Crumb Rubber

…a crumbled tyre is still a tyre and remains toxic, regardless of where you put it…

What is crumb rubber? Crumb rubber is made from recycled tyres – they are quite literally ground up into crumbs. These rubber crumbs are then used for a number of purposes including as the infill in artificial turf systems for sports fields. Artificial or synthetic turf has been used since the 1960s – older fields were generally comprised of hard mats of nylon grass and many athletes using these fields complained that the surface was harder than grass and caused more injuries. Newer synthetic turf fields were developed to simulate natural grass fields by using infill material to make the fields softer and by adding plastic grass on the surface. Increasingly, the infill material of choice is crumb rubber, and it can be found in the playing fields of many schools and GAA football pitches across Ireland. A FIFA report in 2017 found that in the period from 2006 to the completion of the report, 3,437 pitches had been certified with the world governing body in 149 countries. [Sam Wallace,]

Unfortunately, what hasn’t been properly taken into consideration and is only now getting proper attention, is the potential impact of this crumb rubber on human and environmental health – crumb rubber is currently in the pre-registration process for addition to the EU Candidate List of Substances of Very High Concern (SVHC) and scientific studies in the USA are pointing towards respiratory and carcinogenic effects of the rubber crumb infill. On pitches where crumb rubber is moving into surrounding areas or being washed into our waterways, the impact on surrounding ecosystems has yet to be adequately examined. []

HUMAN HEALTH: The two primary concerns are the effects of crumb rubber on respiratory health and the carcinogenic properties of the infill. It has long been known that tyre production factories have reported a “higher than normal” rate of respiratory problems and cancers amongst their workers. A report by Environmental and Human Health, Inc (EHHI) cited studies at the Connecticut Agricultural Experiment Station (CAES), which identified the following chemicals in rubber crumb: (1) Benzothiazole – a skin and eye irritation that is harmful if swallowed; (2) Butylated hydroxyanisole – a recognised carcinogen, suspected endocrine toxicant, gastrointestinal toxicant, immunotoxicant, neurotoxicant, skin and sense-organ toxicant; (3) n-hexadecane: a severe irritant; (4) (t-octyl) phenol: corrosive and destructive to mucous membranes. The study also detected metals that were leached from the tyre crumbs. Zinc was the predominant metal, but selenium, lead and cadmium were also identified. Some of the compounds identified are either known or suspected carcinogens. Crumb rubber also has oils that contain polycyclic aromatic hydrocarbons (PAHs). PAHs generally have a low degree of acute toxicity to humans – their toxicity is accumulative, which means it builds up over time and repeated exposure. The most significant endpoint of PAH toxicity is cancer. Increased incidences of lung, skin, and bladder cancers are associated with occupational exposure to PAHs.

The outcome of the EHHI report was their conclusion that the toxic actions of concern from the materials being released from recycled rubber crumb include severe irritation of the respiratory system, severe irritation of the eyes, skin and mucous membranes, systemic effects on the liver and kidneys, neurotoxic responses, allergic reactions, cancers, and developmental effects. [Peter Britton,]

ENVIRONMENTAL HEALTH: In 2016, global production of natural and synthetic rubber reached 27.3 million tons with approximately 70% being used in the manufacture of vehicle tyres. It is estimated that there are one billion end-of-life tyres generated globally each year. Despite the EU banning tyres from landfill due to toxicity and the risk of pollutant release, production of crumb rubber has been considered an acceptable way of utilising this waste material and, ironically, is often considered recycling. Just for reference (with regards to environmental impact) it is estimated that 100–120 tonnes of crumb rubber are used on a single full-sized artificial football field and that of this 1.5–2.5 tonnes is lost annually with most of this being lost into the surrounding environment. 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. [Antonia Praetorius, Frontiers in Environmental Science]

MICROPLASTIC POLLUTION: In addition to all the direct human and environmental health concerns as outlined above, crumb rubber is classifiable as a microplastic, which is defined as “small plastic pieces less than 5mm long which can be harmful to our ocean and aquatic life” [US National Oceanic and Atmospheric Administration]. We know how detrimental microplastics are to the environment and how extensive the contamination is; the effects of microplastics on human health are also still being investigated, with evidence of microplastics recently being found in human blood and in the placenta. Losses and movement of these crumbs is evident at most sites (as with the pitch seen above) and there is sufficient evidence to suggest quantities are significant. Knowing the potential hazard of these microplastics to soil, freshwater and marine water environments, and to human health, urgent action is needed to curtail and manage this source of pollution.

Based on this range of health and environmental concerns, the European Chemical Agency (ECHA) proposed a ban on the use of rubber infill to the European Commission – this is currently under discussion by member states.

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