Hazards of arsenic in pressure-treated wood used in play equipment 
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 Hazards of arsenic in pressure-treated wood used in play equipment


>A group of us are building a playground set and the use of pressure-treated
>wood had been suggested. I recall a that demonstrated health hazard existed do
>to the arsenic and chromium compounds used, both from physical contact of wood
>surfaces and from subsequent leaching of arsenic and chromium-containing  into
>the immediate soil. My concern is that small children, playing on the
>playground set, would most certainly come into contact with these compounds,
>may put fingers into their mouths, or have snacks without washing up prior to

>I'm looking for papers and, or other info in the scientific literature which
>discusses this issue. I'm proposing to use untreated wood, but to finish it
>with a high quality wood preservitive, such as Thompsons. I'd like to present
>my case from a position of substantive knowledge.

  The most common preservatives are creosote, pentachlorophenol and
inorganic arsenic salts.  The first two are sold as paints for home
application, while the third is used primarily in commercial "pressure
treated" wood.
  The terms pressure treated and preserved seem innocuous enough, but
the chemicals involved are potent pesticides formulated to repel termites,
bacteria and fungi for decades.  Although homeowners want their playsets to
last, the thought of children playing on poisoned wood is repugnant.  It is
not surprising, then, that as wood gained popularity as a play structure
materiel, preservatives came under close scrutiny.  The chemicals are
practical and convenient, but are they safe?
  Ultimately all preservatives pose some risk, although the health hazard
varies from potentially serious to negligible.  Creosote, the smelly black
goo that is smeared on railroad ties and telephone poles is the oldest
industrial wood preservative and has been in use for almost 150 years.
In laboratory animals it causes skin irritation, cancer and genetic damage;
in humans, it has been linked to skin cancer and causes eye and skin
irritations, dermatitis and burns.  It remains potent for years, moving
easily through the wood to affect the soil - and the skin and lungs of
anyone who touches it or breathes its vapors.
  Pentachlorophenol (PCP) is a cleaner alternative to creosote, but is
equally suspect from a health standpoint.  A member of the same chemical
family as 2,4,5-T, it contains dioxins and has caused cancer and birth
defects in laboratory animals as well as short term effects such as
skin, eye, nose and throat irritations.  It is easily inhaled and absorbed
through the skin and continues to give off toxic vapors for as long as seven
years.  The EPA controls the use of both PCP and creosote and recommends
sealing any wood that has been contaminated by these preservatives with two
coats of urethane, shellac or{*filter*}epoxy enamel (shellac is inappropriate
for play structures for it is slippery when wet).
  The pressure treated wood sold in lumber yards is preserved with inorganic
arsenic compounds, either chromated copper arsenic (CCA) or ammoniacal
copper arsenate (ACA).  CCA was developed by Karl Hienrick Wolman in 1913
(hence the term Wolmanized) and has been used for 50 years as an inexpensive
alternate to creosote.  Associated with rats and lace trimmed old ladies
diabolically doing in unsuspecting boarders, "arsenic" strikes a note of
uneasiness in most people, but it is a common element in the environment.
The form of arsenic used in treated wood is the pentavalent state - the
same that is found in shrimp, mushrooms, rice and sardines.  In laboratory
animals, inorganic arsenic compounds can cause cancer, birth defects and
genetic mutations, as well as headaches, dizziness and muscle spasms.  But,
unlike PCP and creosote, the arsenic preservatives bind tightly to the wood
fibers.  Studies show that the chemicals do not migrate to the surrounding
soil and plant tissue and are not absorbed through human skin.  The EPA
concluded that pressure treated wood is "safe for frequent contact because
absorption through the skin is negligible."
  The preservative sometimes leaves a bloom of chemical residue on the lumber,
and while children cannot absorb the arsenic by directly touching it, their
fingers often end up in their mouths.  To assess this danger, the California
State Department of Health conducted a study in which researchers repeatedly
{*filter*}ed their hands after rubbing them over treated wood surfaces.  After
several days of testing, their urine showed no increase of arsenic even
though the measuring device was sensitive enough to detect the effects of
a single sardine.  The authors of `Evaluation of Risk to Children Using
Arsenic-Treated Playground Equipment' concluded that kids have as much chance
of getting skin cancer from the CCA-treated play equipment as they do from
playing in the sun.
  CCA is probably more of a health risk to parents than to their children
since minute amounts of preservative laced sawdust may be inhaled or
swallowed during construction.  Wear a dust mask when sawing or machining
arsenic-preserved wood, and do the work outdoors to avoid contaminating
indoor air with preservative dust.  Because incineration of treated wood
releases arsine, an extremely poisonous gas, wood scraps should never be
burned; bury them or take them to an approved dump site.
  Pressure treating the wood does not inject preservatives right to the core
of the lumber; thus, drilled or cut surfaces have to be brushed with at
least two coats of liquid preservative.  Wear {*filter*} gloves during these
applications, avoid dripping the chemical on plants, and wash hands
thoroughly after any skin contact to remove any residue.  After the
structure is built, hose it down with soap and water to remove any surface
deposits of chemicals.
  Though these three account for the bulk of preservatives sold there are
alternatives: low toxicity preservatives such as copper and zinc napthanate,
copper-8-quinolinolate, polybase, bis[tributyltin]oxide (TBTO), and
TBTO/polybase.  These are not known carcinogens, are not herbicidal or
poisonous in the concentrations used for preserving wood and are relatively
stable.  All effectively prevent damage from mold, mildew and rot by keeping
the wood dry enough to discharge fungi and bacteria.  Copper napthanate, the
active ingredient in Cuprinol, has been on the market the longest (1948).
Often used to treat lumber for greenhouse growing beds, copper napthanate
is the only one of the above chemicals rated to withstand constant ground
contact.  Because it can be difficult to paint over and must be reapplied
if the wood cracks, it is better to use copper napthanate below ground, and
use zinc napthanate or one of the other water-repellant finishes above ground.
These chemicals are not, however, sufficient to protect wood against termites.
Termites feast on copper napthanate as readily as they do cedar, leaving CCA
treated wood as the only alternative for areas with termite problems.

I hope this has helped.


California State Department of Health - "Evaluation of Risk to Children Using
        Arsenic-Treated Playground Equipment'
Canadian Institute of Child Health - "Moving and Growing"
Home Playgrounds - Merilyn Mohr - Camden House

Disclaimer:These are solely the opinions of the author and in no way reflect
           the opinions of Citicorp or it's management.
*Batteries not included, void where prohibited, discontinue reading if a
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* Pete Bellas                   "Cogito ergo spud"                         *
* Citicorp/TTI                       I think therefore I yam.              *
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Tue, 26 Jan 1993 01:58:28 GMT
 [ 1 post ] 

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