Written by Jennifer Vanos (Texas Tech University, USA) and Robert Brown (University of Guelph, Canada). This article originally appeared on UGEC Viewpoints.

When parents send their children off to school they expect them to spend their days in a safe and healthy environment. There’s plenty of evidence of how outdoor play promotes personal health and well-being, and access to a playground in an effectively designed space is a large component of being physically active. But not all playgrounds are as safe as they might appear. With canopy coverage lower than many city averages, children might be exposed to increased levels of ultraviolet radiation (UVR) that can lead to erythema (sunburn) and an elevated risk of skin cancer.  In addition, surfaces that might look to the human eye to be cool and inviting can be extremely hot.  These hot surfaces create two potentially dangerous conditions for children: burned skin from direct contact, and very high infrared radiation load that can increase the risk of hyperthermia.

The use of Evidence-Based Landscape Architecture (Brown and Corry, 2011) can be helpful when designing playgrounds to be safer and healthier through bioclimatic design.  Thermal infrared photography makes hot surfaces visible to the human eye through false-color imaging so hot spots can be identified and ameliorated.  3D Computer modeling programs such as Google SketchUp can be used to analyze sun and shade patterns and test potential designs to determine if children will receive too much, too little, or just the right amount of solar radiation.

Children are more vulnerable to heat stress than adults under high temperature conditions (Falk and Doton, 2008), and also have a higher sensitivity to UVR exposures (e.g., Oliveira et al., 2006). Inconsistencies also exist in the literature with respect to heat-health outcomes in children as compared to adults, and what their true exposures to temperature and radiation may be (Vanos et al., 2015). Two principal reasons exist for these inconsistencies: 1) the actual (or true) exposures of temperature and radiation are unknown due to the use of sparse observations, which may cause exposure misclassifications (e.g., Kuras et al., 2015) who studied individually experienced temperatures); and 2) there are many fewer research studies on the impacts of heat in children compared to those for adults (Falk and Doton, 2008).

Figure 1

Figure 1: Playground study sites in Gilbert, Arizona, illustrating the summer afternoon surface temperatures in sun and shade, with shade greatly improving heat safety. (Image Credits: Jennifer Vanos, Ariane Middel). Photo on left is cover image from Landscape and Urban Planning. Volume 146, February 2016, Pages 29–42.

In terms of play equipment, a green, molded plastic slide with a high density polyethylene coating was measured at 71.7°C in the sun and 43.9°C under tree shade. A beige-colored slide of the same material and coating was measured at 63.9ºC in the sun and 40.6°C under the shade tree. For a point of reference, the burn threshold for the material of which the slide is made is one minute at 60°C, five seconds at 74°C and just three seconds at 77°C (ISO 13732, 2006), meaning a child’s skin does not have to contact the surface for very long to be burned. The temperatures of each piece of equipment are influenced by numerous biophysical variables, such as shade, sky view factor, solar energy, the material and type of equipment, heat capacity, admittance, conductivity, and length of exposure to sun.

To read the rest of this article, visit UGEC Viewpoints.

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