Silica sand

From: Tim Williams (tim.williams@jascoint.co.jp)
Date: Sun Jan 30 2000 - 16:09:46 PST


Date: Mon, 31 Jan 2000 09:09:46 +0900
From: Tim Williams <tim.williams@jascoint.co.jp>
To: cp@opus.hpl.hp.com
Message-Id: <aabcdefg274$foo@default>
Subject: Silica sand

Dear CP growers,

The topic of hazards associated with silica sand and other silica
gardening products is one that crops up periodically in lists such
as ours. I've posted this message before (a few years back...?),
regarding the silica hazard.

Whilst silica dust ("any" dust) is worth ovoiding, the real damage
occurs not from bags of sand from shops used periodically by plant
enthusiasts, but when mining and particularly when cutting through
silicaceous rock. Freshly cut (or crushed) silica is very reactive,
and micron-sized particles find their way deep into the lungs. The
fresh, reactive particle then proceeds to react with lung tissue,
perhaps initiating silicosis.

However, once the dust is wet or "aged", the exposed bonds become
attached to water (hydroxyl groups) and render the silica much less
harmful. This takes place naturally (in moist air) over a few
hours. If you are worried about handling silica containing
products, you have only to wet the stuff before handling it, and of
course wash freshly purchased material to remove the ultrafine
hazardous particles. Storing the sand slightly damp is probably the
best way, as is wearing a face-mask. Plantsmen have after all been
using silica sand for centuries, but never handling it dry (I
guess....)

Tim Williams, Tokyo Japan.

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