From: anachem@bronze.ucs.indiana.edu (mark gilstrap)
Newsgroups: rec.gardens
Subject: Re: pressure treated lumber
Date: 26 Aug 92 21:10:10 GMT
Organization: Indiana University

In article <UeWZDX_00WBNE1AW1k@andrew.cmu.edu> John Davis Raborn <jr3w+@andrew.cmu.edu> writes:
>
>What to believe? My wife is still concerned and wants me to re-coat the
>swing set atleast twice a year 'til I die or the swing set disenegrates
>(which will be a long time thanks to the CCA). Me? I think the OG
>article smells of panic and it make me angry that OG had the ability to
>affect me that way.
>
	Hmmm.... that sounds like one of the symptoms of Arsenic
	poisoning  :)

	Seriously, and I posted this about a year ago here, there is
	a wide variation in the quality of treated lumber. Osmose or
	other well known brands are a lot safer than the small scale
	operations that sell wood cheaply. In every town I've lived
	there are good lumber yards and cheap ones. There usually
	is a reason for the price differential (usually very small)
	in the quality of product. 

	When employees of a local picnic table manufacturer began to
	get ulcers on their forearms and faces, they made the connection
	between the liquid which was forced out of the treated wood
	by the force of nails driven in and their malady. Of course
	the owner of the business was on a tight margin and was using
	cheap wet lumber - not the good stuff. 

	A fellow chemist who was working for the lawyer representing
	these workers bought some samples of various brands of lumber
	and did some testing. We squeezed dry and soaked samples of
	good treated lumber and also some cheap stuff. At 50-75,000
	psi its amazing what you can coax out of wood.

	The liquids freed by this process and by extension, the liquids
	which could migrate into your soil/produce/children, were
	reflective of the cost of the product. True to the technical
	sheets from Osmose, their wood (and Wolmanized) released no
	detectable arsenic or chrome (we didn't use the most sensitive
	method to look at the smallest levels) and very low levels of
	copper (not high enough to affect plants I wouldn'tthink). But
	the cheap wood gushed forth with lots of liquid containing 
	high levels of chromium (it was bright yellow) most of which
	was in the +6 oxidation state which is carcinogenic. The total
	chrome in the worst sample (from the cheapest lumber yard - the
	one the picnic table manufacturer was using) had more than 600
	parts per million chromium. This is a bunch!!!  The arsenic in
	this sample however was as absent as in the others - it
	supposedly binds quickly to the wood.

	Over time treated lumber does degrade or get hit by tiller tines
	etc, and all the metals bound to the wood will eventually be
	released into the soil. Wheher or not this constitutes a hazard
	I can't be sure. But in the case of cheap lumber, the hazard is
	evident from the get go. 

	My opinion is that I will not build a CCA playset for the kids,
	although I doubt that the risk is great after the surface has
	weathered a bit. Most of the commercial sets I have seen look
	to be very high quality and probably low risk. Nothing beats a
	resinous pine railing or playset aethetically - but then y
	you risk being exposed to turpentine which is now known to be nasty.

	I think a safe manner is to avoid all denaturing processes and
	deal with natural products as is (wrt growing food or kids) and
	when dealing with natural products use common sense. If it
	smells or irritates you than its no good for you - not all
	that's natural is safe. Little that is denatured is safe. Its
	just common sense. The problem with denaturing is that it 
	bypasses the natural senses and other inputs for common sense,
	so it is safest to let it alone unless you understand it thru
	education or experience - at which time you can again apply
	common sense.
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