On Tuesday of this week (Aug. 26), Israel officially stopped adding fluoride to its water supplies. The decision has “been lauded by various rights groups, but criticized by many in the medical and dental communities as a serious mistake,” as the Times of Israel put it.

The tasteless, colorless chemical is put into water for the purpose of reducing cavities, but critics say that it amounts to mass medication, and forces people to consume the substance whether they want to or not.

By law, fluoride had been added to public drinking water supplies of large Israeli towns since the 1970s, and until this week about 70 percent of the country was fluoridated. (For comparison, 67 percent of Americans receive fluoridated tap water.)

Health Minister Yael German announced last year that she planned to end the practice, but faced a wave of backlash. Undeterred, she said earlier this month that she had nevertheless decided to end the process effective Aug. 26, and to not even allow optional fluoridation in communities that support it.

While water fluoridation is not practiced in most of Europe or most countries worldwide, it has become widespread in the United States, Canada, Ireland, New Zealand and Australia, and a few others. It remains contentious where it is practiced, especially outside of the United States; however, fluoridation was recently voted against in Portland, Ore. and Wichita, Kan., and controversy has flared up in major cities like Milwaukee and Cincinnati.

One major open question is what constitutes a safe dose of fluoride. Supporters say the small amount put into water is safe, but opponents of the process point out that once the chemical is put into water, its dose cannot be easily controlled or monitored since people drink widely varying amounts of water and have different body weights and ability to process the mineral.

At high levels, fluoride can cause pitted teeth, bone defects and thyroid problems; a study in the medical journal The Lancet earlier this year labeled fluoride a developmental neurotoxin, due to a link between high levels of exposure and reduced IQ in children, mostly in China. At lows levels, it is thought to help prevent cavities.

German “acknowledged that the naturally occurring element is beneficial in preventing dental decay,” the Times of Israel reported, “but strongly defended her position in a letter to a medical group, writing that ‘doctors have told me that fluoridation may harm pregnant women, people with thyroid problems and the elderly.’”