A new look at rubber recycling and recreational surfaces: The inorganic and OPE chemistry of vulcanised elastomers used in playgrounds and sports facilities

Metal and metalloid content in real urban synthetic surfaces made of recycled tire crumb rubber including playgrounds and football fields

The disposal of end-of-life tires (ELTs) is an important issue in the context of solid waste management. In the last decades, the main recycling route consists of the ELTs transformation in crumb rubber, which is widely used worldwide in playgrounds and sports fields as infill material. Crumb rubber represents the largest source of intentional microplastics in the environment. This microplastic material contains high metal concentration including toxic and heavy metals. Few studies deal with the metal(loid) characterization of real crumb rubber samples taken in situ from sports and leisure facilities. Research is especially scarce for playgrounds, despite interest due to the population using these facilities (children). This study aims at addressing the metal(loid) distribution in a large number of real samples from different urban places, most from Galicia (NW Spain) but also from other countries. 32 elements including metals (Ag, Al, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, In, K, Li, Mg, Mn, Mo, Na, Nb, Ni, Pb, Se, Sr, Ti, Tl, U, V, Zn) and 4 metalloids (As, B, Sb, Si) were determined. For comparison purposes, some alternative materials (cork, sand, and thermoplastic elastomers) were collected. The results showed high Zn levels (1-2 %) in crumb rubber, exceeding the safety limits set in the European directives for related matrices. Heavy and toxic elements (Pb, Cr, As, Cd, Sb) were found in all samples, reaching concentrations up to 100 mg kg-1. Co presented concentrations of 200 mg kg-1, well above the safety limits (10 mg kg-1 for toys). ANOVA showed statistical differences between playgrounds and football fields for some elements. The alternative materials proved safer regarding metal(loid) content. This study is the largest one about metal(loid) characterization in crumb rubber surfaces attending the number of samples, origin, and elements analyzed.

Exploring the Human Health Impact of Artificial Turf Worldwide: A Systematic Review

The growing use of artificial turf in place of natural turf in residential, recreational and commercial settings has raised concerns regarding its potential impact on human health. A systematic review of databases revealed 5673 articles of which, 30 were deemed eligible. Those performing total concentration analyses, bioaccessibility analyses or human health risk assessments (HHRAs) of artificial turf fibres or crumb rubber infill were of interest. Health hazards and risks were explored in relation to three groups of chemicals of concern: polycyclic aromatic hydrocarbons (PAH), heavy metals and other rubber additives. Twenty-five studies performed total concentration analyses on samples of artificial turf infill and/or turf fibres. Of these studies, median reported concentrations of eight PAHs, cadmium, mercury and zinc exceeded the European limits used. Eight studies performed bioaccessibility assays using synthetic biofluids and simulated organ systems. PAHs were not found to be bioaccessible except for benzo[a]pyrene in gastric fluid; heavy metals were bioaccessible except arsenic, and rubber additives were mostly bioaccessible except for three plasticisers: diisobutyl phthalate, benzyl butyl phthalate and dibutyl phthalate. Fourteen studies performed HHRAs to determine non-carcinogenic and carcinogenic risk. Cancer risks were identified for ingestion exposure to PAH in children with pica and heavy metal exposure via dermal, inhalation and ingestion pathways. Non-carcinogenic risks were identified for the ingestion of cobalt in a child spectator and the ingestion of arsenic, cobalt, thallium and zinc. Potentially hazardous concentrations of chemicals were found across both artificial turf infill and artificial turf fibre samples; bioaccessibility of these chemicals varied. Definitive conclusions were unable to be derived on the human health risks posed to users of artificial turf under real-world exposure scenarios. Future studies are recommended to explore the risks associated with the potential synergistic toxicities of chemical mixtures found in artificial turf.

Granulated rubber in playgrounds and sports fields: A potential source of atmospheric plastic-related contaminants and plastic additives after runoff events

The use of "crumb rubber" coming from recycling materials in outdoor floors like playgrounds has been a frequent practice during the last years. However, these surfaces are object of abrasion and weathering being a potential source of micro and nanoplastics (MNPLs) to the atmosphere and a potential source of human exposure to them. Our main goal has been to expose different crumb rubber materials to summer weathering effects. The released inhalable fractions were sampled for two months with passive samplers and the composition of MNPLs and plastic additives (organic and inorganic) were evaluated. The ecotoxicological effects of leached materials emulating runoff events was evaluated in freshwater micro crustacean Daphnia magna and the green algae Chlorella vulgaris. The analysis of MNPLs showed the presence of polyethylene, polypropylene, polybutadiene, polysiloxanes and polybutylene at concentrations up to 30,426 ng/m3. In the same fraction, we also identified up to 56 plastic additives, including antioxidants, pigments, copolymers, flame retardants, fungicides, lubricants, plasticizers, UV filters and metal ions. Finally, runoff ecotoxicological effects on D. magna and C. vulgaris showed that leached compounds, either from virgin or aged material, would be toxicants for exposed organisms although at concentrations much higher than those expected to be released to the media.

Recycled tire rubber materials in the spotlight. Determination of hazardous and lethal substances

One way of recycling end-of-life tires is by shredding them to obtain crumb rubber, a microplastic material (<0.5 mm), used as infill in artificial turf sports fields or as playground flooring. There is emerging concern about the health and environmental consequences that this type of surfaces can cause. This research aims to develop an analytical methodology able to determine 11 compounds of environmental and health concern, including antiozonants such as N-1,3-dimethylbutyl-N'-phenyl-p-phenylenediamine (6PPD) or N, N´-diphenyl-1,4-phenylenediamine (DPPD), and vulcanization and crosslinking agents, such as N-cyclohexylbenzothiazole-2-sulfenamide (CBS), 1,3-di-o-tolylguanidine (DTG) or hexamethoxymethylmelamine (HMMM) from tire rubber. Ultrasound assisted extraction followed by liquid chromatography coupled to tandem mass spectrometry (UAE-LC-MS/MS) is validated demonstrating suitability. The methodology is applied to monitor the target compounds in forty real crumb rubber samples of different origin including, football pitches, outdoor and indoor playgrounds, urban pavements, commercial samples, and tires. Several alternative infill materials, such as sand, cork granulates, thermoplastic elastomers and coconut fibres, are also collected and analysed. All the target analytes are identified and quantified in the crumb rubber samples. The antiozonant 6PPD is present at the highest concentrations up to 0.2 % in new synthetic fields. The tire rubber-derived chemical 6PPD-quinone (2-((4-methylpentan-2-yl)amino)-5-(phenylamino)cyclohexa-2,5-diene-1,4-dione), recently linked to acute mortality in salmons, is found in all types of crumb rubber samples attaining concentrations up to 40 μg g-1 in football pitches. The crosslinking agent HMMM is detected in most of the playing surfaces, at concentrations up to 36 μg g-1. The tested infill alternatives are free of most of the target compounds. To the best of our knowledge, this study is the largest study considering the target compounds in tire rubber particles and the first to focus on these compounds in playgrounds including the analysis of HMMM, 6PPD-quinone and DTG in crumb rubber used as an infill material.

Hazardous elements in plastic and rubber granules as infill material from sports facilities? Field Portable-XRF spectroscopy as 'white analytical technique' reveals hazardous elements in fall sports facilities in Rzeszów (Podkarpackie, Poland)

Plastic and rubber granules are commonly used as infill material in all-weather sports facilities, providing an ideal activity surface for millions of Europeans on a daily basis. However, concerns have been raised about the presence of hazardous elements in these granules, which can pose risks both to the environment and human health. Our study focusses on the elemental composition of rubber granules used in fall sports facilities in Rzeszów, (Podkarpackie, Poland) using field portable X-ray fluorescence (FP-XRF) as a non-destructive and 'white analytical technique'. The results show the content of Zn, Fe, Cr, Ba, Br, Ti, Cu, Cd, As, Au, Bi, Pb, Ni, Sb, and Sn in the rubber granule samples. This study highlights the need for stringent quality control measures and regulations to ensure the safety of all-weather sports facilities and protect the well-being of sportsman. When modern FP-XRF spectrometry is employed as a "white analytical technique," for the first time it becomes possible to identify the presence of hazardous elements, addressing the pressing concerns highlighted by the ECHA and enabling proactive measures to mitigate potential risks. This approach ensures the protection of the health and sustainability of sports facilities, contributing to the ongoing hot topics in the field.

Effects of tris (2-chloroethyl) phosphate exposure on gut microbiome using the simulator of the human intestinal microbial ecosystem (SHIME)

Tris (2-chloroethyl) phosphate (TCEP) has been widely used, and its health risk has received increasing attention. However, the rare research has been conducted on the effects of TCEP exposure on changes in the structure of the human gut microbiome and metabolic functions. In this experiment, Simulator of the human intestinal microbial ecosystem (SHIME) was applied to explore the influences of TCEP on the human gut bacteria community and structure. The results obtained from high-throughput sequencing of 16S rRNA gene have clearly revealed differences among control and exposure groups. High-dose TCEP exposure increased the Shannon and Simpson indexes in the results of α-diversity of the gut microbiome. At phylum level, Firmicutes occupied a higher proportion of gut microbiota, while the proportion of Bacteroidetes decreased. In the genus-level analysis, the relative abundance of Bacteroides descended with the TCEP exposure dose increased in the ascending colon, while the abundances of Roseburia, Lachnospira, Coprococcus and Lachnoclostridium were obviously correlated with exposure dose in each colon. The results of short chain fatty acids (SCFAs) showed a remarkable effect on the distribution after TCEP exposure. In the ascending colon, the control group had the highest acetate concentration (1.666 ± 0.085 mg⋅mL-1), while acetate concentrations in lose-dose medium-dose and high-doseTCEP exposure groups were 1.119 ± 0.084 mg⋅mL-1, 0.437 ± 0.053 mg⋅mL-1 and 0.548 ± 0.106 mg⋅mL-1, respectively. TCEP exposure resulted in a decrease in acetate and propionate concentrations, while increasing butyrate concentrations in each colon. Dorea, Fusicatenibacter, Kineothrix, Lachnospira, and Roseburia showed an increasing tendency in abundance under TCEP exposure, while they had a negatively correlation with acetate and propionate concentrations and positively related with butyrate concentrations. Overall, this study confirms that TCEP exposure alters both the composition and metabolic function of intestinal microbial communities, to arouse public concern about its negative health effects.