Grass v. Artificial Turf--Which Is More Toxic?

In our capacity with helping manage youth soccer programs in Arlington, we were today referred to an article in the Charlottesville Daily Progress on potential toxic dangers of artificial turf playing fields: "Synthetic turf: Saving grace or harmful place? Health risks could come along with new fields."

The story cites "concerns" about the potential toxicity of the infill used for synthetic fields, which is made from ground up tires. It also suggests that cuts and scrapes from artificial turf fields can cause a greater danger of staph infection.

So we spent some time looking into this since Arlington has a number of synthetic turf fields, with more in the works. What we found was scant evidence of any significant risk for artificial turf fields, especially when compared to the risks of plain old grass fields.

Let's start with your basic, familiar grass field. (Or, in Arlington--and to be fair, most urban jurisdictions--grass and a lot of bare patches of dirt.) Growing grass requires chemicals. Fertilizer, herbicide, sometimes pesticides. These are potent chemicals that include numerous carcinogens, and they are applied directly to fields on which children will be playing extensively. Yet, when a local parks authority suggests building a new park, or replacing the grass on an existing field, no one goes up in arms about the danger to kids.

There are other dangers, of the more mundane kind--falling on uneven surfaces, getting scraped on the dirt and rocks, etc. A number of studies have shown that turf fields also produce fewer contact injuries and longterm injuries--in part because they present a level, even surface.

So what about synthetic turf?

The primary focus of the Daily Progress story is on a report prepared by an outfit in Connecticut called Environment And Human Health, Inc. We don't learn much about EHHI--where it gets its funding, who its scientists are, etc.

We went to EHHI's website to get the report. It claims that EHHI did some testing that showed the release, when heated, of four potentially hazardous chemicals from the tire infill in synthetic playing fields. But EHHI's report gives no details on that testing--doesn't give us even a clue to the testing protocol.

What we can be pretty sure of is this: that the laboratory testing done by EHHI bore little relationship to the real world conditions in which players are exposed to the fields. We suspect that EHHI took a bunch of shredded tire particles, heated them in an ENCLOSED laboratory apparatus, and then measured the chemicals released. One would hope that EHHI did a study in which it analyzed the chemicals in air, but the report refers to releases under "aqueous ambient temperatures," which means in a water solution.

That's not at all real world. Most of these playing fields are in the open air, where any chemicals released most likely would be quickly dispersed. Moreover, those same chemicals are emitted from tires on highways, and so are already in the air.

A really good study would be to conduct on-site tests at both a synthetic field and a grass field that are near enough to each other to have similar ambient air. The tests would measure the actual air over the field at various times of day, on both fields, as well as in areas away from the fields (to control for the natural "background" amount of chemicals in the air). Such tests are more difficult than those in a laboratory, but they can be done. We suspect you'd find no difference in the air at either field, or you might even find more nasty chemicals over the grass field.

Most of what EHHI has done is to review literature on potential toxicity of ground up tires. But you cannot compare the conditions in a shop that recycles tires with those on a playing field with tire pellets lying in fake green grass. And, in any such study, the key element is the DOSE of the chemical in question.

We were particularly surprised at one claim in the EHHI report, which was that emissions of one of the chemicals of interest would amount to "four to six grams"per square foot of field "on a hot day," i.e., when the surface temperature on the field approaches 140 degrees fahrenheit (which can happen, but not too often). The typical measure of exposure for any toxicological assessment of inhalation risk would be in a unit per cubic meter of air. Putting it in terms of grams is completely meaningless.

Buried in the EHHI report is the concession that "[a]ctual exposure measurements are needed to determine the potential inhalation risks for players on the field or for spectators and nearby residents." Without those measurements, the rest of the report is really not worth the paper its printed on.

In the end, all this amounts to is alarmist science, rather than good science. The report is almost entirely conjecture. It's funny--the authors are quick to dismiss a number of studies that found no problems with synthetic turf, on the ground that such studies inadequately assessed the risks, but they don't apply those same standards to their own work.

Now quickly, what about the claim that synthetic fields pose a higher risk of staph infections? It appears to be based on one study, again in grass-happy Connecticut, after a staph outbreak in a college team. As best we could tell, the study does not show any increased risk of staph on synthetic fields compared to grass fields--to show that, you'd need to follow similar teams playing exclusively on each type of field for a period of time (not that difficult of a study, actually) and then see if either group had more infections. Until that's done, we don't really know.

Some additional research may be warranted--it would be nice to know exactly what the risks are, and be able to compare them to similar risks from grass. But that will require much better science.

In the meantime, we see no reason to worry about kids playing on synthetic turf fields. And this weekend, when our grass fields are likely to be closed due to the much needed rain we're getting, we'll be glad to be playing on those all-weather artificial fields!