My kids love the first opportunity of the season to kick off their shoes, peel off their socks, and run around outside with bare feet. I admit, my toes appreciate a little dirt in between them now and then, too, but more and more these days, I am wondering about what lies beneath. Not so much in my own yard, but at my neighbors and at the park and the playground. I’ve worried about pesticides for years now, but recently a new concern has arisen. It all started when I noticed a big truck dumping new ground covering around my daughter’s school playground. What the heck was it?
After school I followed her back to the playground and smelled its acrid odor before I saw it (my nose is my initial alarm system for toxic intruders and in this case, the bells were ringing loudly). As we stepped closer I saw that the ground covering was a loose fill of what appeared to be shredded tires. Wait a minute, I thought to myself, aren’t tires considered hazardous waste? Isn’t that why we can’t just toss them in the garbage? Why are we using these where our kids play?
This definitely warranted an eco-mom investigation and what I discovered was confusing to say the least.
The Tale of the Tire
Apparently, tires have been a solid waste issue for many decades now and with an increasing amount of vehicles on the road, the issue continues to grow. At the end of 2003 alone, the US had generated close to 300 million scrap tires. Without government intervention regulating disposal, tires were left to pile up creating breeding grounds for mosquitoes and spontaneously igniting into toxic bonfires. They aren’t, as I had initially assumed, hazardous waste. They only necessitate special disposal to avoid the accumulation of tires that prompts the aforementioned breeding grounds and toxic fires.
Fortunately, markets now exist for 80% of scrap tires-up from 17% in 1990. These markets – both recycling and beneficial use – continue to grow. Almost half of the tires are burned for fuel, another 20 percent are used in civil engineering projects, about 8 percent is ground up and recycled into other products and about 4 percent is ground up and used in rubber-modified asphalt. The remainder are exported, retreaded, used “miscellaneously”, or land-filled.
Many of these applications are indeed a beneficial second life for a product so integral to modern life. Still, I questioned the physical make-up of tires and the initial research I was finding demonstrating toxic chemicals and heavy metals leaching out of tires. Studies basically show the levels to be minimal, but the mom and environmental health advocate in me always questions “safe levels.” If there’s a safer alternative, why accept even a “minimal” risk? I am a huge proponent of recycling, but why are we using a potentially risky material where our children play?
A Second Life: Tires as Turf for Athletic Fields and Playgrounds
We’ve been using artificial turf for decades and it takes a variety of forms, including rubberized asphalt, playground surfaces, and landscape mulches. The original AstroTurf fields are beginning to degrade and release alarming amounts of lead into the environment. These fields are being torn up and replaced with the latest fake, partially constituted of old tires. Initially touted as an environmentally responsible way to recycle old tires, more are questioning the logic behind using a material too risky to dispose of in landfills for ground cover where our children play.
While the media is mostly covering the use of what’s known as “crumb rubber” as infill on synthetic athletic field coverings, scrap tires can also be recycled into solid surfaces, as well as used as loose fill like in the situation of my daughter’s school. In this case, the rubber is simply shredded and dumped around the base of a play structure.
My initial research found that contention over the use of this product is growing across the US. Many states and municipalities are halting the continued use of tire turf until more studies are conducted to ensure the safety of the surface.
There are almost no studies on potential health impacts (especially long-term) from using tire rubber, but preliminary reports have found definitive evidence of potential risk. The California Office of Environmental Health Hazard Assessment (OEHHA), in a January 2007 report Evaluation of Health Effects of Recycled Waste Tires in Playground and Track Products, found that 49 chemicals could be released from tire crumbs.
Recycled crumb rubber contains a number of chemicals that are known or suspected to cause health effects. The most common types of synthetic rubber used in tires are composed of ethylene–propylene and styrene–butadiene combined with vulcanizing agents, fillers, plasticizers, and antioxidants in different quantities, depending on the manufacturer. Tire rubber also contains polyaromatic hydrocarbons (PAHs), phthalates, and volatile organic compounds (VOCs).
Rubber leachates are also complex solutions, some of which are known to be harmful to human health; effects of exposure range from skin and eye irritation to major organ damage and even death. Long term exposure can lead to neurological damage, carcinogenesis, and mutagenesis.
While these findings lead one to believe the material is indeed toxic, it is argued that since the rubber is “vulcanized,” the toxins are locked in. Some companies claim the material is indestructible and non-biodegradable, completely safe and non-toxic. Simultaneously, they admit that there is an odor at first (which is evidence of chemicals volatilizing from the material….not locked in after all).
Every study I have come across has only served to emphasize that the devil is in the details. It depends on what form the recycled rubber takes, what degree of usage is endured, and what climate and other environmental factors may impact degradation. Since there are relatively few studies on leaching and health impacts when using scrap tires in these various ways, I have had to try to examine the evidence already available from other uses and make assumptions about what it means for my daughter.
The State of Evidence (or Lack Thereof)
In 1994, the Minnesota Pollution Control Agency found that due to heavy metals and other pollutants in tires there is a potential risk for the leaching of toxins into the groundwater when placed in wet soils. Admitting the almost unpredictable nature of tires, this report stated “research has shown that very little leaching occurs when shredded tires are used as light fill material, however limitations have been put on use of this material; each site should be individually assessed determining if this product is appropriate for given conditions.”
A 1998 study from the University of Massachusetts reviewed all of the existing literature in order to assess the safety of using recycled tires as light fill in civil engineering projects. While they concluded that it appeared safe, they also stated that “it would be prudent to perform field studies on these areas over longer periods of time. It is important to recognize that the impact of scrap tires on the environment varies according to the local water and soil conditions, especially pH value.”
The 2007 study conducted by the California Office of Environmental Health Hazard Assessment concluded that recycled tires posed minimal risk when used as shredded loose fill, but again reiterated the importance of understanding local climate impacts because the tires may degrade differently in different conditions. They also concluded that they needed further research on the potential toxicity of crumb rubber.
Later in 2007, the Connecticut Department of Analytical Chemistry conducted some of the first experiments on the potential toxicity of crumb rubber. “The laboratory data presented here support the conclusion that under relatively mild conditions of temperature and leaching solvent, components of crumb rubber produced from tires (i) volatilize into the vapor phase and (ii) are leached into water in contact with the crumbs…Based on these data further studies of crumb rubber produced from tires are warranted under both laboratory, but most especially field conditions.”
A study released in May 2009 by New York State Agencies “found the presence of dozens of chemicals — including lead, zinc and benzene — but all were below federal safety standards.” (I must point out that these standards are set for individual chemicals, they really don’t know the impact of the mixture of chemicals present in crumb rubber. Also, standards are often estimated based on adult biology and do not take into account a child’s unique vulnerabilities given their developing bodies.)
Each of these studies and others like them have each examined only one small piece of the puzzle. Compiled together, the picture still isn’t very clear. We don’t know long-term impacts. We don’t know how the various heavy metals and chemicals might interact and impact a developing child’s system. We don’t even know how much or which heavy metals and chemicals might leach in any specific application.
Given these gaps in information, the US EPA is revisiting its earlier endorsements of the material. According to internal documents they “identified potential hazards to children playing on surfaces made of tire crumb that include toxics entering the lungs from particulates, fibers, volatile organic compounds, and latex.” The memo also discussed the ingestion of toxic heavy metals and dyes. “It appears that there are valid reasons to take a broader perspective of all potential risks associated with crumb rubber” through an extensive study, said the memo from Assistant Regional Administrator Stephen Tuber.
In the Face of Uncertainty
Our gap in knowledge has prompted actions nationwide and a lot of research is underway. Still, most of these studies are limited at best, only addressing the use of crumb rubber on athletic fields. It’s a legitimate concern, but what about solid surface and loose fill like my daughter’s school playground?
While we wait for the jury’s verdict, I have a few questions of my own. It’s commendable to find alternative uses for old tires, but why where our children play? Why not use old tires for parking lot asphalt or industrial building components? Why not just make tires that aren’t so toxic to begin with? Michelin is beginning to experiment with new formulations since Europe’s new REACH policy will compromise their ability to sell tires there. Will Michelin sell us safer tires, too? And how about creating synthetic turf from safer materials? Or what about nature’s standards, like grass (grown without pesticides, of course) and sand? I know abrasion and impact absorption are factors, but why do we prioritize acute impacts so far above chronic ones?
Aside from my growing list of questions, I’m encouraged by the amazing innovations that address everyone’s concerns. According to the March 2008 issue of Environmental Health Perspectives, one new 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. Company spokesperson Domenic Carapella says, “There are certainly alternatives to crumb rubber. There is no longer a reason to sacrifice the playing quality and more importantly the health of children [playing on synthetic turf].”
So often we dive into the unknown when we start using new products. We assume that they have been comprehensively tested for safety, but they aren’t required to be. When will we learn our lesson? It’s better to be safe than sorry, so while I’m still unclear about whether recycled tires are safe or not, I’m advocating for a moratorium on its use until we know more. I’m still looking, I’m still learning. Watch the Healthy Child blog (http://www.healthychild.org) for updates on what I uncover.