Replies

I’ll put some links below but they touch on the issues - I developed my understanding of the comparison between the radiation in bananas to radioactive contaminants re Fukushima by extensive reading (and a science background)- which included sites like the EPA. For example, the EPA documentation explains that “high energy” radiation can pass through the body causing less damage then “low energy” radiation. This isn’t quantity of radioactive material, it’s a level of energy given off by that material.
This sounds counterintuitive but may be envisioned (modeled) by imagining a high velocity bullet tracing one path in one side and out the other of a human body. In contrast, a low velocity bullet can bounce around off ribs and joints and ultimately cause more damage as it makes multiple passes through tissue. My prof in college suggested that this is how the energy levels differ in human tissue and damage to DNA when exposed to radiation.

I was very surprised to learn that the dosimetry equations that nuke engineers were hurling in my face did not take this into account - their equations are blind to the actually level of damage caused by different types of isotopes. Many ran incorrect calculations to show me that bananas were more harmful than cesium by using a simple equation showing quantity in mg of radioactive potassium (bananas) times the energy of radioactive potassium. They would then compare that to the same amount of cesium in mg times the energy of radioactive cesium. Voila! They sneered that they had mathematically proven that I was wrong and that there is no medical concern re cesium just as there is no medical concern re bananas because the results of their equations showed bananas>cesium. But the energy levels of each material make all the difference in the world. Higher energy levels are damaging but MUCH less so then lower energy levels when speaking of radioactive isotopes and their actual effects on human tissue.
Our bodies already contain tiny amounts of naturally occurring
radioactive (and non radioactive) potassium and if we eat more by eating bananas, our bodies to not take up the additional radioactive potassium, it is excreted so our bodies keep the same level of potassium. Our bodies have “learned” throughout human evolution how to protect themselves from the specific effects of the potassium we have in our tissues. This is not true for cesium. Radioactive cesium is not naturally occurring and our bodies will take up much more (gram for gram) of radioactive cesium than it would the radioactive potassium in bananas. Further - there are characteristics of different isotopes which cause them to cause different types of damage to the body. Radioactie strontium replaces the calcium in bones and there isn’t a method known to remove it once it is taken into the bones. This means that it remains embedded in tissues and continuously irradiates them for a long period of time. Cesium isn’t taken into bones, it is dispersed through soft tissues so it irradiates different locales. So you have Strontium causing more damage to bone marrow than cesium, but then cesium is believed to collect in muscle tissues and the heart is a muscle -that’s why cardiac death has been associated with high levels of cesium contamination. I watched a sad documentary of the scientists who monitored chernobyl after the disaster - they didn’t have proper equipment and basically wore cloth hospital masks as they routinely toured the Chernobyl power plant while monitoring conditions there - throughout the documentary, it noted that members of their team were dying of cardiac failure. Later I would learn that all whom I had watche din the documentary had died of cardiac failure. It’s not that cesium is the only cause of their deaths (they noted their job stress levels were intense!) but that cesium is known to cause cardiac death and they certainly were exposed to high amounts of it.
There are more specific differences among isotopes (e.g., type of radioactive decay and differences of effects on human body, gamma, beta). I’ve heard there’s a great article on the web that gathers all of them together but I’ve never hunted it up to see if it were true. In the meantime, here are some links below and I’ll note that the Department of Transportation requires that Cesium and other radioactive isotopes be transported in lead or other shielded crates and requires certification and the application of many regulations and policies for “safe” handling but has no such strictures about bananas. That’s not the oversight of a hysterical public prone to myths, it’s based on science.

http://boingboing.net/2010/08/27/bananas-are-radioact.html
http://www.globalresearch.ca/fake-science-alert-fukushima-radiation-cant-be-compared-to-bananas-or-x-rays/5329369