Recycled rubber, hailed as an eco-friendly answer to toxic tire dumps and a revolutionary surface for safer playgrounds, has been a hot item.

Apparently, a little too hot.

Recycled rubber strips, mulch and mats have become the industry standard for spreading over the grounds of outdoor swing sets and jungle gyms. The superiority of recycled rubber to turf and grass in reducing children's injuries was cited a decade ago by the U.S. Consumer Product Safety Commission.

But officials and parents are questioning the flammability of the rubber and whether some rubberized landscapes, especially in the summer sun, are simply too hot to handle for young children.