Use care when you clean your old wooden deck using a pressure washer. Although it may look better, you can be exposing yourself, your family, and your pets to dangerous carcinogens.

If your deck was manufactured before 2004, it's made of CCA-treated wood, and contains the carcinogens arsenic and chromium. When wet, the wood releases three times as much arsenic as dry wood, according to a study from the University of Florida.

If you clean with bleach, the toxic brew is even worse. Bleach causes the wood to release chromate, another carcinogen.

Even though decks from CCA-treated wood haven't been built in more than 10 years, a 2007 study found that around 20 million homes still had the decks made from the wood, and since they can last up to 40 years, many of the decks are still being used.

Julia Gress, a postdoctoral scientist in the department of soil and water sciences at the UF Institute of Food and Agricultural Sciences, and colleagues used wipes to collect arsenic from wet 25-year-old treated wood. They then cleaned different pieces of the same deck with either tap water or water containing bleach, then pressure-washed the area.

They found that water alone caused three times more arsenic to form on the surface of wet wood than dry wood, similar to effects from morning dew or light rainfall. Cleaning with bleach caused chromate to form.

In addition, they found that the rinse water contained much higher limits of the carcinogenic chemicals than regulatory limits, showing that an ordinary rainfall can contaminate the soil around decks.

Gress offers the following suggestions to limit your exposure to CCA-treated wood:

• Don’t grow vegetables on soil near the deck.

• Keep children and pets off of the deck when it’s wet.

• Wash children's hands after they play on our near a deck.

• Don't give children snacks to eat while they are in contact with the deck.

• Remove CCA-treated wood and replace them with non-CCA material. Don't cut or burn wood, since the sawdust is high in arsenic and arsenic will be present in smoke and ash.