Unintentional injuries are the leading cause of death and one of the leading causes of hospitalization for children over one year in Canada [1]. Sports and recreation injuries, including injuries on playgrounds, are a common cause of unintentional injury [2]. For example, over a one year period (2004-2005), 8,231 children 14 years of age and under in Ontario visited an emergency department because of a playground injury and of these, almost 6% required at least one night in hospital. More than half (58%) of those injured were between 5 and 9 years of age [3]. Previous studies have identified improving school playgrounds as a promising strategy to prevent these injuries [4, 5]. Upgrading playground equipment may be one way to reduce the burden of playground injuries because injuries due to falls from equipment are more severe than other falls on the playground. One previous study reported that fractures from playground equipment falls are 3.9 times more likely to require hospitalization and or surgery than are fractures from standing height falls on the playground [6].

In general, childhood injuries vary by socioeconomic status (SES). Injury morbidity and mortality are strongly associated with factors such as poverty, single parenthood, low maternal education, poor housing, large family size and parental drug and alcohol abuse [7]. As SES declines, the risk of injury mortality increases [8–11] as does the rate of non-fatal injuries [12–17]. In some cases, this relationship may be linked to the environment in which children live. For example, children living in deprived neighborhoods have higher rates of injury than children from more affluent areas [15]. A previous Canadian study found that children with the lowest SES had 1.37 times higher rates of recreation and play injuries, compared to children with the highest SES [13]. The prevalence of playground hazards has been found to be higher in poorer areas [18, 19].

In the summer of 2000, a program was initiated by the Toronto District School Board to upgrade school playground equipment throughout the city to comply with new Canadian Standards Association (CSA) standards for playground equipment that address equipment height, surfacing of playgrounds, entrapment angles, and other safety issues. Equipment that was deemed to be the most unsafe (potential for falls from heights greater than 2 metres, potential for entrapment, or non-absorbent surfacing) was removed immediately. Equipment that was thought to be able to be repaired was retrofitted. Schools then had the opportunity to replace the equipment, or to leave the schoolyards without new equipment. Subsequent investigation showed that compliance with the playground standards was associated with a reduction in playground injuries [20]. The objective of this study was to determine the association between playground injury and school SES before and after the upgrading of playground equipment to meet CSA guidelines.

This study examined the relationship between socioeconomic status and outdoor injury rates in elementary school children. A significant relationship was found between low SES and playground injury rates. However, subsequent to the modification of the play equipment, the relationship between LOI score and injury on play equipment was not statistically significant. Further, after the playgrounds were modified, the injury rate for play equipment dropped across all schools.

The initial association between SES and all outdoor injuries is supported by previous research related to unintentional childhood injuries and SES [10–16]. However, that there was no significant relationship between the rate of playground injuries that occurred on play equipment and SES status in schools subsequent to the modification of playgrounds may provide important insight into mechanisms for preventing childhood injuries. The play equipment is a controlled environment, and had been modified to meet CSA standards across all the schools in the school board. Our results suggest that the program to improve the play equipment appears to have been successful in equalizing the risk of injury on equipment between schools with different SES scores. This result supports the concept that modification of the built environment is a successful strategy to reduce inequity in childhood injury [22].

In general, the relationship between SES and injury is not consistent across different types of injury. Sports and recreation injuries are more common in children from a higher SES, perhaps because they have increased access to facilities and resources to be able to participate in these types of activities [12, 13, 23–26]. For example, one study found that children of higher SES had a higher injury rate from drowning, because their families were more likely to have a swimming pool at their house than children of a lower SES [23]. Our results cannot be explained by differential access to recreational equipment and facilities since all of the schools had play equipment available that was required to meet the same safety standards. However, it is possible that play equipment at poorer schools was of poorer quality prior to the upgrading of equipment.

Another methodological concern related to a lack a socioeconomic gradient in non-fatal injuries has been explained by claiming that low SES individuals may not have equal access to care and therefore, some non-fatal injuries go unreported [26]. If individuals do not have access to health care, or cannot afford it, they may be less likely to be included in the data for minor and less severe injuries [27–29]. However, this is unlikely to explain our findings because reporting was done by school staff with no consideration of whether the injury was treated at a health facility. Further, schools have standardized guidelines related to the reporting of incidents.

Although the playground injury rate for all injuries decreased subsequent to the upgrading of equipment, a socioeconomic gradient for non-equipment injuries remained. Of particular concern is the increased socio-economic disparity in non-equipment injuries. We hypothesize that the socioeconomic disparity in non equipment related injuries is explained by a difference across schools in playground environment outside the equipment area. Although the schools could not provide us with evidence related to differences between schools with different LOI scores, we believe that differences may be related to the availability of funds to upgrade the outdoor environment and the presence of adults on the playground. For example, schools in wealthier areas may have had the ability to raise funds to make improvements to fields, retaining walls, and other outdoor areas, whereas, poorer schools may have only upgraded the playground equipment. There may also be differences across schools in the presence of adults in the school yard. Parents in wealthier neighbourhoods may be more available to volunteer to oversee students during the midday break. These differences warrant further investigation.

There were several limitations to this study. First, the threshold for reporting injuries is fairly low and there may have been differential reporting of injuries between the schools. It is possible that there was a systematic tendency to report more superficial injuries in lower socioeconomic schools. However, all schools have the same guidelines for reporting an injury, so the variation by SES is not likely to be due to reporting differences. A second limitation is that the validity of the LOI score has not been extensively tested, although it is based on actual census data of the school catchment areas. Finally, it is difficult to determine whether changes in injury rates are a result of the intervention to upgrade playground equipment to a standard safety level throughout Toronto schools or whether other factors, such as increased teacher supervision, or differential exposure to playground equipment in schools with different SES contributed to the difference in injury rates. It is possible that children played less (or more) on equipment after it was replaced. Further studies in this area should include measures of exposure to play where possible.

A goal of the school board that participated in this study is to "identify and eliminate socio-economic class biases and barriers in Board policies guidelines, day-to-day operations, protocols, and practices" [30]. The results of this study suggest that one way to achieve this may be to equalize the risk of injury on playground equipment. The next injury prevention challenge for schools is to find methods to equalize the risk of injury in all areas of the playground. It will be important to identify appropriate strategies for reduction of non-equipment injuries. These strategies may include increased supervision, behavioral intervention programs, more structured activities, and changes to other aspects of the built environment. The school playground is an important learning environment for all children, and it is essential that children have equal opportunity for safe play in all school playgrounds.

Upgrading of school playground equipment to meet CSA standards reduces the socio-economic gradient for this common cause of childhood injury.