Emerson Playground in La Crosse, Wisconsin, before rubber chips were replaced. (Photo courtesy of Jamie O’Neill)
It seems like an environmentally friendly way to keep automobile tires out of landfills: Grind them up into chips and use them as a soft, safe ground cover on playgrounds.
But a team of students and instructors in La Crosse discovered that what looks like an attractive re-use of a ubiquitous and bulky form of industrial waste might be soft — sort of — but its safety is questionable at best. The result has been a community campaign to start removing the rubber mulch from local playgrounds and replace it with safer alternatives.
It all started with a University of Wisconsin-La Crosse student’s senior project three years ago.
Grace Koch graduated in 2021 with a major in biology and a minor in environmental studies. That spring for the environmental studies program she had to complete a capstone project applying scientific research to an issue that had community impact.
“I was very interested in environmental health — how humans interact with their environment,” Koch says.
Working with Jamie O’Neill, a UWL graduate who had stayed on to serve as a mentor in the environmental studies program, Koch decided to investigate the properties of the recycled tire rubber chips that were turning up on playgrounds. The idea arose after hearing from parents who were concerned about whether the ground cover was safe, Koch says.
“I talked to community members who told me how chips were dirty — kids were putting them in their mouths, and they left black residue on their hands,” she says. And baking in the warm summer sun, “they get really hot, too.”
She looked for toxicology research on the rubber chips but didn’t find much. “Tires were never designed for human contact,” she says. “There’s limited research on toxic exposures from them.”
The chemical components of tires include aromatic hydrocarbons such as benzene and volatile organic compounds. They also include zinc, which is “cooked” with rubber in a process called vulcanization to make them flexible. There’s a high lead content as well.
In addition, there are chemicals “picked up on the road when the tires are acting as tires” before they’re disposed of, Koch says.
Chemical components
While rubber chips used as ground cover haven’t been subjected to much research, “there’s research on these specific chemicals and how they interact with children’s health,” she says.
In their new life as playground materials, the rubber’s chemical components “off-gas,” leaching into the air as well as rubbing off on the hands of children who then lick their fingers or breath in the dust as well as the leaching gas, or simply absorb chemicals through their skin, Koch says.
For her project Koch reviewed how the chemical components in rubber affect children’s health, from the organic chemicals to the heavy metals to how hot dark rubber chips get in sunlight.
Adelade O’Neill holds rubber chips after playing on a rubber chip playground in La Crosse, Wisconsin. (Photo courtesy of Jamie O’Neill)
Lead is one important concern because of its longer-term harm to brain development, but Koch cautions that it’s hard to draw a direct line from rubber mulch to lead poisoning.
“We’re not saying that X exposure [from rubber mulch] equals Y health outcomes,” Koch says. “The research is not there to say that. What you’re worried about is how long they’re exposed [to a toxic substance] and how much of it.”
Still, the lead exposure is important to consider because “kids have such a critical developmental window” as they are growing up, she adds.
“This is just one element of what kids can be exposed to in our environment,” Koch says. “Most exposures are beyond our control; this is something we can control and we can take action on.”
For the project, Koch prepared a pamphlet listing bullet points about the problems with rubber chips, healthier alternatives and replacement costs. She did outreach to Parent-Teacher Organizations and the La Crosse school district as well as to UWL.
Community organizing
Local parents, university faculty and other community members formed SPACE — short for Safer Playspaces and Community Environments — to begin spreading the word in the community.
Koch’s project resonated with her professor, Alysa Remsburg, who didn’t like the chemical smell on her toddler’s rubber mulch playground surface.
Remsburg persuaded the university’s child care center to replace the rubber chips on its premises. When Koch’s project was complete, Remsburg, O’Neill and another parent supported Koch in a presentation of her findings to the school district.
Willie Bittner was concerned that his son was eating the rubber chips on the playground at school. When washing his kids’ clothes, “I was looking in all their pockets or they’d wind up in the laundry,” he says
When his children’s school began a fundraiser for new playground swings, “We were able to talk to the school district so that when they were putting in the swings they would put new wood chips in.”
SPACE joined Thriving Earth Exchange (TEX), a project of the American Geophysical Union that links local groups with scientists who can help them address community concerns about the environment, public health and related matters.
“We had all this research,” O’Neill says, and the parents and others in SPACE thought TEX “would help keep us on track toward getting this information out.”
Mackenzie Mindel, a member of the La Crosse city council and chair of the city’s climate action committee, worked with community groups to put funds in the city’s capital budget to replace rubber chips in Emerson Park, one of the city’s parks.
Remsburg, a participant in the La Crosse climate action plan, took part in a project to see whether rubber chip ground cover contributed to urban heat islands. On 95-degree days she recorded temperatures on the dark, rubber chip surfaces of 140 degrees.
Sampling parks and playgrounds
Through Thriving Earth Exchange, O’Neill and SPACE connected with Kristofer Rolfhus, a UWL chemistry professor. He started directly analyzing ground cover materials in use around the community, enlisting his students in the project.
Last year they analyzed 32 samples of materials from 10 city parks and 10 school playgrounds. There were 17 samples of wood chips, 10 of rubber chips, two of “crumb rubber” — a smaller rubber-based ground cover — two of sand and one of plain soil.
“Part of Thriving Earth Exchange’s goal is to have community involvement,” Rolfus says. “Seventeen or 18 community volunteers collected samples for us.”
Because they knew that kids end up ingesting ground cover materials where they’re playing, the researchers submerged the samples in a highly acidic solution to simulate stomach acid.
“What we found is that the rubber chip had more of the metals that we were concerned about, in particular lead,” he says —12 times the amount of lead that the wood chips showed.
The findings confirmed the concerns that Koch identified in her original project — that the chemical components in rubber made a case against using them on playgrounds or wherever kids would be exposed to them.
O’Neill says that SPACE’s philosophy has been to start local and serve as a source of information.
“The SPACE group has never pushed anybody to change,” O’Neill says, opting instead to show up when others in the community turn to it based on its reputation.
This weekend, SPACE is unveiling a 32-page guidebook — or toolkit — to give other interested people across the country a head-start if they want to go after rubber mulch ground cover where they live. While it’s published and distributed online, it can be downloaded and printed out as well.
“We are hoping that it actually will have a reach across the whole United States,” O’Neill says. “We’d like people to be seeing the research, think about it and make an informed decision. The more risks we’ve seen with rubber chips, the more we think we need natural solutions.”
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