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Monroe public works committee debates fluoridation additives, experts say trace impurities are diluted
Summary
City staff and two outside experts reviewed state-allowed fluoridation chemicals, supplier limits and the presence of trace arsenic in source materials; a chemist said impurities are common in mined fluorapatite and, when diluted for water treatment, are typically nondetectable.
The City of Monroe Board of Public Works Committee on the floor discussed which fluoride additive the city should use and whether so-called "medical-grade" products would reduce trace impurities.
Administrator Rindy noted a memo in the meeting packet and that state statute limits the city to three permitted fluoridation chemicals unless the Department of Natural Resources grants special permission. Rindy also offered technical help from a colleague for the committee’s questions.
John Charlton, introduced on the line and identified in the record as a chemist, told the committee that the materials used to make common fluoridation compounds come from mined fluorapatite and commonly contain trace elements, including arsenic. Charlton said those impurities are typically diluted to extremely low concentrations during water treatment: "By the time you go to clean something ... it might be 1000 dollars a gram. That's really cost prohibitive to use in an application that's not medical... you have to put 6 zeros in front of it and that's your concentration, which literally would be nondetectable on an instrument." The chemist added that those traces are expected where phosphate minerals are mined.
Committee members pressed whether assay results showing arsenic should raise public-health alarm. Charlton responded that the relevant regulatory framework (including the Safe Drinking Water Act) and routine dilution mean the measured impurities in the treatment chemical are unlikely to constitute a hazard in finished water. He also described the manufacturing path: dissolving fluorapatite with sulfuric acid produces co-products such as fluorosilicic (fluorosilicic) acid and hydrofluoric acid, and the supply chain can involve several companies and distributors.
Staff advised the committee that a medical-grade labeled product exists but their supplier could not currently obtain it, and that medical-grade does not necessarily go through the same industry standards testing (AWWA/NSF/ANSI) as the commercial products the city uses. Staff further explained operational controls: the liquid additive is delivered in bulk to well houses, pumped into 60-gallon tanks (no direct handling), refilled about every three weeks, and subject to daily in-house testing with monthly samples submitted to the state for verification.
The committee did not take formal action on fluoridation during the meeting; members indicated the product in use appears to meet current testing and state standards and the Chair closed the discussion.
