[phil]

Hi, not sure if this is the right forum but have a question pertaining to Bentonite and Fly-ash.

I'm using bentonite for dust effects on a small film and have been told that it is a potential carcinogen due to the silica present. The person recommended a product called Fly-ash which I have tried to research and have found also contains silica.
I can't find any literature showing the differing amounts of silica per product and wonder if anyone knows the exposure amounts that would make it a harmful product (by that I mean do you need to be in a cloud of dust for hours at a time for it to become problematic as opposed to maybe inhaling a tiny bit of dust from an air mortar for 2 or 3 seconds).

Can anyone help with some useful info or links?

Thanks

[fledarmus]

I can at least link you to some material safety data sheets, but there are different grades of fly ash and possibly different types of bentonite - I would get an MSDS from your source before you make any final decisions.

Bentonite - http://www.naturalsourcing.com/msds/MSDS_Bentonite.pdf

Fly Ash - http://health.state.tn.us/Downloads/TVA_MSDS-TVA-flyash.pdf

From what I can tell, the fly ash has far more silica than the bentonite (~50% vs <2%), but that may differ based on source.

OSHA exposure limits for silica are pretty low - there are numbers across the two MSDSs ranging from 0.1mg/m³ up to 30 mg/m³ based on the form of the silica. For reference, 1 mg of silica will just about cover the head of a tack, and 1 m³ is a cube about the length of your arm, so you can imagine what it would look like if you threw a tack's worth of silica into that much air. This is a very tiny amount of dust.

[phil]

Thanks for that...very useful