I realize this is from the source I get my seaweeds from, but I think I would need more information about what "a ton" constitutes, and how it outweighs the health benefits. Feel free to share your knowledge and experience, we can all learn from one another.
"We test our seaweeds for heavy metals and radioactive elements. All seaweeds naturally contain some heavy metals as part of their high mineral content. This is not a health concern, however, because seaweed polysaccharides (algin, fucoidan etc.) have been shown to bind with heavy metals in the digestive tract and carry them out of the body. In fact, seaweeds and seaweed extracts are commonly used to reduce levels of heavy metals in the body. Of course, seaweeds harvested from polluted waters may contain harmful levels of heavy metals, so be careful where you buy them from."
