The result of such a ban would likely have gone in the direction of parents buying larger, more powerful ATVs as an alternative for their kids to ride, making it much more dangerous for them than if they had been riding ATVs designed for their size and strength.
Banning ATVs may not have been the intent of the CPSC, though. The ban on lead “products” seemed to be brought on because of the possibility of said “products” being consumed by children.
That’s right, eaten.
I can’t speak for everyone, but I don’t remember ever seeing my kids trying to eat the quads. And if they did, I'm sure they can't eat enough to do any real harm, from the lead content that is.
The stay of enforcement is valid for all vehicles made before May 1, 2009. It is also valid for most replacement parts that have less lead than the OEM parts.

