before, during and after the Flint water crisis.
Chlorine reacts with heavy metals, such as lead, and the study suggested that the lead in the water distribution system may have decreased the amount of chlorine through that reaction. While the same amount of chlorine was used in the system as before the switch to the Flint River, the reaction caused the chlorine to be less effective in combating legionella bacteria.
In a normal year the disease would occur between six and 12 times in Flint, however, during the crisis Legionnaires’ disease occurred in approximately 45 cases per year, as reported by National Public Radio (NPR).
“The really striking finding from our research is that the amount of chlorine that needs to be present is actually influenced by other factors in this large municipal water system,” Michele Swanson, a Legionnaires’ expert from University of Michigan involved in the study told NPR. “So, for example, during the Flint water crisis, the amount of chlorine that needed to be present to reduce the risk of disease was much higher than normal.”
The study’s authors are optimistic that the findings will inform policy decisions in regard to the frequency of testing for legionella bacteria.