The University of Northern Iowa-based National Program for Playground Safety has won a half-million dollar grant to study playground surfacing materials made from recycled tires. Heather Olsen, a spokeswoman for the program, says most kids who’re hurt on playgrounds can blame the surface on which they fall. She says over 70-percent of playground injuries are due to falls to hard surfaces. Olsen says many playgrounds in Iowa have surfaces comprised of things like pea gravel, wood chips or sand. Olsen says those are dangerous for kids when they fall.Olsen says the grant will allow the National Program for Playground Safety to test surfaces made from recycled tires that are made in Iowa. At least one manufacturer of rubber playground mats will be chosen to install the mats at a number of randomly chosen playgrounds across Iowa. Data on injuries at the playgrounds will be collected before and after installation of the mats to determine whether the mats made any difference. The money for the study comes from the state. Olsen says 97-percent of the money will be used to purchase and install the mats.