Uses of Halogens in the Health Industry

By Ron B. Davis Jr., Georgetown University

Diatomic chlorine gas, the first element ever discovered from group 17, contains some of the most reactive elements on the periodic table. Over the years, ionic compounds like halide ions have found their way into the health industry due to their numerous benefits.

Ionic Compounds of Halogen

Halogens are often found in ionic compounds. They are just one electron shy of a coveted octet of electrons in their valence shell. This is noticeable in trends for electron affinity and electronegativity, where the entire halogen group rises far above all other elements.

Metallic elements, which prefer to lose electrons, make it especially easy for halogens to steal electrons, giving us such compounds as sodium chloride, in which chlorine acquires sodium’s lone valence electron.

Ionic compounds that contain halide ions like fluoride, chloride, bromide, and iodide are not only common, but they also have a number of beneficial uses.

Fluoride for Tooth Enamel

In 1931, a Colorado Springs dentist, Frederick McKay realized that a remarkable lack of cavities in patients from his area correlated with a high level of fluoride ions in the local drinking water.

The source of the fluoride was determined to be 10,000-year-old deposits of the mineral fluorite, or calcium fluoride, deposited in central Colorado as the glaciers from the last ice age retreated northward. This mineral was slowly dissolving into the water supply, producing an effect on his patients.

After extensive testing, it was determined that the same effect could be produced by the addition of a small amount of the ionic compound sodium fluoride to drinking water or toothpaste. Fluoride ions have an amazing ability to toughen tooth enamel.

When your body forms bones or teeth, that’s a calcium mineral called hydroxyapatite, which also contains hydroxide ions with the formula OH minus.

Fluoride Reduces Tooth Decay

Fluorine and oxygen are neighbors in the periodic table, and their sizes are very similar. This means that a fluoride ion fits quite nicely into the place of the hydroxide ions in the structure of apatite minerals, owing to similar size and charge. This allows fluoride to substitute for the hydroxide ions in tooth enamel.

Tooth decay results when small amounts of hydroxyapatite dissolve in acids from our food or are produced by bacteria in our mouths. Once that material is dissolved, it is gone forever.

But if there is dissolved fluoride around, the new mineral fluorapatite can form from the components of the dissolving hydroxyapatite. Fluorapatite has a much lower acid solubility than ordinary enamel, and so it is resistant to further erosion by acids from beverages and bacteria.

In 1945, Grand Rapids, Michigan became the first city to deliberately add fluoride to the water supply, and today most major US cities do the same in the hopes of replicating the positive public health impact that the natural fluoride had on Colorado Springs residents.

This article comes directly from content in the video series Understanding the Periodic Table. Watch it now, on Wondrium.

Benefits of Chloride Ions

Not to be outdone by its smaller group member, chloride ions are equally important. But chlorine’s role in maintaining public health is different.

Consider a patient with a deficiency of potassium, a crucial nutrient. However, it is not advisable to prescribe metallic potassium as a remedy.

So, the remedy in this case would be to combine potassium with chlorine to make potassium chloride. In this ionic compound, the potassium is already ionized, and the chloride provides charge balance for the potassium ions that the patient needs.

Chloride for Better Absorption of Drugs

More complex drugs, like the painkiller oxycodone, are sometimes not absorbed well by the body in their neutral molecular form—they can also benefit from the inclusion of chloride ions. Oxycodone, for example, is not absorbed well in its neutral molecular form.

So, drugs like oxycodone are often reacted with hydrochloric acid to produce a hydrochloride salt. Again, the drug itself becomes positively charged, and therefore more easily absorbed by the body. Chloride provides the necessary negative charge to make the overall product neutral.

In both of these examples, it is the cation—the positively-charged ion—that has the medicinal value. But the negatively charged chloride ion plays the important role of safely charge-balancing the material so that it can be placed on the pharmacy shelf for years and remain effective.

Uses of Bromide and Iodide

Bromide found usage in the early 1900s, as a sedative medication. In this case, the bromide is actually the active ingredient, competing with chloride ions in brain tissue where electrical signals involving the central nervous system are reduced by the bromide.

Many commercial table salts of sodium chloride are fortified with sodium iodide to ensure that we are all getting enough of this critical nutrient. As the iodide in iodized table salt is absorbed into the bloodstream, it eventually makes its way to the thyroid where it becomes covalently bonded to carbon in the hormones that help us maintain proper health.

Potassium iodide is a stable salt of iodine that has low toxicity and a long shelf-life. It is sometimes used to treat thyroid disorders in which the thyroid gland is underproducing important hormones that contain iodide.

So, simply by giving the halogens what they want—one extra electron—any of the common halogens can be transformed from toxins to medicines.

Common Questions about the Uses of Halogen in the Health Industry

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