Thanks Steve, I took many science classes and worked professionally in biotech for years, but I do not have much knowledge of physics and engineering. I understand the basics of radioactivity since i did radiolabeling studies and took health physics training at my first job out of school. Looking back I wish I took some coursework in college but it wasnt required for my major. I see what you are saying. I understand that many isotopes decay in short periods of time, but what about Cesium 137 which had a half life of 30 yrs. can this not conceivably enter the food chain and amplify to dangerous levels?
Is this the same person asking about Fukushima again? After I stressed number?
NUMBERS! Aside from what's generated via cosmic rays, I assume you're referring to 137Cs which comes from Fukushima. It can enter the oceans and be detected in fish immediately around the reactor bay area, yes. What can be detected is approximately a billion times what I would consider insignificant and a trillionth of what I would call (in medical exposure terms) a significant but not "hot" source of radioactive material. What is easily detected is probably a millionth of insignificant and a billionth of significant-but-not-risky. That's right, billionth. What they administer for a cardiac stress test is over 30 times what I would consider significant-but-not-risky. The material does not "amplify" over time, it decays. The fish absorb a certain amount of it that doesn't get stuck in their bones (don't eat the bones?), flush most of it...good luck detecting it in any American west coast caught sushi tuna. And that's detecting it, not a billion times that.
A liter of fish meat is about a thousand (guesstimate) pieces of sushi. So unless you're prepared to eat 30 trillion pieces of sushi (these are realistic numbers, even if they are order of magnitude estimates), then stop bugging me about Fukushima and 137Cs and go eat your sushi in peace! Or, like I said, find another real expert with a real Ph.D. in nuclear physics and ask them if this estimate (for their reference, femtocuries total activity is for underground labs, picocuries/liter is standard environmental monitoring, and 30 millicuries is roughly one cardiac stress test activity dose) is way off or not.
The fish is safe, Fukushima really is half a world away, and stop panicking.