“And of course, potassium 40 is harmless to humans compared with radioactive cesium.”
Not on a Bq to Bq comparison. K40 has much higher energy gammas than Cs137. K40 usually exists in very low concentrations (like in bananas and soil) because it is not too useful, but Cs137 can be found in pretty concentrated form (because it’s used in medicine and industry). Nobody takes a pile of KCl and concentrates the K40 out of it, or makes K40 in an accelerator to get a couple millicuries in one pellet. Cs137 at the concentrations that K40 is found is about as dangerous as K40, at that concentration. Cs is not retained and K40 gets flushed out as new K40 comes in. Cs137 has a much, much shorter half-life, so a given mass is more dangerous.
The health calculations do indeed consider isotope. The articles posted here generally do not. The biggest factors are half-life of the isotope and biological half-life, so K40 washes out quickly and has a long half-life. Am241 has a shorter half-life and a long time in the body and is much more dangerous biologically. I have tools, as I said, for calculating ingested and inhaled isotopes in people, but calculating body dose for a fish presents some math challenges.
I agree that most public discussions of radiological health issues lack depth and accuracy. It’s not just the posters on FR, but a deep ignorance among “journalists”, who generally never learned any math or science in their education, or have an agenda of their own (or of their bosses). Add to this the complexity of converting a concentration in bq to dosimetry in REMS after ingestion and you go beyond what “journalists” can report.
I said:
“And of course, potassium 40 is harmless to humans compared with radioactive cesium.”
You replied:
Not on a Bq to Bq comparison. K40 has much higher energy gammas than Cs137.
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That’s why all the dosimetry calculations I’ve had thrown in my face are wrong. K40 has much higher energy gammas than Cs137. And according to the EPA and other sources, “human tissues are relatively transparent” to higher energy gammas. This is the Grand Canyon in the calculations I’ve been seeing. One professor I had theorized that lower energy gammas do not pass through tissues one time, possibly missing the DNA strand all together - whereas lower energy gammas are thought to Richter around in tissues, passing multiple times through cells and therefore more likely to hit and damage DNA.
Look at the energy levels of uranium - low compared with K40, right? So the first thing the dosimetry calculations do is multiply quantity times energy and obliterate medical relevance from the rest of the equation.
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You said: The biggest factors are half-life of the isotope and biological half-life, so K40 washes out quickly and has a long half-life.
I say: This is wrong. Energy level is a huge issue as is where and how long the isotope is stored. Strontium is taken up in the bones in teeth and chelating or other efforts to remove it fail. Cesium collects in the muscles and the heart is a muscle, hence the relationship to cardiac death. No calculations capture the tendency of Strontium to collect in bones and irradiate bone marrow (leukemia). Isotope exposure suppresses immune response - no calculation has shown the relative amounts of immune response suppression among isotopes. That dosimetry calculation fails to take into account medical impact.
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You said:
but calculating body dose for a fish presents some math challenges.
I say: It’s generally done by sample the tissues of the fish. 5 months after Fukushima, a San Diego marine biologist finds trace amounts of Fukushima isotopes in 13 out of 13 fish sampled. Now, with continuous dumping into the ocean for another 2 years non-stop, and further concentration of the isotopes in the food chain, it’s not unreasonable to guess that the amounts in fish are increasing. And, the dumping into the ocean will not stop - it will continue unabated because no one knows how to stop it.