What do you mean by a consumer product?
A good place to start. By consumer product, I mean a product or item that is commercially available and that can be sold to the public on the open market.
What does that have to do with radioactivity?
In this brief tutorial, we would like to offer you a glimpse into the category of consumer products that emit ionizing radiation. Yes, there are quite a number of those out there.
Really? How long have they been around?
Essentially since human beings began bartering for and purchasing or selling items . . . A very long time! Of course, the fact that radiation and radioactivity are associated with certain products is only a recent discovery. Therefore, it would be more accurate to say that the discovery of x-rays in 1895 (by Roentgen) and radioactivity in 1896 (by Becquerel) really set the stage on this issue. And, over the last 100 years or so, these products have routinely come and gone, only to be replaced by others.
You mean these products that contain radioactivity are readily available for purchase?
That’s right. Any member of the general public, including you, can not only receive and possess these products, but use, transfer, or deliver them to others without requiring formal permission from regulatory authorities.
While these products do emit radiation in the normal course of their use, the radiation level is typically low and of trivial significance in relation to any potential health effects. In almost all instances, the benefit obtained from using the product for a specific purpose by far outweighs any risks. The most outstanding exceptions are the dose to the lungs of cigarette smokers from tobacco in cigarettes and radioactivity in domestic water supplies. We’ll talk more about these later.
Okay. But if these products emit ionizing radiation, shouldn’t federal/state regulatory authorities get involved?
They do get involved. Some of these products require the manufacturer to obtain a radioactive materials license issued through a federal agency such as the U. S. Nuclear Regulatory Commission (USNRC). Regulatory authorities also get involved when a potential or known hazard from a product’s use is identified. In general, however, regulatory authorities rely initially on the manufacturer to either meet the license conditions and/or impose voluntary guidelines on the emission of radiation. When this fails for any reason or if other concerns arise, congressional and regulatory actions have been required.
Why is radiation even associated with these products?
Well, there are four reasons why this occurs. First, electronic devices in the product can generate radiation (e.g., x-rays associated with color television sets). Second, the product may contain naturally occurring radionuclides (witness thorium in eye glass lenses). Third, the product may have a radionuclide purposely added to it, as in the case with smoke detectors. Lastly, the product may be contaminated with a radioactive material, like certain jewelry, resulting in the emission of radiation. As we get on through this discussion, we will organize it according to these four categories.
Okay. But before we begin, are there products that were once readily available to consumers but that have been recalled because of radiation-related reasons?
Most definitely. There are several products that are either no longer available, have been discontinued, or no longer manufactured because of health concerns that developed after a period of use. In other words, they once qualified as consumer products, but they don’t any longer.
Well, we hate to keep you in suspense, so if you must know, scroll down for a moment and read about the classic example of shoe-fitting fluoroscopes. (But come back up here when you’re done!) Another is the addition of uranium to glass enamels, such as with cloisonne jewelry, which was banned for sale to the public in 1983.
Well, now I’m really curious about this fascinating topic. What products will be discussed?
There are numerous examples of consumer products which, as noted previously, either contain radioactive material or generate radiation through other means. There are so many, in fact, that we cannot possibly cover them all in this brief tutorial. We will try to hit on the important ones, like television sets, airport x-ray inspection systems, shoe fitting fluoroscopes, smoke detectors, ceramics (e.g., Fiesta-Ware), porcelain dentures, lantern mantles, optical lenses, tobacco, low sodium salts, brazil nuts, kaolin, cat litter, static eliminators, radioluminescent products (e.g., aircraft gauges, certain wrist watches and alarm clocks, and tritium exit signs), and welding rods.
Okay, let’s go.
All right. But as you read through this section, look for some particular things: Is the radiation produced essential to the proper performance of the device, or alternatively, incidental/extraneous to its design? What radionuclide(s) are present (if applicable)? Why does the product exist in the first place? What are the radioactivity concentrations and/or radiation levels present? What are the potential risks (if any)?
Will do. So where do we start?
Good question. The answer is . . . with electronically generated radiation. The best and most widely-used example of a consumer product that produces radiation through electronic means is the tried-and-true television set. Other examples are video display terminals (VDTs), airport inspection systems and shoe-fitting fluoroscopes.
What type of radiation are associated with these devices?
In each of these cases, we are speaking of x-rays, a type of photon radiation produced when high energy electrons impact a stationary object, such as the television picture tube or a computer monitor.
Are the x-rays necessary for the operation of a television set?
No. This is one of the many examples where the radiation is a byproduct, meaning it is incidental or extraneous to the purpose for which the consumer product was originally designed.
What affects the x-ray intensity in television sets?
The operating voltage is the primary factor. As the voltage is increased, the x-ray intensity increases. To counter this, the use of thick walls in picture tubes can reduce the x-ray emissions.
Is x-ray emission a health problem with my TV?
No longer, although it became an issue in the 1960’s. Relatively speaking, the highest x-ray emission levels recorded were produced in two particular years, i.e., 1968 and 1969, when color television sets first became popular. These levels have since diminished markedly with technological advancements such as solid-state designs.
Are there legal limits for x-ray emissions around these popular devices?
All television sets must meet a limit of 0.5 milliroentgen per hour (mR/hr) at a distance of five (5) centimeters (cm) from any accessible point on the external surface of the set. These limits are based on recommendations originally issued in 1960 by the International Commission on Radiological Protection (ICRP) and the National Council on Radiation Protection and Measurements (NCRP). They were subsequently passed into law by the United States Congress in 1968 and are currently enforced by the United States Food and Drug Administration (FDA).
Well, those are the limits, but what are the typical exposures?
Actually, they are not very high at all, especially since the disappearance of pre-1970 televisions. Recent estimates place the annual radiation dose to the U.S. population at much less than one millirem (mrem) from color televisions, and even lower for black and white sets.
I’ve seen several articles over the years concerning possible effects from video display terminals (VDTs) . What can you tell me about these devices?
Essentially, video display terminals, such as a computer screen, are identical to television receivers. According to the NCRP, there has always been a mistaken assumption that VDTs constitute a source of personnel exposure worthy of attention. Studies conducted on x-ray emissions from these devices show no differences in comparison to televisions. In addition, studies conducted on possible health effects associated with the use of VDT’s, such as cataracts, birth defects, and others, have to date found no evidence of health hazards. An annual dose of much less than one mrem has been estimated for VDT use as well.
Let’s move on to airport inspection systems. I see these gadgets quite frequently. How do they work?
You take your luggage, place it on a small conveyor belt, and watch as it passes under a source of x-rays that is housed in a shielded cabinet. X-rays are intentionally produced to generate a picture of the luggage contents. The intent is to identify such items as concealed guns, dangerous weapons, potential explosives and incendiary devices as a means of protecting the flying public. If nothing out of the ordinary is observed, you collect your luggage at the opposite end of the conveyor and proceed accordingly.
Won’t my luggage be radioactive after x-rays are taken?
Absolutely not. The luggage has been “irradiated”, but, because it is not “contaminated” with radioactivity, it does not become radioactive. It is just as safe to pick up the luggage after it exits the shielded cabinet as it was when you put it on the conveyor belt in the first place. Consult other “Radioactivity Basics” sections of our website (e.g., “Radiation Exposure”) to learn more about the phenomenon of making things radioactive and why this doesn’t occur with airport inspection systems.
Why would these systems be classified as a consumer product?
The dose from this electronically-generated source of radiation is quite low in relation to the benefit derived by protecting the flying public from potential highjackings, terrorist activities, bomb threats, and other hazards.
As with television sets and VDTs, federal requirements limit exposure rates to 0.5 mR/hr at five (5) centimeters from the surface of the unit, with the primary goal being protection of the operators who stand by these devices during their work shifts. Airline passengers, on the other hand, receive substantially less dose – on the order of 0.002 millirem or less as he/she passes by the unit. This is truly a negligible dose in light of exposures we receive from other sources every day of our lives.
And shoe fitting fluoroscopes? What’s the deal with these?
Shoe fitting fluoroscopes were very popular many years ago. First manufactured in 1924, the intent was to aid the salesperson in more accurately determining the customer’s shoe size.
How did they work?
These devices consisted of a vertical cabinet with an opening at the bottom into which the feet were placed. There were also three viewing ports situated on top of the device.
Sounds like a good idea. What went wrong?
While the idea seemed like a good one at the time, the dose incurred by the individual using these devices, even for short exposure times, was rather significant. Estimates placed the absorbed dose to the feet, for example, at seven (7) to 14 rads (7,000 to 14,000 millirads) for a twenty second exposure. And considering children were especially interested in placing their feet into the device to see their bones, it didn’t take long for public health officials to realize that, from a radiation safety perspective, the practice needed to be discontinued. Further justification for banning these devices was that they are simply not necessary for determining someone’s shoe size. Thus it was eliminated as a consumer product.
In 1957, individual states began prohibiting the use of these devices. Today, these devices are completely prohibited by the Conference of Radiation Control Program Directors (CRCPD) – an organization made up of individuals from each state and major local radiation control agencies. Shoe-fitting fluoroscopes now exist strictly as a historical reminder of a popular product whose time came and went.
Is there a moral to the shoe-fitting fluoroscopes story?
Simply this: If the benefit does not outweigh the radiation-related risk from the product’s use, it’s continued availability on the open market should be re-evaluated. With that said, let’s leave electronically generated radiation behind and discuss those consumer products with radionuclides naturally present in the product’s composition.
All right, then. Where do we start?
Tobacco. Since tobacco is a crop grown in the soil, it will contain members of the naturally occurring uranium and thorium series and potassium-40 (K-40), a ubiquitous naturally occurring beta-gamma emitter with a long half-life (over one billion years). Of greatest importance from a radiological perspective, tobacco contains polonium-210 (Po-210) and lead-210 (Pb-210) – radioactive progeny (daughter products) produced in the uranium series.
Why these two particular radionuclides?
There are at least three plausible reasons. First, Po-210 and Pb-210 are radionuclides which are present on tobacco leaves from the deposition and subsequent decay of airborne progeny of radon-222 (Rn-222). Secondly, the tobacco plant also has a preference for concentrating lead found in the soil. Lastly, phosphate fertilizers, routinely used in tobacco fields, contain measurable concentrations of Pb-210 and Po-210 (from the decay of uranium found in the phosphate).
Surely there must be health concerns associated with this product.
There are. The effects of tobacco on human health and the link to lung cancer is widely cited and discussed, but that is not the focus of this discussion. No matter the assumed or known health effects, tobacco is an ingrained component of our culture and will not be abolished in the foreseeable future. Radiologically, it has been estimated that the amount of Pb-210 and Po-210 residing in the lungs and bones of U.S. smokers is approximately four (4) times and two (2) times that of non-smokers, respectively. Lastly, the additional annual dose equivalent to a particular region of the lung – the bronchial epithelium – from smoking the daily average consumption of thirty (30) cigarettes is around 15,000 millirem.
Okay. What other examples do you have?
Let’s discuss radioactivity in building materials.
You mean my home is radioactive?
Without question! It’s simply a fact of life: Naturally occurring radionuclides are found in a variety of common building materials.
Like isotopes of uranium, thorium, and potassium. Emissions from these elements include alpha, beta, and gamma radiation.
Does the type of home construction I live in make a difference?
It certainly does. As an example, the external dose received from homes constructed of brick and concrete is higher than those made from wood.
What sorts of dose are we talking about?
They aren’t very high, especially when compared to the annual natural background in a given state. Rough estimates by the NCRP and the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) place the average annual whole body external dose at seven (7) to 11 millirem from homes of masonry and concrete construction.
Is there anything else I should be aware of with respect to my home?
Yes. Remember, the home is constructed on soil that also contains naturally occurring materials. Decay of uranium and thorium results in the formation of gaseous radon isotopes and daughter progeny – a well-known contributor to an (internal) lung dose. In addition, naturally occurring radioactive materials can appear in well water used inside a home as a domestic water supply. This constitutes another source of radon exposure.
Which source – external or internal – is of greater importance?
Internal, especially in poorly-ventilated or tightly-enclosed homes. For this reason, the U.S. Environmental Protection Agency (USEPA) has advocated for several years that homeowners evaluate their homes for the presence of airborne radon gas. Further information concerning how to accomplish this objective can be found in the “Radon” chapter of the “Radioactivity Basics” section of the Plexus-NSD website.
Earlier you mentioned low-sodium salts. What’s the deal with them?
For health reasons, certain individuals cannot utilize salt in its normal chemical composition, which is sodium chloride or “NaCl”. Instead, potassium chloride (KCl), or “low-sodium” salt, is used as a replacement.
So what does that have to do with radioactivity?
Potassium contains both radioactive and non-radioactive isotopes. In particular, K-40, a naturally occurring radionuclide mentioned previously, is present in low concentrations . . . not only in salt, but in everything else you could name.
Is the presence of K-40 a valid reason to not use this product?
Absolutely not! This is a primary example where the health benefits clearly override any radiological considerations. (You’re not going to stop eating bananas, are you, simply because they contain some K-40?!) And we should add that even regular use of low-sodium salts would lead to only a slight increase in the K-40 levels in the body, since the body maintains what is called a “tight homeostatic control” on potassium (i.e., we only hold on to what we need, and get rid of the rest).
Can you provide any other products for human consumption that contain naturally occurring radionuclides?
Most definitely. Aside from bananas, the best example is that of brazil nuts, considered the world’s most radioactive food!
How can that be?
Those individuals with a chemistry background know that calcium, barium, and radium are chemically similar. The brazil nut tree readily absorbs radium that is naturally-occurring in soils and concentrates it in the endosperm or “meat” of the nut. Barium is also readily accumulated in this tasty treat.
What radium isotopes are in brazil nuts and in what concentrations?
There are two particular radium isotopes of interest, i.e., radium-226 (Ra-226) and Ra-228. Maximum and average concentrations of Ra-226 have been reported as 6.6 picocuries per gram (pCi/g) and two (2) pCi/g, respectively. Slightly higher values apply to Ra-228 concentrations.
I love brazil nuts. Please tell me you are not suggesting I refrain from eating them!
No, we are not, and would certainly not presume to do so. But please remember one thing: moderation has its place in a healthy lifestyle. Brazil nuts are no exception!
Tell me more about radioactivity in consumer products. This is getting to be quite interesting!
All right. Try this one on for size . . . kaolin is a material, specifically a white clay found in Georgia and Alabama, which contains elevated levels of the uranium and thorium decay series.
How is it used as a consumer product?
It is used in two principal ways. The first is to produce that eye-catching glossy look in magazines and photographs. And it is also found in kaopectate . . . a pleasant-tasting concoction used to combat the onset of diarrhea.
I suspect you’re going to tell me the radiation levels and radioactivity associated with these consumer uses are not a problem, right?
As a matter of fact, yes. The radiation exposure rate associated with reading a high-gloss magazine is fractions of a microrem per hour (on the order of one thousand times less than the natural background dose equivalent rate we are all exposed to). As for kaolin in kaopectate, the effective (whole body) dose equivalent (EDE) per gram ingested is approximately 0.001 millirem. Unless an individual were to ingest mass quantities of this material, the dose is trivial indeed.
How about one more – cat litter!
That’s right! Cat litter contains clay which acts as a natural absorbent. It also contains members of the uranium and thorium series, as well as the ever-present K-40.
What radiation and radioactivity levels are we talking about?
As a benchmark, estimates using a popular brand of cat litter have revealed the following concentrations: four (4) pCi/g for members of the uranium series, three (3) pCi/g for members of the thorium series, and eight (8) pCi/g for K-40. This equates to approximately 0.0001 millirem per hour at a height of six inches above the litter box. Once again, this is a trivial exposure rate.
Is that it as far as radioactivity as a natural component of a product?
No. There are many examples beyond those already discussed. These include highway and road construction materials, mining and agricultural products (e.g., fertilizers and other phosphate products), and combustible fuels (coal, oil, natural gas, etc.). Certain optical lenses not for human use are noted for their thorium content (and consequently may contain elevated levels of thorium) because this element often appears as an impurity in the rare earth oxides used to produce certain types of glass. But let’s move on to our next category.
Is that radionuclides intentionally added to the product?
Yes it is. This category contains several items, including, but not limited to, smoke detectors, radioluminescent products, static eliminators, uranium glazes and ceramics, dental fixtures, gas lantern mantles, ophthalmic glass, and welding rods.
Sounds interesting. Tell me about smoke detectors.
Smoke detectors are one of the most common consumer products. Used to signal the presence of smoke/fire, these detectors typically contain an americium-241 (Am-241) source with a small amount of radioactivity . . . on the order of one microcurie.
How do they work?
When smoke particles enter the detector, they disrupt the flow of current (electrons) created by the ionization of alpha particles produced from the decay of the americium. This disruption triggers an alarm. For this reason, they are known as “ionization-type” smoke detectors.
Am I not getting irradiated when my family and I routinely walk by these devices in our home?
The radiation levels emitted from these devices cannot be distinguished from background levels. To further make a point, it has been estimated that the annual average dose equivalent to the U.S. population from these devices is about 0.008 millirem, which is far below the annual natural background in the United States.
How do I dispose of these devices when I need to get rid of one?
You don’t, or at least you shouldn’t. With the long half-life of Am-241 (approximately 433 years), there should be no reason for disposing of them as long as the other (non-radioactive) components are in good working order and the battery(ies) are replaced on a regular basis. Regardless, instructions for disposal can be found on the detector housing. In brief, the device should be returned to the manufacturer for proper disposal. Disposal by you, the owner, into the trash/public landfill is discouraged.
Radioluminescent products also sound like a topic worthy of discussion.
You bet. Let’s begin with how these products developed. Electricity was not always a plentiful commodity in this country (witness the beginning of the 20th century) and, for that reason, products that could produce light through other means were important.
I take it the word “radioluminescent” is the key term in this section, correct?
Absolutely. Taken separately, the words “radio” indicate the presence of radioactivity and “luminescent” that light will be emitted. Together, the interaction of a particular radionuclide emitting radioactivity with a particular luminescent material, i.e., a “scintillator”, results in the emission of light.
What radionuclides are typically found in these products?
The radionuclides used are almost exclusively limited to Ra-226, promethium-147 (Pm-147), and tritium (H-3). Ra-226 is an alpha/gamma emitter with a half-life of 1,600 years. Pm-147 is a beta emitter with a half-life of 2.6 years. Tritium, a radioactive isotope of hydrogen, has a relatively short half-life of 12.3 years.
And the scintillator?
Zinc sulfide (ZnS) is the most commonly used scintillating material for this application.
So how exactly do these gadgets work?
They are actually fairly simple devices. The radionuclide and the scintillator are mixed together and then captured in some kind of container, like a glass tube. The radionuclide decays and emits a particular type of radiation. For example, Ra-226 is primarily an alpha emitter; Pm-147 and H-3 are beta emitters. When either of these radiations interacts with the zinc sulfide, a small flash of light is produced. Presto! We have light without an electrical source!
Where were these devices used?
Here’s a classic for you. Prior to 1950, aircraft contained radioluminescent gauges in the cockpit as an alternative to lack of electricity. The radionuclide was Ra-226 mixed with ZnS. Today, we no longer need this type of device, so you will not see them in modern aircraft.
What happened to the old gauges?
Many of them were melted down in the 1950’s – along with the aircraft – as a source of recyclable aluminum. Some can still be encountered at military surplus sales, although the light produced by them isn’t so impressive any more because the scintillator is “spent”. However, because of the long half-life of the Ra-226, they still produce significant exposure rates.
What do you mean by “significant”?
When these gauges were originally present inside the aircraft, estimates placed the exposure rates at 1,000 to 5,000 mR per hour at the location where the pilots sat. This range is also a good approximation of the exposure rates in storage bins at surplus sales. Of course, the actual exposure rates noted would be affected by several variables including the number of gauges present, their proximity to each other, and the location of the individual relative to the gauges.
Where else can I find radioluminescent products?
Try watches and clocks. Ra-226, Pm-147, and H-3 have all been used in combination with (primarily) ZnS, though the vast majority of these devices today use the beta emitters Pm-147 and H-3. Watches and clocks employing Ra-226 have not been produced in the United States since 1968 and 1978, respectively, although there are a number of these old antiques still floating around.
Are there restrictions on their use?
Yes. In this country, the USNRC requires the manufacturer to obtain a radioactive materials license for watches/clocks containing either Pm-147 or H-3. The USNRC also limits the amount of radioactivity that may be present in an individual timepiece. For Pm-147, there is an additional limitation on the permissible dose rate.
How would I know if my watch/clock contains a radioluminescent product?
The presence of radium or promethium can be detected with a basic Geiger counter. If you can borrow one, simply place it close to the clock/watch face and observe the reading on the instrument readout device relative to the background radiation level on the instrument. An elevated response indicates the presence of radioactive material.
What about tritium-containing timepieces?
The beta particles emitted from the decay of tritium are too weak to be detected by Geiger counters and other conventionally-designed survey instruments. You will need to rely upon the manufacturer giving you a clue as to its presence.
Are there any concerns associated with the use of these devices?
As noted above, the use of radium has been discontinued in this country, partially for health-related concerns. Timepieces containing tritium have been known to occasionally leak, resulting in a small whole body dose from inhalation or absorption through the skin and contamination of clothing, surfaces, etc. There is no particular concern with Pm-147, although specific dose rate limits are cited for this radionuclide at a stated distance (e.g., 1 cm, 10 cm) from the timepiece depending on its type (i.e., wrist watch, pocket watch, clock). For both H-3 and Pm-147, the estimated annual dose equivalent to an individual user is much less than one (1) millirem.
What can you tell me about other applications involving tritium?
Tritium is used in a variety of applications. Aside from timepieces, these include self-luminous aircraft and commercial exit signs (those red things with the blue-colored light that you see at the bulkheads of airplanes), luminous dials and gauges, and the production of luminous paints.
Have any problems been encountered in the use of tritium for these purposes?
Well, yes. Probably of most importance initially, care must be taken with its production and use because the weak beta emission energy – 18 kiloelectron volts (keV) maximum, about six (6) keV average – is essentially impossible to detect with conventional survey instruments. Therefore, if a leak occurs, for example, in a production facility, an entire facility can become contaminated and the problem potentially not discovered for some time unless specialty instruments are used for routine surveillance. This situation has occurred (though fortunately, rarely.) More importantly, however, is the fact that, in the last few years, there have been instances where tritium exit signs have been stolen. (These devices are “generally licensed” by the USNRC and may contain up to 25 curies (Ci) of tritium). In one case, it was reported that an exit sign was illegally taken from a business in New Jersey by a teenage boy. Upon deliberately taking apart the sign and tampering with the tubes containing the radioluminescent material, the boy and his bedroom were contaminated, necessitating a concerted cleanup effort by state regulatory officials.
Can you cite any additional examples of radioluminescent products?
Sure. Miscellaneous items in this interesting category (all containing radium) include pull chains on light bulbs, switches, chamber pot lids, doorknobs, religious statuary, telephone dials, fishing lures, and markers at military bases. It is surprising how many places radioluminescent devices turn up.
How is radiation used in static eliminators?
These devices have been used for a number of years in an industrial setting to reduce electrical charge buildup in various materials. In a more general application in the United States, Po-210, an alpha emitter produced eventually from the decay of uranium-238 (U-238), is incorporated into so-called “static eliminators” to reduce/eliminate the static charge produced during the manufacture and use of photographic film and phonograph records. Regarding the latter, those individuals familiar with phonograph records (before the advent of CD’s, DVD’s, etc.) may well have used a Po-210-bearing static eliminator to reduce the amount of dust attracted to the static charge on the record surface. In brief, ionizations from the polonium alpha particles neutralize the charge on the dust particles, reducing their accumulation on the surface being cleaned.
You mean my old record cleaner could be a problem?
No. And let me tell you why. One nice feature of Po-210, i.e., the short half-life of 138 days, required the user to periodically return the device to the store for replacement (usually each year). Not only was that good for business, but a very nice radiation safety feature due to the rapid decay of the radionuclide! Another nice feature in the composition of these devices is that the Po-210 is encased in a so-called ceramic “microsphere”. This makes assimilation of the material in the body impossible even if ingested. The size of the microspheres (approximately 40 micrometers) prevents them from remaining airborne, thereby rendering the inhalation pathway an unlikely source of concern as well.
You mentioned uranium in consumer products. How is this interesting element utilized?
Ceramics for one. Different chemical forms of uranium were used as far back as the 1920’s to produce a variety of colored glazes. Colors included black, brown, green, and pretty much the spectrum from yellow to red.
What has happened since their original introduction?
With the advent of World War II, uranium was needed for the war effort. Accordingly, the use of uranium compounds in ceramics diminished. With the advent and availability of other, more economical materials, there is little interest in re-vitalizing the uranium process.
Could I produce these glazes if so inclined?
Technically, yes, if you had a good reason to do so. According to Title 10 of the Code of Federal Regulations, Part 40 (10CFR40), “Domestic Licensing of Source Material”, the USNRC permits the production of these glazes within certain limits. The specific citation is found in 10CFR40.13, “Unimportant quantities of source material”.
Was any particular color more popular than the others?
Beginning in the 1930’s, the orange color was quite popular in the production of a particular line of dinnerware known as “Fiesta-Ware”. While the current manufacturer of Fiesta-Ware no longer uses uranium in their process, you can still find the old stuff in flea markets and in many homes.
What radiations are emitted from this interesting consumer product?
Primarily beta and gamma radiation. Even though alpha particles are emitted during the decay of uranium, these radiations are absorbed by the glaze.
And the radiation levels from them?
The radiation emanating from Fiesta-Ware is readily apparent using any basic radiation detection device such as a Geiger counter. (Take a Geiger counter shopping with you if you are searching flea markets for these heirlooms. But please try to be a bit “discrete” about it and keep the audio off or wear earphones!) External surface dose rates range from 0.5 to 20 millirad per hour, with an average dose rate from a complete Fiesta-Ware setting being about three (3) millirad per hour at a distance of one inch (the approximate distance to the hands). The dose rate to the whole body would be 10 or more times lower.
Should I be concerned?
If there is a concern, it is not with the radiological component. Rather, it has occasionally been reported that a chemical toxicity hazard is associated with uranium and lead as leachable components. This situation could potentially occur, for example, through the use of acidic foods placed on the dinner plate, leading to possible ingestion of the glaze containing these elements. Thus it is wise to keep your Fiesta-Ware collection for display purposes only. Besides, continued use increases the probability of breakage! You would hate to lose one of these old collector’s items.
I see you mentioned dental fixtures earlier. What’s up with them?
This is another interesting application of radioactivity in consumer products. There are millions of Americans wearing some type of dentures (false teeth) made of either acrylic compounds or porcelain. Older vintage porcelain dentures contain a trace of uranium, a naturally occurring radionuclide. Over 50 years ago, it was discovered that mixing the uranium with cerium provided a natural color and brightness that was similar to that of real teeth.
Why is this?
The uranium fluoresces (glows in response to certain wavelengths of light), giving the dentures a bright, white look. Without it, the porcelain teeth would appear dingy and greenish under artificial light.
How much uranium is allowed in false teeth?
The USNRC limits the amount of uranium in dental fixtures, whether produced domestically or imported, to less than 0.05 percent by weight. Manufacturers currently fall easily below this limit.
Do these dentures contain any other radioactive materials?
Yes, they do. In addition to uranium, K-40 is present as well. Unlike the uranium, however, there are no regulatory limits regarding the K-40 content in dentures.
Should wearers have any radiological concerns?
The long half-lives of uranium and K-40 mean that a small, but continuous dose is delivered to localized areas of the individual’s mouth. The principal radiation of concern with uranium is alpha emission. However, the short range in tissue of this radiation, along with attenuating factors such as the presence of saliva, food, other residues, etc., reduce the exposure rates to those that are considered to be insignificant.
Doesn’t uranium also emit beta and gamma radiation?
You were listening before, weren’t you? Yes, they do. And they have a greater range in tissue. Corresponding dose estimates vary widely based on the assumptions employed. Using an average concentration of uranium in U.S. dental porcelain of 0.02 percent, an annual estimate of 500 mrem is calculated. Added to the estimated annual maximum K-40 contribution of 190 mrem, the total dose equivalent on a yearly basis is approximately 700 mrem.
That seems high. Is there any good news?
Apparently, uranium is no longer used in porcelain . . . at least by domestic manufacturers. Acrylics, containing non-radioactive materials, now comprise the majority of dental products. So if you purchased your dentures fairly recently, radiological issues are not a concern.
Tell me about gas lantern mantles.
Certainly. This is another consumer product that first appeared at the beginning of the 20th century, originally for the purpose of providing a high intensity light source in theaters. Its primary use over the years, however, has been for campers using portable lanterns. Other uses include its application in residential and commercial outdoor lights, residential indoor lights, and in recreational vehicles.
How are mantles produced?
A nylon or silk mesh bag is dipped into a solution of thorium nitrate. The thorium is then converted to an insoluble oxide by exposing it to ammonia vapors.
What about the intense light you mentioned? How does that come about?
It results from the heating of the thorium-containing mantle.
What concentrations of thorium are typically present in lantern mantles?
The thorium we are speaking of consists of two different isotopes: Thorium-232 (Th-232) and Th-228. The typical amounts associated with these two isotopes are 300 milligrams (mg) of each.
Are there any limits on the amount of thorium that can be used in mantles?
Unlike the uranium limits mentioned previously for ceramics glazes, 10CFR40.13 has no limits on the quantity of thorium that may be incorporated in lantern mantles.
Are there any health concerns associated with this product?
From a radiological perspective, the annual average whole body dose equivalent is quite small, i.e., on the order of 0.2 mrem. However, the dose equivalent to the lungs, which results from inhalation of airborne radioactivity as the mantle is heated, is estimated at approximately four (4) millirem for campers. There can also be a small, but measurable bone dose. Put into perspective, these values are well within the natural background dose received on a yearly basis. Nonetheless, thorium-bearing gas mantles should only be used in well-ventilated places, particularly upon initial ignition.
Because of the radioactivity?
Only partially. Mantles also contain chemicals such as beryllium, cerium, magnesium, and silicon. Beryllium, in particular, has become an increasingly important health issue in the workplace because of the potential to cause a debilitating respiratory disease. So light those lanterns outside of your tent.
Okay, I’ll be careful.
Actually, although thorium lantern mantles are a very popular consumer product for campers, with millions sold on an annual basis, the traditional mantle has been increasingly replaced by a non-radioactive form. In fact, it is getting harder and harder to find thorium-bearing mantles.
Anything else of interest in the category of radionuclides intentionally added to the product?
We mentioned earlier that thorium can be found naturally in the oxides used to produce certain types of glass. Alternatively, it can, and has been, purposefully added to glass for a variety of reasons. Another example where thorium products are encountered are in welding rods.
Tell me about the addition of thorium to glass. When did this situation unfold?
In the 1970’s, thorium was added to eyeglasses to produce a pink tint. Another application involved its incorporation into very high quality lenses in order to improve the transmission of light. This characteristic has been used by the military in their night sights, for example. It has also been used in older vintage 35 mm Pentax cameras and television cameras.
Are there restrictions on the amount of thorium allowed in lenses?
The limits appear in the USNRC regulation, 10CFR40.13. For contact lenses, eyeglasses, binoculars, etc., that come in close contact with the eye, this regulation places a limit of 0.05% by weight of thorium. For lenses that are not designed for eye contact, limits up to 30% by weight are permitted.
Is there any reason to be concerned about the thorium in eye glasses?
Older lenses still in use could result in non-trivial doses to the outer (germinal epithelial) layer of the cornea. For example, eyeglasses containing the maximum (0.05%) thorium limit could result in an annual dose of 4,000 millirem to this area. Because of this, direct exposure of the eye to lenses at a close distance for extended periods of time should be avoided. There have also been isolated cases reported where higher than permitted thorium quantities (greater than 0.05% by weight) were added to eyepieces without proper marking/labeling signifying the addition of thoriated glass. There is, of course, little an uninformed consumer can do in this situation.
Talk to me about welding rods. What are they used for?
There are several applications for these devices, including use in the construction, aircraft, petrochemical and food processing equipment industries.
Why is thorium used in welding rods?
Welding rods contain tungsten intermingled with thorium (“thoriated tungsten”) to produce easier starting, greater arc stability, and less weld metal contamination.
Do a lot of people work with these devices?
Yes. According to the NCRP, about 300,000 people work either directly or indirectly with thorium-bearing welding rods.
What dose would that entail to the welder?
Doses from welding rods result through their distribution, use, and disposal. However, actually using the devices is the primary source of exposure. Welding rods contribute both an external whole body dose and an internal (inhalation) dose from radon-222 and its progeny. The latter pathway predominates. While doses from external exposures are estimated to be less than one mrem per year, the whole body and bone dose commitments from internal exposures varies widely depending on the relative use (“heavy”, “occasional”, personnel assisting the welder, etc.). The highest whole body and bone dose estimates are 14 millirem and 2,000 millirem, respectively.
The last major category you mentioned earlier was the consumer product being contaminated following the addition of a radionuclide. What occurred in these cases?
Unfortunately, sometimes a radionuclide is either carelessly or unintentionally introduced into a metal, resulting in contamination of the product. In other cases, use of a particular irradiation mechanism (e.g., neutron radiation) results in the formation of a radioactive material (that was not radioactive prior to irradiation). This is known as “induced activity”. It is important to note that if radioactivity is present in a quantity exceeding applicable federal or state regulations, it cannot be sold to the general public.
Can you cite an example?
The best examples involve the contamination or irradiation of precious metals and gems (jewelry). In the 1960’s, contamination was discovered in platinum and gold. In the latter case involving gold, “seeds” were recycled which contained Rn-222 for use in cancer therapy. It is believed radon decay products (lead-210 and bismuth-210) attached to the interior surfaces of the gold seeds.
What happened next?
Concern over this situation prompted a search for these materials which eventually uncovered hundreds of contaminated gold jewelry items – mainly rings – located primarily in the state of New York.
Were any adverse health effects noted in the owners of these items?
Unfortunately, yes. About one-third of the individuals wearing this contaminated jewelry developed either skin dermatitis or skin cancer.
What about the issue of neutron irradiated gems?
Because radioactivity can be induced in jewelry by exposing them to neutron radiation for the purpose of improving their visual quality, the USNRC published an “information notice” on this very topic just a few short years ago. The notice was precipitated because of potential radiological concerns over import and distribution of irradiated gemstones. We invite you to read this short, but interesting notice, that can be found on the internet at http://www.nrc.gov/NMSS/BPR/infonote/1990/in90062.htm.
You’ve covered a lot of information in this chapter!
Yes, so maybe we should come to the end of the road . . . at least for now. All that is left is to summarize key points of this discussion.
So what can we say about radiation exposures from consumer products?
We can say that with very few exceptions, they result in low exposures to the public in this country, and that their use/benefit outweighs the potential radiological risks.
Remind me about the exceptions once more . . .
There are three consumer products in particular that merit another comment. These are the dose contribution to cigarette smokers from the presence of lead in tobacco products, the influence of radioactivity in building materials, and airborne radon exposures from domestic water supplies. The first and third sources primarily impact on a single organ (the lung). These three sources involve large numbers of people and a resulting large dose equivalent.
A friend was telling me about garden fertilizer and radioactivity. Is there anything to that?
As a matter of fact there is. Commercial fertilizers contain potassium, phosphorus and nitrogen in various concentrations. Therefore, they are radioactive because of the presence of naturally-radioactive potassium, and because the phosphorus can sometimes be derived from phosphate ore that contains elevated levels of uranium.
Does that mean food is radioactive?
Yes, but not necessarily because of the fertilizer used to grow fruits and vegetables. Food contains many types and amounts of natural radioactivity, although the quantities of food we store in our homes is far too small to reveal detectable radioactivity. However, bulk shipments of some foods have been know to set off the alarms of radiation monitors if they happen to pass one on their journey from farm to store.
Interesting. But what about home medical products that contain radioactivity? I’ve seen old advertisements for them, but nothing recently. Are they still around?
From the 1920’s through to the 1950s, a lot of radioactivity-bearding products were sold as “cure-alls”. Some of the more common were radium-containing pills, pads, solutions and devices designed to add radon to drinking water.
For the longest time, radium and radon daughter were onsidered to be a miracle cures, and were used to treat such things as arthritis and even mental illness. Today, however, we know better.
So they are not around any more?
No, you can still find these types of medical supplies if you look for them, but they are no longer used for that purpose. Instead, they have become collector’s items. However, in the US, the states have regulatory atuhority over them and they may require that they be registered or licensed by their owners if the quantity of radioactivity present in them is high enough. Most of these old devices are relatively harmless, but occasionally you can run into one that contains potentially hazardous levels of radium so its a good idea for collectors to contact their state radiation control program office for advice.
You know, there certainly are a lot of consumer products that contain radioactivity; more than I ever thought. On an effective whole body basis, what can we conclude is the estimated dose to the U.S. population from exposures to consumer products in our daily lives?
With the exception of tobacco products, the NCRP estimates that the average effective dose equivalent is on the order of five (5) to 13 millirem per year.
That doesn’t sound bad!
You’re right. When we look at the exposures on a whole body basis, the dose contribution is rather small. However, if the contribution from tobacco products were included, the EDE would be significantly higher.
Are there lessons to be learned from our past and present use of radiation-bearing consumer products?
Absolutely. For one, history tells us that we can now categorize certain sources as those that serve little (even no) useful purpose. Examples include the use of Ra-226 in radioluminescent products and glazes in ceramic products. Another category involves those products that serve a useful purpose, but an alternative means exists to accomplish the same goal with no radiation exposure. Certain applications of static eliminators are included here.
There are those practices that result in elevated exposures, but that are difficult to eliminate because of their long-standing societal impact. These include tobacco products, certain building materials, domestic water supplies, and combustible fuels.
Is there more?
Yes! Consider those consumer products that assist us in performing some task either quicker, cheaper, or in a technologically better way. Examples include airport inspection systems and smoke detectors. Or consider those devices where radiation is an unwanted byproduct of their use, like television sets. (As we have noted earlier, television designs have improved noticeably over the years, resulting in much, much lower radiation exposures.) Don’t be too quick to rule out the use of one of these products simply because of the trivial amount of radiation exposure associated with them. Imagine a life without television!
Where can I learn more about the association of radiation with certain consumer products?
First, we suggest you review the other “Radioactivity Basics” sections of the Plexus-NSD web page. There you will improve your understanding of the information that was presented in this topic through the definition of terms and discussion of basic concepts. In addition, don’t forget the “Tools” section of the website, specifically the category of “Common Radiation Exposures”! There you will find information on consumer products presented in a different manner.
Are there other sources I can turn to?
Many of them. Here are just a few to get you started. NCRP Report No. 95, “Radioactivity in Consumer Products”, published in 1987, was the primary reference utilized for the preparation of this topic. It is available for a fee through the NCRP (http://www.ncrp.com/) or a technical library. On the internet, the USNRC has issued a publication (NUREG/BR0217) entitled “The Regulation and Use of Radioisotopes in Today’s World”. This document contains supplementary information germane to this discussion of consumer products. The web citation is http://www.nrc.gov/NRC/NUREGS/BR0217/br0217.html. Lastly, to take a “visual” tour of selected items, we encourage you to examine the historical collection of early nuclear devices provided by the Oak Ridge Associated Universities (ORAU) Professional Training Programs (PTP). The ORAU website is located at http://www.orau.gov/ptp/histcol.htm.