You should understand the difference between “radiation” and “radioactive contamination”. You won’t find “radiation” on vegetables, or on anything else for that matter, which is not either a natural emitter of radiation, or pretty highly contaminated with radiation. And in the case of a “natural emitter”, the radiation is inherent in the material.

So, for example, a radioactive source, such as Cobalt-60 or Iridium-192 (both industrial materials used in the nondestructive examination of welding), “emits” radiation, because those materials are radioactive. But when an NDE technician examines a weldment by exposing the radioactive source to it in order to capture a film image of the exposure, and then re-houses the source in its shielded container, there is no “radiation” found on the weldment. That is, the source is encapsulated for the entire time of its use, including when it is exposed to the weldment, so that no particles of it remain behind after use.

However, otherwise non-radioactive materials (including metals) can become radioactive through long-term exposure to high levels of radiation, or simply from being rubbed against a radioactive material and retaining some of that material. (If iron were radioactive, for example – and it’s not – then “rust” that you can get on your hands and clothing would represent “radioactive contamination”.) That’s why many materials and surfaces inside nuclear plants (including even the dust and water) can become radioactive, because they are “radioactively contaminated” by virtue of their exposure to radioactive materials.

Radioactive contamination is a problem in the immediate vicinity of the Japanese nuke plants because their containments have been breached to some degree and because they have been releasing contaminated gases and liquids in order to relieve the pressure buildup inside the containment vessels. Radioactive contamination is a potential problem at any operating nuclear plant, and most do a very fine job at detecting and eliminating exposures and leaks.

It’s unlikely that measurable levels of contaminated dust or liquid from the Japanese plants would find its way across the Pacific Ocean to California accidentally. Please note both qualifiers in that statement: “measurable” and “accidentally”.

There is natural background radiation detectable nearly everywhere on Earth. (You may find some deep caves where cosmic and background radiation are nearly nil, but you won’t be living there.) Since radioactivity varies so much by elevation (there’s more cosmic radiation at higher elevations than there is at sea level) and by geology (granite is naturally radioactive at low levels, and so are concrete and coal), and isn’t a perfectly measurable quantity in any case, it’s going to be hard to detect “new” radiation from “what has always been present ‘here’ (wherever ‘here’ happens to be)”. That addresses the issue of “measurable”.

And it’s always possible that someone could deliberately spread radioactive contamination in an area in order to further some Luddite agenda that we should shut down every potential source of man-made radiation / contamination. But that wouldn’t be accidental.

@wasCy: In your statement, ” It’s unlikely that measurable levels of contaminated dust or liquid from the Japanese plants would find its way across the Pacific Ocean to California accidentally. Please note both qualifiers in that statement: “measurable” and “accidentally”.”

The other word that I would say is the important qualifier is “unlikely.”

Thanks for making the distinction between radiation and radioactive contamination—it is the latter, of course, to which I was referring. What with the jet stream from Japan heading directly to CA and the west coast, it did occur to me that perhaps there might be some radioactive contamination of our food, and our milk too, for that matter, and I was wondering if anyone was looking at or measuring for that, since we are also feeding our babies, young children, and pregnant women here as well.

Without being alarmist, because of the nature of radiation, there is probably “some” radiation from nearly every high-level radioactive source on Earth, and many from the rest of the cosmos, that is passing through you at this moment. But that’s what makes up “background” radiation. And that’s why you won’t be able to measure the insignificantly tiny additional part that does come from the accidents in Japan: the additional bit that by now probably has drifted across the ocean is so immeasurably small compared to what is already there (and has always been there) that you won’t be able to detect the difference.

http://xkcd.com/radiation/ <—Everyone should read that. Keep in mind the guy who did it worked for NASA. So he probably knows a bit more about science than you do.

I like it, @math_nerd. I can’t vet all of the values, but the perspective is good, and the relative values seem sensible.

Again…. the press is dumbing up America. If you want to have nightmares of radiation contamination for a proper reason read about Hanford Washington. http://www.hanfordwatch.org/

Our instruments are so sensitive that we can measure tiny elevations of radioactivity in the US, in Iceland and even in Switzerland from particles carried by the wind from Fukushima. These tiny elevation are totally harmless at this point in time. Whenever you board a plane your body will be exposed to a lot more.

The only way for vegetables to be a problem for you is when farmers near Fukushima export them to the US. Which isn’t the case. The people in Tokyo should be more worried, but screening measures are in place.

@mattbrowne I would feel more confident about all this if we hadn’t just learned that the radiation detectors for most of CA have not been functioning all last week—and won’t next Monday either, due to budget cuts. Really!

@skfinkel – But many other radiation detectors in other states and other countries are. At this point in time there are only tiny elevations which is absolutely logical. Why? We do have rough numbers of radioactive particles in and around Fukushima. We know the size and weight of the atmosphere and our oceans. We can calculate dilution. And we have meteorological data.

Fresh vegetables from Fukushima are unlikely to end up in California at this point in time. Freighter ships are even avoiding the whole region around Fukushima. Ship captains are scared of radioactivity as well. Mid-term we might get a problem if crooks try to sell contaminated tea leaves for example which would normally have to be handled as toxic waste in Japan. I am anti-nuclear, but right now we need to keep things in perspective. We should be scared when it is really necessary to be scared. Of course the CA detectors have to be fixed. We should be glad that someone found out. They will be fixed despite budget cuts.

@mattbrowne

It’s not that “ship captains are afraid of radioactivity”, since so many have served already in nuclear navies. No, I think that they have a healthy respect and a good understanding of the danger, or lack of it. What’s more likely is that shippers (that is, cargo owners, ship owners and insurers, all together) are concerned with the perception that their goods will have been somehow tainted by proximity to the accident site and therefore unsalable to skeptical consumers, or the quite reasonable concern that the containers may be scanned by radiation detectors at some port or ports and result in a quarantine of part or all of the cargo or the ship itself.

It’s also not unlikely that the “ordinary seamen” on the ships (or their union representatives) may have presented demands to the captain that they wanted the additional distance or they may present grievances or health claims.

@WasCy – I read reports that some civilian ships avoid northeastern ports in Japan because of radiation fear. Yes, military commanders will have much better knowledge. But they won’t pick up Japanese vegetable shipping them to California either.