Friday, July 25, 2008

A Playground for Retired Tires?

by Catherine Zandonella
Green Guide
July 22, 2008

Recycled rubber is finding favor in playgrounds both because it does a good job of cushioning falls and because turning rubber into playground matting helps deal with the 290 million scrap tires generated nationwide. Although we ecologically minded types would very much like to find uses for those mounds of discarded tires, shoveling them into playgrounds is probably not the answer.

To prepare them for playground surfaces, manufacturers wash old tires, pulverize them, and use magnets to remove metals and contaminants. Then they mix the grains with a binding agent such as polyurethane and either pour the mixture directly into the playground or make it into tiles for later installation. They can also make rubber mulch (or "crumb"), which can be coated in outlandishly bright colors and is commonly spied at playgrounds headed for a toddler's open mouth.

But those ground-up tires release 49 different chemicals, according to the California Office of Environmental Health Hazard Assessment (OEHHA), including volatile organic compounds (VOCs), which get released when surfaces are exposed to light and heat and as they age; heavy metals, such as zinc, lead, cadmium, chromium and arsenic; and tiny bits of latex-containing tire dust small enough to lodge in the lungs. Of those 49 chemicals, seven are carcinogens.

The OEHHA surveyed all the available safety studies on these surfaces and estimated that an average three-year old who ingests a fistful (10 grams) of tire crumb would likely suffer no more than an upset tummy from ingesting too much zinc. However, several other environmental health organizations have raised concerns about the multitude of chemicals that kids inhale playing so close to the ground. The California survey didn't look at health problems posed by inhaling all those 49 chemicals, and there is evidence that new rubber surfaces, at least, can emit VOCs at unhealthy levels for up to two years.

As for their safety benefits, crumb rubber has been found to protect against falls better than wood mulch, but about two-thirds of the playgrounds sampled by the OEHHA had at least one piece of equipment without a rubber surface underneath thick enough to protect kids from falls.

When you factor in possible ecological contamination, the mats get even less appealing. Laboratory studies have found that concentrated leachate from shredded tires poses dangers to fish, frogs, plants and other aquatic life.

The recycled-rubber mats should be less of a health risk than shredded crumb given that the bonded solid mat is less likely to contain small particles that can be ingested or inhaled, but given the uncertainty surrounding the health risks of these materials, it's better to stick with pesticide-free wood chips and mulch, which don't offgas chemicals, trigger asthma, or kill fish. Just be sure the wood chips and mulch are properly installed and replenished frequently enough to offer proper protection against falls.

© 1996-2008 National Geographic Society

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