And of course, potassium 40 is harmless to humans compared with radioactive cesium. Naturally. So comparisons with bananas are always meaningless.
WHen I experimented with Cesium-137 long ago, I used Rads. THe Director of Isoptope therapy in a Japanese institute postulated that the reason Tepco and the Japanese government kept releasing information in beq’s re foods consumed (school lunches, beef, fish, rice, wheat, tea leaves), it was intentional, used to make it hard to understand and relate the impact on human health.
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You said:
(I can calculate human exposure if I know how much was ingested, but I’d need a while with a whiteboard to figure out the body dose for a fish swimming in a given concentration of contaminated water.)
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Thus far, standard dosimetry calculations commonly displayed on FR are useless in that they do not take into account what isotope is involved (aside from energy level). That’s how the old banana routine gets employed. But there are vast differences among the ways that different isotopes affect health - the dosimetry equations are blind to these differences.
“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.