Tooth decay can begin very early in a child's life. If five states ban fluoride in drinking water, the costs to Medicaid for a significant increase in kids with cavities could top $40 million within three years, a new analysis finds.

The Environmental Protection Agency launched the first step of its expedited review to determine safe levels of fluoride in drinking water, according to a notice posted in the Federal Register on Wednesday, advancing a priority of the Trump administration's "Make America Healthy Again" agenda.