Car Tire Crumb Rubber: Does Leaching Produce a Toxic Chemical Cocktail in Coastal Marine Systems?

Abstract

Crumb rubber granulate (CRG) produced from end of life tires (ELTs) is commonly applied to synthetic turf pitches (STPs), playgrounds, safety surfaces and walkways. In addition to fillers, stabilizers, cross-linking agents and secondary components (e.g., pigments, oils, resins), ELTs contain a range of other organic compound and heavy metal additives. While previous environmental impact studies on CRG have focused on terrestrial soil and freshwater ecosystems, many sites applying CRG in Norway are coastal. The current study investigated the organic chemical and metal additive content of 'pristine' and 'weathered' CRG and their seawater leachates, as well as uptake and effects of leachate exposure using marine copepods (Acartia and Calanus sp.). A combination of pyrolysis gas chromatography mass spectrometry (py-GC-MS) and chemical extraction followed by GC-MS analysis revealed similar organic chemical profiles for pristine and weathered CRG, including additives such as benzothiazole, N-1,3-dimethylbutyl-N-phenyl-p-phenylenediamine and a range of polycyclic aromatic hydrocarbons (PAHs) and phenolic compounds (e.g., bisphenols). ICP-MS analysis revealed g kg −1 quantities of Zn and mg kg −1 quantities of Fe, Mn, Cu, Co, Cr, Pb, and Ni in the CRG. A cocktail of organic additives and metals readily leached from the CRG into seawater, with the most abundant leachate components being benzothiazole and Zn, Fe, Co (metals), as well as detectable levels of PAHs and phenolic compounds. Concentrations of individual components varied with CRG source material and CRG to seawater ratio, but benzothiazole and Zn were typically the organic and metal components present at the highest concentrations in the leachates. While organic chemical concentrations in the leachates stabilized within days, metals continued to leach out over the 30-day period. Marine copepods exposed to high CRG leachate concentrations exhibited high mortalities within 48 h. The smaller lipid-poor Acartia had a higher sensitivity to leachates than the larger lipid-rich Calanus, indicating speciesspecific differences in vulnerability to leachates. The effect on survival was alleviated at lower leachate concentrations, indicating a dose-response relationship. Benzothiazole and its derivatives appear to be of concern owing to their proven toxicity, while bisphenols are also known to be toxic and were enriched in the leachates relative to the other compounds in the CRG.

Quantification of Non-Exhaust Particulate Matter Traffic Emissions and the Impact of COVID-19 Lockdown at London Marylebone Road

“…Typically, they consist of a mixture of natural and synthetic rubbers (40-60%), fillers (20-35%), vulcanization agents (2-5%), additives (5-10%), textile and metal reinforcements (5-10%), and process oils (12-15%) [36][37][38][39][40]. Steel cords (Fe, C) are used in tyres to provide rigidity, whilst Zn is an important element used for rubber vulcanisation and typically comprises approximately 1-2% (by mass) of the tyre [5,41,42]. A recent study examining metals leaching in crumb rubber granulates from end-of-life tyres found that Zn concentrations were substantially higher than other trace metals [41].…”

“…Steel cords (Fe, C) are used in tyres to provide rigidity, whilst Zn is an important element used for rubber vulcanisation and typically comprises approximately 1-2% (by mass) of the tyre [5,41,42]. A recent study examining metals leaching in crumb rubber granulates from end-of-life tyres found that Zn concentrations were substantially higher than other trace metals [41]. As a result, tyres have been predicted to be the main anthropogenic source of roadside Zn in the atmosphere, approximately 4 times that of brake wear and greater than other potential sources such as galvanised street furniture, car bodies, and engine oil [39,41,43].…”

Effect of environmentally relevant concentrations of potentially toxic microplastic on coastal copepods

“…In addition, car tire leachates can have a low pH, which might increase the bioavailability of the compounds (Capolupo et al, 2020). Indeed, the leachates from car tires have been demonstrated to have detrimental effects on algae, crustaceans, mussels, zebra fish and copepods, already at relatively low concentrations (Nelson et al, 1994;Wik and Dave, 2006;Wik et al, 2009;Capolupo et al, 2020;Halsband et al, 2020).…”

“…TWPs contain a wide variety of chemical substances including synthetic and natural rubber polymers, fillers such as black carbon, and different types of softeners, as well as metals from brake-abrasion (Baumann and Ismeier, 1998). The most common type of RGs are made from scrap tires, and thus contain most of the same chemical substances as TWPs (https://echa.europa.eu/hot-topics/microplastics), including high amounts of bio-accessible heavy metals such as zinc (Zn), copper (Cu) and cobalt (Co) (Canepari et al, 2018;Halsband et al, 2020).…”

Oceanic Long-Range Transport of Organic Additives Present in Plastic Products – An overview

“…The polymer composition of plastic litter observed in remote regions covers mostly five polymers: polyethylene (PE), polypropylene (PP), PE terephthalate (PET), polystyrene (PS) and polyvinyl chloride (PVC). Tire--wear particles (TWP) are an additional category and consist mainly of synthetic styrene-butadiene rubber (SBR) (Kreider et al 2010;Jan Kole et al 2017;Halsband et al 2020). All of the mentioned six plastic/rubber types are known to contain a large number of additives, with PVC and TWP containing a different mix and amount of additives than the others.…”