Rubber playground surfaces may contain high lead levels

By Carolyn Crist

Rubber playground surface material may protect kids from some injuries but could be harboring a different source of harm, a study in Boston suggests. 

Researchers tested lead levels in the soil, sand, mulch or rubber surface materials in 28 playgrounds and found the rubber surfaces often averaged two or three times the lead levels of the other materials. Many of the highest lead levels were also found in soil surfaces, making sand and mulch the healthier surface choices for playgrounds, the study team writes in PLoS ONE. 

“Playgrounds use a variety of materials to protect children against injuries. However, we should always consider the full suite of health effects associated with materials that children come into contact with,” said study author Nick Arisco of the Harvard T.H. Chan School of Public Health in Boston. 

Most research on lead exposures in children’s outdoor play areas has focused on soil contamination. Rubber surfaces have been used more in recent years for injury prevention and to recycle waste tyres, he said. 

“Understanding the benefits and risks of using different materials can help inform healthier playground design moving forward,” he told Reuters Health by email. 

Arisco and colleagues examined lead levels in poured-in-place rubber and compared them to levels in soil, sand and wood mulch materials from randomly selected playgrounds in neighbourhoods representing every socioeconomic category in the city. They chose Boston in part because from 2009 to 2013, the lower-income neighbourhoods of East Boston, North Dorchester, Roxbury and Mission Hill contributed a disproportionate number of the entire city’s cases of elevated blood lead levels in children. 

In the study, each playground tested had at least two types of surface material, so a total of 85 samples were included in the analysis. Overall, the testing found that average lead levels in soil surfaces were 66 microgrammes, or parts per million, per gram of soil. For rubber surfaces, the average was 22 microgrammes per gram, and mulch averaged 9 microgrammes per gram with sand averaging 8.5 microgrammes per gram. 

For rubber and soil, however, there were wide ranges of readings. One soil sample exceeded the 400-microgramme limit set by the Environmental Protection Agency for play areas, the study team notes. In addition, nine playgrounds had a soil sample greater than 80 microgrammes. 

Two playgrounds had a rubber sample with greater than 80 microgrammes of lead per gram, which exceeds the 80-microgramme limit set as a residential soil guideline in California. Public health experts prefer to use the California limit, especially for play areas where children as young as 6 months old play. 

“One reason children are especially vulnerable to exposures to lead and other chemicals is because they spend a lot of time on the ground, touching things and then putting their hands to their mouth,” Arisco said. 

Parents can encourage children to wash their hands after playing on playgrounds and remove their shoes at the door to prevent contaminated soil from tracking inside. For outdoor play areas at home, parents can cover the soil with a top layer of clean sand or mulch, he added. 

In addition, the Centres for Disease Control and Prevention created an online guide to preventing lead poisoning that also answers frequently asked questions. No safe blood lead level in children has been identified, and even low levels can affect attention and academic achievement, according to the CDC. 

“Unfortunately, urban soils are often invisibly and severely contaminated with lead dust generated from multiple sources,” said Howard Mielke, an environmental health researcher at Tulane University School of Medicine in New Orleans, Louisiana. 

Mielke, who wasn’t involved with the research, noted that one option to reduce lead exposure used by some childcare centres he has studied was to import low-lead soil from outside of the city to put in play areas. 

“The public needs to be aware that urban soils became invisibly lead-contaminated [in past decades] as a result of industrial activities,” he said by email. “Fortunately, the amount of lead in soil is decreasing since lead was banned in gasoline.”