For years, Portland has ranked as one of America's greenest cities. While its eco-minded culture has been famously lampooned in Portlandia, the city's environmentally friendly reputation is well earned, as (Seattle-based) Gristnotes:

So how is it possible that the citizens of a city lauded for its ecological values, a place "where every day feels like Earth Day," as one magazine has written, can be so irrational about something that the U.S. Centers for Disease Control (CDC) calls one of the ten greatest public health achievements of the 20th century? I'm referring to the latest voter rejection by Portlanders of a measure to fluoridate the city's water. Just so we're clear: the scientific consensus on the benefits and safety of fluoridated water is well established, as Slate recently laid out:

Almost every credible national, state, and local health and science organization—private and public—gives its blessing to optimal levels of water fluoridation: The American Medical Association, the American Dental Association, the Environmental Protection Agency, the World Health Organization, American Academy of Family Physicians, and the Centers for Disease Control and Prevention..They all agree that fluoridated water is perfectly safe and extremely effective at preventing tooth decay.

Portland's anti-fluoridation history is a curious thing. Much of the United States accepts fluoridated water, though pockets of resistance have sprouted up in the last decade (helped by the internet, it seems).The Slatepiece gets at the reasons underlying Portland's holdout:

Almost everyone interviewed cited the same argument for the ferocity of the opposition, even in the face of near-universal scientific consensus about the safety and benefits of fluoridation: Portlanders’ attachment to their status as one of the greenest big cities in America, a sense of identity tied up with a perceived link to an unsullied environment. (“Industrial byproducts don't belong in our drinking water" is “the No. 1 reason” that Clean Water Portland opposes fluoridation.)

This sentiment is fascinating. At its core is an appeal to nature that mirrors the animating force of the anti-vaccine and anti-GMO movements. Unfortunately, that emotive power makes opponents of vaccines, GMOs, and fluoridated water impervious to science. I have argued that this fetishizing of nature prevents a dominant wing of environmentalism from modernizing. The citizens of Portland, despite their embrace of trailblazing sustainability and urban planning initiatives, remain wedded to some outdated philosophical concepts that put the city at odds with science. A Portland politician quoted by Slate bemoans the fetish of fluoride opponents in his city:

“This obsession with the quality of the water … There isn’t anything new in [Clean Water Portland’s] arguments,” says Rep. Earl Blumenauer (D), who represents much of Portland and was in the state legislature during the late 1970s statewide fight over fluoride. “Since then we’ve had 30 years more experience, and we don’t have people growing extra heads; the supposed dangers haven’t materialized. It truly is not a science-based rational argument.”

UPDATED: I'm rounding up articles and reactions on the Portland news. The AP has a write-up, as does the Verge. A local station reports that "new battle lines may be drawn in the future." Scientific American has an excellent piece called, "Why Portland is wrong about water fluoridation." This post asks how you can tell someone is from Portland?

The backyard chickens, the beard, the inability to pump gasoline. And perhaps we should add a lack of a full set of teeth.

Sarah Kliff at the Washington Postnotes:

The vote makes Portland one of the largest American cities not to fluoridate its water supply, second only to San Jose. Over-under on when we’ll have a Portlandia episode on the subject? I’m guessing next season.

**For additional reading, see my Discover blogging colleague, George Johnson, the Washingon Post'sSarah Kliff at Wonkblog and Steven Novella at the Science-Based Medicine blog. Some historical context: In 1955, fluoridated water was considered by some to be part of a communist plot, along with the polio vaccine. Source for image/Wikimedia commons.