The ground-up tire rubber filling playgrounds in Minnesota and across the country is facing fresh scrutiny in Minneapolis amid growing concerns the bouncy surface contains toxic chemicals.

On Friday, the Minneapolis City Council will debate whether the city should use whatever leverage it can to discourage the use of tire mulch on playgrounds and athletic fields. Those decisions are largely left to school and park officials, but some City Council members are so concerned about the potential dangers to Minneapolis residents that they want to ensure city money isn’t spent on the material.

“I’m convinced the stuff is potentially dangerous enough that we should use alternatives,” said Council Member Cam Gordon, who has spearheaded the effort to curb their use.

The debate echoes one being held in communities around the country, as school and park officials search for the most safe and durable surfaces for athletic fields and playgrounds. While studies into the health effects of recycled tires have not been conclusive — major studies led by health officials in California and the U.S. Environmental Protection Agency are still underway — the concern is the presence of toxic chemicals.

In Edina, parents raised concerns about the material in 2016 when the school district proposed replacing four grass athletic fields with synthetic turf with crumb rubber infill. But school officials opted to proceed with the projects, saying the material is strong and safe.

The Park Board doesn’t use tire mulch on playgrounds in Minneapolis, but has crumb rubber infill in eight synthetic athletic fields, making them far more durable than natural fields and providing a consistent playing surface for sports like soccer.

The city does not control any playgrounds or playing fields that use waste tires for cushion, but the city is a significant contributor to parks funding.

Last year, the City Council agreed to a 20-year Neighborhood Park Plan that would provide $11 million annually for park maintenance and rehabilitation. That money, and how it is used, could be affected by the council’s vote, though neither Gordon nor Park Board officials are certain.

Park officials say a city prohibition on the material would disrupt plans to expand the Currie Park field in Cedar Riverside and put a dome over it, since the field uses crumb rubber for cushion. The soccer field at Stewart Park in the Phillips neighborhood was the first to be installed with crumb rubber six years ago.

“We are the recreation experts, the city is not,” said Park Board Commissioner Scott Vreeland. “The discussion of the city micromanaging our fields concerns me.”

It’s not clear to the Park Board or the City Council whether action by the city would prevent the Park Board from using crumb rubber on athletic fields. Lawyers for the Park Board said the body has broad discretion on how to use the money from the 20-year Neighborhood Park Plan.

“There was some question that the Park Board funding flows through the city, so this is what caused the big kerfuffle,” Gordon said.

Park Board Superintendent Jayne Miller said the main priority is safe fields, and crumb rubber from tires appears to be the safest for now because the proposed alternatives “need to be examined by science and research.”

Using natural turf is a lot of work, Miller said, requiring long growing periods, fertilizers and irrigation, and maintenance, especially for heavily used fields.

The Park Board said it wants the City Council to delay action for 30 days to give its lawyers time to investigate whether the city has authority to enact the crumb rubber ban.

And if the city doesn’t allow a delay, the Park Board requests a moratorium on city-financed projects using crumb rubber, but no prohibition on projects funded through the 20-year Neighborhood Park Plan.

The City Council is expected to vote on the matter Friday morning.