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Kyodo News Q&A: Fugu or Cesium? Points of caution in consuming contaminated fish

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flamingdem Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Apr-07-11 12:36 AM
Original message
Kyodo News Q&A: Fugu or Cesium? Points of caution in consuming contaminated fish
Edited on Thu Apr-07-11 12:38 AM by flamingdem
Q&A: What are points of caution in consuming contaminated fish?

TOKYO, April 7, Kyodo

---- snip

Q: What are points to be careful of when cooking fish?

A: For vegetables, it is effective to wash or peel them as radioactive materials get attached to the surface. For fish, however, radioactive materials could be drawn into the body through seawater and feed, so they can be eliminated significantly by removing offal. It is also important to wash the fish because there may be some radioactive materials left on the surface. It is recommended to avoid eating fish skin.

Q: Is it only fish that are affected by radioactive contamination in the sea?

A: It is said that seaweed and shellfish around the nuclear plant are more susceptible to radioactive contamination than fish which swim around in the sea. Seaweed also has the tendency to accumulate radioactive iodine. But radioactive iodine has a half-life of eight days, meaning that its effect will be reduced to half in eight days, one-fourth in 16 days and one-sixteenth in 32 days. So there should not be too much concern about consuming frozen, processed or dried fish as a certain amount of time has passed after they were caught.

Q: What effects does radioactive cesium have?

A: Cesium tends to accumulate in the muscle and has a half-life of 30 years. It is also possible for it to become concentrated in bigger fish in the food chain. There is a study which shows that half the cesium taken in by fish is eliminated in 50 days as it will be discharged to seawater in the form of urine as well as from the skin and gills. (I SMELL SOMETHING FISHY ABOUT THIS STATEMENT, SOMEBODY IS IN DENIAL.. 50 DAYS??)
But fish need to be monitored thoroughly over a long period of time if seawater is found to contain high levels of radioactive cesium.
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TheMadMonk Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Apr-07-11 03:00 AM
Response to Original message
1. It's called a biological half-life. It's a measure of how quickly...
...a substance is excreted after being taken up by the body. And it has nothing to do with it's radiological half-life.

Strontium goes to the bones so it has a long biological half-life.

Iodine is cycled so quickly through the thyroid (short biological half-life) that high doses of non-radioactive iodine will dilute any of the radioactive kind present causing it to be excreted in urine.

Heavy metals tend towards a long stay in the body. But caesium is also a volatile element meaning it is quite mobile.

Caesium thus I think tends not to stick around in the body like lead, mercury et al. It should also be noted that while radiocaesium is taken up by muscle tissue, it does not appear to have any detectable radiological effect even at significantly elevated levels.

Unless levels are very elevated, I suspect mercury in fish will continue to be the consumption limiting factor, not its caesium content.

I see absolutely nothing wrong with this advice on food handling. Permissible consumption levels are first of all set based upon an assumption the the consumption would continue for a full year and secondly set several orders of magnitude below the minimum levels known to cause elevated cancer levels in a large population. Occasional, or even frequent meals for a short period of time are not going to cause any measurable harm.
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flamingdem Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Apr-07-11 09:38 AM
Response to Reply #1
2. You need to show links, you are dismissive of the cancer causing effects of cesium + misleading
Implying that it goes through a process that reduces half life is misleading and is misleading in the Kyodo Q&A.

Here's the EPA:
Drinking cesium-137 contaminated water, would also place the cesium-137 inside the body, where it would expose living tissue to gamma and beta radiation.


Facts about cesium-137: toxicity of whole-body radiation, as discussed in poison (physiology): Toxicities of whole-body ionizing radiation:
Radioisotopes that are absorbed and distributed evenly throughout the body also can result in whole-body irradiation. Examples are tritium and cesium-137, both of which release beta particles that can lead to bone marrow toxicities and even, in the case of cesium-137, to death. The toxicity of tritium is less severe than that of cesium-137 because the beta particles generated by tritium are...

NOTE: this was March 24th, levels are far worse now and have been detected in the US water and milk supply

Thu Mar 24, 2011 3:25pm EDT

Below are the three radioactive substances health experts are most concerned about, the detected levels in Japan, and what they mean for human health:

CESIUM-134 and CESIUM-137

Vegetables in Japan have also been tainted with up to 14,000 becquerels of cesium for every kilogram.

That exceeds the EU limit by over 11 times.

Eating a kilogram of such tainted vegetables every day for a month would accumulate radiation equivalent to a full body CT scan - or 20 millisieverts.

External exposure to large amounts of radioactive cesium can cause burns, acute radiation sickness and death. It can also increase the risk of cancer. Ingesting or inhaling cesium allows it to be distributed in soft tissues, especially muscle tissue, increasing cancer risk. It can also cause spasms, involuntary muscular contractions and infertility.

Unlike iodine, uptake of radioactive cesium cannot be prevented once the person is exposed.

This substance is of more concern than iodine-131 because it is very hardy and takes far longer to disintegrate.

Cesium-137 has a half life of 30 years, meaning it takes that long to reduce its radioactivity by half. It will take at least 240 years for this contaminant to exhaust all its radioactivity.

Cesium-134 has a half life of 2 years, which means it will take about 20 years for it to become harmless.
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TheMadMonk Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Apr-07-11 12:58 PM
Response to Reply #2
5. The links are/were links in other posts by other people.
Ingested iodine does we know cause thyroid cancer and at a relatively low dosage.

Ingested caesium, does not appear to behave similarly despite its affinity for a specific tissue type. It may well increase cancer risk, but if so it's at a rate below the statistical detection threshold and the existence any such cancers could only be inferred to exist in a sufficiently large population.

Strontium is the bastard which is most likely to get into our bones and damage bone marrow at lowish doses.

Spasms and infertility are toxic effects of the metal caesium . Oh and if you do swallow it in metalic form, expect to see your insides on the outside (not to mention walls) toot sweet.

Extended external contact with bulk anything with a half-life less than a century is pretty much guaranteed to cause burns. No surprises there.

We might also note that most of the contamination on vegetables is just that ON them. A good wash removes most of it. Thus 11 times might easily become 2 or 3 times after a rinse. And at that level it would take a good deal of effort to pick up a year's dose in a year.

Oh and where exactly did I imply that some special process reduced the radioactive half-life of caesium? I said, that it's BIOLOGICAL half-life is probably lower than other heavy metals because it is highly reactive and thus rather mobile in the environment. Just looked some up. Lead looks to be actually quite low, 28 days, Mercury, 80+, and cadmium almost 30 years. Uranium a year, Pu fergedit @ 200 years. Caesium's seems to be all over the place (2 to in excess of 80 days) I'm willing to call 50 days optomistic, or allow that it's takeup into muscle tissue is at least somewhat dependent on the speed at which those muscles are growing.

Thus, not so good for children and musclebuilders, not apparently a problem at all for the rest of us. Having allowed that take up is high in one valuable and one valueless segment of the population, (we might call that a wash :P ) but let's not and just appeal to the evidence. Which is no epidimoligical evidence that radiocaesium has any specific radiotoxic effect like those of Iodine or Strontium.

And while it is certainly possible to statistically identify an elevated cancer rate in a large enough population, there is at least some evidence in Faluja, the Balkans, and badly managed waste dumps in Russia that straight up heavy metal toxicity kicks in hard, well before radiotoxicity takes off into appreciably dangerous territory when it comes to chronic exposure at least.

In no way am I saying that exposure is ever desirable, of course it's not. What I am saying is that any given individual is very unlikely to be adversely affected. It's only when you examine very large exposed populations that a excess events (cancers) show up. The numbers might seem large at first blush in a population as large as Tokyo's, but compared to things like tobacco, coal and traffic pollution it really is tiny.
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FBaggins Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Apr-07-11 09:47 AM
Response to Reply #1
3. Yes, but biological half life doesn't matter while exposure is ongoing.
Then it's really just a question of what the equilibrium level of the substance is in the fish's body.

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TheMadMonk Donating Member (1000+ posts) Send PM | Profile | Ignore Thu Apr-07-11 09:58 AM
Response to Reply #3
4. For the fish. You and I are suposedly smart enough to manage...
...our risks.
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