We warned you about the dangers, now the feds are banning pressure-treated lumber.

MORE ON THIS STORY Questions and Answers from CPSC

The ban means that as of Jan. 1, the production of pressure-treated wood will be halted for good. Manufacturers have been phasing it out for months after investigations like ours turned up serious questions about how safe it is, especially for children.

It's supposed to be where children are safest: their own back yard.

So when Chuck Whittrock built his kids a swing set out of pressure-treated wood, he didn't give it a second thought.

"Everybody uses it, we thought it must be safe," he said.

But, later, after their two young boys were found to have high levels of arsenic in their blood, the Whittrocks called KIRO 7 Consumer Investigators.

We tested the children's swing set and found shockingly high levels of arsenic both on the surface of the wood and in the soil.

"That's not good, not good at all."

CCA-treated wood is preserved with arsenic and can be found in some 50 million homes across the U.S. Research shows that kids who play on it -- like the Whitrock boys -- have a higher risk of developing lung and bladder cancer, although authorities insist the risk is small.

"What we found is a relatively small risk. Essentially, you're looking at numbers between 2 and 100 per million that would face an increased risk over their lifetime," said Eric Criss, of the Consumer Product Safety Commission.

Experts say kids are especially vulnerable, because the arsenic on the surface of the wood rubs off on their hands, then they place their hands in their mouths.

Question: "You ever put you hand on the wood?"
Answer: "Uh-huh."

But even though the manufacture of new lumber has now been banned, you can still find pressure-treated wood in local home improvement stores.

Manufacturers say the current supply could last for months.

The government has some safety suggestions concerning pressure treated lumber:

--Keep food out of contact with wood, such as picnic tables.
--Children playing on it should wash their hands before eating.
--It should not be burned.
--And wear a mask dust mask, goggles and gloves when working with it.

The ban is only for residential use. Use in commercial buildings is still allowed.