GRAND RAPIDS, Mich. (WOOD) — Fluoride in drinking water has become a point of contention across the U.S.

NBC News reports 74 cities have voted to remove fluoride from their water in the past five years, and at least three more cities will be deciding on fluoridated water during their November elections. 

In 1945, Grand Rapids became the first city in America to start adding fluoride to its water in a United States Public Health Service experiment without notifying residents. After 11 years, researchers found cavity rates had dropped by 60 percent among kids in Grand Rapids.

The Centers for Disease Control has praised fluoridated water as one of the top public health achievements of the 20th century — mostly due to its role in greatly reducing cavity rates. Nearly 75 percent of Americans drink water that contains fluoride, and 92 percent of people drink it in Michigan.

According to the NBC, those against fluoride view it as a toxin and believe it could be unhealth, pointing to some studies making a connection between the chemical and lower IQ rates. Others push conspiracy theories which claim the government is using fluoride to control minds.

Experts dispute those claims because many of the studies were done in other countries where other factors like pollution were at play.

Anti-fluoridiationists are spreading the word not just online, but in the polls. While much of the anti-fluoride push is on the fringes, the Texas Republican Party opposed water fluoridation in its official 2018 platform.