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SAN FRANCISCO -- Levels of the trace metal vanadium in drinking water may play a role in promoting nontuberculous mycobacterial infection (NTM), a researcher said here.

Each 1-log increase in vanadium concentration in groundwater supplying homes on the Hawaiian island of Oahu was associated with a 22% increase in local rates of Mycobacterium avium complex (MAC) infection, said Ettie Lipner, PhD, MPH, of the National Institute of Allergy and Infectious Diseases in Bethesda, Maryland.

Perhaps more striking was a pair of maps Lipner showed when presenting the data at the . Both indicated the principal aquifers that supply drinking water on Oahu. Orange-to-red shading on the left illustrated which areas had the highest rates of MAC infection; on the right, the same shading was used to show which had the highest vanadium levels.

They were nearly identical.

What could explain the association? A likely possibility is that vanadium -- and potentially other trace metals and minerals in drinking water -- promotes growth of mycobacteria in water. NTM, which includes MAC and related species such as M. abscessus, are considered water-borne pathogens, although infection is not as common as with E. coli and other more familiar contaminants.

Lipner and colleagues had previously found associations between vanadium and fellow trace mineral molybdenum in waterways and local NTM rates in and . Hawaii has the nation's highest rate of NTM infections, Lipner said, and thus was a promising place for another study.

These studies and the new one on Hawaii drew on test data from monitoring conducted by the Environmental Protection Agency and the U.S. Geological Survey nationwide. For the new study, data on NTM infections came from the Kaiser Permanente system's Hawaii division, covering 2005-2019.

During that span, 348 individuals on Oahu were diagnosed with MAC infections, and another 122 with M. abscessus. Vanadium levels were significantly associated with the former but not with the latter. (In some previous analyses elsewhere, the reverse was true.) However, the researchers also found that sulfate levels were associated with MAC infection risk, albeit to a lesser degree (12% per 1-log increase) than with vanadium.

Lipner noted that the highest levels of vanadium and of NTM infections were in the island's center.

In response to an audience member's question, Lipner said she couldn't exclude the possibility that vanadium and molybdenum may act directly on humans to make them more susceptible to NTM. That will require additional research, and she also acknowledged that the mechanism by which these trace metals promote NTM growth in water (if they indeed do) is not at all clear with MAC infection risk.

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