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 that I do, from a scientific perspective.

Thanks for the OT Q!