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permaculture - Re: [permaculture] Heavy metal issues

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Chronological Thread  
  • From: Rick Valley <bamboogrove@cmug.com>
  • To: <permaculture@lists.ibiblio.org>
  • Subject: Re: [permaculture] Heavy metal issues
  • Date: Sat, 28 Sep 2002 20:55:59 -0700

> The problem to begin with is that we've extracted heavy metals from
> their 'safe storage places' via mining and/or smelting (nickel,
> cadmium, lead, boron, etc.) or concentrated them via
> agriculture/irrigation practices (selenium, etc.). So now we've got
> toxic concentrations of them to deal with.

For sure we've set lots loose- but in Oregon at least, the are some wells
full of natural arsenic, and springs with enough selenium to kill you not
too slowly, and lakes where you can take your 20 mules and haul away borax
(which is a halide, not a heavy metal, no?) It's a very complex subject,
each element is unique, and popular misconceptions abound. One of the most
common in Pc circles is that the most common and deadly pollution in an
urban/suberban lot will be from the street, when frequently if there's lead
present in dangerous levels, it's coming from housepaint.
see attached forward of interest

-Rick

New rules for pressure-treated wood
Inman News Features
2002-09-20


EPA phasing in new, more expensive, more environmentally
friendly wood treatments

If you have any type of outdoor structure around your home a
fence, a deck, a gazebo chances are it was constructed in whole
or in part using pressure-treated lumber. In fact, some of the
components in your house, such as sill plates and other structural
members that are directly in contact with concrete, are also made
from pressure-treated lumber.

Treated lumber has been around for decades, and is generally
considered to be a very safe product. Recently, however, some
controversy has arisen around CCA Chromated Copper Arsenate
one of the most common chemical compounds used in the
pressure-treating process. As a result, on February 12, 2002 the
Environmental Protection Agency (EPA) announced a voluntary
decision by the pressure-treatment industry to move away from
CCA to other types of preservatives by the end of 2003. By
January, 2004 CCA-treated lumber which currently accounts for
about 90 percent of the pressure-treated materials on the consumer
market will no longer be available for residential use.

CCA is a blend of three chemicals: Chromium, which binds the
chemicals to the wood fibers; Copper, which makes wood
decay-resistant and also acts as a pesticide for certain types of
insects; and Arsenate, a derivative of arsenic, which acts as a
pesticide to stop wood-destroying insects.

The EPA has long maintained and continues to do so today that
CCA-treated wood is completely safe. However, in light of some
data that indicates arsenic may leach out of the wood and become a
potential source of soil and ground water contamination, they have
deemed it prudent to reduce this potential as much as possible.

What's taking its place?

Even with the removal of CCA from the residential marketplace (it
will still be used in some commercial applications),
pressure-treated lumber will still be readily available in
lumberyards and home centers. The only difference will be new
chemical compounds used in the treatment process and an
estimated 10 to 20 percent jump in price.

Two new compounds will be, at least for the time being, the
preservatives of choice for pressure-treating lumber. The most
common is ACQ Amine Copper Quat which will still utilize
copper as its primary ingredient. Gone will be the chromium and
arsenic, which are being replaced by a solution of ammonia.
Manufacturers state that ACQ-treated lumber will look very much
the same as CCA-treated wood, with perhaps a slightly browner
color.

The second, copper-azole, has been used in Europe and Japan for
some time but is fairly new in the United States. As with ACQ,
copper-azole compounds do not contain any chemicals that are
listed with the EPA as carcinogens, and are in fact utilized by some
growers for the treatment of fruit. Wood treated with copper-azole
a brownish tone.

Three manufacturers are currently moving to market with these
next generation pressure-treated woods. These include
"NatureWood" and "Preserve," both of which use ACQ for their
preservative, and Wolman's "Natural Select," which is currently the
only product using copper-azole compounds.

What about the CCA-treated stuff I already have?

The EPA has stated repeatedly that CCA-treated wood "does not
pose any unreasonable risk to the public or the environment". As
such, the EPA is not recommending that you do anything with
currently existing structures made with pressure-treated lumber
containing CCA.

Since it was the potential risk to children that was of primary
concern to the industry and that helped prompt the voluntary
changeover, the EPA does offer a few common-sense tips for
dealing with CCA-treated lumber. These include not burning
treated wood, keeping food out of direct contact with it, and
thoroughly washing hands after working with treated lumber or
playing on structures that are built with it. For even more
protection, you can coat CCA-treated lumber with exterior paint or
exterior clear sealants.

For more information, check with your lumber dealer or visit the
EPA Web site at www.epa.gov.





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