Power Washing the Fence? ... Maybe Not.
Thinking about power washing that fence? You may want to
reconsider.
If you have a pressure treated wood fence built before
2004, it is likely made with Chromated Copper Arsenate
lumber (CCA for short) and contains arsenic. Due to health
concerns, this type of lumber is no longer available for
residential use, in Canada or the United States, effective
December 31, 2003. It has been replaced by new, safer,
chemically treated woods.
The voluntary cancellation of this lumber for residential
use was precipitated by the release of a risk assessment in
February 2003 by the U.S. Consumer Product Safety
Commission. The assessment concluded that children playing
on playground equipment built with this type of lumber have
a slightly increased risk of developing cancer. The report
is available on it's website www.cpsc.gov/.
Many municipalities have already removed playground
equipment and other stuctures made with the wood in public
areas, but currently, neither the EPA (Environmental
Protection Agency) in the U. S. or Health Canada's Pest
Management Regulatory Agency (PMRA) require or recommend
that people remove existing CCA wood structures from their
properties. These regulatory bodies however do strongly
suggest that people try to reduce their potential exposure
to arsenic from this wood.
Although studies show that depending on a number of
factors such as climate, rain, soil acidity and age there
can be some chemical leaching, generally if left alone, the
wood is not considered a problem. Most risk issues are
related to the possibility that some of these toxic
chemicals might be ingested after contact with the wood.
There may be additional risk if some of these chemicals are
released from the wood, which occurs when it is burned,
sanded, sawed, drilled, and of course, power washed.
Power washing or pressure-washing actually drives the
arsenic out of the wood. Using an acid deck wash or a
brightener will hasten this leaching. Simply cleaning with
many common cleaning products will also hasten the
leaching.
Wooden fences, especially those with boards placed in a
louvered fashion and those with lattice, allow water to pass
through when power washing. The risk of leaching is not just
confined to the power washed side of the fence. You have to
worry about what is on the other side of that fence. Is it a
garden, a children's play area, a fish pond? It does
matter.
The other thing to consider is how far the power wash
spume travels. I have personally watched a spume travel over
20 metres from the site of the power washing, possibly
contaminating everything it touched.
You have to consider where the arsenic is going.
Generally, if it is a fence, it's your neighbour's yard that
you are putting in jeopardy. Remediation of contaminated
soil can be quite costly.
Let's get this straight. You have a wood that resists rot
and aside from a little greying, which occurs in the first
few years, will remain pretty much the same for decades. Why
would you want to power wash it? The wood has been treated
with chemicals specifically to protect it from insects and
microbial agents. Power washing forces out the very
chemicals that make the wood long lasting. You're damaging
the wood, shortening the life of the structure and putting
harmful chemicals where they don't belong.
Best advice. Leave it alone.
It should be noted that the EPA is studying the
effectiveness of certain sealants that could possibly reduce
the amount of arsenic being rubbed or leached from the wood.
If you are thinking of using a sealant, note that sanding or
power washing may not be a good idea even if it is
recommended on the sealant label!
For More Information:
Health
Canada Fact Sheet on Chromated Copper Arsenate (CCA)Treated
Wood
Pressure
Treated Wood (CCA) Information, Public Health and Social
Services, Thurson County, Washington.
U.S.
Consumer Product Safety Commission CPSC, CCA- Pressure
Treated Wood, Guidance for Outdoor Wood Stuctures
Information about sealants:
U.S.A.
EPA Chromated Copper Arsenate
If you have any other structures made with CCA treated
lumber here are a few suggestions for limiting arsenic
exposure:
- Wash hands after having any contact with the wood
especially before eating or handling food. This is
especially important for children who often put their
fingers in their mouths.
- Do not allow food and drinking water to come in
contact with CCA wood.
- When eating on picnic tables that could be made from
this wood, use a tablecloth, or at the very least use
dishes so that the food is never placed directly on the
wood.
- Do not grow vegetables in beds lined with pressure
treated wood. Allow at least a 15 inch buffer between the
wood and any edible plants. If you have a vegetable
planter constructed with CCA-treated wood, install a
plastic liner before filling the planter with soil to
reduce exposure to CCA.
- Wear gloves, goggles, dusk mask and long sleeves when
sanding, sawing or drilling arsenic treated wood.
- Any work with pressure treated wood should be done
outside.
- Launder the clothing worn when handling CCA treated
wood separately.
- Never ever burn the wood. The smoke and ash are
highly toxic.
- Dispose of any leftover wood debris from constuction
(endcuts, sawdust etc.) in accordance with local
regulations
- Avoid power washing. What applies to fences applies
to other structures as well. The arsenic will leach
out.
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