Here's the continuation of the list of radioactive consumer products that I posted yesterday...

Antidiarrhea Medication

Kaolin is a white clay (found primarily in Georgia and Alabama) that contains elevated levels of the uranium and thorium decay series. This clay is believed to be derived from the weathering of granites which are know to contain elevated levels of these radionuclides. Kaolin was the primary ingredient in the antidiarrhea medication Koapectate (hence the latter's name). Alas, Kaopectate no longer contains kaolin. Many years ago there was a television commercial in which a Mexican family had a rough time during their vacation to the US, and Kaopectate came to the rescue. As I recall, it was announced in that commercial that Kaopectate was new and improved. The kaolin was taken out of Kaopectate.

Glossy Magazines

For decades, glossy paper, the type used in magazines, was made using a white clay called kaolin (named after the Chinese region Kao-Ling where it was mined to produce porcelain). The clay is used to fill the spaces between the fibers in the paper and to coat the paper so that it will have a smooth surface. This makes the paper more suitable for the reproduction of photographs, especially color photos.

Kaolin has other uses (e.g., as a filler in paint and plastic, and as the active ingredient in antidiarrhea medicine), but its largest use is in the paper industry. This might change. There seems to be a gradual move towards the use of less expensive calcium carbonate. The state of Georgia is concerned because it is the world's single largest producer of kaolin. As a result, kaolin is sometimes referred to there as "white gold."

Since kaolin contains elevated levels of the uranium and thorium decay series, glossy magazines have a higher radioactive content than ordinary paper. The activity of such magazines is not high enough to be detected with a simple survey meter, but it is possible that a truck with a load of magazines could trip a radiation monitor.

Brazil Nuts

Brazil nuts contain high levels of radium. First reported in the 1950s (Turner et al 1958).

Radium is radioactive. To be specific, the radium in Brazil nuts is a mix of Ra-226 and Ra-228. Of course, the various decay products of Ra-226 and Ra-228 are also present. Although the radioactivity is not high enough to be detectable with a simple survey instrument, a one to five minute count on the powdered meat of the nut with a pancake GM or ZnS detector connected to a scaler will indicate that the beta and alpha activities are significantly above background.

Brazil nuts are the seeds of Bertholletia excelsa, a large tree that is grown in various parts of world, not just Brazil. The nuts, in groups of 12 to 25 much like the sections of an orange, form the globular (4-6? diameter) fruit of the tree. It is not true, as is sometimes thought, that the high concentration of radium in Brazil nuts is due to elevated levels of the uranium and/or thorium series in the soil in which the tree grows. The accumulation of the radium is due to the very extensive root system of the tree. For what its worth, measurements by Penna-Franca et al indicated that higher radium concentrations are found in the leaves and cork of the tree than in the nut.

As might be expected, the reported concentration of Ra-226 and Ra-228 vary, but overall, the radium concentrations in Brazil nuts are 1000 times higher than those in other foods.

Radioactive Spark Plugs

Polonium-210 was incorporated into the electrodes that formed the spark-gap of the spark plug. More specifically, the polonium was added to the molten metal (a nickel alloy) from which the wires that were used to produce the electrodes were drawn. The alpha particles emitted by the decay of the polonium would ionize the gas within the spark gap and this would presumably result in a longer and/or ?fatter? spark. The November 1941 issue of the Science Digest reported that tests had indicated that ?30 percent fewer revolutions were required to start the motor as compared with other spark plugs.? According to the company?s advertising, the sparkplugs resulted in a ?smoother motor performance . . . faster pick-up . . . quicker starting . . . save more gasoline.?

That there was any real benefit to using these spark plugs is somewhat questionable (other than the improved performance you get whenever you install new plugs). First of all, the half-life of the polonium-210, 138 days, meant that any effectiveness would be short-lived. Second, the inevitable accumulation of deposits on the surface of the electrodes would attenuate the alpha particles and prevent them from doing their job.

Low Sodium Salt

The great thing about a low-sodium salt substitute, aside from the fact that it is measurably radioactive, is that people put it on their food! Not to worry ? consuming a salt substitute doesn?t increase your radiation exposure.

Salt substitutes are radioactive because they contain potassium chloride, and all potassium contains the radioactive beta-gamma emitter potassium-40.

Salt substitutes vary in their composition, but their main ingredient is always potassium chloride. For example, the listed contents of the Nu-Salt are: potassium chloride, cream of tartar, drier and natural flavor derived from yeast. Contains less than 20 mg of sodium per 100 grams. The contents of the NoSalt are: potassium chloride, potassium bitartrate, adipic acid, mineral oil, fumaric acid and silicon dioxide. The ingredients of another salt substitute, not shown here, are: potassium chloride, L-glutamic acid, mono-potassium glutamate, tri-calcium phosphate and 0.01%potassium iodide.

Thoriated Camera Lens

In designing optical lenses, it is often desirable to employ glass with a high index of refraction. The greater the index of refraction, the greater the bending of the light. Since this reduces the necessary curvature of the glass, the lens can be made thinner and lighter. Unfortunately, glass with a high refractive index can also have a high dispersion. By adding thorium to the glass, a high refractive index (over 1.6) can be achieved while maintaining a low dispersion.

Camera lenses known to have contained thorium include:

Canon FL 58mm f1.2

GAF Anscomatic 38mm f2.8 (Anscomatic 726 camera)

Kodak Ektanar 38mm f2.8 (Instamatic 804 camera)

Kodak Ektanon 46mm f3.5 (Signet 40 camera)

Kodak Ektanon 50mm f3.9 (Kodak Bantam RF camera)

SMC Takumar 50mm f1.4 (Asahi Optical Co.)

Super Takumar 35mm f2.0, 50mm f1.5, 55mm f2 (Asahi Optical Co.)

Super Takumar 6x7 105mm f2.4 (Asahi Optical Co.)

Super-multi-coated Macro-Takumar (Asahi Optical Co.)

Yasinon-DS 50mm f1.7 (Yashica)

The gamma and beta emissions from high thorium content lenses in photographic cameras have the potential to degrade the film if the latter was left in the camera for a substantial period of time. In addition, the self-irradiation of the camera lens leads to a gradual darkening of the glass that reduces light transmission. As a result, it is not unusual to see a reddish brown color to the glass of older lenses.

The last part will be posted next time. So, for the meantime, you checked for the named items in your stocks, and ask a pro if your type of product/s is/are radioactive.