Across the nation, discarded rubber tires are being recycled and reused in innovative ways that promote safety and represent ingenuity. In as many as 100 studies in state after state, researchers have reached the same conclusion…
The Environmental Protection Agency (EPA) has endorsed the use of recycled rubber to cushion the surfaces of children’s playgrounds. For more information, visit: www.epa.gov/osw/conserve/tools/cpg/products/playgrnd.htm and www.epa.gov/nerl/features/tire_crumbs.html
The Office of Environmental Health Hazard Assessment of the California Environmental Protection Agency tested skin sensitization by playground surfaces made of recycled tires and found no sensitization observed suggesting that these surfaces would not cause skin sensitization in children, nor would they be expected to elicit skin reaction in children already sensitized to latex.
Study dated January 2007 can be viewed at: www.ciwmb.ca.gov/Publications/Tires/62206013.pdf
ChemRisk, Inc. in Pittsburgh conducted a review of exposure to recycled tire rubber found on playgrounds and synthetic turf fields. They concluded that no adverse human health or ecological health effects are likely to result from these beneficial reuses of tire materials.
Study dated July 17, 2008. Detailed information and more studies can be found at:
Rubber Mulch and Crumb Rubber products have been tested at great length by the Environmental Protection Agency (EPA) and other private and government agencies. This page provides a comprehensive collection of crumb rubber health and environmental impact studies conducted between 1994 and 2008 and cross-references such research to the related issues in question, including:
The fifty-two studies and reports referenced have been obtained from government organizations, academic institutions, NGOs and non-profit organizations worldwide and focus primarily on the application of recycled tire rubber in playground surfaces and athletic fields.
This reference is meant to facilitate a thorough and objective examination of environmental and human health concerns related to the use of recycled rubber in surfacing materials.
Lead does not occur in native tire tread by composition, but may become entrained in the tread upon contact with the road surface and thus be detectable in recycled rubber surfaces. A 2007 report from the Office of Environmental Health Hazard Assessment (OEHHA) examined the effects of lead in crumb rubber surfaces for increased cancer risk in humans and found no indication of an elevated health hazard.
Additionally, risk of groundwater contamination through lead runoff from a shredded tire embankment was addressed in a 10-year Virginia Field Study. Lead levels were found to be 9 parts per billion or less, well below the Maximum Contaminant Level (MCL) of 15 parts per billion. A 2008 report by the engineering firm Milone & MacBroom confirmed that the levels of heavy metals found in runoff from turf fields are comparable to those expected to leach from native soil.
Lead concentrations in artificial turf leachate analyzed in a 2004 study in Norway found levels below the normative values established by the Norwegian Pollution Control Authority, wherefore no elevated risk to human health or the ecosystem were concluded. The findings pertaining to human health were confirmed in a 2008 study by the Consumer Product Safety Commission, which tested specifically for risk to children in contact with artificial turf blades and consequent ingestion of lead.
Click for: Lead-Related Studies and Findings
Off-gassing of volatile organic compounds (VOCs) from rubber infill in outdoor locations is expected to be greatest in high temperatures. Temperature gradients and wind in such installations have shown to dilute gases quickly and leave low concentrations of VOCs in the breathing zone. A 2008 report by the engineering firm Milone & McBroom also analyzed VOC levels in the breathing zone of outdoor turf fields, particularly volatile nitrosamine, benzothiazole and 4-(tert-octyl) phenol and found no detectable concentrations of the first and latter and low concentrations of benzothiazole directly above one of two fields that had recently been groomed. A 2007 field turf study conducted by the French government (EEDEMS) found that off-gassing of VOCs and aldehydes did not pose a health concern to the general public, athletes or outdoor installers.
In contrast, a limited 2005 study of an indoor hall with recently laid rubber granules suggests higher-than-normal levels of total VOCs, but due to a number of variables, the authors suggest further research. A 2006 study conducted in Oslo, Norway, found no evidence linking total VOCs released from indoor recycled rubber surfaces to adverse effects on human health. However, due to information gaps, individual substances identified as part of the VOC fraction could not be conclusively assessed for potential health effects. A 2007 study conducted by the Office of Environmental Health Hazard Assessment in California also found no elevated cancer risk following in-depth analysis of VOCs. The 2007 EEDEMS report mentioned above raised concerns about health effects on the crews installing crumb rubber athletic fields in poorly ventilated indoor areas and recommends a minimum air renewal rate of 2 vol.h-1. A 2006 study conducted in Norway drew a similar conclusion, stating that, while no evidence of health risks from the internal use of recycled rubber surfaces could be determined, proper ventilation is always recommended. These recent findings are consistent with those of a 1999 Taiwanese study that identified temperature and age of the recycled rubber material as the primary factors in VOC emission rates.
Click for: Off-Gassing-Related Studies and Findings
This section will include studies pertaining to ecotoxicological issues, concerns regarding carcinogens, mutagens, endocrine disruptors and other substances known for their adverse effects on human health. The examination of indoor air where recycled rubber surfaces were present by the Norwegian Institute of Public Health determined that the presence of benzene and polycyclic aromatic hydrocarbons (PAHs) does not increase the risk of cancer in individuals exposed to it. These findings agree with a 2007 report from the Office of Environmental Health Hazard Assessment (OEHHA), which analyzed the absorption of aluminum, arsenic, barium, cadmium, cobalt, chromium, iron, lead, manganese, mercury, nickel, selenium and zinc traces in crumb rubber and concluded that serious non-cancer health effects are not expected following a one-time ingestion of the material. The study further concluded very low environmental toxicity from surface runoff upon examining the soil and groundwater adjacent to crumb rubber surfaces, pointing out that previous studies produced the leachate in a laboratory setting, wherefore it may have been more concentrated than naturally occurring runoff, although various laboratory studies, such as the 1999 experiment performed by the Chelsea Center, also agreed that drinking water quality would not be compromised by recycled rubber chip applications.
A 2004 study in Norway found the total concentration of lead, cadmium, copper and mercury in recycled rubber granulates to be below the Norwegian Pollution Control Authority’s normative values for most sensitive land use and concluded that it is not probable to constitute an unacceptable environmental risk in the short or the long term.
Click for: Toxicity-Related Studies and Findings
An extensive study conducted in the Netherlands determined that the zinc content of recycled tire surfaces in athletic fields poses no risk to public health, as human toxicity of zinc is low and levels detected in drinking water conform to the standards of the World Health Organization (WHO). Ecotoxicological effects were of concern, however, specifically the accumulation of zinc in groundwater and soil through runoff from aging crumb rubber. These findings confirmed a 2005 report by the Norwegian Institute for Water Research, which concluded “that the concentration of zinc poses a significant local risk of environmental effects in surface water which receives run-off from artificial turf pitches. In addition, it is predicted that concentrations of alkylphenols and octylphenol in particular exceed the limits for environmental effects in the scenario which was used (dilution of run-off by a factor of ten in a recipient). The leaching of chemicals from the materials in the artificial turf system is expected to decrease only slowly, so that environmental effects could occur over many years. The total quantities of pollution components which are leached out into water from a normal artificial turf pitch are however relatively small, so that only local effects can be anticipated.” (NIVA, 2005) Zinc concentrations in artificial turf leachate analyzed in a 2004 study in Norway furthermore found levels above the normative values established by the Norwegian Pollution Control Authority. It also determined that the content of potentially harmful substances can vary significantly by manufacturer and suggested the enforcement of uniform guidelines to improve recycled rubber quality across the industry.
An extensive study conducted by the California Integrated Waste Management Board (CIWMB) and the Office of Environmental Health Hazard Assessment in 2007 further analyzed zinc ingestion and found no elevated health risk, even in small children, aside from gastrointestinal discomfort. The study also analyzed groundwater and soil surrounding artificial turf areas and concluded a very low risk of environmental impact, pointing out that previous studies, such as the Norwegian 2004 report mentioned above, produced the leachate in a laboratory setting, wherefore it may have been more concentrated than naturally occurring runoff.
Groundwater contamination risk was furthermore addressed in a 10-year Virginia Field Study for the use of ground tires in an embankment. Zinc levels were found to be 0.13 parts per billion, far below the Secondary Maximum Contaminant Level (SMCL) of 5 parts per million. A 5-year groundwater study from the University of Maine and the University of Texas agrees with these findings, stating that tire shreds placed below the groundwater level have negligible off-site effects on water quality. The 2007 report by Dr. Robert Moretto on the short and medium-term effects of artificial turf on groundwater concurs with this assessment. The most recent field study available on leaching of zinc was conducted over a seven year period in the Netherlands and evaluated five artificial turf fields. Researchers concluded that the concentration of zinc in drainage is comparable to the zinc concentration in rain and poses no added health risks. The study did point out that leaching would probably occur 230-1800 years after installation.
Tires stockpiled in landfills present a significant hazard to the ecosystem. They degrade slowly, contribute to fires that release combustion products, including volatile organic hydrocarbons and dioxins, and leach into the water supply as they decompose. Runoff from playground surfaces and athletic fields has shown toxicity in examined aquatic organisms for the first three months after installation. After the aging period of the surface product, this activity ceased. A 2006 study conducted in Norway examined the environmental impact from runoff and found the associated risk to be small and local and depending on factors including soil composition and regional sensitivity, as well as particle size, pH value and the age of the rubber material. The Swedish Chemicals Inspectorate consequently recommended additional research and the phasing out of potentially hazardous materials from the tire production process.
Ingestion of crumb rubber products can occur directly, by ingestion of surface water runoff, through inhalation of dust and through dermal absorption. In vitro mutagenicity research and hazard analysis suggest very low risk associated with the use of crumb rubber product in playground and athletic field surface applications. A fact sheet issued by the Connecticut Department of Health (CDH) confirms low public health risks and points out that the amount of crumb rubber particles entering the air through surface wear compares to amounts generally found in suburban and urban air from wearing of tires, car exhaust fumes, foods, consumer products, flooring and furnaces. The CDH does acknowledge gaps in information that warrant further investigation. A Norwegian study conducted in 2006 examined the risk of ingestion through inhalation, oral ingestion and skin absorption of recycled rubber used in indoor athletic surfaces and found that exposure to phthalates, alkyl phenols, and airborne dust was too low to cause elevated health risks. A 2007 study conducted by the California Integrated Waste Management Board confirmed these findings and further tested multiple carcinogenic and non- carcinogenic substances occurring in crumb rubber. It determined that no elevated health risk is to be expected following a one-time ingestion of 10 grams of the material.
An extensive study conducted by the California Integrated Waste Management Board (CIWMB) and the Office of Environmental Health Hazard Assessment in 2007 analyzed carcinogenic substances, including arsenic, cadmium, lead, benzene, trichloroethylene, aniline and naphthalene in crumb rubber and concluded that a one-time ingestion would not exceed de minimis risk levels. The findings of these recent studies agree with the findings of a 2003 genotoxicity study that found no DNA or chromosome damaging chemical release upon crumb rubber ingestion.
Click for: Ingestion-Related Studies and Findings
As pointed out by the New York State Department of Health, studies concerning an increased occurrence of infection on artificial turf versus natural turf have been inconclusive. A disease outbreak investigation did not identify playing fields, natural or artificial, as contributors to an increased risk of staph infections. A 2005 report from the Illinois Department of Public Health attributes such outbreaks primarily to the sharing of equipment and matters of hygiene combined with increased skin abrasions, cuts incurred from body shaving and close contact between athletes.
Research by the San Francisco Synthetic Playfields Task Force in 2008 found no evidence for concern regarding an increase in staph infection risk from playfields and recommends posted guidelines near such fields, stating basic hygiene and first aid instructions.
Click for: Staph Infection-Related Studies and Findings
This section lists a number of studies pertaining to concerns regarding latex to which approximately 6% of the general population is allergic. Latex allergies caused by tire dust as it occurs in urban air pollution must be distinguished from the risk potential for such allergies in recycled rubber surfaces. The vulcanized chemistry of tire manufacture destroys these allergens, which typically eliminates the risk of allergies through contact with the rubber surface. This observation was confirmed by research from the Norwegian Institute of Public Health, although the risk of developing latex allergies or causing asthma attacks in those who have previously developed it could not be excluded for sensitive individuals exposed to tire dust from rubber surfaces in indoor areas. The California Integrated Waste Management Board conducted a controlled skin sensitization study in 2007 and concluded that playground surfaces made from recycled tire rubber do not constitute a skin sensitization risk to children.
Click for: Allergy/Latex-Related Studies and Findings
Significant consideration should be given to the benefits of using recycled tire materials over alternative landfill disposal of tires in environmental and resource preservation efforts. As discussed in a 2003 Tellus Report, discarding of tires in landfills carries multiple disadvantages, ranging from toxic runoff and tire pile fire emissions to the rise in mosquito borne diseases and unfavorable land use. According to the report, 281 million scrap tires were generated in the year 2001 alone.
In addition to the studies listed above, which primarily address the use of recycled tire rubber in playfield applications, research has also been conducted on crumb rubber effects in construction processes, landfill runoff barriers, asphalt pavement and landscaping mulch. The findings of these studies in matters of human and environmental health generally agree with those of the playfield studies. Research is furthermore available on the risk of injury from falls onto rubber surfaces as compared to alternative materials. Findings conclude an overall decreased risk of injury where rubberized surfaces have been installed.
Click for: Additional Studies and Findings