We live in an environment that is full of chemicals – some which are bad for us and yet are completely natural. We don’t subscribe to the notion that man-made is absolutely bad and natural is absolutely good – botulism is completely natural and can kill you just as dead. But sometimes we adopt products for our use in ways that can hurt us, because we don’t pay attention to the chemicals that are contained in that product nor of how we use the product. Recently, the crushed up tires that are appearing in playgrounds and as the playfield surface of schools around the country have become an object of concern, so let’s take a look at those.
Discarded rubber tires are the bane of waste management – according to the EPA, we generate 290 million scrap tires each year. Obviously finding a market for these slow-to-decompose materials is desirable, and many innovative uses have been developed, including using ground up tires on playground and sports field surfaces. According to the Synthetic Turf Council, this “crumb rubber has been installed in approximately 11,000 U.S. fields, tracks and playgrounds in the United States. And the California Office of Environmental Health says that recycled rubber tires have become one of the top choice materials for surfacing children’s playgrounds.
Crumb rubber is a black, pellet-like substance the size of a cracker crumb. Run your hand through the field, and you’ll pick up black dust, similar to the consistency of pencil graphite. It’s easy to spread, and can easily get into your mouth, shoes, clothing and nostrils. Routes of exposure, especially in the case of infants, can include dermal absorption, inhalation, and even ingestion directly from the material.
Here’s a story about crumb rubber from NBC news:
Various studies have identified the chemicals found in tires, which are made of 40-60% rubber polymers, carbon black (20-35%), silicas, process and extender oils (up to 28%), vulcanization chemicals and chemical anti-degradents, and plasticizers and softeners. It is well known that rubber tire debris contains toxic compounds such as highly aromatic oils and other reactive additives.
The EPA has identified a number of compounds which may be found in tires, though they’re quick to point out that not all are contained in every tire:
- heavy metals ( cadmium, chromium, iron, lead, magnesium, manganese, molybdenum, selenium, sulfur, and zinc, which can be as much as 2% of tire mass) – most of which have documented health consequences including damage to the central nervous system.
- Plasticizers (such as phthalates)- phthalates act as estrogens once absorbed by the body. They are considered endocrine disrupting chemicals (EDC’s); conditions associated with EDC’s include infertility; breast, prostate and ovarian cancers; asthma; and allergies.
- Styrene butadiene – associated with risk of leukemia; known to be genotoxic
- Benzene – known to be a human carcinogen; also impacts the nervous and immune systems
- Chloroethane, which causes cancer in mice, is also a neurotoxin
- Halogenated flame retardants – need we reiterate how these impact human health?
- Methyl ethyl ketone and methyl isobutyl ketone – there is no evidence of carcinogenicy or mutagenicy but studies show impairment of central nervous system; both are on the Hazardous Substances List by OSHA.
- Naphthalene – a group C carcinogen (possible human carcinogen); also causes neurological damage.
Another concern is the smell that wafts up from the playing field – like old tires – coupled with the fact that the fields often are 10 – 15 degrees warmer than the ambient temperature, and many of the compounds evaporate at temperatures as low as 77 degrees F. Compounds found to be present in the air in a study done by the Connecticut Agricultural Experiment Station include: 
- Benzothiazole: A skin and eye irritation, harmful if swallowed. There is no available data on cancer, mutagenic toxicity, teratogenic toxicity, or developmental toxicity.
- Butylated hydroxyanisole: A recognized carcinogen, suspected endocrine toxicant, gastrointestinal toxicant, immunotoxicant, neurotoxicant, skin and sense-organ toxicant. There is no available data on cancer, mutagenic toxicity, teratogenic toxicity, or developmental toxicity.
- n-hexadecane: A severe irritant based on human and animal studies. There is no available data on cancer, mutagenic toxicity, teratogenic toxicity, or developmental toxicity.
- 4-(t-octyl) phenol: Corrosive and destructive to mucous membranes. There is no available data on cancer, mutagenic toxicity, teratogenic toxicity, or developmental toxicity.
- Polycyclic aromatic hydrocarbons (PAHs): heavy occupational exposure leads to risk of lung, skin or bladder cancers; genotoxic, leading to malignancies and heritable genetic damage in humans.  In 2010, the EPA concluded that in the case of PAHs, “breathing PAHs and skin contact seem to be associated with cancer in humans.” The total concentration of PAHs in crumb rubber exceedes the Norwegian Pollution Control Authority’s normative values for most sensitive land use.
A 2012 study analyzing rubber mulch taken from children’s playgrounds in Spain found harmful chemicals present in all, frequently at high levels. Twenty-one samples were collected from 9 playgrounds in urban locations and screened for various pollutants. The results showed that all samples contained at least one hazardous chemical, with most containing multiple PAHs found at high concentrations. The authors concluded that the use of rubber recycled tires on playgrounds “should be restricted or even prohibited in some cases.”
Many, if not most, of the compounds present in tire crumbs and shreds have been incompletely tested for human health effects, so there is no data available to evaluate the chemicals (as evidenced by the four compounds above).
Artificial turf and rubber crumb manufacturers point to the fact that no research has linked cancer to artificial turf – yet most studies add the caveat that more research should be conducted.
According to Dr. Joel Forman, associate professor of pediatrics and preventive medicine at New York’s Mt. Sinai Hospital, in all these studies, data gaps make it difficult to draw firm conclusions. As he says, “None of [the studies] are long term, they rarely involve very young children and they only look for concentrations of chemicals and compare it to some sort of standard for what’s considered acceptable,” said Dr. Forman. “That doesn’t really take into account subclinical effects, long-term effects, the developing brain and developing kids.” Forman said that it is known that some of the compounds found in tires, “even in chronic lower exposures” can be associated with subtle neurodevelopmental issues in children.
“If you never study anything,” said Dr. Forman, “you can always say, ‘Well there’s no evidence that shows you have a problem,’ but that’s because you haven’t looked. To look is hard.”
Another notable critic of the stuff is Dr. Phillip Landrigan of the Mount Sinai School of Medicine, who submitted a letter to the New York City Planning Department last year expressing concerns over the carcinogens in tire crumbs.
He wrote that the principal chemical components of crumb rubber are Styrene and Butadiene — Styrene is neurotoxic, and Butadiene is a proven human carcinogen that has been shown to cause leukemia and lymphoma.
“There is a potential for all of these toxins to be inhaled, absorbed through the skin and even swallowed by children who play on synthetic turf fields,” Dr. Landrigan wrote. “Only a few studies have been done to evaluate this type of exposure risk.”
So if it walks like a duck, quacks like a duck and looks like a duck…
And as if to add insult to injury, wood chips were found to do a better job of protecting children from head trauma!
Remember that children are much more likely to be harmed by exposure to chemicals in their environment than adults because they’re smaller (therefore exposure is greater) and their bodies are still developing. So what’s a concerned parent to do?
- First – ignore the tire crumb playgrounds and find a good old wood chip or grass site.
- Teach your children the importance of frequent hand washing as many chemicals enter bodies via the mouth.
- And persuade local officials to use wood chips rather than recycled rubber.
 Llompart, Maria et al, “Hazardous organic chemicals in rubber recycled tire playgrounds and pavers”, Chemosphere, Vol. 90, issue 2, January 2013, pages 423-431
 Santos-Burgoa, Carlos; “Lymphohematopoietic Cancer in Styrene-Butadiene Polymerization Workers”, American Journal of Epidemiology, Volume 136, issue 7, pp. 843-854.
 Norppa, H and Sorsa, M; “Genetic toxicity of 1,3-butadiene and styrene”, IARC Scientific Publications, 1993 (127): 185-193.
 US Department of Health and Human Services, Agency for Toxic Substances and Disease Registry, “Toxicological Profile for Chloroethane”, December 1998 http://www.atsdr.cdc.gov/toxprofiles/tp105.pdf
Mattina, MaryJane et al; “Examination of Crumb Rubber Produced From Recycled Tires”, The Connecticut Agricultural Experiment Station, 2007, http://www.ct.gov/caes/lib/caes/documents/publications/fact_sheets/examinationofcrumbrubberac005.pdf
 US Environmental Protection Agency (EPA). Polycyclic Aromatic Hydrocarbons (PAHs)-Fact Sheet. January 2008. http://www.epa.gov/osw/hazard/wastemin/minimize/factshts/pahs.pdf
 Llompart M, Sanchez-Prado L, Lamas JP, Garcia-Jares C, et al. “Hazardous organic chemicals in rubber recycled tire playgrounds and pavers”. Chemosphere. 2012; Article In Press. http://dx.doi.org/10.1016/j.chemosphere.2012.07.053
 State of California-Office of Environmental Health Hazard Assessment (OEHHA), Contractor’s Report to the Board. Evaluation of Health Effects of Recycled Waste Tires in Playground and Track PrRememoducts. January 2007. http://www.calrecycle.ca.gov/publications/Documents/Tires%5C62206013.pdf
 State of California-Office of Environmental Health Hazard Assessment (OEHHA), Contractor’s Report to the Board. Evaluation of Health Effects of Recycled Waste Tires in Playground and Track Products. January 2007. http://www.calrecycle.ca.gov/publications/Documents/Tires%5C62206013.pdf