Personally I have played sports my entire life. I’ve played basketball, baseball, lacrosse, soccer, and ran cross country throughout my athletic career. For a majority of these sports, many of them required the use of an outdoor grass field. A field like this requires constant maintenance. The field has to be watered properly, mowed every week, new lines have to be spray painted on for certain sports, and when it rains the field is usually rendered unable to use. To combat this synthetic turf was created.
Synthetic turf fields, as most of you may know, are fields that mimic grass fields without using real grass. The actual turf part is made out of synthetic fibers, usually containing nylon, polyethylene, and polypropylene. None of these materials are necessarily harmful to humans in the format they are being used in. To base the turf, a combination of sand and crumb rubber is used.
Crumb rubber is where the problem lies.
Crumb rubber are the little black pellets that lie within the strands of artificial grass. The crumb rubber is usually made from recycled tires, and other recycled rubbers. Because it is made from recycling other objects, the exact ingredients within each granule of crumb rubber could be different. Some of these ingredients have also been proven to be harmful. A usual scrap tire contains 70% recoverable rubber, 15% steel, 3% fiber, and 12% of filler materials. In order to make the crumb rubber, the tire goes through an ambient process in which the recoverable rubber is separated out from the rest of the materials. Each company has its own ambient process and this is currently unregulated which can lead to harmful granules being produced.
So what exactly is harmful about the crumb rubber?
Other than the lack of regulation, many studies have bee done to examine what is really harmful in the crumb rubber. One study conducted by the University of Connecticut Health Center (UCHC) studied air concentrations on five different active fields, and looked for 200 different chemicals. The study was looking for any volatile organic compounds (VOC) or semi-volatile organic compounds (SVOC) found in the air surrounding the fields or within the crumbs themselves. The four most common VOCs found within the rubber crumbs were acetonitrile, methylene chloride, methyl alcohol, and methyl isobutyl ketone. As far as compounds in the air, the SVOC Benzothiazole was the most common. Not much is known about these compounds in regards to human consumption, although they all contain acute-toxicity. Benzothiazole (BZT) is known to cause respiratory issues and dermal sensitization. BZT has also been found in salmonella during metabolic activation, which means when the compound is broken down by the body, a carcinogen could be activated and mutations could occur, which is what causes cancer.
Another study conducted by The Connecticut Department of Public Health once again revealed toxic compounds on synthetic turf fields. Four fields were studied, an adult outdoor and indoor field, and a children’s outdoor and indoor field. Two VOCs that cause the greatest risk for cancer were found in the fields were benzene and methylene chloride. BZT was found in higher numbers in the indoor fields, as the compound is airborne, and the indoor facilities contain it more than the outside fields. Because of this, the indoor field cancer risks were two-fold that of the outfield. Although it was concluded that even though cancer risks were slightly above the minimum regulatory levels, the cancer risk was not to be published as a public safety concern.
Lead was found in a study by Connecticut Department of Environmental Protection where runoff from turf fields was tested for different leached metals. Along with this, high levels of zinc were found and were proved to be harmful to the surrounding groundwater and surface water.
As shown by these studies multiple toxins and possible carcinogens have been proven to be within and emitted by crumb rubber pellets. The main problem is a lack of testing. Many of these toxins have unknown effects on humans, and there potential as carcinogens is unknown. There are also an extreme amount of confounding variables as each granule can differ in what it contains, as well as the fact that each company could use different tires, materials, and methods to produce them. This makes creating a statistically significant result that is widespread very challenging There is also discrepancy on high the levels of these VOCs and SVOCs have to be to cause an effect on humans, but either way more testing has to be done in order to solve this potential issue.