Ladapo said he was recommending against fluoride in the water because of the “neuropsychiatric risk associated with fluoride exposure” and cited the wide availability of fluoride through other means, like toothpastes, mouthwash and in-office dental applications.

Arkansas lawmakers put forward proposed legislation on Wednesday which could end mandatory fluoride treatment of municipal drinking water in the state. In the early 20 th century, it was discovered that naturally occurring amounts of the mineral fluoride in certain well water prevented tooth decay.

The newfound national attention on fluoride injects the intense partisan passions of a Trump presidency into an issue that historically has been hyperlocal.