Playground Shade Availability and Socioeconomic Position of Students at St Louis Public Elementary Schools

Abstract

This study quantifies shade availability on public elementary school playgrounds in a US city and determines whether shade is associated with the socioeconomic position of students’ families.

Elementary schools should provide a minimum of 20 minutes of daily recess.¹ Although outdoor play is important for child wellness, a lack of proper sun protection can increase the risk of developing skin cancer. Approximately 40% to 50% of UV exposure occurs before 20 years of age²; therefore, school playgrounds must provide adequate shade to help protect children from the dangers of sun exposure. Few studies have focused on quantifying playground shade, especially in the United States. Recent New Zealand and German estimates range from 11.6%³ and 14.5%⁴ to 41%.⁵ Two-thirds of US school principals reported that their playgrounds had less than 20% shade cover.⁶ Herein we quantify shade availability on public elementary school playgrounds in a US city—St Louis, Missouri—and determine whether shade is associated with the socioeconomic position of students’ families.

Methods

All St Louis public elementary schools except charter schools were included, including 139 from St Louis County (constituting 20 school districts) and 35 from the city of St Louis, for a total of 174. The proportion of students using free and reduced-price lunch (FRL), which reflects students’ household income and serves as a socioeconomic indicator, was obtained from the Missouri Department of Elementary and Secondary Education’s Comprehensive Data System (https://apps.dese.mo.gov/MCDS/home.aspx). Google Earth Pro, version 7.3/2/5776 (Google LLC), satellite data and imagery were obtained to visualize and measure the area of each school playground and respective shade cover from trees and shade structures. All playgrounds were evaluated with Google Earth Pro by both authors independently. Adjacent grassy fields and kindergarten playgrounds were noted. Multiple linear regression was performed using SPSS, version 24.0 (IBM Corp), with the outcome variable being the percentage of playground shaded by trees or shade structures, and predictor variables being the percentage of students using FRL, total playground area (in square meters), and presence of a kindergarten playground. The latter 2 variables were included in the analysis to account for potential confounds. A 2-sided analysis of variance was used to calculate significance (P < .05). Because this study did not involve human participants or data, an institutional review board application and informed consent were not needed.

Results

Among the 174 schools sampled, the mean (SD) percentage of each playground shaded was 7.6% (7.3%), and the median was 5.6% (range, 0%-38.5%). Twenty-one schools (12.1%) had no shade. The percentage of students using FRL ranged from 6.1% to 94.9%. We found a negative association between shade and percentage of students using FRL, which translated to approximately 2 m² (22 ft²) of shade lost per 1% increase in students using FRL when accounting for the mean playground size of 3647 m² (R = −0.25; P < .01). This trend remained significant when controlling for total playground size and presence of a kindergarten playground, neither of which affected shade cover.

Discussion

Our measurements of shade cover are lower than what previous studies have found (7.6% mean vs ≤41%).⁵ With a large proportion of lifetime UV exposure occurring in childhood,² increasing playground shade may be an important step in minimizing skin cancer risk. We also found that shade cover is indeed negatively associated with student FRL, with shade availability decreasing as proportion of students with FRL rises. This finding may suggest that students at schools with less affluent children are subject to higher UV exposure during the school day, contributing to risk of skin cancer or complicating care of photosensitizing conditions.

Our study is limited to data from 1 city. Importantly, we measured tree cover in August during peak foliage; because most trees in St Louis lose their leaves in winter, our study may overestimate shade in a year-long context. In addition, we did not analyze where children spend the most time on these playgrounds or whether play equipment was shaded, which also influences UV exposure. Nonetheless, this research exposes an actionable gap in shade availability on these playgrounds and provides a template for further work in other geographic locations.