Study asks: How safe is crumb rubber used as mulch in some playgrounds?

Olivier Le Queinec /

Safety is a main consideration when designing playgrounds for children. One popular material used when designing soft surface playgrounds for children safety is crumb rubber made from shredded recycled tires, but this material may bring additional health risks.

In a new student-led study, Texas A&M University School of Public Health doctoral student Leanne Fawkes along with Environmental and Occupational Health Capstone students Brenda Gonzales, Kathryn Klumb and Christine Yeboah-Agyapong, assessed the level of heavy metal exposure risk in playgrounds around the Bryan-College Station area. The study measured heavy metal concentrations in crumb rubber mulch and compared them against safety standards from the United States and European Union.

The research team collected several samples of crumb rubber mulch from 16 parks in Bryan and College Station. They then analyzed those samples in the laboratory to measure concentrations of heavy metals like lead, chromium and zinc. Next, they combined the results for samples from each park to produce average values and compared those values to existing safety standards. The research team chose research methods and safety standards that are comparable to those used when testing toys for heavy metals in the United States and Europe.

The analysis detected 14 different heavy metals in the samples, four of which had concentrations too low to be compared to safety guidelines. This left 10 heavy metals for comparison; however, all 10 were well within American and European safety guidelines. These results agree with previous studies of crumb rubber used in athletic fields and show that crumb rubber mulch use in playgrounds presents minimal risks that are offset by injury risk reduction.

Although these findings are reassuring, the study focused solely on heavy metals and did not address other potentially harmful substances that could be present in crumb rubber. The study also concerned itself with hand-to-mouth and object-to-mouth exposure routes, which are common heavy metal exposure routes in children and as such are used when assessing toys. However, this study only measured heavy metals in crumb rubber and did not evaluate the extent of heavy metal ingestion in children. Additionally, the study did not look into other exposure routes such as skin contact or inhalation of off gassing substances or particles from deteriorating materials.

The researchers note that future studies should investigate additional exposure routes and compare heavy metal concentrations between different types of crumb rubber.

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