Two senators have asked President Barack Obama to launch a "comprehensive" study into the potential health risks posed by "crumb rubber" turf, a surface made of recycled tires used on playgrounds and athletic fields across the country.
In a Thursday letter to Obama, Sens. Bill Nelson of Florida and Richard Blumenthal of Connecticut said the possibility of a link between turf and cancer warrants more scrutiny, and asked for the White House to "spearhead" a study that draws on the expertise of the Environmental Protection Agency, the Consumer Product Safety Commission and the Centers for Disease Control.
"Given that millions of children and young athletes play on crumb rubber synthetic surfaces every day," wrote the senators, any possible "correlation with cancer cannot be ignored."
A White House spokesperson said, "We have received the letter [and] we appreciate the concern of the senators on this issue. The administration is aware of the issue and will respond to the senators soon."
Related: Read the Original NBC News Report
CPSC Chairman Elliot Kaye told NBC News he believes the senators' request is "consistent with what I hope to see and is a wiser public policy approach than asking different agencies to conduct different investigations of the same topic."
The EPA referred NBC News to a published statement from Nov. 18 that said the agency "supports more comprehensive efforts to identify potential exposures to tire crumbs and better assess risks." The CDC did not immediately respond to a request for comment.
The two senators are the latest congressional officials to call for research on crumb rubber since NBC News begin airing and publishing a series of reports on the playing surface in 2014.
Related: Watch the Original NBC News Report
No studies have linked crumb rubber to cancer or any disease, but some experts believe more tests are needed to determine whether the product is safe for use. The turf industry says that dozens of studies have shown there is no health risk, but also believes the federal government should take a clear position.
In response to Nelson and Blumenthal's letter, a coalition of artificial turf manufacturers reiterated the industry's belief that all available evidence shows the surface is safe.
"We certainly support any additional research," said the Safe Fields Alliance in a statement. "However, we strongly believe that, when considered in aggregate, the existing body of research presents a clear scientific case that playing on synthetic turf fields with crumb rubber poses no more of a health risk than would result from playing on natural grass fields."
Nelson and Blumenthal's letter to the White House comes two months after a letter to Kaye in which they asked the CPSC to "devote additional resources to conclusively determine whether these products can be safely played on by young children and people of all ages."
The senators noted that the CPSC said in September it would provide technical assistance to an evaluation of crumb rubber now being conducted by the California Office of Environmental Hazard, but said the CPSC should "lead the independent federal investigation on this important matter."
CPSC spokesman Scott Wolfson said at the time that the agency has "deep respect" for Blumenthal and that the CPSC continues to plan to provide support to California's upcoming study.
In Thursday's letter to the president, Nelson and Blumenthal lauded the CPSC's support for the California study, but said "a more comprehensive federal study" that enlists the CPSC, the CDC and the EPA was necessary.
In October, the House Committee on Energy and Commerce sent a letter to the EPA asking the agency to weigh in on whether crumb rubber is safe for young athletes, and cited the NBC News reports.
At the time, EPA spokeswoman Liz Purchia said "new science" was needed to answer questions about turf safety and that "existing studies do not comprehensively address the recently raised concerns about children's health risks from exposures to tire crumb."
"We know communities want more information as they make decisions to repair and replace their playing fields or as they consider a number of alternate materials available in the market today."
The EPA is "actively engaged" with the California study, said Purchia, and EPA scientists have been providing technical advice to study planners.
Purchia cited previous studies done by federal, state and local agencies and said "none of these studies showed any elevated health risk from playing on fields with synthetic turf or crumb rubber."