Yeah, I have a Japanese friend who looks like she has dental fluorosis, I figured it was from the tea she drinks all day...maybe seaweed plays a part in that also.
Kelp tablets have arsenic in them because kelp does...seaweed is the same. There is even a warning on kelp capsules sold in California.
I bet overtoxication (is that a word?) with one element might have some of the same effects as another.