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
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:
Info on cleanup of processing site in Minneapolis:
Info on asbestos-inducted mesothelioma is here:
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.