Washing your deck can make it toxic

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Pressure washing the old wooden deck in your yard might look better, but you can create a carcinogenic hazard that will put your family and pets at risk.

Wooden decks made before 2004 are made from CCA-treated wood that contains arsenic and chromium – both of which are carcinogens. Wet wood releases arsenic three times faster than dry wood, a new study shows.

Adding bleach makes matters worse. It causes the wood to also release chromate, another carcinogen.

The discovery could be relevant to millions of Americans: In 2007, housing industry researchers estimated that 20 million single-family homes had CCA-treated wood decks. Since the wood can have a lifespan of up to 40 years, most of these decks are still in use, posing a continued risk of arsenic exposure.

Polluted floor

“The arsenic and chromate levels on the surface of the panels after cleaning with bleach and in the rinse water show the potential for soil and water pollution as well as effects on public health,” says Julia Gress, postdoctoral fellow in the soil and water sciences department at the university from Florida.

For the study, published in Environment International magazine, researchers used standard wiping methods to collect arsenic from the wood surface of a 25-year-old deck in South Florida. Although the CCA wood only comes from one deck, it’s representative of wood decks built before 2004, says Gress.

The researchers put water on the wood and then wiped it off to see how much arsenic was present. They then cleaned different parts of the pavement with either tap water or a bleach solution, followed by pressure washing.

Water alone caused three times more arsenic to build up on the surface of damp wood than on dry wood, much like morning dew or light rain, and the use of bleach caused the build-up of chromate. These chemicals were also found in amounts that are well above the legal limit values ​​in the rinse water. This can pollute the floor around decks and pose a risk of exposure.

Protective steps

CCA treated wood has been used on many residential decks built before 2004 because it is very resistant to termites. In 2003, the U.S. Environmental Protection Agency pressured industry to stop using CCA to treat wood intended for domestic use, including outdoor decks, after it was discovered that arsenic was leached out of it.

The results show the importance of avoiding skin contact with wet patios, especially right after cleaning with bleach, says Gress.

CCA wood continuously releases arsenic into the environment through normal rainfall and contaminates the soil around decks, says Lena Maa, professor of soil and water sciences.

Do you have concerns about your deck or porch? These tips can provide protection:

  • Do not grow vegetables on soil near the CCA treated deck.
  • Keep children and pets away from CCA treated wood when it is wet.
  • Wash hands after children play outside on or near a CCA treated deck.
  • Do not give food to children, such as finger foods, to eat while they are playing outside and inside
    Contact with the deck.
  • Remove CCA treated materials and replace them with non-CCA wood. When you remove it, don’t cut it into pieces. Researchers say the sawdust is rich in arsenic and easily dissolves in the soil. They also say not to burn it. The arsenic in smoke and ash can harm people and animals.

Source: University of Florida

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