There exists a simmering controversy about the safety of playing sports on artificial turf. For those who have engaged in any type of activity on this surface, you would know that they heat up in the sun a whole lot more than natural grass. So much more so that players experience a greater risk of heat exhaustion. They also complain of carpet burns and blisters on the feet. But the bigger concern is potential toxicity.
The first synthetic playing surface was developed by Monsanto in the 1960s. Named “ChemGrass,” at a time when it was still acceptable to use a chemical connection in a positive way, it was made by melting together nylon pellets and a pigment, and then extruding the hot mix through spinnerets to produce ribbons which could be woven into a fabric. It was durable enough, but falling on it was no fun even though the nylon carpet was supported by a soft foam layer of polyurethane. When it was installed in Houston’s Astrodome as “AstroTurf,” ballplayers had to add “carpet burn” and “turf toe” to their vocabulary.
“Field Turf,” a Canadian company took the complaints to heart and came up with an improved version. Out went the stiff nylon fibers and in came soft, elastic polyethylene fibers lubricated with silicone oil. These were tufted into a rubberized plastic mat, just like a giant shag rug. The “tour de force,” though, was the “infill” composed of sand and granules of “crumb rubber”, made by grinding old rubber tires and the soles of athletic shoes into pellets, which kept the fibers upright and provided shock absorbency. It is this that would eventually become the subject of much heated debate.
The issue is that tires are made of a mix of natural and synthetic rubbers and contain an incredibly complex array of chemicals ranging from natural contaminants such as lead to zinc oxide used in the vulcanization process and polycyclic aromatic hydrocarbons in the oil blended with the rubber to provide proper texture. There are vulcanization accelerators like benzothiazole, amines added as antioxidants and butadiene and styrene residues from the synthetic rubber component. Many of these are known, probable or possible carcinogens. Carbon black, used as a reinforcing filler, can harbour “nanoparticles” which some researchers claim are carcinogenic and can penetrate cells, even finding their way to the brain. Lead-based pigments, now phased out, but once used to colour the grass, are another worry. There is also concern that dust from the rubber pellets can trigger allergies and asthma.
Of course the major question is extent of exposure, which can be caused by the inhalation of volatiles or dust that is released as the crumb rubber crumbles under stress. There is also the possibility of swallowing any particles that are kicked up by action on the field, a special concern to goalkeepers who often dive to make a save and end up stirring up the rubber pellets. Can this be of any consequence? A preliminary collection of data by a soccer coach in the US suggests an unusual number of cancer cases among athletes who have spent a lot of time playing on artificial surfaces, and in the case of soccer, a greater incidence among goalkeepers than other players. So far this evidence is anecdotal, but science often starts with someone noting such a relationship and saying, “hmmm, isn’t that interesting?”
Given that the sporting landscape is dotted with artificial turf, and that thousands and thousands of children, who are more prone to the effects of toxins, play on such surfaces, further investigation is in order. Solid epidemiological data are needed to determine if there is indeed a link between artificial turf and cancer incidence, and we need experimental data about the extent and effects of exposure. The latter can be addressed by sampling the air above artificial fields for chemicals wafting out and by immersing samples of turf in fluids that simulate sweat, lung mucus and digestive juices. So far, the few experiments that have been carried out along these lines found that the chemicals detected were below what is considered to be hazardous, but there is great variation between turfs produced by different companies. Small surveys therefore cannot yield conclusive results. Furthermore, such studies do not address the possible cumulative effect that may be proportional to the time spent playing on artificial turf.
At this point it is impossible to quantify the toxicological risk, if any, of playing on artificial turf that may look like grass, even feel like grass, but does not behave like grass.
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