When it comes to athletic field surfaces, artificial turf has gained ground on natural grass. In recent years, synthetic turf has replaced grass on municipal and school fields that bear nearly year-round traffic of football, soccer, field hockey, lacrosse, baseball and softball games — not to mention the daily workouts for which those teams use the fields.

For decades, safety concerns primarily focused on injuries caused by landing roughly on the unforgiving surface, or knee injuries suffered by athletes on the man-made fields. Now, the synthetic surfaces are being linked to cancer in some athletes who have played on artificial turf.

That tie came to light after Amy Griffin, associate head coach for the women's soccer team at the University of Washington, brought attention to the issue after visiting a cancer-stricken soccer goalie at a Seattle hospital. When NBC News took up the story, interest in a possible connection and potential dangers in the fields spiked coast to coast.

Now, Congress is encouraging the Environmental Protection Agency (EPA) to investigate the safety of the fields particularly the crumb rubber infill. A letter from members of the House Committee on Energy and Commerce issued in late October prodded the EPA to explore the question of whether athletes are being exposed to carcinogens by playing on the fields.

In recent years, synthetic turf has replaced grass on municipal and school fields that bear nearly year-round traffic of sports.

Artificial turf got its start in the 1960s but has advanced considerably since Monsanto developed what later be came to known as AstroTurf. The Ford Foundation, which aimed to improve children's fitness, led Monsanto to produce the durable surface that could be used for athletics. When Houston built the Astrodome, an indoor stadium for the city's Major League Baseball team, the turf was a logical and natural fit, giving the surface its name.

Over the years, technology improved on the fields, leading to today's incarnation, which can consist of several layers of footing that allow for drainage, topped by fake synthetic fibers that look like grass. A variety of infills are used to cover the space between the "grass" fibers, but crumb rubber made from crushed recycled tires has drawn heavy attention.

This isn't the first time the safety industry has taken a look at the fields. Last decade, lead in the coloring of the artificial grass led to a study by the U.S. Consumer Product Safety Commission, which determined the lead was of no danger to athletes exposed to it.

That didn't address the concerns about crumb rubber, but the New York State Department of Environmental Conservation and the New York State Department of Health took up that topic in research about the same time. Agencies in New Jersey and Connecticut also looked into the fields and stated that no evidence was offered to show the fields posed health hazards to athletes or the communities in which the fields were placed.

That hasn't stopped the questions. Sports media giant ESPN tapped World Cup and Olympic soccer star Julie Foudy for a report on the fields. Rubber industry representatives have weighed in also, pointing out the lack of conclusive evidence of a link between the fields and cancer.

Still, there's enough concern to lead school districts and municipalities to pause before moving ahead with plans to install the surfaces. California has committed to a $3 million study on the topic, and a Florida city put the brakes on plans to install the turf at its sports complex because of worries about the potential health risks.

With questions and concerns swirling around the artificial surfaces, even after numerous studies, the issue will continue to cause divisions no matter what the EPA determines.