Abstract
Crumb rubber granulate (CRG) produced from end of life tires (ELTs) is 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. This 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 species-specific differences in vulnerability to leachates. The effect on survival was alleviated at lower leachate concentrations, indicating a dose-response relationship. Benzothiazole and its derivatives are 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.
Highlights
In 2016, global production of natural and synthetic rubber reached 27.3 million tons (54% synthetic) (International Rubber Study Group, 2017), with ∼70% used in the manufacture of vehicle tires
The current study aimed to investigate the organic chemical and metal profiles in crumb rubber granulate (CRG) materials and their associated seawater leachates, as well as assessing the toxicity of CRG leachates to two coastal arctic species of copepod (Acartia longiremis and Calanus sp.)
Each CRG material and corresponding leachate extract was analyzed by three different gas chromatography mass spectrometry (GC-MS) approaches: (i) a non-target full-scan analysis to identify all GC-amenable additive chemicals, (ii) a selected ion monitoring (SIM) method targeted toward polycyclic aromatic hydrocarbons (PAHs), and (iii) a SIM method targeted toward benzothiazole
Summary
In 2016, global production of natural and synthetic rubber reached 27.3 million tons (54% synthetic) (International Rubber Study Group, 2017), with ∼70% used in the manufacture of vehicle tires. EU REACH regulations (Annex XVII entry 28) require that carcinogens such as the EU-8 PAHs are not to be supplied to the general public above certain concentration limits (0.01– 0.1% by weight; 100–1000 mg kg−1), while the concentration of individual PAHs may not exceed 0.0001% (1 mg kg−1) when present as PAH mixtures in consumer products (REACH Annex XVII entry 50) These concentrations are, regularly reached or exceeded for certain chemicals and metals in CRG derived from ELTs given the inhomogeneous nature of CRG sources (Diekmann et al, 2019). The current study aimed to investigate the organic chemical and metal profiles in CRG materials and their associated seawater leachates, as well as assessing the toxicity of CRG leachates to two coastal arctic species of copepod (Acartia longiremis and Calanus sp.). CRG leachates were produced and used to investigate their toxicity to marine copepods (Acartia longiremis and Calanus sp.)
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