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"Crumb rubber" is recovered from scrap tires or from tire retreading. The rubber is used in road construction, as safety surfacing under play-ground equipment, for running tracks and as a soil additive on sports and playing fields.


Editor's note: Over the last couple years we've received a number of letters objecting to landscape architects specifying playground safety surfacing or artificial turf that uses tire crumb material.

Oxford Garden
Toro
Rain Bird
Tru-Power
Structure Studios RH Peterson, Inc.
Fire Science Inc. OneSource Aquatics
Sport Turff John Deere
Senna Tree Hortica
Playworld

For instance, the "Forsyth School's Creative Outdoors" featured in our June 2008 issue pictured elementary age children at the St. Louis, Mo. school playing on a synthetic track and play field, both made from crumb rubber.

That project elicited this comment from Jack Rossi, RLA of Strafford, Vermont:

"This letter is by no means a criticism of the design and technical competence and integrity evident in the Forsyth School project ("Forsyth School's Creative Outdoors," June issue). My concern and continued frustration is raised in reading of the project's use of artificial turf and a sport's track of "styrene budadine rubber--from tires, hoses, etc.", and speaks to an issue beyond any single project and to the profession in general and the larger environmental challenges facing our society.

"Over the past couple of years numerous studies have been conducted and validated indicating tire crumbs in artificial turf contain significant amounts of volatile organic compounds, including benzothiazole, hexadecane, 4-(tert-Octyl)-phenol and butylated hyroxyanisole. These chemicals are irritants at the least and carcinogens at the worst. Furthermore, summer heat tends to outgas these substances at a much quicker and concentrated rate.

"As recently as June 18, 2008, the CDC issued a warning regarding the use of artificial turf based on high levels of lead found in field dust. They also advised that children ages six and younger are most susceptible to lead's harmful health effects and to protect the public, in particular young children, facilities should consider posting signs indicating:

'After playing on the field, individuals are encouraged to perform aggressive hand and body washing for at least 20 seconds using soap and warm water.'"

Results of EPA's Tire Crumb Study

So, does the use of tire crumb pose health dangers? We've been following the research. The U.S. Environmental Protection Agency (EPA) just released results of a limited field monitoring study of artificial-turf playing fields and playgrounds constructed of tire crumb. The study--"A Scoping-Level Field Monitoring Study of Synthetic Turf Fields and Playgrounds"--was prepared by the National Exposure Research Laboratory and intended to gain experience conducting field monitoring of recreational surfaces that contain tire crumb.

"The limited data EPA collected during this study, which do not point to a concern, represent an important addition to the information gathered by various government agencies," explains Peter Grevatt, director of EPA's Office of Children's Health Protection. "The study will help set the stage for a meeting this spring, where EPA will bring together officials from states and federal agencies to evaluate the existing body of science on this topic and determine what additional steps should be taken to ensure the safety of kids who play on these surfaces." The study collected air and wipe samples at three locations near EPA laboratories at Raleigh, N.C., Athens, Ga. and Cincinnati, Ohio. Sampling also was conducted in the Washington, D.C. area. The limited study, conducted in August through October 2008, found the concentrations of materials made from tire crumb were below levels considered harmful.

The researchers pointed out that given the limited nature of the study (limited number of constituents monitored, sample sites, and samples taken at each site) and the wide diversity of tire crumb material, it is not possible, without additional data, to extend the results beyond the four study sites to reach more comprehensive conclusions.




The Forsyth School in St. Louis, featured in our Campus issue (June 2008) www.landscapeonline.com/research/article/10706 opted for a FieldTurf field and track made from cryogenic crumb rubber (and silica sand), one of the two categories of in-fill crumb rubber used in the artificial/synthetic sports field industry.
Photo: SWT Design



Study Approach

The primary goal of the study was to "evaluate readily available methods and approaches for characterizing environmentally available concentrations of selected contaminants at synthetic turf fields and playgrounds that include tire crumb material." The researchers noted when beginning the study there were "no known validated sampling and analysis methods for these types of installations and materials." Based on professional evaluation, the team chose "integrated and/or grab air, wipe and material sample collection and analysis methods. Where available, standard methods used routinely to characterize the targeted environmental contaminants in other microenvironments were selected. However, because of time and resource constraints, none of these methods were evaluated for the intended study application."

According to the researchers, the study confirmed most of the methods tested were accurate, reproducible and appropriate for measuring concentrations of tire crumb constituents and therefore can be used in future studies.

Findings

Particulate matter, metals and volatile organic compound concentrations were measured in the air samples and compared with areas away from the turf fields (background levels). The levels found in air samples from the artificial turf were similar to background levels.

No tire-related fibers were observed in the air samples.

All air concentrations of particulate matter and lead were well below levels of concern.

More than 90 percent of the lead in the tire crumb material was tightly bound and unavailable for absorption by users of the turf fields.

Zinc, which is a known additive in tires, was found in tire crumb samples. However, air and surface wipe monitoring levels of zinc were found to be below levels of concern.

EPA says studies by other agencies were undertaken or completed while this survey was under way. EPA is planning a 2010 meeting with federal and state agencies to review all new study data.
You can view and download the complete study at www.epa.gov/nerl/documents/tire_crumbs.pd
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October 15, 2019, 10:52 pm PDT

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