Research Article: Playground lead levels in rubber, soil, sand, and mulch surfaces in Boston

Date Published: April 25, 2019

Publisher: Public Library of Science

Author(s): Khaled S. Almansour, Nicholas J. Arisco, May K. Woo, Anna S. Young, Gary Adamkiewicz, Jaime E. Hart, Jamie C. DeWitt.


Rubber surfacing is often used in playgrounds due to its potential injury prevention benefits and as a way to recycle waste tires. Available research on chemicals in recycled rubber has focused on synthetic turf applications, but is limited for playground rubber surfacing. Potential lead contamination from vulcanizing agents used in rubber surfacing are a possible concern; however this has not been researched. We examined levels of lead in poured-in-place rubber and compared them to levels in soil, sand, and wood mulch materials from 28 randomly selected playgrounds in Boston, MA, USA using X-ray fluorescence. To evaluate the association between material type and lead concentrations, we conducted a two-way ANOVA with repeated measures and built a linear regression model controlling for distance to major roadway, neighborhood-level status as an environmental justice area, peeling paint on the playground, and rubber condition. Average lead levels were 65.7 μg/g for soil, 22.0 μg/g for rubber, 8.5 μg/g for sand, and 9.0 μg/g for mulch. Our finding of lower concentrations of lead in sand and mulch compared to rubber and soil should be used to inform playground design to optimize children’s health, alongside other chemical and safety considerations.

Partial Text

Rubber surfacing has become more widespread in playground design due to its potential injury prevention benefits [1–3]. From 2005 to 2015, the amount of ground tire manufactured for playground use rose from 19,000 to approximately 225,000 tons [4]. Several types of playground surfaces are constructed from tire rubber: rubber tiles, poured-in-place rubber, bonded rubber, loose-fill rubber mulch, and synthetic turf [5]. In addition to its shock-absorbent qualities, rubber surfacing is also a useful and environmentally sustainable application for recycled waste tires. Roughly 300 million auto tires are disposed of in the United States every year, and are often restricted from landfills to reduce the potential for tire fires and mosquito breeding habitats [3, 6–8].

Baseline prevalence of the covariates of interest are summarized in Table 1 and Table 2 shows summary statistics for average lead levels measured in each material type. Sand had, on average, the lowest lead levels while soil had, on average, the highest lead levels. Rubber had the second highest average lead level. The highest average lead level in any playground was 336.6 μg/g in soil. Among all the non-averaged sample measurements, one soil sample reached 613 μg/g lead. All other measurements ranged from below LOD to 217.1 μg/g. Nine playgrounds had a soil sample greater than 80 μg/g and two playgrounds had a rubber sample greater than 80 μg/g.

Our sample of 28 playgrounds in Boston demonstrated that sand and mulch had lower lead concentrations compared to poured-in-place rubber and soil. Soil lead concentrations (mean 65.66 μg/g) were typical for Massachusetts [37]. At our sample sites, soil was typically found on the edges of playgrounds, outside main play areas. As a result, children may not be exposed to soil lead with as much frequency as the other materials assessed. Rubber surfaces were commonly found directly underneath and around play structures. Rubber lead concentrations were similar in range compared to those found in recent crumb rubber infill samples from synthetic turf surfaces in New York City (


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