HOME IMPROVEMENT: Pressure-treated woods leach arsenic


MADISON, Wisc. – Pressure-treated wood has been used for years for decks and outdoors play structures. It is popular because it is both inexpensive and resistant to decay.

But recently the danger of arsenic leaching from wood pressure-treated with chromated copper arsenate is creating a big stir of concern.

“For some time, it has been known that people who regularly work with wood that has been manufactured with this common type of pressure treatment should wear gloves and masks that prevent inhalation of dust from sawing,” said John Merrill, a housing specialist for University of Wisconsin Extension.

“It has also been clear that burning scrap lumber of this kind of pressure-treated wood is dangerous.

Tragic case. “There was a tragic case in northern Wisconsin in which a worker in a plant that processed the wood brought home scrap and burned it in a wood stove. Ashes containing arsenic ended up on the floor of the home.

“Vegetables from the family garden where ashes had been dumped also contained arsenic. Because of the exposure, the children experienced severe health problems.”

In addition to being a known poison, arsenic is also a recognized human carcinogen. Arsenic can enter the body when breathing dust containing arsenic, swallowing arsenic-laden dust, or getting arsenic on the skin.

Up until now, however, structures using chromated copper arsenate treated wood have been considered safe for use by children since because it was believed that the chemicals were bond tightly to the wood, and the possibility of arsenic leaching from the wood was predicted to be minimal.

Play equipment. Recent tests of soil around some play equipment, however, have make this assumption questionable.

Some soil samples taken from around the play structures have had significant amounts of arsenic. The surfaces of the play structures have also shown significant amounts of arsenic.

The U.S. Environmental Protection Agency is investigating the significance of the arsenic found in soil samples.

While this determination is being made, the pressure treated wood industry has agreed to initiate a campaign to alert the public to the potential risks of arsenic-treated wood.

Warnings required. Any item made from the wood should now have an end-tag stating five things:

* That arsenic is in the pesticide used to treat the wood;

* That the treated wood should not be burned;

* That a dust mask and goggles should be worn when cutting the wood;

* That gloves should be worn when handling pressure treated wood;

* That a toll free number is provided for more information.

While the reassessment of the risks is in progress, Merrill said, there are several things consumers can do to reduce risks associated with pressure-treated wood structures.

First, be sure that children wash their hands after playing on pressure-treated wood play structures, and discourage them from playing in dirt at the base of any pressure- treated structure.

Stain coating. Second, consider coating the structure with a semi-transparent stain or other water repellent.

According to preliminary work at the U.S. Forest Products Laboratory in Wisconsin, this can reduce the leaching of arsenic dramatically, and sealing the wood also extends its life.

While pressure-treated wood is decay-resistant, it is subject to damage from ultraviolet light and from water. Applying a penetrating stain or water repellent can reduce this damage. These coatings need to be renewed every few years to be effective.

Paints and varnish reduce arsenic leaching even more efficiently, but have the disadvantage of cracking with time and requiring sanding when they are prepared for recoating, which can release arsenic.

Alternative. If you have building plans that use pressure-treated wood, Merrill suggested, use copper quat treated wood which is arsenic-free and uses ingredients that appear to be less toxic.

It is about 20 percent more expensive than chromated copper arsenate treated wood, but appears to be just as durable.


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