NBC News recently did an investigative report on the safety of our children's playgrounds and sports' fields. For over five years now, there have been a slew of studies looking to see if there is a link between the rise of cancer cases among athletes and the surfaces they play on. Artificial turf fields can be found all over the United States as the popular alternative to natural grass fields which require a lot more upkeep; however, the chemicals involved in making the turf has been drawing some concern.

Of the most concern is artificial grass that uses infill called crumb rubber made of pieces of old tires. This is what makes these fields more bouncy, protecting players better from more serious injuries like concussions. The downside is that when players' bodies connect with the field, little pieces of the infill fly up and scatter everywhere. After a game or practice, players will find these crumbs not only in their uniforms, but in their hair and inside cuts and abrasions they received on the field. For goalies however, with their full body dives to the ground, these crumbs can also get in their mouths during play.

Because different types of tires made from a large variety of materials are used to make the turf, it is hard to pinpoint the particular chemicals that could be causing the increase in cancer rates. The EPA lists mercury, lead, benzene and arsenic as well as other chemicals and carcinogens as being the ingredients in tires.

Field Turf, a maker of artificial turf, assures its customers that the ways these chemicals are manufactured makes them safe.

David Gill, vice president for marketing, said to the NBC, "If you look at the ingredients that go into a car tire, some people take those ingredients and turn them into health concerns, but after the vulcanization process, those ingredients are inert."

Many scientific studies have been performed over the last few years, but no real link has been found between cancer and artificial turf fields. At the most, they conclude that more research needs to be done. More data especially needs to be collected on what happens to the body if you ingest these crumbs while you are playing on the field.

Dr. Davis Lee, of the Synthetic Turf Council said, "We've got 14 studies on our website that says we can find no negative health effects."

Both the Environmental Protection Agency (EPA) and the Consumer Product Safety Commission have done their own studies which indicated that there was no reason to be concerned. More recently, however, the EPA told NBC News that "their studies were limited and that more testing needs to be done." But apparently we can't expect them to conduct any future research because they consider the use of artificial turf a "state and local decision."

While all studies have found the exposure to harmful chemicals very low, one study done by the state of Connecticut reported that more investigation is needed on whether more chemicals are released in the air in hot weather when turfs grow more than 10 degrees hotter, and in indoor facilities.

One 2013 study while concluding that the turf presented little risk, did express concern over the levels of lead and its potential affect on young children and an article in Chemospheres called for more regulatory concern.

While not a formal scientific study, a compilation of patient stories gathered by Amy Griffin, associate head coach for the University of Washington's women's soccer team, disagrees with the findings so far. She has discovered 38 American soccer players (34 of them goalies) who have cancer, the most prominent diagnosis being lymphoma and leukemia. Her mission started in 2009 when she was visiting athletes in the hospital while they were undergoing chemo treatment. One day when she was sitting with a young goalie who had non-Hodgkin lymphoma, the nurse made an off-hand comment about how many goalkeepers she treated that week. It was a connection she couldn't ignore.

While it is unlikely there will be anymore research on a national level, industry voluntary standards for lead content is in the works and certain cities are opting to use artificial turf with safer infill like coconut fiber and cork. The New York City Parks Department hasn't used crumb rubber since 2008 and the Los Angeles Unified School District followed suit the next year. In Maryland and in San Francisco advocacy groups have been showing concern as well.

Do you know what your kids are playing on?

[NBC News]