If you want to know why Nashua doesn’t add cavity-fighting fluoride to the city drinking water supply, check the Facebook comments that readers attached to a Sunday Telegraph letter to the editor that advocated the practice.

“I hope they keep it out of the water and not force people to drink a substance that can be harmful to them. If someone wants fluoride, and what’s in their toothpaste is not adequate, then let them get the drops,” wrote Elizabeth Taylor-Wiggins, one of 10 people who commented on the paper’s Facebook page or on the letter on the paper’s website.

All of the commenters opposed the idea.

“Why is it OK to medicate people without their knowledge or consent, many of whom may already be taking fluoride or have a major problem with it?” asked Glynis Gordon.

Phil Falardeau quoted from FluorideAlert.org, the website of a group that has long fought against fluoridated municipal water supplies, while a reader with the screen name Alaska NH Castines emphasized the position like this: “It is another load of crap fed to us by so-called experts.”

Such fierce opposition shouldn’t be a surprise, because the idea of adding fluoride to city water supplies has long been controversial even though it is strongly supported by medical and dental groups.

For example, Nashua-based Science Cafe New Hampshire has held more than 30 monthly discussions in local bars concerning topics, but only the session concerning fluoridation – not the session about controversial topics including climate change, or about vaccinations, or about Lyme disease – grew heated enough that the moderator had to tell people to calm down.

Nashua is the largest New Hampshire city that doesn’t fluoridate its water supply: Manchester, Portsmouth, Concord, Dover and Rochester all add it, as does the Pease Tradeport.

The letter writer, Nashua resident Jill Queenan, said she assumed that all cities added the inexpensive chemical to the water supply as an easy and safe way to cut cavities, until she took her son to the doctor.

When her pediatrician told her to buy fluoride drops for her child, Queenan wrote, “Why in the world would a town not fluoridate its water, when studies by the Centers for Disease Control suggest a 50-70 percent reduction in cavities among children who drink fluoridated water? And why would parents be forced to administer (and, ahem, remember) nearly 3,500 doses of fluoride per child, when simply drinking water out of a faucet would do the job?”

Queenan said her research indicates “the majority of those opposed to the practice of water fluoridation just don’t want the government to make them take medicine – regardless of the root canals they could be spared.”

“I get it, we live in New Hampshire – Live Free or Die. But I have to wonder: When the benefits so far outweigh the risks in this case, and we have an opportunity to improve the overall health of our community with one simple, cheap step, how is this still a thing?” she wrote.

Pennichuck Water Works could add fluoride to the water if a citywide referendum supports it.

If the petition is valid, a referendum vote on fluoridation must be held and the majority opinion honored for at least two years before the fluoridation question can be placed on ballot again.

No referendum has ever come in Nashua, and the push to fluoridate water hasn’t exactly been on the front burner. Manchester was the last city to add fluoride, back in 2000; before that, it was Dover in 1990. Most fluoridation systems in New Hampshire were approved in the 1970s or earlier.

And just in case you thought that this was one topic that could avoid politics, we’ll end with a comment from reader Jonathan Kohanski: “Sounds to me like she’s been drinking the liberal Kool-aid.”