Are the Current Thresholds Adequate in the ASTM F1292 Specification for Impact Attenuation of Surfacing Materials Within the Use Zone of Playground Equipment?

This article was written in early 2009 for publication in the Today’s Playground now called the Playground Magazine published by Harris Publishing, Inc., 360 B Street, Idaho Falls, ID 83402

by Kenneth S. Kutska, CPSI
Executive Director, International Playground Safety Institute, LLC
January 28, 2009

Since the very beginning of tracking and analyzing playground injuries to children it has been know that “Falls to the Surface” has been the number one most common cause of serious injuries to children. Who falls to the surface, how they fall, where they fall from, what part of the body first impacts the surface, and what they fall upon including a myriad of surface material physical properties and environmental factors. All these variables can have a profound impact on the type and severity of impact injuries to children. The playground industry standard commonly used is the ASTM F1292 Standard. The scope of this standard is to reduce serious head injuries. Any surface system installed within the use zone of a public playground must have a maintained critical height which exceeds the fall height of the equipment. The critical height of a surfacing system is the height in full feet below which a life-threatening head injury would not be expected to occur on the surfacing system. The critical height of a surface system is the fall height when tested in accordance with ASTM F1292 which results in a peak deceleration to the head during impact of 200 g’s or less and/or peak deceleration of the head during impact related to the duration of deceleration of 1000 HIC or less.

In recent years there has been a large increase in the use of unitary surface systems as a means of complying with the ADA/ABA Accessibility Guidelines. Regardless of all the improvements to impact attenuating surface systems since 1991 there has been an increase in fall related injuries primarily in arm and leg injuries. Why is this? Is it a lack of maintenance? Is it a lack of sufficient depth of loose-fill materials? Is it environmental factors or loss of impact attenuation properties as a result of aging coupled with environmental factors?

It is probably a combination of all of these factors. The major increase in injury data seems to be directly related to the type of surface system. More arm and leg fractures are occurring on unitary surface systems versus loose-fill surface systems. Is this because of ADA/ABA accessibility requirements? Do loose-fill surface systems allow for displacement of surface materials or initial dispersment of energy at initial impact?

Advocates for injury prevention on children’s playgrounds have been questioning the effectiveness of the current industry safety standards and challenging the scope of the ASTM F1292 standard and the compliance thresholds established to reduce serious head injuries to children.

I recently participated in an in-depth session on understanding the various factors that determine a playground owner/operator’s compliance to all the standards related to accessible public playground impact attenuating surfacing systems within the use zones of playground equipment. It is imperative owner/operators understand their responsibility to purchase, install, maintain, inspect, and document their standards compliance of the surfacing system throughout the life of the playground equipment it is installed around.

Challenges to this statement will be made in the event of a serious injury to a user even if the injury is not a life-threatening head injury. If it is not compliant to all the standards it will be argued the injury may not have occurred. In addition, many have been arguing growth plate fractures are permanently debilitating even though the ASTM F15.29 Subcommittee has repeated stated that long bone fractures of any type were not within the current scope of the standards. Arguably, advocates for injury prevention would like to see a decrease in public playground injuries requiring emergency room treatment. The reality of this goal would be to lower heights of equipment, reduce motion in equipment, and all but eliminate the element of risk and challenge within children’s environment. The elimination of challenge and risk in play environments is known by child development experts to significantly reduce the value of the play experience and the developmental benefits of play.

Before we go any further with the analysis of playground safety surfacing systems a thorough search and documentation of research studies completed prior to and after 1990. The last thorough search and analysis was conducted for the United States Consumer Product Safety Commission by the COMSIS Corporation of Silver Springs, Maryland and completed in March of 1990. The conclusion of this study as it relates to safety surfacing systems focused on the criterion for determining impact attenuation thresholds for the reduction of life threatening permanently debilitating head injuries to children. The study recommended the following:

“ Recommendations for the peak g criterion

Further research is needed to determine the appropriateness of the current 200 peak g criterion in the CPSC guidelines. Furthermore limitations and uncertainties associated with the peak g model for head injury and with the 200 peak criterion include the following:

• The peak g model does not take into account the effects of impact duration, angular acceleration, impact locations other than frontal head impact, and directions of impact other than the anterior-posterior direction associated with frontal head impact.

• The peak g model has not been correlated with the risk of structural or functional brain damage, particularly for children.

• The 200 peak g tolerance limit is based on linear skull fracture data, yet functional and structural brain damage can occur at impact levels well below those produced by skull fracture.

• The 200 peak g tolerance limit is based primarily on adult data, but there are important differences in the skull characteristics and head impact responses of children and adults.”

The study also questioned the 200 g-Max and 1000 Head Injury Criterion (HIC) and its ability to reduce most serious head injuries.

In lieu of the increase in long bone fractures to children ages 5 through 12 the question has been raised as to whether a lower g-Max and HIC threshold would significantly eliminate serious temporary and long term head injuries and concussions as well has reduce the number of long bone fractures. What reductions in these current impact thresholds need to occur to demonstrate a quantifiable decrease in these types of injuries? In 1990 the conventional wisdom within the industry was that most available loose-fill compacted surface systems at a minimum depth of 12 inches would result in a fall impact that would well bellow the current thresholds at a fall of 10 feet or less. With ADA/ABA requirements and increased popularity of unitary surface systems there was a concern with the industry’s ability to deliver compliant surface system solutions that were within the budget realities of most public playground owner/operators.

The last major revision to ASTM F1292 allowed for the development of the first field test instrument whose use would soon begin to challenge manufacturer’s product warranty, installation compliance, and allow the owner/operator to verify their maintenance and surface system compliance throughout the life of the playground. This has led to some initial studies of various surface systems by government granting agencies and an increase in requirements for procurement of surfacing systems to assure standard compliance and protect the owner, designer, manufacturer, and installer prior to the opening of the playground.

There are international standards development organizations and various advocacy groups who have conducted more recent studies that unfortunately are providing inconclusive data that lead to recommendations and conclusions that can only muddy the waters for the industry as a whole. Studies in Great Britain and Australia have stated there appears to be no conclusive evidence that surfacing systems reduce the frequency and severity of injuries from falls to the surface. Some have concluded because of incomplete data or incomplete gathering of pertinent information related to this analysis that only by reducing the fall height can there be any significant reduction of injuries from falls.

I for one do not subscribe to this notion and believe that a well thought out research study that analyzes all the factors related to the cause and effect of falls injuries will show:

• Non-compliant surfacing systems result in serious head injuries and life threatening permanently debilitating injuries.

• Environmental factors outside the scope of the current standard have a negative impact on impact attenuation and will render some surface systems non-compliant

• Compliant surface systems, i.e. 200 g-Max or less and 100 HIC or less will still result in some statistically verifiable percentage of serious head injuries and permanently debilitating injuries.

• Reducing the current threshold for establishing the critical height of a surfacing system to 150 g-Max or less and 850 HIC or less will significantly reduce the frequency and severity of both serious head injury and long bone fractures.

• Verifying where the fall occurred and the fall height of equipment from where the injury occurred is consistent with the Standard’s stated fall height of the equipment involved in the injury.

Only when we can document this information can we begin to address any reduction in serious head injuries and life threatening permanently debilitating injuries plus some reduction in long bone fractures. Can this be accomplished while maintaining a quality educational playground environment without significantly reducing challenge or risk.

How the industry goes about formalizing and developing the scope of this research project will be the next challenge. Determining who should take the lead and who should fund this project is the biggest obstacle to moving forward. This research project should be a multi-disciplined effort. We should be able to capitalize on all related research that has just been completed and is currently underway throughout the world. A project of this scope will take several years to complete and the children cannot afford for us to procrastinate any longer.

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