Does Boiling Water Remove Fluoride?

A worked example

The example starts with water at 0.7 mg/L, the level the U.S. Public Health Service recommends for community water systems that add fluoride.

A concentration is an amount of fluoride divided by a volume of water. Boiling leaves the amount where it was and makes the volume smaller, so the concentration that is left is the starting level divided by the share of the water that remains. If four fifths of the water remains, the level is divided by four fifths; if half remains, it is divided by one half.

The kettle row is the reason re-boiling comes up. In this example, the second boil starts from the level the first one left and takes away another tenth of the water, with all of the fluoride staying behind.

These rows are illustrations computed from the starting level, not measurements of any pot or kettle. The last row is the arithmetic of a doubling: the concentration doubles once half the water is gone.

Why boiling does not remove fluoride

Idaho DEQ states that boiling water does not remove fluoride. The University of Nebraska–Lincoln Extension's guide to distillation describes what boiling does in a distiller: it turns water into steam, while inorganic impurities are not vaporized and are left behind, in water with a much higher concentration of impurities. The guide lists fluoride among the compounds distillation removes.

A study in Mexico, cited in Environmental Health Perspectives, found that boiled water had double the fluoride concentration of unboiled water. In the arithmetic above, a doubling is what happens when half of the water boils off.

In the arithmetic above, the level rises with the share of the water lost: the smaller the share that boils away, the smaller the change.

Distillation is not boiling

The University of Nebraska–Lincoln Extension's guide to distillation describes a distiller this way: it boils water to produce steam, which rises into a cooling section, condenses back to a liquid and flows into a storage container. Inorganic impurities are not vaporized and are left behind in the boiling chamber, where the remaining water has a much higher concentration of impurities and is drained and discarded. The guide lists fluoride among the compounds distillation removes.

A pot or kettle keeps the opposite part: the water that did not turn to steam. Idaho DEQ states that point-of-use distillation and reverse osmosis have proven effective for removing fluoride.

Do water filters and distillers remove fluoride?

What does reduce fluoride

EPA lists activated alumina and reverse osmosis, each centrally applied, as the best available technologies for meeting its fluoride limit. For point-of-use treatment, the methods our sources name are reverse osmosis and distillation. Idaho DEQ states that point-of-use distillation and reverse osmosis have proven effective for removing fluoride. Each method and the evidence behind it are on our removal page.

Methods that do remove fluoride

More on fluoride

• Fluoride in water: overview
• Methods that do remove fluoride
• Do water filters remove fluoride