Arsenic is a deadly poison so what's it doing at the playground? Since the 1970s, wood filled with arsenic has been hammered into outdoor decks, benches, picnic tables and playsets. The federal government banned arsenic-treated wood in 2004 for playgrounds and home use. But if the climber or deck your child plays on was built before 2004, chances are it's loaded with arsenic.

Thirty years ago it seemed like a good idea. Suck the water out of wood and inject chromated copper arsenate (CCA) to create a highly rot-resistant wood. This is the greenish-gray tinted wood commonly called pressure-treated, or Wolmanized. CCA-wood stands up to weather, mold and pests but we now know the arsenic leaks out, which means kids are literally playing with poison. Today the pressure-treated wood you'll find in stores is made from preservatives that are less toxic.

Arsenic causes cause cancer, including skin, bladder and lung cancer. It's much more toxic than scientists once believed, even at very low levels. Young children's growing bodies are extra vulnerable to the cancer-causing poison. Kids tend to ingest arsenic by putting their hands in their mouths after touching treated wood. Arsenic can also cause nerve damage, immune system and hormone disruption, diabetes, high blood pressure and heart disease.

"The key is to get it off the hands before the hands go in the mouth," says Dr. Gina Solomon, a NRDC Senior Scientist.  "Don't have a picnic at the park.  There's no level of arsenic that's considered safe."

Fully 90% of all outdoor wooden structures are CCA products. What's more, tests reveal high levels of arsenic on kids' hands, soil and mulch under wooden structures get contaminated, too, and arsenic leaching doesn't decrease over time-even structures 15 years old release just as much arsenic as newer ones.

What can you do to keep your child safe? Be vigilant about contact with treated lumber and wash hands thoroughly. Don't allow food anywhere near arsenic-treated surfaces such as old picnic tables. Don't store toys under decks, and don't let kids play there. Keep kids and pets away from soil under decks and nearby treated wood. Soil from 40% of US backyards and parks exceeds the EPA's Superfund levels for hazardous waste cleanup.

The best option is to seal the wood with a solid or semi-transparent deck stain. Inspect your deck every six months and seal it at least once a year. Sealing a solid or semi-transparent deck stain has an immediate effect on arsenic exposure but varnishes and clear sealers do not give adequate protection.

The safest step is to replace all arsenic wood, plus the top few inches of soil or wood chips around it. Replace high traffic areas like railings and steps first if full replacement isn't practical. But beware: Never burn treated wood and minimize all sawing. Inhaling arsenic dust or gas is worse than swallowing it and can cause acute poisoning. Contain any demolition dust with a tarp and treat both the tarp and junk wood as hazardous waste. Likewise, never sand or pressure-wash arsenic-treated wood.

For new construction, look for naturally rot-resistant wood (Forest Stewardship Council certified cedar and redwood are good choices), wood composites, recycled plastics or less toxic pressure-treated lumber.