THE HIDDEN DANGER OF MANTLE LAMPS

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It now appears that the lantern—long a standby source of light—may pose a health threat.

by Mary Anderson

The warm yellow glow of an open-flame kerosene lamp is comforting and—under the right circumstances—even romantic, but almost anyone who's tried to read by the light of one of the standard wick-type lanterns fully appreciates the usefulness of the mantle lamp. When the mantle (a small cylindrical hood, which—when placed over a flame—becomes white hot and gives off very bright light) was incorporated into the design of gas, kerosene, and oil lamps about 100 years ago, the light intensity of such devices jumped from about 15 watts to nearly 60. With this refinement, folks were significantly more able to continue their daytime activities after darkness fell than they'd ever been before!

Today, many campers and residents of nonelectrified areas (as well as individuals who have chosen to do without electricity) rely on light provided by mantle lamps for reading, sewing, and other close work . . . and they've been pretty clanged grateful for that eye-saving illumination, too. However, although most people are unaware of the problem, the mantles in such lamps are actually radioactive . . . possibly enough so to threaten the health of folks who depend on them.

The mantles used on modern lanterns acquire their radioactive properties during the manufacturing process. First, the fabric that will eventually form the small rayon mesh pouches is dipped into a solution of thorium and cerium nitrates. The nitrates are then precipitated into the cloth with ammonia, and—after it's dried—the mantle is coated with nitrocellulose, which fixes the ammonia salts and improves the preburning capability of the material. Occasionally, a manufacturer will also add a small amount of beryllium to give the ash (the residue that's left behind after the lantern's nitrocellulose-assisted initial burn) greater strength. However, it's the thorium in the mantle that incandesces and gives off the functional white light.

Unfortunately, that same element is radioactive. It is—to be more precise—an alpha-particle-emitting radioisotope which has a decay series of ten radiodaughters (a "daughter" is an element that is an immediately produced by-product of the disintegration of a radioactive element). The first radiodaughter is radium 228, a betaemitter which—in time—produces subsequent alpha-emitting radiodaughters.