A federal court trial underway in San Francisco could spell the beginning of the end of water fluoridation in America, potentially affecting drinking water for hundreds of millions of people across the U.S.

Although fluoride can occur naturally in water, many water utilities add the chemical with the goal of improving dental health. But an alliance of groups led by Food & Water Watch, a government accountability nonprofit, have sued the Environmental Protection Agency to force it to limit or ban adding fluoride altogether. They contend that the chemical presents an “unreasonable risk’’ of causing neurological damage, especially to young children and babies in the womb.

In opening statements today, plaintiffs lawyer Michael Connett said it ”will be undisputed in this case that babies who are bottle-fed with fluoridated water receive the…