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Re: Don't use pool grade diatomaceous earth

Square Foot Gardening List - http://www.flinet.com/~gallus/sqft.html

I believe that the heating of the DE, called calcining, both reduces the
utility of the material as a bug killer/snail deterrent, and increases the
amount of crystalline silicates, which, compared to the amorphoous
silicates, are the ones that increase your risk of lung cancer, via
silicosis....

I'll quote here from Occupational Health: Recognizing and Preventing
Work-Related Disease, 3rd Edition, Levy and Wegman, 1995:

"Diatomaceous earth is an amorphous silica material mined predominantly in
the western United States. It is used as a filler in paints and plastics, as
a heat and sound insulator, as a filter for water and wine, and as an
abrasive. In contrast to the various forms of crystalline silica, amorphous
silica has relatively low pathogenicity.  However some processes using
diatomaceous earth include heating (calcining) it to remove organic
material. This heating process can produce up to 60% crystalline silica as
cristobalite, which is highly fibrogenic."

Frank Teuton
-----Original Message-----
From: Cyndi Norman <cnorman@BEST.COM>
To: OGL@LSV.UKY.EDU <OGL@LSV.UKY.EDU>
Date: Wednesday, May 05, 1999 1:25 PM
Subject: Don't use pool grade diatomaceous earth


>   Date:         Wed, 5 May 1999 12:51:27 -0400
>   From: Walker Bennett <WBennett@CALDWELLSPARTIN.COM>
>
>           This is available in most garden supply stores, chemical
supplies,
>   or (and the last time I suggested this, I was flamed for days by
>   environmental purists) swimming pool supply stores.  Yes the pool-grade
has
>   been chemically treated (primarily by chlorides); yes it has been
>   heat-treated (which makes some of the powder less sharp microscopically;
but
>   YES it costs about 1/10 the garden variety.  Being expedient (read that
>   _cheap_), I can get a 25-lb bag of pool filter DE for around $8 (US)
that
>   works just fine for keeping slugs away from my tomatoes, et. al.
>
>It's not the impurities, it's your lungs.  Pool grade DE is a different
>degree of fineness from garden grade DE.  You don't want to be breathing
>the stuff as you strew it around.  Also, I don't think it works the same.
>You should wear a mask when applying any kind of DE but please be
>extra-cautious if you choose to continue using the non-garden variety.
>
>Cyndi
>
>___________________________________________________________________________
____
>Oakland, California            Zone 9 USDA; Zone 16 Sunset Western Garden
Guide
>Chemically sensitive/disabled - Organic Gardening only by choice and
neccessity
>___________________________________________________________________________
____
>"There's nothing wrong with me.  Maybe there's                     Cyndi
Norman
>something wrong with the universe." (ST:TNG)
cyndi@consultclarity.com
>
http://www.consultclarity.com/
>_________________ Owner of the Immune Website & Lists
http://www.immuneweb.org/
>


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