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Fukushima Radiation Nears California Coast, Judged Harmless
sciencehabit writes After a two-and-a-half year ocean journey, radioactive contamination from the Fukushima nuclear disaster in Japan has drifted to within 160 kilometers of the California coast, according to a new study. But the radiation levels are minuscule and do not pose a threat, researchers say. The team found a high of just 8 becquerels of radiation per cubic meter in ocean samples off the coast. U.S. Environmental Protection Agency guidelines for drinking water allow up to 7400 becquerels per cubic meter.
So 2 tonnes of water has the same amount of radiation as 1 banana.
https://en.wikipedia.org/wiki/...
There are more different units for distance. Actually its all the units for brightness that confuse me the most.
There are actually really only 2 physical units,
Activity, i.e. decays per second, Becquerel
Absorbed does, i.e. joule per kg, Greys
and a bonus biologically adjusted
Equivalent dose, like Greys adjusted by biological harm, Sievert
The others are obsolete (only used in USA).
A becquerel is the radioactive decay of a single atom per second. Your body has 4400 becquerels of radiation due to a naturally-occurring radioactive isotope of Potassium. If you drank a liter of seawater that would mean Fukushima has increased your radiation dose by 0.008 becquerel - less than a 0.0002% increase in radiation internally in your body. This is literally less than a drop in a bucket. The salt is far more likely to kill you than the radiation.
Fortunately it is incredibly dilute. Here's some fun facts. If you can manage to drink a cubic meter of the ocean water (after removing the salt so it won't kill you), you will be slightly less radioactive for a while due to potassium loss. Don't try it all at once though, it could kill you due to 'water poisoning').
If you're the sort to panic, you will add more radiation to your body by taking potassium iodide pills than the water will contribute.
Cesium accumulates in your body because it's chemically similar to potassium, which your body needs for nerves to function (among other things). So it can accumulate no more than potassium does.
Potassium has a naturally occurring radioactive isoltope, K-40, which like Cesium undergoes both beta and gamma decay. The amount of K-40 in the typical human body contributes 4000-5000 becquerel to your natural radiation dose. So your contention that there is "no safe minimum dose once it is in your body" is clearly wrong. Everyone who has ever lived has been exposed to a relative "huge" amount of radiation from K-40 throughout their entire lives, and our species is still here.
You would have read this:
The findings are reassuring, Buesseler says. He measured a high of just 8 becquerels of radiation per cubic meter in the samples. Of that, he says, less than 2 becquerels came from cesium-134 traced to Fukushima. The remainder is largely from strontium-90 and cesium-137: Some of that is fallout from mid-20th century atomic bomb tests in the Pacific, and some may have come from Fukushima—these isotopes lack the half-life fingerprint that ties cesium-134 to the Japanese disaster. The total level of radiation is hardly worth worrying about, Buesseler says: U.S. Environmental Protection Agency guidelines for drinking water allow up to 7400 becquerels per cubic meter. Buesseler is presenting his latest findings Thursday at the Society of Environmental Toxicology and Chemistry North America’s annual meeting.
So, that's 6 Bq that was most likely deposited by aboveground or underwater Pacific nuke testing.
You can now return to your previously scheduled freakout over "ZOMG RADIATSHUNS!"