Crumb rubber

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Handful of crumb rubber UTB8VWb0DOaMiuJk43PTq6ySmXXaY.jpg
Handful of crumb rubber

Crumb rubber is recycled rubber produced from automotive and truck scrap tires. During the recycling process, steel and tire cord (fluff) are removed, leaving tire rubber with a granular consistency. Continued processing with a granulator or cracker mill, possibly with the aid of cryogenics or by mechanical means, reduces the size of the particles further. The particles are sized and classified based on various criteria including color (black only or black and white). The granulate is sized by passing through a screen, the size based on a dimension (1/4 inch) or mesh (holes per inch : 10, 20, etc.). Crumb rubber is often used in artificial turf as cushioning.

Contents

Background

The first synthetic grass was placed over concrete in 1964 and became known as “Chem Grass”. It was later named "AstroTurf" when it was installed in the Houston Astrodome in 1966. Athletes did not like playing on these fields because of the risk of injury due to the hard surface. A new artificial turf system was developed in the early 2000s based on "crumb rubber." The black crumbs are small pieces of styrene-butadiene rubber made from grinding up old vehicle tires. The tire crumbs are poured in between the artificial grass blades, giving the artificial fields more cushion and support. This reduced major injuries compared to AstroTurf. [1]

Recycled pavement material

Rubberized asphalt is the largest market for crumb rubber in the United States, consuming an estimated 220 million pounds (100 kt), or approximately 12 million tires annually. [2] Crumb rubber is also used as ground cover under playground equipment, and as a surface material for running tracks and athletic fields. [2]

Grading

The following are common classifications of crumb rubber: [3]

Retreaders tire buffings shall consist of clean, fresh, dry buffings from tire retread preparation operations.

No.1 - Tire Granule shall consist of granulated tire crumb, Black Only Guaranteed MetalFree, sized. Magnetically separated materials are not acceptable. Fluff from tire cord removed.

No.2 - Tire Granule shall consist of granulated tire crumb, Black & White Guaranteed MetalFree, sized to minus 40 Mesh. Magnetically separated materials are not acceptable. Fluff from tire cord removed.

No.3 - Tire Granule shall consist of granulated tire crumb, Black Only Magnetically Separated, sized. Fluff from tire cord removed.

No.4 - Tire Granule shall consist of granulated tire crumb, Black & White Magnetically Separated, sized. Fluff from tire cord removed.

No.5 - Tire Granule shall consist of unclassified granulated tire crumb, Sized, Unseparated, not magnetically separated, fluff from tire cord not removed.

Purposes

Benefits

When dealing with asphalt overlays, reflection cracks can arise and cause an unwanted crack pattern beneath the pavement. Rubber-modified asphalt uses stress absorbing membranes that reduce the reflective cracking because of its elastic properties. With fewer cracks, there are fewer repairs, so crumb rubber assists in reducing maintenance costs. The pavement has an increased lifespan because after multiple uses and exposure to different elements, regular asphalt loses elasticity over time. The use of the artificial rubber resists the formation of cracks and has an anti-aging effect that keeps the asphalt in a better condition. [5]

Concerns

Scientific research

Crumb rubber infill has been a widely studied topic. To date, there are nearly 100 studies and reports, from government bodies and independent researchers, that have assessed the potential for health risks based on various pathways of exposure. Connecticut’s Department of Public Health conducted an extensive study and published three peer-reviewed studies on the safety of crumb rubber [6] and determined that there is “no scientific support for a finding of elevated cancer risk from inhalation or ingestion of chemicals derived from recycled tires used on artificial turf fields.” [7] In 2015, the Massachusetts Department of Public Health also studied crumb rubber and came to a similar conclusion. [8]

The US Environmental Protection Agency (EPA) was about to conclude a peer led study of all US studies in mid to late 2018, using peer and public evidence to fill in the information gaps between the avenues of study and real life anecdotal concerns, experiences with medical scientific perspectives included. In the EU, the European Chemicals Agency (ECHA) had also produced a report titled ANNEX XV which specifically looked at rubber crumb chemical make up and at concerns. It too overall concluded that the risks were extremely low compared to the benefits of health and exercise. However, as recently as 2017 and again in 2018, further chemicals have begun to be scrutinized further which were previously unregistered in that incarnation of the ANNEX report on rubber crumb. Substances of Very High Concern (SVHCs) are carcinogenic chemicals, endocrine disruptive chemicals, and chemicals dangerous to aquatic life that are being identified as in need of restriction in the ECHA REACH2018 program. Chemicals such as chrysene, benzo(a)pyrene, benzo(e)pyrene, benzene and others are now on the restricted chemicals Candidate List, ready to be included in the next incarnation of the ANNEX XIV report. [9]

Athletics

Artificial turf fields are found all over the United States and are most commonly found at major high schools and athletic facilities. Crumb rubber is used as the infill in artificial turf systems to make the surface safe. The Synthetic Turf Council says there are about 13,000 fields using crumb rubber, with about 1,500 new installations annually. [10]

Volumes of research and testing from academics, federal and state governments including New York, California, Massachusetts and Connecticut, and school systems have examined everything called into question about synthetic turf. Many of these studies concluded that no health risks exist. Contradicting studies have found that the raw source material (automotive tires) contains high levels of polycyclic aromatic hydrocarbons and metals such as zinc which have proven dermal, acute, and long-term health effects. The EPA is (as of fall 2015) investigating the health effects of exposure to crumb rubber and the initial results of this study were expected at the beginning of 2016.

The Connecticut Department of Public Health concluded "Based upon these findings, the use of outdoor and indoor artificial turf fields is not associated with elevated health risks. However, it would be prudent for building operators to provide adequate ventilation to prevent a buildup of rubber-related volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) at indoor fields. The current study did not evaluate new fields under hot weather conditions and so the potential for acute risks under this circumstance is another uncertainty. The current results are generally consistent with the findings from studies conducted by New York City, New York State, the USEPA and Norway which tested different kinds of fields and under a variety of weather conditions. Thus, it appears that the current results are reasonably representative of conditions that can be encountered at indoor and outdoor crumb rubber fields, although this tentative conclusion could benefit from the testing of additional fields.." [11]

A study by Brian T. Pavilonis, et al. found “ that for the products and fields we tested, exposure to infill and artificial turf was generally considered de minimus[ sic ], with the possible exception of lead for some fields and materials.” [12]

FIFA’s Chief Medical Officer Prof. Jiří Dvořák says that “The majority of the studies have been on higher surface area particles and have concluded they are currently acceptable. Therefore the larger granules used in artificial turf will have even less potential for emissions. For example a study undertaken by the Danish Ministry of the Environment concluded that the health risk on children’s playgrounds that contained both worn tires and granulate rubber was insignificant. The available body of research does not substantiate the assumption that cancer resulting from exposure to styrene-butadiene (SBR) granulate infills in artificial turf could potentially occur.” [13]

Scientific Instrument Services, Volatile Organic Emissions from Automobile Tires, 1999, Santford V. Overton & John J. Manura : Tire "Brand A were found to contain numerous straight and branched chain hydrocarbons, aldehydes, alcohols, ketones, furans and benzene derivatives." Tire brand B was..."found to contain high concentrations of the compounds sulfur dioxide (DOT), 2-methyl-1-propene, 2-propanone, 2-methyl-2-pentene, 2,4-pentanedione, acetic acid and 2,4-(1H, 3H) pyrimidinedione." Chemicals extracted from raw tires in this study would be found in crumb rubber, which is made by grinding feedstock tires. The chemicals listed above include carcinogens, and other chemicals with dermal and endocrine disrupting impacts. [14]

Current bans and restrictions

Environmental impacts

Crumb rubber is used as a filling in artificial turf fields. In 2007, use in this capacity prevented about 300 million pounds of rubber from polluting landfills. Generally, it takes 20,000–40,000 scrap tires to produce enough filling to cover an average football field (City of Portland, 2008) [19]

Due to its small size, crumb rubber is however considered a significant source of microplastics pollution. [20] A 2022 study uncovered the "potential adverse consequences of extensive rubber crumb application and exposure to environmental conditions." The crumb rubber examined was found to contain high levels of PAHs, as well as zinc at concentrations that may "pose a risk to aquatic organisms in particular". [21]

The Connecticut Department of Environmental Protection found in a 2010 study that stormwater passing through crumb rubber regularly exceeded aquatic acute toxicity for zinc. Additionally, copper, barium, manganese and aluminum were found at elevated levels after stormwater contacted the materials. Semi-volatile organic compounds and PAHs were found to be elevated as well. The levels of most of these compounds were higher than background but were below levels regulated in waterways for environmental protection. [22]

Disposal

A synthetic turf field has a lifespan of about 10 years, requiring up to 330 million pounds of waste disposal annually from replaced fields. [10] Although the rubber itself is recycled, the crumb is difficult to reuse further and is largely disposed of in landfills. [10]

Related Research Articles

Coal tar is a thick dark liquid which is a by-product of the production of coke and coal gas from coal. It is a type of creosote. It has both medical and industrial uses. Medicinally it is a topical medication applied to skin to treat psoriasis and seborrheic dermatitis (dandruff). It may be used in combination with ultraviolet light therapy. Industrially it is a railroad tie preservative and used in the surfacing of roads. Coal tar was listed as a known human carcinogen in the first Report on Carcinogens from the U.S. Federal Government.

<span class="mw-page-title-main">Tire</span> Ring-shaped covering that fits around a wheels rim

A tire or tyre is a ring-shaped component that surrounds a wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide traction on the surface over which the wheel travels. Most tires, such as those for automobiles and bicycles, are pneumatically inflated structures, which also provide a flexible cushion that absorbs shock as the tire rolls over rough features on the surface. Tires provide a footprint, called a contact patch, that is designed to match the weight of the vehicle with the bearing strength of the surface that it rolls over by providing a bearing pressure that will not deform the surface excessively.

<span class="mw-page-title-main">Dichloromethane</span> Chemical compound

Dichloromethane is an organochlorine compound with the formula CH2Cl2. This colorless, volatile liquid with a chloroform-like, sweet odor is widely used as a solvent. Although it is not miscible with water, it is slightly polar, and miscible with many organic solvents.

<span class="mw-page-title-main">Asphalt concrete</span> Composite material used for paving

Asphalt concrete is a composite material commonly used to surface roads, parking lots, airports, and the core of embankment dams. Asphalt mixtures have been used in pavement construction since the beginning of the twentieth century. It consists of mineral aggregate bound together with bitumen, laid in layers, and compacted. The process was refined and enhanced by Belgian-American inventor Edward De Smedt.

<span class="mw-page-title-main">Butadiene</span> Chemical compound

1,3-Butadiene is the organic compound with the formula CH2=CH-CH=CH2. It is a colorless gas that is easily condensed to a liquid. It is important industrially as a precursor to synthetic rubber. The molecule can be viewed as the union of two vinyl groups. It is the simplest conjugated diene.

<span class="mw-page-title-main">Carbon black</span> Chemical compound

Carbon black is a material produced by the incomplete combustion of coal and coal tar, vegetable matter, or petroleum products, including fuel oil, fluid catalytic cracking tar, and ethylene cracking in a limited supply of air. Carbon black is a form of paracrystalline carbon that has a high surface-area-to-volume ratio, albeit lower than that of activated carbon. It is dissimilar to soot in its much higher surface-area-to-volume ratio and significantly lower polycyclic aromatic hydrocarbon (PAH) content. However, carbon black can be used as a model compound for diesel soot to better understand how diesel soot behaves under various reaction conditions as carbon black and diesel soot have some similar properties such as particle sizes, densities, and copolymer adsorption abilities that contribute to them having similar behaviours under various reactions such as oxidation experiments. Carbon black is used as a colorant and reinforcing filler in tires and other rubber products; pigment and wear protection additive in plastics, paints, and ink pigment. It is used in the EU as a food colorant when produced from vegetable matter (E153).

<span class="mw-page-title-main">FieldTurf</span> Brand of artificial turf used for athletic playing fields

FieldTurf is a brand of artificial turf playing surface. It is manufactured and installed by FieldTurf Tarkett, a division of French company Tarkett. FieldTurf is headquartered in Montreal, Quebec, Canada, and its primary manufacturing facility is located in Calhoun, Georgia, United States. With a design intended to more accurately replicate real grass, the new product rapidly gained popularity in the late 1990s.

<span class="mw-page-title-main">Artificial turf</span> Surface of synthetic fibers made to look like natural grass

Artificial turf is a surface of synthetic fibers made to look like natural grass, used in sports arenas, residential lawns and commercial applications that traditionally use grass. It is much more durable than grass and easily maintained without irrigation or trimming, although periodic cleaning is required. Stadiums that are substantially covered and/or at high latitudes often use artificial turf, as they typically lack enough sunlight for photosynthesis and substitutes for solar radiation are prohibitively expensive and energy-intensive. Disadvantages include increased risk of injury especially when used in athletic competition, as well as health and environmental concerns about the petroleum and toxic chemicals used in its manufacture.

<span class="mw-page-title-main">Ethylbenzene</span> Hydrocarbon compound; precursor to styrene and polystyrene

Ethylbenzene is an organic compound with the formula C6H5CH2CH3. It is a highly flammable, colorless liquid with an odor similar to that of gasoline. This monocyclic aromatic hydrocarbon is important in the petrochemical industry as a reaction intermediate in the production of styrene, the precursor to polystyrene, a common plastic material. In 2012, more than 99% of ethylbenzene produced was consumed in the production of styrene.

<span class="mw-page-title-main">Chloroprene</span> Chemical compound

Chloroprene is the common name for 2-chlorobuta-1,3-diene (IUPAC name) with the chemical formula CH2=CCl−CH=CH2. Chloroprene is a colorless volatile liquid, almost exclusively used as a monomer for the production of the polymer polychloroprene, better known as neoprene, a type of synthetic rubber.

<span class="mw-page-title-main">Tire manufacturing</span> Process of tire fabrication

Pneumatic tires are manufactured according to relatively standardized processes and machinery, in around 455 tire factories in the world. With over 1 billion tires manufactured worldwide annually, the tire industry is a major consumer of natural rubber. Tire factories start with bulk raw materials such as synthetic rubber, carbon black, and chemicals and produce numerous specialized components that are assembled and cured.

Rubbertown is a neighborhood of Louisville, Kentucky, located along the Ohio River. During World War II, it became the home of many industrial plants which remained after the war and led to its name. Its largest businesses include American Synthetic Rubber, Borden Chemical, DuPont Dow Elastomers, Noveon, Dow Chemical, and Zeon Chemicals.

Rubber mulch is a type of mulch used in gardens and landscaping that is made from recycled rubber, most often crumb rubber sourced from waste tires.

<span class="mw-page-title-main">Tire recycling</span> Reuse of waste tires

Tire recycling, or rubber recycling, is the process of recycling waste tires that are no longer suitable for use on vehicles due to wear or irreparable damage. These tires are a challenging source of waste, due to the large volume produced, the durability of the tires, and the components in the tire that are ecologically problematic.

Rubberized asphalt concrete (RAC), also known as asphalt rubber or just rubberized asphalt, is noise reducing pavement material that consists of regular asphalt concrete mixed with crumb rubber made from recycled tires. Asphalt rubber is the largest single market for ground rubber in the United States, consuming an estimated 220,000,000 pounds (100,000,000 kg), or approximately 12 million tires annually.

Micronized rubber powder (MRP) is classified as fine, dry, powdered elastomeric crumb rubber in which a significant proportion of particles are less than 100 µm and free of foreign particulates. MRP particle size distributions typically range from 180 µm to 10 µm. Narrower distributions can be achieved depending on the classification technology.

<span class="mw-page-title-main">Artificial turf–cancer hypothesis</span>

Artificial turf is surface of synthetic fibers resembling natural grass. It is widely used for sports fields for being more hard-wearing and resistant than natural surfaces. Most use infills of crumb rubber from recycled tires; this use is controversial because of concerns that the tires contain carcinogens.

<span class="mw-page-title-main">Tire recycling in the United States</span>

Tire recycling in the United States is the disposal and reuse of waste tires.

Rubber pollution, similar to plastic pollution, occurs in various environments, and originates from a variety of sources, ranging from the food industry processing chain to tire wear. Synthetic and natural rubber dust and fragments now occur in food, airborne as particulates in air pollution, hidden in the earth as soil pollution, and in waterways, lakes and the sea.

References

  1. ↑ Rappleye, Hannah (8 October 2014). "How Safe is the Artificial Turf?". NBC.
  2. 1 2 EPA. "Management of Scrap Tires" . Retrieved 2007-06-12.
  3. ↑ "Granulated Rubber (Tire Crumb)" . Retrieved July 15, 2012.
  4. ↑ "Artificial Turf: Exposures to Ground Up Rubber Tires - Athletic Fields, Playgrounds, Garden Mulch". Environment and Human Health Inc.
  5. ↑ "Benefits of Rubberized Asphalt". Clemson. Archived from the original on 2015-01-19. Retrieved 2015-01-08.
  6. ↑ Health, Department of Public. "DPH: Artificial Turf Fields". ct.gov. Retrieved 2016-04-28.
  7. ↑ "Archived copy". Archived from the original on 2016-04-06. Retrieved 2016-04-28.{{cite web}}: CS1 maint: archived copy as title (link)
  8. ↑ "Archived copy" (PDF). Archived from the original (PDF) on 2016-05-13. Retrieved 2016-04-28.{{cite web}}: CS1 maint: archived copy as title (link)
  9. ↑ "Candidate List of substances of very high concern for Authorisation - ECHA".
  10. 1 2 3 FairWarning, Marjie Lundstrom, Eli Wolfe (2019-12-19). "The Dangerous Pileup of Artificial Turf". The Atlantic. Retrieved 2020-01-02.{{cite web}}: CS1 maint: multiple names: authors list (link)
  11. ↑ "Department of Energy and Environmental Protection" (PDF).
  12. ↑ Pavilonis, Brian T.; Weisel, Clifford; Buckley, Brian; Lioy, Paul J. (2014). "Bioaccessibility and Risk of Exposure to Metals and SVOCs in Artificial Turf Field Fill Materials and Fibers". Risk Analysis. 34 (1): 44–55. doi:10.1111/risa.12081. PMC   4038666 . PMID   23758133.
  13. ↑ "Archived copy" (PDF). Archived from the original (PDF) on 2016-02-22. Retrieved 2016-04-18.{{cite web}}: CS1 maint: archived copy as title (link)
  14. ↑ "Note 37: Volatile Organic Emissions from Automobile Tires". sisweb.com.
  15. ↑ "Turf War: One Suburb Bans Crumb Rubber, Another Says It's Safe". NBC News . 2 October 2015. Retrieved January 13, 2023.
  16. ↑ "Moratorium on crumb rubber artificial turf" . Retrieved January 13, 2023.
  17. ↑ "RTM proactively bans crumb rubber artificial turf". 13 December 2018. Retrieved January 13, 2023.
  18. ↑ "COMMISSION REGULATION (EU) …/… of XXX amending Annex XVII to Regulation (EC) No 1907/2006 of the European Parliament and of the Council concerning the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) as regards synthetic polymer microparticles" . Retrieved January 15, 2023.
  19. ↑ "Review of the Impacts of Crumb Rubber in Artificial Turf Applications". Liberty Tire. Archived from the original on 2015-01-08.
  20. ↑ "Scientific committees: EU-wide restriction best way to reduce microplastic pollution".
  21. ↑ Fořt, Jan; Kobetičová, Klára; Böhm, Martin; Podlesný, Jan; Jelínková, Veronika; Vachtlová, Martina; Bureš, Filip; Černý, Robert (2022). "Environmental Consequences of Rubber Crumb Application: Soil and Water Pollution". Polymers. 14 (7): 1416. doi: 10.3390/polym14071416 . PMC   9003429 . PMID   35406290.
  22. ↑ "Department of Energy and Environmental Protection" (PDF).
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