By Brett Rosenberg
There are many factors to consider when saying “radioactivity is hazardous.” Here is an attempt to summarize them in five points.
Radiation is not an age-old reality; in fact, the discovery of radiation is fairly recent. Becquerel, whose name is now used as a unit for an amount of radioactivity, discovered in 1896 that uranium salts were emitting energy. In the early 1900s, he discovered medical uses for radioactivity. Soon, scientists began studying the various uses radioactive elements including the medical field and industrial fields, like with radioluminescent dials and, of course, its potential as a weapon.
Then came the first atomic bomb. We entered the atomic age in the 1940s following World War I, and the amount of research that was conducted in the decades to follow did not reach the public as quickly as the media. Godzilla in the 1950s, comic book characters like the Fantastic Four and the Incredible Hulk in the 1960s, the Three Mile Island accident in 1979, the Chernobyl disaster in 1986, and the orphan radiotherapy source in Goiânia in 1987 all paint a gruesome picture of radioactivity: radiation causes mutations and horrible deaths. The assassination of Alexander Litvinenko in 2006 by a radioactive isotope of polonium further proves the point, right?
Radiation is just like any other substance – the dose makes the poison. There is water all around you, but too much of it can kill you. There is a similar philosophy for medications in that too much of something will exceed a therapeutic dose and result in a lethal dose. We live in a sea of radioactivity, although some people receive more than others. People who live at higher altitudes receive higher doses from cosmic radiation, and those who live in areas with natural uranium deposits get higher doses from radon. Airline pilots receive even higher doses from cosmic radiation because there is less atmosphere shielding them. Miners have been evaluated for lung cancer because of their higher exposures to radon, although the prevalence of smoking among them complicates the evaluations.
We have incorporated the use of radioactive americium in smoke detectors, tritium in exit signs and thorium in lantern mantles. There is uranium in the ceramic glaze of Fiestaware, and radioactive cesium in game meat because of fallout from weapons testing. Radiation, both natural and man-made, is everywhere, but we have not been able to observe adverse health effects at current regulatory levels.
There are many factors to consider when saying “radioactivity is hazardous.” Here is an attempt to summarize them in five points:
1. How much radioactivity is there? We all have measurable quantities of naturally occurring radioactive potassium in our body, as it emits both beta particles and gamma rays. A similar statement can be said about uranium, depending on your source of drinking water, except uranium emits alpha particles and has an extensive decay chain with lots of radioactive progeny—including polonium! But we are not suffering the fates of the radium dial painters and Litvinenko because our bodies are able to repair themselves when exposed to low levels of radioactivity.
2. How long is the exposure to the radioactivity? If you keep your exposure time low, the amount of energy you receive from the radioactive material is minimized. Examples of this include cancer treatments with external beam radiation therapy (short-term exposure) versus brachytherapy (placing sealed radioactive sources in the body).
3. What does too much radiation cause? The effects of radiation can be observed at the cellular level for acute (short-term) doses exceeding 10 rem (0.1 Sv), but there would be no visible radiation-induced symptoms until the body receives at least 200 rem (2 Sv). Such symptoms may include nausea, vomiting, and diarrhea. The lethal dose for half of a population is approximately two-times that. Certain cancers are also latent (delayed) effects, often by more than a decade for acute doses exceeding 10 rem.
The regulations are set so that radiation workers receive no more than 5 rem (0.05 Sv) per year, and members of the public receive no more than 0.1 rem (0.001 Sv) per year from radiological operations. An individual receives an average of approximately 0.3 rem from natural background radiation over the course of a year. If that entire dose were acute, there would be no observable health effects.
4. What is the source of the radiation? The source of the radiation will help you evaluate the type of radiation emitted and the energy. Radioactive material that emits alpha particles does more damage to the body when ingested, inhaled or injected. Tritium is certainly not harmful when ingested in small quantities because it emits a very low energy beta particle, but there is still a limit on intake based upon the 5 rem per year limit for radiation workers. Radioactive cesium and potassium emit gamma rays as well as beta particles, but their annual limits on intake differ because of the energies and intensities of their radiations.
Many people associate radiation from cell phones and microwaves with radioactivity. These devices emit non-ionizing radiation, which carries less energy than ionizing radiation emitted from radioactive material. The primary effects of non-ionizing radiation involve heating. Other examples of sources that emit this type of radiation are tanning beds (UV radiation), communications towers (radio waves) and lasers. There are occupational exposure limits for non-ionizing radiation that depend on several factors, including the wavelength and power of the radiation.
5. Is the exposure to radiation necessary? It can be argued that, without medical X-rays and CT scans, the quality of medical care would be much different. More invasive techniques would be required for medical diagnoses. Also, cancer treatments have come a long way combining chemotherapy, radiation therapy, and surgical techniques.
Medical exposures to radiation are received by choice, and environmental radiation cannot be easily avoided. However, occupational sources of radiation, although potentially greater by orders of magnitude, should be controlled and monitored to ensure regulatory compliance and worker health and safety.
Detectable Does Not Mean Dangerous
When considering what makes radioactivity hazardous, remember that detectable does not mean dangerous. Different detectors measure different types of radioactivity, and some are far more sensitive than others. For example, some detectors can distinguish the energies of the radioactive emissions, whereas others cannot. Detectors that can distinguish energies tend to be used in a laboratory setting to identify the sources of the radioactivity. For instance, are the gamma ray emissions coming from an isotope of cesium, or are they coming from an isotope of bismuth (in the decay chain of radon)? Are there any uranium isotopes present in unusual quantities that would indicate an occupational—instead of environmental—exposure to uranium instead? Making these determinations require the right tools and expertise, and confirmation of an occupational exposure may result in an exaggerated response. We need to remember: detectable does not mean dangerous.
Furthermore, there have been occupational exposures to radiation around the world. Some of them have been fatal, like those associated with Chernobyl, but the vast majority are not. When someone suspects an exposure to radioactive material has occurred, it could be a very stressful situation. The stress may cause nausea, diarrhea, or maybe even vomiting. (By the way, those are the symptoms of radiation sickness after an acute exposure to over 200 rem.)
Perspective is important: If the public already receives a couple of hundred millirem (a fraction of a rem) on average from background, what’s the harm in a couple of millirem more from an occupational exposure? Or a couple hundred millirem from X-rays? Or a relaxing vacation to Guarapari resort in Brazil where the dose rate on the beach can exceed tens of thousands of millirem per year from the natural uranium and thorium?
Knowledge is Power
Not only is the source of radiation important to know, but the source of information is also of great importance. There are professional societies, academic institutions and regulatory agencies that evaluate the effects of low doses of radiation and determine the levels of radiation that can be considered safe. Communication is essential throughout an incident that results in an exposure to radioactivity or radioactive material, regardless of how big or small it may be. Health physicists (radiation protection professionals) understand the hazard, and these are the experts to talk to regarding exposures to radiation and radioactive material.