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Rubber Crumb and Synthetic TurF:
Research on the potential danger behind the plastic infill
With 1.5 billion tyres reaching end-of-life globally, there has been a call to reevaluate the tyre disposal process. In an attempt to recycle end-of-life tyres through the Tyre Stewardship Scheme, there has been an increase in the use of rubber crumb as soft fall surfaces on playgrounds and as infill in synthetic turf sporting fields. Rubber crumb material was developed with the aim to reduce the environmental, health, and safety impacts from the common incineration process at the end of the tyre life cycle. But is this causing more harm than good?
As a nationwide citizen science program, AUSMAP aims to quantify microplastic pollution with the primary goals of identifying litter hotspots and assisting in source reduction. Since 2018, AUSMAP and its community of volunteers and partners have collected over 600 samples and removed over 5 million microplastics from Australian waterways. In doing so, it has become apparent that sustained inputs of synthetic grass and rubber crumb are commonplace in both freshwater and coastal samples in NSW.
Revelations of environmental impacts and significant research gaps in the recent NSW Chief Scientist and Engineers Report (CSE) Synthetic Turf in Public Spaces (2023) have highlighted these materials as a critical concern.
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What is Rubber Crumb and synthetic turf?
Rubber Crumb is produced through shedding processes that mechanically break apart tyre material. The resulting rubber crumb granules are microplastics measuring <5mm. The granules are comprised primarily of synthetic rubber polymer and other reinforcing agents, aromatic extender oils, vulcanisation additives, antioxidants, and processing agents. The resulting granules are commonly used as road base, to fill synthetic sports fields and as a soft fall surface on playgrounds.
PHOTO: Horseshoe Bay playground, QLD | SOURCE: Tangaroa Blue
What is the Problem with Synthetic Turf fields and playgrounds?
In addition to the voluntary introduction of microplastics into the environment, there is a limited understanding of the potential impacts rubber crumb can have on human and environmental health.
Potential Human Health Impacts of synthetic turf fields
As of 2023, there are 181 synthetic sport fields in New South Wales alone. As this number increases, the impact that Australia’s climate has on the lifespan of rubber crumb surfaces has been a cause for further investigation. With an ambient air temperature of 26℃, artificial surfaces can reach over 60℃, posing a significant safety hazard. Additionally, of the 306 chemicals that are found in rubber crumb, 197 meet the theoretical criteria for carcinogens. There is currently limited research on the impact these materials have on children and athletes that frequently come into contact with rubber crumb, highlighting the need for more research
Adverse Environmental Impact
From both soft fall playgrounds and loose synthetic field infill, the small particle size enables rubber crumb to be highly mobile in aquatic environments. Additionally, the chemicals found in rubber crumb material can leach into the soil and waterways, potentially affecting environmental health. One chemical in particular is 6PPD- quinone, which is the result of 6PPD (an additive to prevent tyre degradation) interacting with ozone in the atmosphere. It was demonstrated to cause acute toxicity in Coho salmon and has been found in low concentrations in 5 key urban centres around Queensland. Similar to the extent of knowledge on human health, there is currently limited understanding of the environmental impacts of these materials therefore more research is needed in this area.
Rubber Crumb and synthetic turf in Australia
There is little known about the loss of rubber crumb and its potential impacts. That is where AUSMAP has stepped in.
Beginning with a collaboration between AUSMAP and Tangaroa Blue as part of the ReefClean Project, rubber crumb loss was assessed at playgrounds in the Great Barrier Reef catchment. More recently, AUSMAP has expanded their program to research the loss of rubber crumb and synthetic grass from synthetic turf fields.
During AUSMAPs ongoing efforts, it has become apparent that sustained inputs of synthetic grass and rubber crumb are commonplace in both freshwater and coastal samples in NSW, with potentially significant environmental implications.
Community education and empowerment is critical to raise further awareness and make actionable change. AUSMAP is working closely with partners and councils to address key knowledge gaps and evidence is being presented to local, state, and national governments.
Rubber Crumb Projects
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Rubber Crumb Research in QueenslanD
In the Rubber Crumb Loss Report with Tangaroa Blue, cores were collected from distances of 0, 2 and 4 metres from soft fall playground sites along the GBR coast. The estimated total loss for entire playground areas ranged from 22,620 to over 9.7 million rubber pieces. In the study, play area condition and play area cover were evaluated to examine factors that influence rubber crumb loss.
Results found that playgrounds greater than 5 years old had significantly higher loss than play areas less than 5 years old. It was also found that areas with full cover and partial cover had significantly lower rubber crumb loss than play areas with no cover. This factor could be due to consistent exposure to high UV levels.
NSW Findings in Synthethic Turf Research
Poulton Park was raised as an area of concern by the Oatley Flora and Fauna Society. The park consists of two synthetic fields situated next to Poulton Creek, which flows into the Georges River.
Community volunteers were trained by the AUSMAP team to follow a similar procedure to the Queensland study. Core samples were taken at three distances (0, 4 and 8 metres) from the sites. Results found that there were approximately 1 million pieces of rubber crumb or synthetic grass coming off those fields. These findings were presented to the local council and are being used to implement mitigation strategies.
AUSMAP completed toxicity studies to evaluate the impact of rubber crumb leachate on freshwater and marine species. Rubber crumb was leached for 18 hours. A freshwater water flea as well as larval marine mussel and sea urchin were exposed to diluted concentrations of the leachate.
Results found that concentrations of 1-3% affected 50 percent of the populations. This is likely due to concentrations of zinc which were significantly higher than the Australian Water Quality Trigger Value. Although other chemicals such as 6 PPD-q and HMMM were also recorded but further toxicity trials are needed to ascertain their impacts to local aquatic life.
Recently, AUSMAP has been working with Ku- ring- gai Council in Sydney’s north-west to quantify microplastic loss from a synthetic turf field and the efficacy of stormwater pit traps to reduce this loss. Results have highlighted that >100,000 particles of rubber crumb and synthetic grass are captured in most trap samples, representing 82% of the loss. However, sampling of the runoff water into a nearby creek found both crumb and synthetic grass to be prevalent. Key findings from this investigation highlight extreme microplastic loss from this surface that would enter the environment unabated without the presence of stormwater mitigation traps. The full impact of mitigation approaches is yet to be reported - and invariably, to date, are not common practice.
REFERENCES
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AUSMAP. (2021, December 1). BREAKING - Rubber Crumb Research released. Ausmap. https://www.ausmap.org/post/rubber-crumb-research-released
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Chittella, H., Yoon, L. W., Ramarad, S., & Lai, Z.-W. (2021). Rubber waste management: A review on methods, mechanism, and prospects. Polymer Degradation and Stability, 194, 109761. https://doi.org/10.1016/j.polymdegradstab.2021.109761
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Independent review into the design, use and impacts of synthetic turf in public open spaces Final report. (2022). https://www.chiefscientist.nsw.gov.au/__data/assets/pdf_file/0004/54223/CSE-Synthetic-Turf-Review-Final-Report.pdf
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Li, X., Berger, W., Musante, C., & Mattina, M. I. (2010). Characterization of substances released from crumb rubber material used on artificial turf fields. Chemosphere, 80(3), 279–285. https://doi.org/10.1016/j.chemosphere.2010.04.021
Perkins, A. N., Inayat-Hussain, S. H., Deziel, N. C., Johnson, C. H., Ferguson, S. S., Garcia-Milian, R., Thompson, D. C., & Vasiliou, V. (2019). Evaluation of potential carcinogenicity of organic chemicals in synthetic turf crumb rubber. Environmental Research, 169, 163–172. https://doi.org/10.1016/j.envres.2018.10.018
Rauert, C., Vardy, S., Daniell, B., Charlton, N., & Thomas, K. V. (2022). Tyre additive chemicals, tyre road wear particles and high production polymers in surface water at 5 urban centres in Queensland, Australia. Science of the Total Environment, 852, 158468. https://doi.org/10.1016/j.scitotenv.2022.158468
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Daniele Coppola, L. M. (2014). Release of Polycyclic Aromatic Hydrocarbons and Heavy Metals from Rubber Crumb in Synthetic Turf Fields: Preliminary Hazard Assessment for Athletes. Journal of Environmental & Analytical Toxicology, 05(02). https://doi.org/10.4172/2161-0525.1000265
Schneider, K., de Hoogd, M., Haxaire, P., Philipps, A., Bierwisch, A., & Kaiser, E. (2020). ERASSTRI - European Risk Assessment Study on Synthetic Turf Rubber Infill – Part 2: Migration and monitoring studies. Science of the Total Environment, 718, 137173. https://doi.org/10.1016/j.scitotenv.2020.137173
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