For many athletes who play on artificial turf, the tiny granules of rubber that pad the field are familiar and ubiquitous. The black specks often get trapped in folds of clothing, carried home in shoes or embedded in scrapes and under fingernails.

Crumb rubber infill — the most common material used in artificial turf fields across the country — is intended to improve safety and create a more accessible, easily maintained playing field. But after recent public concerns about possible health risks from exposure to crumb rubber, several local jurisdictions are searching for clearer answers about its potential dangers and considering alternatives.

The issue is a modern one.

Synthetic turf with an “infill” system — involving a layer of tiny granules of rubber, sand, or other material between the turf fibers and a backing layer — was introduced in the late 1990s and has since become a popular alternative to natural turf fields, according to the Synthetic Turf Council. More than 11,000 synthetic turf athletic fields are in use at schools, colleges, parks and professional stadiums across the country, the council said. In the Washington area, where public school systems started transitioning to artificial turf in the mid- to late 2000s, crumb rubber is the most common infill choice. Organic alternatives are generally more expensive.

Artificial turf has often been considered preferable to natural grass because synthetic fields are easier to maintain, more durable and can be used in a variety of weather conditions. The padded surface has also been shown to reduce the likelihood of impact injuries. Some athletes, however, including numerous professional soccer players, have complained about the way artificial turf affects the game.

“There is no player in the world, male or female, who would prefer to play on artificial grass,” U.S. women’s soccer star Abby Wambach has said.

Public concern grew last fall after an NBC investigation into the potential risks for athletes exposed to crumb rubber, which is made from pulverized car tires and can contain potentially dangerous chemicals and carcinogens. The NBC report, which emphasized that researchers have found no definitive link between crumb rubber and any health problems, included a soccer coach from Seattle who found that dozens of high school athletes — particularly soccer goalies — had developed cancer after exposure to crumb rubber.

Although the soccer coach’s evidence was anecdotal, the story reverberated across the country, including in the Washington area.

Responding to the concerns of parents and residents, the Montgomery County Council resolved this year to support the use of plant-based infill, which is often a mix of coconut fiber, cork or rice husks, over crumb rubber. In the District, officials established an Artificial Turf Task Force to examine alternative materials to fill turf fields. In Loudoun, which has 10 turf fields with crumb rubber infill and five more under construction, parents launched a Change.org petition to urge the school system to abandon the material.

The Loudoun petition, asking school officials to ban the use of crumb rubber on all new and existing turf fields, received more than 900 signatures, as well as impassioned personal pleas.

“My daughter loves to play goalie,” Sara Tyndall of Chantilly wrote on the petition. “We were on turf twice this week. . . . I would rest easier knowing that she is diving into something safe. Please protect our kids!”

Dawn McKenna of Chantilly wrote: “My entire family plays lacrosse on these fields multiple days a week. This stuff is all over my house after every practice and game.”

Loudoun school officials replied with a statement noting the findings of previous safety reviews by the U.S. Environmental Protection Agency, the Centers for Disease Control and Prevention, and state agencies in California, Connecticut, New Jersey and New York, none of which found conclusive evidence that crumb rubber posed a risk to the health of athletes who played on it.

That same information is also touted by the Synthetic Turf Council, which issued a statement this year to emphasize that “hundreds of tests and hundreds of pages of reports” have found no clear link between crumb rubber and health problems.

“All of that research provides confidence that there is no elevated human health or environmental risk from the ingestion, inhalation or dermal contact with synthetic turf,” the statement said.

But Loudoun Health Department Director David Goodfriend told a county committee in the summer that more comprehensive research is needed. As a result, health officials in Loudoun and other Northern Virginia jurisdictions are focused on gathering more information.

“As a region, we’re following up on it,” Goodfriend said. “My daughter plays soccer on an artificial crumb rubber field. If I thought there was any risk to the children, I would want to make sure that that information went out right away. If there is a danger, we want to know.”

Goodfriend said that officials have contacted the Virginia Health Department to see whether the state cancer registry might reflect any possible association between artificial turf and a spike in pediatric cancer cases in the area.

“We want to get a sense of whether childhood cancers are increasing . . . and whether incidence rates have changed over time since artificial turf fields have become more common in Northern Virginia,” he said. “Our hope is that we’ll get some information relatively soon.”

Officials from Fairfax County, home to more than 80 turf fields with crumb rubber infill, have also contacted officials in the Seattle area, where the NBC investigation originated. But officials in Washington state said they had not completed their report and could not yet offer any data, said Tony Castrilli, Fairfax County director of public affairs.

In a July memorandum to the Fairfax Board of Supervisors, County Executive Edward Long Jr. emphasized that county officials would continue the “extensive effort” of requesting additional studies and reviewing local cancer rates.

Meanwhile, Castrilli said, the artificial turf fields in Fairfax will stay as they are.

“Until peer-reviewed published scientific data supports the need to change the infill product, we will continue to use crumb rubber as infill for synthetic turf fields,” he told The Washington Post in an e-mail.

Montgomery County has taken a different approach, with county staff members encouraging the use of organic infill, which would “offer the opportunity to allay ongoing community concerns,” a county staff analysis said.

About a half-dozen Montgomery public schools, as well as several private schools and county fields, use crumb rubber. But the Montgomery council and the county school board have asked that all future projects use an alternative infill, Montgomery school spokesman Dana Tofig said.

“As new fields are built, and as we replace existing fields, they will be transitioned over” to a new material, he added.

The recent attention to the issue has drawn diverse opinions from parents, he said, including some who have emphasized the benefits of artificial turf fields.

“We’ve heard from some parents who have concerns about the use of artificial turf, and we also hear from parents who are big advocates for it,” he said. “We’re a big county, and we hear a range of opinions.”

Artificial turf fields tend to get more regular use, not only from the schools but from the community, and they are less expensive to maintain, Tofig said. But despite the benefits, he said, “student safety is the number one concern.”

That sentiment was echoed in the District, where the Artificial Turf Task Force will make recommendations to replace crumb rubber infill, which is now used in about three dozen fields at schools and parks, said Darrell Pressley, a spokesman with the Department of General Services.

Pressley added that the task force is finalizing its report, which will then be evaluated by the D.C. government. Meanwhile, crumb rubber infill is no longer used on newly constructed fields, and “there are no plans to use crumb rubber infill on any future artificial turf projects,” he said.

Goodfriend said that health officials in Loudoun will present their findings to a joint School Board and Board of Supervisors committee in December — or sooner, if they come across information that might raise additional concerns. So far, they haven’t found anything, he said, but officials are still waiting for answers to lingering questions.

“Is there something happening in Washington state? Are we seeing something happening in this area?” he said. “Both are important questions to answer, so I can tell parents, and I can tell my wife, that it’s perfectly safe for our daughters and sons to be playing on those fields.”

More coverage:

Team USA’s Sydney Leroux says playing the World Cup on artificial turf is like running on cement

Is there a link between artificial turf and cancer in soccer goalies?

Loudoun officials address concerns regarding synthetic turf fields