While parents often feel more secure having their children frolic in playgrounds as opposed to playing in the streets, a national investigation of public playgrounds - including 47 in Maryland - found that they can have their own hazards.

The survey, which was prepared by several Public Interest Research Groups and the Consumer Federation of America, looked at more than 1,000 playgrounds in 36 states and Washington. Several Baltimore playgrounds were surveyed, as were sites in Lutherville, Timonium, Catonsville and Towson. Six in College Park and four in La Plata also were included.

Among the dominant issues addressed by the survey, the results of which were announced recently by the Maryland Public Interest Research Group, were playground surfaces, because 80 percent of playground injuries occur when children fall on hard surfaces. On that score, Maryland ranked better than the national average: Although researchers found that 75 percent of playground surfaces nationally were inadequate, the Maryland results showed that 67 percent were not up to par.

The safety advocates said playgrounds should have a 9-inch loose surface or a soft surface that would cushion a child's fall.

A task force appointed last year by Baltimore Mayor Martin O'Malley, consisting of city parks officials and representatives from nonprofit groups, examined all 300-plus parks in the city for a comprehensive fix.

"We're doing a lot of playground renovation, knowing there's a huge problem," said Mary Porter, a design planner in the city's Recreation and Parks Department. "The mayor's task force priority was to fix the playgrounds that serve the most number of kids, so that meant the largest parks and the schools. We've covered a big sweep of town."

The playground safety survey found that 53 percent of climbers, such as jungle gyms, and 29 percent of slides in Maryland playgrounds were more than 6 feet tall, which is considered the maximum acceptable height. Nationally, 52 percent of climbers and 42 percent of slides exceed 6 feet.

Statistics show that children are more likely to suffer serious injuries when they fall from equipment that is too high or land on hard surfaces.

Nearly 190,000 children were treated in emergency rooms last year as a result of injuries suffered on public playground equipment, according to the U.S. Consumer Product Safety Commission. Nationally, about 15 to 20 children died last year as a result of playground injuries, the survey said.

"Playgrounds can be wonderful places for children to have fun and face new challenges," said Ryan Alvarez, the Maryland PIRG campaign director, "but far too many playgrounds contain hazards that can injure and even kill."