The question of whether replacing natural grass with synthetic grass is a hotly debated one with passionate views expressed on both sides of the argument. I have already devoted a couple of posts about the benefits of synthetic grass, so now I will report some of the arguments put forward in opposition to it. You may agree with the arguments, you may disagree, but the debate continues.

Some people are flat out against synthetic grass on principle, “Grassroots organizations have been working hard to have pesticide use reduced or banned in places where it is unnecessary,” says Tanya Murphy, a board member of Healthy Child, Healthy World, an advocacy organization. “Now we’re going from the frying pan and into the fire when replacing grass with synthetic turf.”

Rubber Infill

Rubber infill is one of the main sources of concerns. The crumbs become airborne and can be breathed in and tracked into homes on clothes and athletic gear. There are also questions about dermal and ingestional exposures, and about ecosystem effects.

For athletes, the little black rubber pellets may seem little more than a nuisance. Others express more concern, especially when it comes to children’s exposure to the infill. Patti Wood, executive director of the nonprofit Grassroots Environmental Education, argues, “This crumb rubber is a material that cannot be legally disposed of in landfills or ocean-dumped because of its toxicity. Why on earth should we let our children play on it?” Some studies suggest that the same chemicals that can be released profusely during a tire fire may also be released slowly during deterioration of crumb rubber.

The California Office of Environmental Health Hazard Assessment (OEHHA), in the January 2007 report Evaluation of Health Effects of Recycled Waste Tires in Playground and Track Products, concluded that 49 chemicals could be released from tire crumbs. In a hand-wipe experiment, the OEHHA calculated an increased cancer risk of 2.9 in 1 million for ingestion of chrysene (a suspected human carcinogen found in tire rubber) via hand-to-mouth contact with crumb rubber infill. This estimate assumed regular playground use for the first 12 years of life and was termed by the authors to be “slightly higher” than the 1 in 1 million di minimis risk threshold.

Synthetic Grass Health and Injury Concerns

A study conducted by the Centers for Disease Control and Prevention and published in the 3 February 2005 issue of the New England Journal of Medicine showed that, although synthetic turf itself did not appear to harbor MRSA, the greater number of turf burns caused by the abrasive friction of this type of surface increased the probability of MRSA infection, especially among professional athletes playing on hard surfaces.

There is, however, some evidence to suggest that synthetic turf may harbor more bacteria. For example, an industry study sponsored by Sprinturf, a maker of synthetic turf, found that infill containing a sand/rubber mixture had 50,000 times higher levels of bacteria than infill made of rubber alone.

There is also the concern that our children are being exposed to too much of the synthetic (unreal) world and need to come into more contact with outdoor nature. William Crain of the City College of New York Psychology Department presents the idea that replacing grass with synthetic turf can hinder children’s creative play and affect their development. “Today’s children largely grow up in synthetic, indoor environments,” he says. “Now, with the growing popularity of synthetic turf fields, their experience with nature will be less than ever.”

Heat Issues with Synthetic Grass

One drawback that both fans and critics of synthetic turf agree on is that synthetic grass fields can get much hotter than natural grass. Stuart Gaffin, an associate research scientist at the Center for Climate Systems Research at Columbia University, initially became involved with the temperature issues of synthetic turf fields while conducting studies for another project on the cooling benefits of urban trees and parks. Using thermal satellite images and geographic information systems, Gaffin noticed that a number of the hottest spots in the city turned out to be synthetic turf fields.

Direct temperature measurements conducted during site visits showed that synthetic turf fields can get up to 60° hotter than grass, with surface temperatures reaching 160°F on summer days. “Exposures of ten minutes or longer to surface temperatures above 122°F can cause skin injuries, so this is a real concern,” said Joel Forman, medical director of the Pediatric Environmental Health Specialty Unit at Mount Sinai School of Medicine, speaking at a 6 December 2007 symposium on the issue.

Although it is often argued that one of the advantages of synthetic turf is that it does not need irrigation, some installations must be watered to control the excessive heat. In addition to heat control, the International Hockey Federation requires that college teams saturate synthetic turf fields before each practice and game to increase traction.

The EHHI study addressed the question of whether synthetic turf fields can contribute to increased water contamination from rain or from spraying or misting. The study found that 25 different chemical species and 4 metals (zinc, selenium, lead, and cadmium) could be released into water from rubber infill. Moreover, because synthetic turf is unable to absorb or filter rain-water, chemicals filter directly into storm drains and into the municipal sewer system without the beneficial filtration that live vegetation provides.

What Happens To Used Synthetic Grass?

Finally, what happens to synthetic turf fields when they are no longer usable? Industry estimates that synthetic turf fields have a lifespan of 10 to 12 years, whereupon the material must be disposed of appropriately. Rick Doyle, president of the Synthetic Turf Council, says the infill could be cleaned and reused; put to another purpose, such as for rubber asphalt; incinerated; used in place of soil to separate landfill layers; or otherwise recycled. Typically, however, it is landfilled.

Work is progressing on a replacement for rubber granule infill. In Italy a thermoplastic material is being developed and Mondo, a manufacturer of floor surfaces, produces Ecofill, a patented polyolefin-based granule used in synthetic turf. Another alternative is infill made from plant-derived materials. Synthetic turf manufacturer Limonta Sport produces Geo Safe Play, an infill made from coconut husks and cork.

The news is that work is being done to address many of the arguments against using synthetic grass for our sporting fields.