@soryang

of analysis of various seaweed samples back in the months after Fukushima: I built a hobby-quality gamma spectrometer, calibrated it with some known samples, and went prospecting for radionuclides. And I did indeed find measurable levels of 137Cs in a number of the samples, as well as some traces of 131I. The 131I will have long since decayed away at this point (half-life is on the order of 12 days), but the 173Cs will still be out there- although heavily diluted by now.

Even at its peak, it took about a week in the spectrometer to build up enough gamma detections to see the concentrations in the dried seaweed- none of them crossed the threshold of posing a profound risk, IMHO. I had a greater concentration of 137Cs from the hay collected from my own pasture, immediately after the passage of the plume: we had a rainout event. You could see that 137Cs photopeak begin to develop in just a day or so. And that was definitely concerning.

I stopped making those nori measurements after 6 months or so, as the levels dropped off. I should do it again now with my new spectrometer- the original one didn't survive the fire, and scared the firefighters half to death when it crashed through the floor of my second-floor office and ended up in the basement. The new one is easier to calibrate, and has better resolution. Next time I'm at H-Mart, I'll pick some likely looking nori samples and run them. I'll bet that it will take a minimum of a 1-month run to see anything at this point- but I could be wrong. It will be fun to look for that.

Japan has a long history of misfortune with industrial waste, unfortunately: the Minamata experience comes immediately to mind. I personally would prefer that the levels of 137Cs be very low indeed, on the order of normal background, but the Japanese authorities have their own ideas about what constitutes an acceptably low level.

We still regard Bikini Atoll as uninhabitable, for example, even after all these years (the last test was in 1958). Some of it is barely above natural sea-level background (~0.1uSv/hr). The problem is the parts that aren't. Some are still cooking along at 10uSv/hr, a factor of 100 above background, and it isn't all 137Cs- they have lots of 90Sr, 241Am, and on and on...

Time will tell, both in Japan and elsewhere. We continue to learn new lessons every day.

I'm not a scientist so I don't know much about this. I've been somewhat concerned about seafood from the western Pacific since Fukishima. Particularly with respect to seaweed but also any imported fish. Very recently I'd been hearing anecdotally about a high incidence of thyroid disorders in East Asian women. Different types of seaweed are now apparently drawing the P65 warning. I don't know the different types of seaweed by name, but I'm particularly concerning with kim, a dried seaweed consumed by Koreans and Japanese often. Another I learned of from the P65 website was hijiki. I perhaps mistakenly thought that the risk in seaweed there would be iodine or cesium related, but the known risk apparently is arsenic. This link came from my seaweed query at the P65 website:

https://www.p65warnings.ca.gov/fact-sheets/arsenic-inorganic

This risk of arsenic is also reportedly elevated in rice, which is a staple for us and even water in some places. We eat rice every day, go figure. This is from Maangchi's website on a customary seaweed soup dish, which is generally regarded as healthy by Koreans.

Miyeokguk is a soup made of edible seaweed and is traditionally eaten on birthdays or after giving birth, although you can eat anytime you like. Miyeok is rich in iodine, iron, and calcium and many people eat it to lower their cholesterol. This version of the soup is made with beef, which is the most popular type.

I don't know if any of my suspicions are grounded in fact. Koreans put seaweed in soup all the time. I was at a church lunch the other day, it was dumpling soup, but I didn't touch it, because it was garnished with some type of dried seaweed. I just told the others at the table, I was full. Miyeok is also used as a base for flavor in many different Korean soups. I don't like miyeok either, like the American in Maangchi's story. https://www.maangchi.com/recipe/miyeokguk

Hijiki seems to be a seaweed food popular in Japan. Only tangentially related is this story on contaminated soil from the Fukishima disaster:

The government decided Tuesday to begin reusing in regional cities soil generated from decontamination work following the 2011 meltdown at Tokyo Electric Power Company Holdings’ Fukushima No. 1 nuclear power plant.

https://www.japantimes.co.jp/news/2026/08/26/japan/reuse-fukushima-soil/

(edit- wrong link, the recent link is Japan Times, excerpt above)

https://www.theguardian.com/world/2025/may/28/fukushima-radioactive-soil...

IAEA approved this sort of thing about two years ago, or at least that's the first I had heard of it. Also planned to use this contaminated dirt in roadbeds and embankments. I think the initial use was in public flowerbeds in Tokyo. I'm sure others here at C99 know more about this sort of risk than I do, from a scientific perspective.

Thanks for the OT Q!

@QMS

.
with the help of the librarian
able to get into emails and found the
order was never placed. OK then. Start
over. Turns out the way algos work, every time
you check prices or try to order it goes up a hundred bucks.
On time pricing! Rains have stopped spilling out of the sky today.
Steam bath. Awaiting the oil delivery so can face a real shower.

Cheers