Since nobody really seems to know much about this but everyone's posting what they *think* they know, I'll do so as well. The asbestos issue with vermiculite is ("as far as I know") a problem with naturally occuring contamination of the vermiculite processed at the W.R. Grace mines in Libby, MT. This stuff was shipped all over the country as insulation (typically under the brand "Zonolite") and soil additive for nursuries. The EPA recommends simply not disturbing any suspect asbestos in residential settings-- you'll cause more problems trying to remove it than to just cover and let it sit. You're better off just insulating over it and forgetting about it.
Occupational exposure to asbestos is a hazard. My grandfather died of lung disease related to his work in shipyards surrounded by asbestos. But the small amounts one would encounter in a residential setting (outside of Libby, MT, and other factory sites where apparently it was spread around people's yards and kids played in piles of tainted vermiculite processing spoils) aren't worth worrying about. If they were, we'd have a nation-wide epidemic of mesothelioma. But it remains quite rare, despite the mountains of asbestos in homes, schools, and workplaces around the country.
Info on Libby and vermiculite:
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Info on cleanup of processing site in Minneapolis:
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Info on asbestos-inducted mesothelioma is here:
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Hope this helps-- the point is jus leave it alone and insulate your attic over it with something modern and more effective.
2" of vermiculite is about R-0 today, after it's settled.
-Kiwanda