I may have missed it, but where's the statement about what those black spots are in the micrographs and how that was determined. It seems like they're just decl

I may have missed it, but where's the statement about what those black spots are in the micrographs and how that was determined. It seems like they're just declared as atmospheric particulates but where's that determined exactly? It would be great to purify them somehow and run the slurry under an electron microscope. Something along these lines of https://www.bloomberg.com/news/articles/2014-04-02/the-microscopic-beauty-of-air-pollution https://www.bloomberg.com/news/articles/2014-04-02/the-micro... to see how such raw particulates accumulate in some tissue in the body.