Hazardous organic chemicals in rubber recycled tire playgrounds and pavers

Oxidative damage and cardiotoxicity induced by 2-aminobenzothiazole in zebrafish (Danio rerio)

There is limited information available on cardiovascular toxicity of 2-Aminobenzothiazole (NTH), a derivative of benzothiazole (BTH) commonly used in tire production, in aquatic organisms. In the present study, the zebrafish embryos were exposed to varying concentrations of NTH (0, 0.05, 0.5, and 5 mg/L) until adulthood and the potential cardiovascular toxicity was assessed. NTH exposure resulted in striking aberrations in cardiac development, including heart looping failure and interference with atrioventricular canal differentiation. RNA-sequencing analysis indicated that NTH causes oxidative damage to the heart via ferroptosis, leading to oxygen supply disruption, cardiac malformation, and ultimately, zebrafish death. Quantitative real-time polymerase chain reaction (qPCR) analysis demonstrated the dysregulation of genes associated with early heart development, contraction, and oxidative stress. Additionally, reactive oxygen species accumulation and glutathione/malondialdehyde levels changes suggested a potential link between cardiac developmental toxicity and oxidative stress. In adult zebrafish, NTH exposure led to ventricular enlargement, decreased heart rate, reduced blood flow, and prolonged RR, QRS, and QTc intervals. To the best of our knowledge, this study is the first to provide evidence of cardiac toxicity and the adverse effects of ontogenetic NTH exposure in zebrafish, revealing the underlying toxic mechanisms connected with oxidative stress damage. These findings may provide crucial insights into the environmental risks associated with NTH and other BTHs.

Precipitation contributes to alleviating pollution of rubber-derived chemicals in receiving watersheds: Combining confluent stormwater runoff from different functional areas

The release of rubber-derived chemicals (RDCs) in road surface runoff has received significant attention. Urban surface runoff is often the confluence of stormwater runoff from specific areas. However, the impact of precipitation on RDCs contamination in confluent stormwater runoff and receiving watersheds remains poorly understood. Herein, we investigated the profiles of RDCs and their transformation products in confluent stormwater runoff and receiving rivers affected by precipitation events. The results showed that 34 RDCs are ubiquitously present in confluent stormwater runoff and surface water, with mean concentrations of 1.03-2749 and 0.28-436 ng/L, respectively. The most dominant target compounds in each category were N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), 6PPD-quinone, 2-benzothiazolol, and 1,3-diphenylguanidine. Total RDCs concentrations in confluent stormwater runoff decreased spatially from industrial areas to business districts to college towns. A significant decrease in RDCs levels in surface water after rainfall was observed (P < 0.01), indicating that precipitation contributes to alleviating RDCs pollution in receiving watersheds. To our knowledge, this is the first report of N,N'-ditolyl-p-phenylenediamine quinone (DTPD-Q) levels in surface waters in China. The annual mass load of ∑RDCs reached 72,818 kg/y in confluent stormwater runoff, while 38,799 kg/y in surface water. The monitoring of confluent stormwater runoff is an efficient measure for predicting contamination loads from RDCs in rivers. Risk assessment suggested that most RDCs posed at least medium risks to aquatic organisms, especially 6PPD-quinone. The findings help to understand the environmental fate and risks of RDCs in the confluent stormwater runoff and receiving environments after precipitation events.

Tire and road wear particles in the aquatic organisms - A review of source, properties, exposure routes, and biological effects

With the continuous development of the modern social economy, rubber has been widely used in our daily life. Tire and road wear particles (TRWPs) are generated by friction between tires and the road surface during the processes of driving, acceleration, and braking. TRWPs can be divided into three main components according to their source: tire tread, brake wear, and road wear. Due to urban runoff, TRWPs flow with rainwater into the aquatic environment and influence the surrounding aquatic organisms. As an emerging contaminant, TRWPs with the characteristics of small particles and strong toxicity have been given more attention recently. Here, we summarized the existing knowledge of the physical and chemical properties of TRWPs, the pathways of TRWPs into the water body, and the exposure routes of TRWPs. Furthermore, we introduced the biological effects of TRWPs involved in size, concentration, and shape, as well as key toxic compounds involved in heavy metals, polycyclic aromatic hydrocarbons (PAHs), N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), and benzothiazole on aquatic organisms, and attempted to find the relevant factors influencing the toxic effects of TRWPs. In the context of existing policies that ignore pollution from TRWPs emissions in the aquatic environment, we also proposed measures to mitigate the impact of TRWPs in the future, as well as an outlook for TRWPs research.

Effects of environmental concentrations of 6PPD and its quinone metabolite on the growth and reproduction of freshwater cladoceran

The widespread occurrence and accumulation of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) and its quinone metabolite, 6PPD quinone (6PPD-Q), have been globally recognized as a critical environmental issue. However, knowledge on the adverse effects of 6PPD and 6PPD-Q on freshwater invertebrates is limited. This study investigated the effects of 6PPD and its oxidative byproduct, 6PPD-Q, on the growth and reproduction of Daphnia pulex. Through 21-day exposure experiments, we measured the uptake of 0.1, 1, and 10 μg/L 6PPD and 6PPD-Q by D. pulex and assessed the effects on growth and fecundity of D. pulex. While 6PPD and 6PPD-Q did not affect the mortality rate of D. pulex, 6PPD-Q exposure inhibited the growth of D. pulex, indicating potential ecological risks. In particular, the reproductive capacity of D. pulex remained unaffected across the tested concentrations of 6PPD and 6PPD-Q, suggesting specific toxicological pathways that warrant further investigation. This study underscored the importance of evaluating the sublethal effects of emerging contaminants such as 6PPD and 6PPD-Q on aquatic invertebrates, and highlighted the need for comprehensive risk assessments to better understand their environmental impacts.

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.

Endocrine Disruptors: Focus on the Adrenal Cortex

Endocrine-disrupting chemicals (EDCs) are exogenous substances known to interfere with endocrine homeostasis and promote adverse health outcomes. Their impact on the adrenal cortex, corticosteroids and their physiological role in the organism has not yet been sufficiently elucidated. In this review, we collect experimental and epidemiological evidence on adrenal disruption by relevant endocrine disruptors. In vitro data suggest significant alterations of gene expression, cell signalling, steroid production, steroid distribution, and action. Additionally, morphological studies revealed disturbances in tissue organization and development, local inflammation, and zone-specific hyperplasia. Finally, endocrine circuits, such as the hypothalamic-pituitary-adrenal axis, might be affected by EDCs. Many questions regarding the detection of steroidogenesis disruption and the effects of combined toxicity remain unanswered. Not only due to the diverse mode of action of adrenal steroids and their implication in many common diseases, there is no doubt that further research on endocrine disruption of the adrenocortical system is needed.

Exploring the Occurrence of Organic Contaminants in Human Semen through an Innovative LC-HRMS-Based Methodology Suitable for Target and Nontarget Analysis

Understanding the potential impact of organic contaminants on male fertility is crucial, yet limited studies have examined these chemicals in semen, with most focusing on urine and blood. To address this gap, we developed and validated a robust LC-HRMS methodology for semen analysis, with a focus on polar and semipolar chemicals. Our methodology enables the quantitative (or semiquantitative) analysis of >2000 chemicals being compatible with suspect and nontarget strategies and providing unprecedented insights into the occurrence and potential bioaccumulation of diverse contaminants in this matrix. We comprehensively analyzed exogenous organic chemicals and associated metabolites in ten semen samples from Spanish participants collected in an area with a large presence of the chemical industry included in the LED-FERTYL Spanish study cohort. This investigation revealed the presence of various contaminants in semen, including plastic additives, PFAS, flame retardants, surfactants, and insecticides. Notably, prevalent plastic additives such as phthalic acid esters and bisphenols were identified, indicating potential health risks. Additionally, we uncovered previously understudied chemicals like the tire additive 2-mercaptobenzothiazole and specific organophosphate flame retardants. This study showcases the potential of our methodology as a valuable tool for large-scale cohort studies, providing insights into the association between contaminant exposure and the risk of male fertility impairments.

Assessing biodegradation of roadway particles via complementary mass spectrometry and NMR analyses

Roadway particles (RP) that can be collected with on-vehicle system, consist of a mixture of Tire and road wear particles (TRWP) with other traffic-derived particles (exhaust or non-exhaust) and/or biogenic compounds and represent a significant source of xenobiotics, susceptible to reach the different environmental compartments. The study of the RP fate is thus a major challenge to tackle in order to understand their degradation and impact. They offer a variety of carbon sources potentially usable by microorganisms, ranging from the tire-derived plasticizers, vulcanizing agents, protective agents and their transformation products, to other traffic, road and environmental-derived contaminants. A multi-analytical approach was implemented to characterize RP and study their biodegradation. Kinetics of RP extractions were monitored during 21 days in water, methanol, acetone and chloroform to identify leaching and extractable compounds and monitor the particle composition. The results confirmed that hundreds of readily leachable chemicals can be extracted from RP directly into water according to a dynamic process with time while additional poorly soluble compounds remain in the particles. Mass spectrometry (LC-HRMS and GC-MS) allowed us to propose 296 putative compounds using an extensive rubber database. The capacity of 6 bacterial strains, belonging to Rhodococcus, Pseudomonas and Streptomyces genera, to biodegrade RP was then evaluated over 14 days of incubation. The selected strains were able to grow on RP using various substrates. Elastomer monitoring by 1H NMR revealed a significant 12 % decrease of the extractable SBR fraction when the particles were incubated with Rhodococcus ruber. After incubation, the biodegradation of 171 compounds among leachable and extractable compounds was evaluated. Fatty acids and alkanes from rubber plasticizers and paraffin waxes were the most degraded putative compounds by the six strains tested, reaching 75 % of biodegradation for some of them.

Chemical characteristics of fine tire wear particles generated on a tire simulator

Tire wear is one of the major sources of traffic-related particle emissions, however, laboratory data on the components of tire wear particles (TWPs) is scarce. In this study, ten brands of tires, including two types and four-speed grades, were chosen for wear tests using a tire simulator in a closed chamber. The chemical components of PM2.5 were characterized in detail, including inorganic elements, water-soluble ions (WSIs), organic carbon (OC), elemental carbon (EC), and polycyclic aromatic hydrocarbons (PAHs). Inorganic elements, WSIs, OC, and EC accounted for 8.7 ± 2.1%, 3.1 ± 0.7%, 44.0 ± 0.9%, and 9.6 ± 2.3% of the mass of PM2.5, respectively. The OC/EC ratio ranged from 2.8 to 7.6. The inorganic elements were dominated by Si and Zn. The primary ions were SO42- and NO3-, and TWPs were proven to be acidic by applying an ionic balance. The total PAHs content was 113 ± 45.0 μg g-1, with pyrene being dominant. In addition, the relationship between the chemical components and tire parameters was analyzed. Inorganic elements and WSIs in TWPs were more abundant in all-season tires than those in winter tires, whereas the content of PAHs was the opposite. The mass fractions of OC, Si, and Al in the TWPs all showed increasing trends with increasing tire speed grade, but the PAHs levels showed a decreasing trend. Ultimately, to provide more data for further research, a TWPs source profile was constructed considering the tire weighting factor.

Micron-size tire tread particles leach organic compounds at higher rates than centimeter-size particles: Compound identification and profile comparison

Tire tread particles (TTP) are environmentally prevalent microplastics and generate toxic aqueous leachate. We determined the total carbon and nitrogen leachate concentrations and chemical profiles from micron (∼32 μm) and centimeter (∼1 cm) TTP leachate over 12 days. Dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) were used to measure the concentration of leached compounds. Nontargeted chemical analysis by comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC/TOF-MS) was used to compare the chemical profiles of leachates. After leaching for 12 days, DOC was 4.0 times higher in the micron TTP leachate than in the centimeter TTP leachate, and TDN was 2.6 times higher. The total GC×GC/TOF-MS chromatographic feature peak area was 2.9 times greater in the micron TTP leachate than the centimeter TTP leachate, and similarly, the total relative abundance of 54 tentatively identified compounds was 3.3 times greater. We identified frequently measured tire-related chemicals, such as 6PPD, N-cyclohexyl-N'-phenylurea (CPU), and hexa(methoxymethyl)melamine (HMMM), but nearly 50% of detected chemicals were not previously reported in tire literature or lacked toxicity information. Overall, the results demonstrate that smaller TTP have a greater potential to leach chemicals into aquatic systems, but a significant portion of these chemicals are not well-studied and require further risk assessment.

Assessing children's potential exposures to harmful metals in tire crumb rubber by accelerated photodegradation weathering

Whether a tire crumb rubber (TCR) playground would expose children to potentially harmful chemicals such as heavy metals is an open question. The released metals available for pickup on the surface of TCR tiles was studied by accelerated 2-year aging of the TCRs in the NIST-SPHERE (National Institute of Standards and Technology Simulated Photodegradation via High Energy Radiant Exposure). The dermal contact was mimicked by a method of composite surface wiping from US Environmental Protection Agency throughout the weathering process. The surface release of ten most concerned harmful metals (Be, Cr, Cu, As, Se, Cd, Sb, Ba, Tl, Pb) was monitored through the course of aging. The cumulative release of Cu, As, Tl, and Sb reached potentially harmful levels at various times within 3 years, although only Cr was found at a harmful level on the surface of the tiles. Taking the cleansing effect of precipitation or periodic cleansing with rain into account, TCR playgrounds may still be safe for use.

1,3-Diphenylguanidine, benzothiazole, benzotriazole, and their derivatives in soils collected from northeastern United States

1,3-Diphenylguanidine (DPG), benzothiazole (BTH), benzotriazole (BTR), and their derivatives are high-production-volume chemicals widely used in tires, corrosion inhibitors and plastic products. Vehicular traffic is an important source of these chemicals in the environment. Despite this, little is known about the occurrence of these chemicals in roadside soils. In this study, we determined the concentrations, profiles, and distribution patterns of 3 DPGs, 5 BTHs, and 7 BTRs in 110 soil samples collected from northeastern United States. We found widespread occurrence of 12 out of the 15 analytes measured in roadside soils, at detection frequencies ≥71 % and median concentrations in the range of 0.38-380 ng/g (dry weight). DPGs were the predominant chemicals accounting for 63 % of the sum concentrations of three chemical classes determined, followed by BTHs (28 %) and BTRs (9 %). The concentrations of all analytes (except for 1-, 4-, and 5-OH-BTRs) exhibited significant positive correlations (r: 0.1-0.9, p < 0.01), suggestive of their common sources and/or similar environmental fates. Higher concentrations of DPGs, BTHs and BTRs were found in soils from highways, rubberized playgrounds, and indoor parking lots than those from gardens, parks, and residential areas. Our findings suggest the release of DPGs, BTHs and BTRs from rubber products, especially automobile tires. Further studies are needed to investigate the environmental fate and toxicities of these chemicals to humans and wildlife.

Analysis, environmental occurrence, fate and potential toxicity of tire wear compounds 6PPD and 6PPD-quinone

Tire wear compounds N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) and its derivative 6PPD-quinone have been considered as emerging pollutants and attracted much attention recently. As an antioxidant and antiozonant widely used, 6PPD would be released during the production or use of rubber-related products. Because of the mass production and wide use of rubber-related products, 6PPD and 6PPD-quinone have been identified to be ubiquitous in the environment. In this study, we firstly reviewed the current available literature on the analytical procedures, concentrations and distribution of 6PPD and 6PPD-quinone, and then investigated the potential toxic effects of these two compounds on aquatic organisms. Current studies have been mainly focused on the occurrence of 6PPD and 6PPD-quinone in dust and water, while available information on atmosphere, soil, sediments and organisms is limited. The fate and distribution of 6PPD and 6PPD-quinone would be influenced by environmental factors such as temperature, illumination, and storm events, etc. Although 6PPD and 6PPD-quinone have potential adverse effects on aquatic organisms, and 6PPD-quinone has species-specific toxicity, toxicological mechanisms of these compounds are still unclear. Based on the review and analysis of current studies, some suggestions for future research of 6PPD and 6PPD-quinone are given.

Organic chemicals associated with rubber are more toxic to marine algae and bacteria than those of thermoplastics

The current study investigated the chemical complexity of fifty plastic (36) and elastomer/rubber (14) methanol extracts from consumer products, focusing on the association with toxicity in two screening assays (bacteria luminescence and marine microalgae). The chemical composition varied considerably between the products and polymers. The most complex sample (car tire rubber) contained 2456 chemical features and the least complex (disposable water bottle) only 39 features, with a median of 386 features across all products. Individual extract toxicity also varied significantly across the products and polymers, with the two toxicity assays showing comparable results in terms of defining low and high toxicity extracts, and correlation between medium toxicity extracts. Chemical complexity and abundance both correlated with toxicity in both assays. However, there were strong differences in toxicity between plastic and elastomer extracts. Overall, 86-93 % of the 14 elastomer extracts and only 33-36 % of other polymer extracts (n = 36) were more toxic than the median. A range of compounds were tentatively identified across the sample set, with several concerning compounds being identified, mostly in the elastomers. While the current focus on plastic chemicals is towards thermoplastics, we show that elastomers may be of more concern from an environmental and human health perspective.

In situ biomonitoring using caged lumpfish (Cyclopterus lumpus) eggs reveal plastic and rubber associated chemicals in a harbour area in Central Norway

Plastics- and rubber-derived chemicals are given increasing focus due to their migration into the environment and potential for causing detrimental effects. The current study demonstrates the use of a novel biomonitoring platform using caged fertilized eggs of lumpfish (Cyclopterus lumpus) in combination with gas chromatography tandem mass spectrometry analysis of a selection of target chemicals extracted from the lumpfish eggs after deployment. A monitoring campaign in the Trondheim harbor and off the coast of Trøndelag in Norway was executed using the described system. Here we found accumulation of UV stabilizers (benzophenone and benzothiazoles), plasticizers (n-butylbenzenesulfonamide), reagents, and polymer synthesis precursors (bisphenol A, acetophenone, phthalide, and phthalimide) in deployed eggs. Several of the compounds were detected in concentrations above previously quantified legacy contaminants in the same study areas.

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

We revisit current understanding of the chemical complexity of different kinds of particulate vulcanised elastomers widely used in playgrounds and sports fields, adding new data on trace element and organophosphate ester contents of used tyre and EDPM crumb rubber. Enrichments in elements such as Zn, S, Co, Bi and Nd relate to the vulcanised mixtures created during manufacture. Zinc concentrations vary across an order of magnitude, being highest in our used tyre particulate samples (up to 2.4 %). In contrast, other trace element variations are due to coloured pigments causing increases in Cu and Zr (blue), Cr (green), and Fe and Sn (red and yellow) concentrations. The use of pale fillers such as CaCO₃ and clay minerals (rather than carbon black) strongly influences Ca and Al concentrations, which are much higher in the coloured EPDM than in black used tyre crumb rubber. Representatives from all three of the main organophosphate ester (OPE) groups, namely chlorinated (e.g. TCEP, TCIPP, TDCPP), alkyl (e.g. TEHP, TEP, TNBP, TBOEP) and aryl (e.g. TPHP, EHDPP, TCP) were identified, confirming how these chemicals are commonly used in modern rubber compounding as flame retardants and plasticisers. Elevated concentrations of TEHP (up to 117 μg/g) in coloured-coated used tyre turf infill crumb rubbers were traced to the coating rather than the crumb rubber itself. The presence and weathering behaviour of OPEs in recreational crumb rubber materials deserve closer investigation. The ecological "onehealth" impact of potentially toxic substances present in recreational crumb rubbers will depend on if and how they are released during play and sports activities, maintenance procedures, and natural weathering. We argue that detailed chemical data on these materials should be available to buyers, as manufacturers strive to reduce ecotoxin content as part of the quest towards sustainable use and recycling of vulcanised elastomers.

Assessment of the bioaccessibility of PAHs and other hazardous compounds present in recycled tire rubber employed in synthetic football fields

Recycled tire crumb rubber (RTCR) surfaces contain harmful and carcinogenic substances, which can be ingested by the users of these facilities, mainly athletes and children. In this work, the potential in-vitro oral bioaccessibility of eighteen polycyclic aromatic hydrocarbons (PAHs) from RTCR employed as infill in synthetic football fields was studied in human synthetic body fluids (saliva, gastric, duodenal and bile), prepared according the Unified Bioaccessibility Method. Solid-phase extraction (SPE) using commercial sorbents and a new green material based on cork (cork industry by-product) were used to isolate the bioaccessible PAHs before gas chromatography-tandem mass spectrometry analysis. The method was optimized and validated attending the analytical figures of merit. The feasibility of cork biosorbent for the extraction of the compounds was demonstrated, as well as the suitability of the UBM method to perform the digestion with good precision. The application to real samples collected from football fields demonstrated the presence of 17 of the 18 target PAHs in the biofluids. Most volatile PAHs such as NAP, ACY, ACE, FLU, PHN and ANC, achieved the highest bioaccessibility percentage levels. The carcinogenic B[a]P was detected in 75 % of the samples at concentrations up to 2.5 ng g^-1 (bioaccessible fraction). Children exposure assessment was carried out to identify potential risk. Other hazardous and environmentally problematic compounds such as N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-quinone), recently related with the dead of coho salmon, and hexamethoxymethylmelamine (HMMM), among others, were also detected. This is the first study in which the bioaccesibility from real crumb rubber samples of 15 out of the 16 PAHs considered as priority pollutants by the United States Environmental Protection Agency (EPA) and the presence of 6PPD-quinone and HMMM in the bioaccessible fractions is reported.

Characterization of synthetic turf rubber granule infill in Japan: Polyaromatic hydrocarbons and related compounds

Although the health effects of artificial turf fillings have been investigated in Europe and the United States, the actual situation in Japan is unclear. To address this issue, the concentrations of 46 polyaromatic hydrocarbons (PAHs) and related compounds in rubber infills were analyzed prior to their use in synthetic turf fields in Japan. Based on information obtained from the sample suppliers, the investigated samples were divided into five categories: discarded tires, industrial rubber, combinations of these products or unidentified components (mixture/unknown), synthetic rubber specifically manufactured for synthetic turf, and special-purpose thermoplastic elastomers (TPEs). The industrial rubber samples were mixtures of styrene butadiene rubber, natural rubber, and ethylene propylene diene rubber (EPDM). The synthetic rubber samples consisted only of EPDM. A few or none of the PAHs were detected in the synthetic rubber and TPE samples. However, in the discarded tire and industrial rubber samples, benzo[a]pyrene, cyclopenta[cd]pyrene, and 30 other compounds were detected. A comparison between these two categories indicated that the discarded tire samples exhibited higher concentrations of the target compounds than the industrial rubber samples. This finding can be attributed to the presence of EPDM in almost all of the industrial rubber samples, which were not present in the discarded tire samples. The maximum PAH concentrations obtained in the present study were equivalent to or lower than the previously reported PAH concentrations. The total concentrations of the eight PAHs included in the European Chemical Agency (ECHA) assessment of health risks were lower in the present study than those reported by the ECHA. Furthermore, elution testing was performed with four simulated biofluids (gastric and intestinal juices, saliva, and perspiration). The actual elution amounts of all compounds were less than the limits. This report provides basic data for the risk assessment of PAHs in rubber infills.

Characterization of synthetic turf rubber granule infill in Japan: Rubber additives and related compounds

We have conducted several studies with an overall goal of assessing the effects of rubber granules in synthetic turf on the health of athletes, other players, and children in Japan. As part of these studies, the investigation reported herein was aimed at analyzing the concentrations of rubber additives (vulcanization accelerators, antioxidants, and cross-linking agents) and related chemicals in 46 rubber infills prior to their use in synthetic turf fields in Japan. Of the 36 chemicals selected for targeted analysis, 26 were detected and quantified. Nontargeted analyses further identified and quantified 16 compounds derived from vulcanization accelerators, plasticizers, and other additives. The types and concentrations of the detected compounds varied both between products and within the same product; in the case of rubber infill products made from recycled rubber, this variation was caused by the different types of rubber products recycled as raw materials. Elution tests with four simulated biofluids (gastric juice, intestinal juice, saliva, and perspiration) revealed that the elution rates varied between compounds and were affected by the presence of coatings. Most compounds had low elution rates in all the simulated biofluids, with many at or below the limit of quantification. The data reported herein will be utilized in the risk characterization part of our subsequent study on the health risk assessment of rubber infill.

Characterization of synthetic turf rubber granule infill in Japan: Volatile organic compounds

There has been extensive studies on the composition of tires and industrial rubber. However, there is insufficient information on volatile organic compounds (VOCs) emitted from rubber granule products used to fill synthetic turf fields. In this study, we applied a passive sampling method for assessing the VOCs emitted from rubber granule products used for filling synthetic turf fields. We also performed a quantitative component analysis using a gas chromatography-mass spectrometer (GC-MS). The component analysis results of 46 rubber granule-based products showed the predominant presence of benzothiazole and methyl isobutyl ketone. The level of benzene, which the International Agency for Research on Cancer classifies as a substance with sufficient evidence for carcinogenicity to humans, was below the lower quantification limit in the products tested in this study. Our study included most of the rubber granule products used for synthetic turf fields in Japan (>95% of the products in the current domestic market of Japan). Therefore, we obtained a comprehensive overview of the VOCs emitted from the rubber granule-based products used in Japan's synthetic turf fields. Estimating the exposure to these airborne VOCs is essential to evaluate the adverse health effects of the VOCs emitted from these rubber granule-based products. Our sampling method and results can help provide key data for such risk assessment studies in the future.

Volatile organic compounds emission in the rubber products manufacturing processes

Volatile organic compounds (VOCs) emission from rubber products manufacture processes, mixing, shaping and vulcanization were investigated in four rubber products factories in China. The source emission air was passively sampled by pre-vacuumized stainless steel canister and analyzed by gas chromatography-mass spectrometry-flame ionization detection (GC/MS-FID). The species profile of 107 VOCs in the emission processes were obtained. We calculated the photochemical ozone formation potential (OFP) and carcinogenic risk (CR) of the VOCs for each manufacture process. The results showed that mixing process mainly released dichloromethane (14.53%), carbon disulfide (CS₂) (6.88%), styrene (5.72%), 4-methyl-2-pentanone (5.22%) and naphthalene (3.69%) for solvents used and raw rubber degradation in the process. The C6-C8 alkanes, especially heptane and isomers of heptane (44.71%), were dominated in shaping process. The major species released from vulcanization process were carbon disulfide (29.72%), naphthalene (8.17%), acetone (7.73%) and dichloromethane (4.26%). VOCs emitted from vulcanization process had the highest OFP, which contributed by naphthalene, m/p-xylene, o-xylene and carbon disulfide. VOCs emission from mixing process had the highest CR, and 1,2-dibromoethane, 1,2-dichlorethane and 1,3-butadiene were the main contributors to CR. We also estimated the total VOCs emissions into the atmosphere from tires manufacturing in China, which were 7.58 × 10⁵ t in 2018 and contributed about 9% of total industry processes VOCs emissions.

Examination of aryl hydrocarbon receptor (AhR), estrogenic and anti-androgenic activities, and levels of polyaromatic compounds (PACs) in tire granulates using in vitro bioassays and chemical analysis

Tire granulates recovered from end-of-life tires contain a complex mixture of chemicals, amongst them polyaromatic compounds (PACs), of which many are recognized to be toxic and persistent in the environment. Only a few of these PACs are regularly monitored. In this study a combined approach of chemical analysis and a battery of CALUX® in vitro bioassays was used to determine PAC concentrations and estrogenic, (anti)-androgenic and aryl hydrocarbon receptor (AhR) activities in tire granulates. Tire granulates from a recycling company was analyzed for PAHs, alkyl-PAHs, oxy-PAHs and heterocyclic PACs (NSO-PACs), in total 85 PACs. The concentrations of PACs were between 42 and 144 mg/kg, with major contribution from PAHs (74-88%) followed by alkyl-PAHs (6.6-20%) and NSO-PACs (1.8-7.0%). The sum of eight priority PAHs were between 2.3 and 8.6 mg/kg, contributing with 4.7-8.2% of ∑PACs. Bioassay analysis showed presence of AhR agonists, estrogen receptor (ERα) agonists, and androgen receptor (AR) antagonists in the tire granulate samples. Only 0.8-2.4% of AhR-mediated activities could be explained by the chemical analysis. Benzo[k+j]fluoranthenes, benzo[b]fluoranthene, indeno[1,2,3-cd]pyrene, 2-methylchrysene, and 3-methylchrysene were the major contributors to the AhR-mediated activities. The high contribution (98-99%) of unknown bioactive compounds to the bioassay effects in this study raises concerns and urges for further investigations of toxicants identification and source apportionment.

A Deep Dive into the Complex Chemical Mixture and Toxicity of Tire Wear Particle Leachate in Fathead Minnow

The ecological impact of tire wear particles in aquatic ecosystems is a growing environmental concern. We combined toxicity testing, using fathead minnow (Pimephales promelas) embryos, with nontarget high-resolution liquid chromatography Orbitrap mass spectrometry to characterize the toxicity and chemical mixture of organic chemicals associated with tire particle leachates. We assessed: 1) exposure to tire particle leachates after leaching for 1-, 3-, and 10-d; and 2) the effect of the presence and absence of small tire particulates in the leachates. We observed a decrease in embryonic heart rates, hatching success, and lengths, as well as an increase in the number of embryos with severe deformities and diminished eye and body pigmentation, after exposure to the leachates. Overall, there was a pattern whereby we observed more toxicity in the 10-d leachates, and greater toxicity in unfiltered leachates. Redundancy analysis showed that several benzothiazoles and aryl-amines were correlated with the toxic effects observed in the embryos. These included benzothiazole, 2-aminobenzothiazole, 2-mercaptobenzothiazole, N,N'-diphenylguanidine, and N,N'-diphenylurea. However, many other chemicals characterized as unknowns are likely to also play a key role in the adverse effects observed. Our study provides insight into the types of chemicals likely to be important toxicological drivers in tire leachates, and improves our understanding of the ecotoxicological impacts of tire wear particles. Environ Toxicol Chem 2022;41:1144-1153. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Tests of rubber granules used as artificial turf for football fields in terms of toxicity to human health and the environment

Rubber waste, in the form of granules of styrene butadiene rubber and ethylene-propylene-diene-monomer with a particle size of 0.5 to 4 mm, is broadly used for the construction of synthetic surfaces of sport fields. This method of recycling may be significantly limited due to the restrictions on polycyclic aromatic hydrocarbons (PAHs) content in rubber granules in the European Union since 2022. This also applies to the recommendations of the European Chemicals Agency in relation to the identification of other hazardous chemicals in this waste, including metal elements. The scope of the research included the identification of organotin compounds, PAHs content and 18 elements leached from recycled rubber granules in terms of substances harmful to human health and to natural environment. The research covered 84 samples of rubber granules collected from the surface of football pitches or supplied by recyclers in Poland. The test results showed an over-standard content of PAHs in rubber granules. This result confirms the need to develop alternative directions of rubber granules application: construction and hydro construction, reinforcing soil and roadsides, asphalt pavements, making retaining walls, anti-shock and anti-vibration slabs, soundproofing and damping screens, paving stones and landscaping elements.

New Evidence of Rubber-Derived Quinones in Water, Air, and Soil

p-Phenylenediamines (PPDs) have been extensively used in the rubber industry and found to be pervasive in various environmental compartments for decades, while their transformation products and associated ecological and human health risks remain largely unknown. Herein, we developed and implemented a mass spectrometry-based platform combined with self-synthesized standards for the investigation of rubber-derived quinones formed from PPD antioxidants. Our results demonstrated that five quinones are ubiquitously present in urban runoff, roadside soils, and air particles. All of the identified sources are closely related to mankind's activities. Among the identified quinones, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone has been recently found to be highly toxic, causing acute mortality of coho salmon in the Pacific Northwest. Ultrahigh-performance liquid chromatography coupled with triple quadrupole mass spectrometry was then applied for quantification of the five quinones and their corresponding PPD antioxidants. The results revealed interesting distinct distribution and concentration patterns of PPD-derived quinones in different environmental matrices. Daily intake rates of these quinones in a compact city of Hong Kong were estimated to be varied from 1.08 ng/(kg·day) for adults to 7.30 ng/(kg·day) for children, which were higher than the exposure levels of their parent compounds. Considering the prevalence of the use of rubber products, the outcome of this study strongly suggests for additional toxicological studies to investigate potential ecological and human health risks of the newly discovered quinones.

Environmental Consequences of Rubber Crumb Application: Soil and Water Pollution

End-of-life tires are utilized for various purposes, including sports pitches and playground surfaces. However, several substances used at the manufacture of tires can be a source of concerns related to human health or environment’s adverse effects. In this context, it is necessary to map whether this approach has the desired effect in a broader relation. While the negative effects on human health were investigated thoroughly and legislation is currently being revisited, the impact on aquatic or soil organisms has not been sufficiently studied. The present study deals with the exposure of freshwater and soil organisms to rubber crumb using the analysis of heavy metal and polycyclic aromatic hydrocarbon concentrations. The obtained results refer to substantial concerns related to freshwater contamination specifically, since the increased concentrations of zinc (7 mg·L⁻¹) and polycyclic aromatic hydrocarbons (58 mg·kg⁻¹) inhibit the growth of freshwater organisms, Desmodesmus subspicatus, and Lemna minor in particular. The performed test with soil organisms points to substantial concerns associated with the mortality of earthworms as well. The acquired knowledge can be perceived as a roadmap to a consistent approach in the implementation of the circular economy, which brings with it a number of so far insufficiently described problems.

Global evaluation of the chemical hazard of recycled tire crumb rubber employed on worldwide synthetic turf football pitches

Social and environmental concern about the use of crumb rubber from end-of-life car tires in the construction of different sport and recreational facilities is increasing due to the presence of hazardous compounds. The aim of this research was the assessment of 42 organic chemicals, including polycyclic aromatic hydrocarbons (PAHs), phthalates, adipates, antioxidants and vulcanisation agents in a large number of infill samples (91) from synthetic turf football pitches of diverse characteristics and geographical origin. Samples were taken worldwide, in 17 countries on 4 continents, to show the global dimension of this problem. Ultrasound assisted extraction was employed to extract the target compounds, followed by gas chromatography coupled to tandem-mass spectrometry (UAE-GC-MS/MS). Seventy-eight crumb rubber samples as well as thirteen samples of alternatives materials, such as cork granulates, thermoplastic elastomers and coconut fibre, were analyzed. The results highlight the presence of all target PAH in most rubber samples at concentrations up to μg g^-1, including the eight ECHA (European Chemicals Agency) PAHs considered as carcinogenic, and anthracene (ANC), pyrene (PYR) and benzo[ghi]perylene (B[ghi]P), catalogued as substances of very high concern (SVHC). Endocrine disruptors such as some plasticizers (mainly phthalates), and other compounds like benzothiazole (BTZ) and 2-mercaptobenzothiazole (MBTZ) were found reaching the mg g^-1 level. This confirms the presence of the hazardous substances in the recycled crumb rubber samples collected all around the world. Three crumb rubber samples exceeded the limit of 20 μg g^-1 for the sum of the eight ECHA PAHs. Regarding the chemical composition of other infill alternatives, cork appears to be adequate, while the thermoplastic elastomers contained high levels of some plasticizers. In addition, the plastic infill as well as the crumb rubber both are microplastics. Microplastics are considered contaminants of emerging concern since they do not biodegrade and remain in the environment for a long time.

Profiling and assessing soil-air exchange of polycyclic aromatic hydrocarbons (PAHs) in playground dust and soil using ex situ equilibrium passive sampling

Cancer risk can be associated with exposure to polycyclic aromatic hydrocarbons (PAHs) in playground dust and soil. This study investigated the profiles and sources of PAHs from poured rubber-surfaced playground dust and uncovered playground surface soil, by applying an ex-situ equilibrium passive sampling technique. Surface dust and soil samples were collected from 15 different playgrounds in Seoul, Republic of Korea. The total 16 EPA PAHs concentrations in surface dust and soil varied from 198 to 919 μg kg^-1 dw and 68-169 μg kg^-1 dw, respectively. 4- to 6-ring PAHs were dominant, accounting for approximately 53.8%-94.5% of the total PAHs in surface dust and soil. The diagnostic ratios and principal component analysis suggested that a mixed coal combustion and vehicular emission was likely the main source of PAHs in the surface dust and soil. The higher total organic carbon content can explain the higher PAH accumulation and lower fugacities of PAHs. The fugacity comparison of phenanthrene and pyrene in dust, soil, air, and playground surface material indicated that atmospheric deposition is the main source of PAHs in the dust and soil on rubber-surfaced and uncovered surfaced playgrounds. This study contributes to the understanding of PAHs sources in dust and soil samples in children's playground and helps policymaker determine the right contamination sources for risk management.

Occurrence of microplastics and phthalate esters in urban runoff: A focus on the Persian Gulf coastline

Urban runoff seems an obvious pathway for the transfer of microplastics (MPs) and phthalate acid esters (PAEs) from land-based sources to the marine environment; an issue that still lacks attention. This study presents the first results on MP and PAE levels in the urban runoff into the northern part of the Persian Gulf during the dry season. Average concentrations of MPs and PAEs in the urban runoff of eight selected sampling sites (N = 72) along the Bushehr coast were 1.86 items/L and 53.57 μg/L, respectively. MPs with a size range of 500-1000 μm had the highest abundance, and the mean levels of PAEs in MPs were 99.77 μg/g. The results of this study show that urban runoff is a main source of MP and PAE contaminants that are discharged into the Persian Gulf. Therefore, to decrease these pollutants from entering the aquatic environment, decision-makers in the area should consider this problem and stop the direct discharging of urban runoff into water bodies.

Probing the chemical complexity of tires: Identification of potential tire-borne water contaminants with high-resolution mass spectrometry

Tire wear particles are not only the type of polymer particles most prevalent in the environment but also act as source of various organic micropollutants, many of which are likely still unknown. We extracted particles prepared from nine tires in artificial freshwater (28 d) with the goal to characterize leachables (max intensity >10⁵ in artificial freshwater), which are tire-borne water contaminants. A subsequent extraction of these particles with acetone (3 h) was used to assess the long-term leaching potential. A suspect and nontarget screening in aliquots of each extract led to the detection of 214 organic substances of which 145 were classified as leachables. The intrinsic polarity of some leachables (mean log D (pH 7.4) 3.9), which facilitates an increased aquatic mobility, highlights their potential as environmental water contaminants. With N,N'-diphenylguanidine (DPG) and benzothiazole, two of the ten unequivocally identified leachables, are classified as potential persistent, mobile and toxic substance by the German Environment Agency. Of the identified chemicals DPG showed the highest intensities in aqueous extracts and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6-PPD), the precursor of 6-PPD-quinone, in acetone extracts. A comparison between the 69 detected suspects and 174 high-intensity signals (>10⁶) detected in the nontarget screening led to an overlap of only 29 features. A detailed investigation of the remaining high-intensity suspects revealed the presence of 13 proposed DPG reaction products, further highlighting the chemical complexity of tires. Consequently, we conclude that there are many, often still unrecognized chemicals entering the aquatic environment through leaching from tire wear particles.

Exploring the impacts of microplastics and associated chemicals in the terrestrial environment - Exposure of soil invertebrates to tire particles

Abrasion of tire wear is one of the largest sources of microplastics to the environment. Although most tire particles settle into soils, studies on their ecotoxicological impacts on the terrestrial environment are scarce. Here, the effects of tire particles (<180 μm) on three ecologically relevant soil invertebrate species, the enchytraeid worm Enchytraeus crypticus, the springtail Folsomia candida and the woodlouse Porcellio scaber, were studied. These species were exposed to tire particles spiked in soil or in food at concentrations of 0.02%, 0.06%, 0.17%, 0.5% and 1.5% (w/w). Tire particles contained a variety of potentially harmful substances. Zinc (21 900 mg kg^-1) was the dominant trace element, whilst the highest concentrations of the measured organic compounds were detected for benzothiazole (89.2 mg kg^-1), pyrene (4.85 mg kg^-1), chlorpyrifos (0.351 mg kg^-1), HCB (0.134 mg kg^-1), methoxychlor (0.116 mg kg^-1) and BDE 28 (0.100 mg kg^-1). At the highest test concentration in soil (1.5%), the tire particles decreased F. candida reproduction by 38% and survival by 24%, and acetylcholinesterase (AChE) activity of P. scaber by 65%, whilst the slight decrease in the reproduction of E. crypticus was not dose-dependent. In food, the highest test concentration of tire particles reduced F. candida survival by 38%. These results suggest that micro-sized tire particles can affect soil invertebrates at concentrations found at roadsides, whilst short-term impacts at concentrations found further from the roadsides are unlikely.

Organic Markers of Tire and Road Wear Particles in Sediments and Soils: Transformation Products of Major Antiozonants as Promising Candidates

Tire and road wear particles (TRWPs) are one of the main sources of particulate traffic emissions, but measured data on TRWP contents in the environment are scarce. This study aims at identifying organic compounds suitable as quantitative markers for TRWPs by a tiered multistep selection process involving nontarget screening and subsequent identification by liquid-chromatography high-resolution mass spectrometry. Starting from several thousands of signals recorded in the extract of tire particles, the rigorous selection process considered source specificity, tendency of leaching, analytical sensitivity and precision, and stability during aging. It led to three transformation products of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6-PPD) as the most suitable marker candidates: N-formyl-6-PPD, hydroxylated N-1,3-dimethylbutyl-N-phenyl quinone diimine, and 6-PPD-quinone. A linear response in standard addition experiments with tire particles and the correlation with TRWP contents in a diverse set of environmental samples imply that these compounds are promising candidates as markers for the quantification of TRWPs. Organic markers for TRWP contents in the environment would allow TRWP quantification with the traditional tandem MS (LC-MS/MS) equipment of an organic trace analytical laboratory and, thus, allow easy generation of data on TRWP occurrence in sediments and soils and other environmental matrices.

First study on the presence of plastic additives in loggerhead sea turtles (Caretta caretta) from the Mediterranean Sea

Loggerhead turtles (Caretta caretta) voluntarily ingest floating plastic debris and hence are chronically exposed to plastic additives, but very little is known about the levels of these compounds in their tissues. This work studied the presence of organophosphate esters (OPEs) on sea turtles collected from two different areas in the western Mediterranean, some of their prey and some floating plastic debris. OPEs were detected in all the samples analysed and ∑OPEs ranged from 12.5 to 384 ng/g wet weight (ww) in the turtles from the Catalan coasts, with a mean value of 21.6 ng/g ww, and from 6.08 to 100 ng/g ww in the turtles the Balearic Islands, with a mean value of 37.9 ng/g ww. Differences in ∑OPEs were statistically significant, but turtles from the two regions did not differ in their OPE profiles. As per turtle's prey, ∑OPEs ranged from 4.55 to 90.5 ng/g ww. Finally, marine plastic litter showed ∑OPEs concentrations between 10.9 and 868 ng/g. Although most compounds were present in both potential sources of contamination, prey and plastic debris, the OPE profiles in loggerhead turtles and these sources were different. Some OPEs, such as tris(2-isopropylphenyl) phosphate (T2IPPP), tripropyl phosphate (TPP) and tris(2-butoxyethyl) phosphate (TBOEP), were detected in plastic debris and turtle muscle but not in their prey, thus suggesting that ingestion of plastic debris was their main source. Contrarily, the levels of triethyl phosphate (TEP), diphenyl cresyl phosphate (DCP), 2-isopropylphenyl diphenyl phosphate (2IPPDPP) and 4-isopropylphenyl diphenyl phosphate (4IPPDPP) in turtle muscle were much higher than in jellyfish, their main prey, thus indicating a biomagnification potential. Regular ingestion of plastic debris and contamination from their prey may explain why ∑OPEs in loggerhead turtles is much higher than the values reported previously for teleost fishes and marine mammals from the western Mediterranean.

Analysis of recycled rubber: Development of an analytical method and determination of polycyclic aromatic hydrocarbons and heterocyclic aromatic compounds in rubber matrices

Recycled crumb rubber (CR) is rich in compounds with unrecognized toxic potency; this study aims at the development of an analytical method that would allow identification and quantification of a very wide range of organic compounds extractable from the complex rubber matrix. The analytical set-up includes target analysis of polycyclic aromatic hydrocarbons (PAHs) and methyl-PAHs and suspect screening of raw extracts to tentatively identify primary organic compounds present, but not included in the standard target analysis of recycled rubber, followed by analytical method development and target analysis of identified compounds. Analyzed samples included weathered and new CR originating from football turf granulates, rubber mats, and end-of-life car tires (ELTs). The developed analytical method involves sonication extraction, followed by solid phase extraction (SPE) fractionation that enables simple and efficient separation of analytes with broad polarity scale. The application of SPE fractionation resolves coelution problems and simplifies the chromatograms. This analytical approach allowed to identify and quantify 46 sample specific compounds, including several heterocyclic PAHs like 2-methylthiobenzothiazole, benzonapthothiophenes, benzonaphthofuranes and aromatic amines like diphenylamine and N-phenyl-2-naphthylamine, which to our knowledge were not determined before. The PAHs concentrations determined in CR tiles purchased in Dutch and Spanish shops exceed the EU limits for articles marketed for use by the public. Furthermore, sets of methylated PAHs, dibenzothiazoles and aromatic amines were identified and quantified, and several other compounds were tentatively identified. The obtained results stress the need for expanding the list of target compounds analyzed in CR and the need for longitudinal studies on weathering processes taking place in CR.

Phytotoxicity of Tires Evaluated in Simulated Conditions

Illegal dumps and landfills with disposed of tires are a fact of today, which should not be neglected as they represent a great ecological burden for the environment, affect the surrounding nature and disturb the landscape. This research was focused on testing the phytotoxicity of aqueous leachates from the fractions of tires in two sets of experiments—to simulate laboratory conditions (tire leaching in distilled water) and natural conditions (tire leaching in water from a recipient) using the Phytotoxkit testing kit (kit for the establishment of inhibition/stimulation effect on the root development) and the watercress test of phytotoxicity (biological method for the assessment of leachate phytotoxicity). Plants whose seeds were selected for the test were watercress (Lepidium sativum L.) and white mustard (Sinapis alba L.). The aqueous leachate was tested for 38 weeks. During the experiment, physical and chemical parameters were measured at intervals of 14 days by the testing instrument HACH TEST KIT: electric conductivity (EC), amount of dissolved oxygen (LDO) and pH. Results of root growth inhibition (IR) on the seeds of Lepidium sativum L. and Sinapis alba L. exhibited values ranging from 11.73% to 47.74% in the tested samples. Results of germination index (GI) on the seeds of Lepidium sativum L. exhibited values below 66% in the tested samples, which indicated the leachate phytotoxicity. In spite of the fact that similar studies are tackling the acute toxicity of leachates from tires (particularly to algae, embryos and animals), this research brings complementary information in testing the acute phytotoxicity of tire leachates to higher plants.

A review of potentially harmful chemicals in crumb rubber used in synthetic football pitches

Recycling end-of-life tires (ELTs) reduces waste and provides a low-cost source of energy and materials such as crumb rubber, used as infill in artificial turf football pitches. However, some concerns were raised and remain about its safety. The potentially toxic human exposure to chemicals such as polycyclic aromatic hydrocarbons (PAHs), metals and others (volatile organic compounds (VOCs), plasticizers, antioxidants and additives) existing in ELTs (and in the resulting crumb rubber) is being studied, with no definitive conclusions. The literature existing so far suggests the possibility of their release from synthetic turf infill into the environment as water leachates and to the air surrounding the pitches, but there is the need of further research, also to assess the contribution of other materials present in synthetic turf. The database available comprised crumb rubber infill studies from pitches in 6 countries (USA, Norway, Netherlands, Portugal, Italy, Spain) and revealed a myriad of hazardous chemicals, with benzo[a]pyrene (n.d.-4.31 ± 3.95 mg/kg) and zinc (n.d.-14150 ± 1344 mg/kg) often exceeding the established limits. A dependence on indoor/outdoor conditions and the age of the source material was evaluated, often showing significative differences. From this standpoint, this review is intended to add knowledge about the presence of contaminants in this recycled material, aiming to ensure the safety of end-users and the environment.

Evaluation of chemicals of environmental concern in crumb rubber and water leachates from several types of synthetic turf football pitches

Nowadays concern exists about the safety for both football players and the environment of recycled tire rubber used as infill in synthetic turf football pitches. In this study 40 target compounds, including polycyclic aromatic hydrocarbons (PAHs), plasticizers, antioxidants and vulcanization agents were determined in 50 synthetic football pitches of diverse characteristics to estimate environmental risks. This is the first study of crumb rubber sport facilities in Portugal. Analyses were performed by ultrasound-assisted extraction followed by gas chromatography-tandem mass spectrometry (UAE-GC-MS/MS). To evaluate the transfer of the target chemicals from the crumb rubber to the runoff water, water leachates collected from several football pitches were analyzed by solid-phase microextraction (SPME-GC-MS/MS). In addition, lab-scale runoff simulation experiments were performed to assess whether a persistent inflow of the target compounds from the football pitches into the runoff water wcould exist. Results revealed the presence of most of the target PAHs in crumb rubber at total concentrations up to 57 μg g^-1, next to a high number of plasticizers and vulcanization agents. Runoff water collected from the football pitches contained up to 13 PAHs as well as other chemicals of environmental concern. In addition, continuous leaching of chemicals from the crumb rubber to the surrounding water was demonstrated. The transfer of target chemicals into the runoff water poses a potential risk for the aquatic environment.

UV/chlorine process for degradation of benzothiazole and benzotriazole in water: Efficiency, mechanism and toxicity evaluation

Benzothiazole (BZA) and benzotriazole (BTZ) as emerging contaminants were found persistent in aquatic environments and toxic to aquatic organisms. The degradation of BZA and BTZ by UV/chlorine was systematically investigated in this study, and the results showed that BZA and BTZ can be remarkably removed by UV/chlorine compared with UV alone and dark chlorination. The radical quenching tests showed that degradation of BZA and BTZ by UV/chlorine involved the participation of reactive chlorine species (RCS), hydroxyl radical (HO·), and UV photolysis. HO· dominated BZA degradation at neutral and alkalinity, while RCS dominated BTZ degradation. The second-rate order constants for ClO· and BZA and BTZ were 2.22 × 10⁸ M^-1 s^-1, and 2.40 × 10⁸ M^-1 s^-1, respectively. Besides, the second-order rate constants for HO· and BZA and BTZ were also determined at pH 5.0, 7.0, and 9.0, respectively. The degradation efficiency of BZA by UV/chlorine was substantially promoted at acidic conditions, while the degradation efficiency of BTZ was promoted at both acidic and specific alkaline range mainly due to the reactivity of radical species and deprotonated form. The influence of Cl^- was negligible, but the suppression effect of humic acid was slight during the BZA and BZT degradation by UV/chlorine. The transformation products were detected and the possible pathways were proposed. Seven disinfection by-products (DBPs) were identified both in BZA and BTZ degradation and trichloromethane was the main DBP. The toxicity assessment performed by luminescent bacteria and ECOSAR analysis indicated that the detoxification of BZA could be achieved by UV/chlorine, whereas the toxicity of BTZ was increased mainly due to the formation of intermediates. The findings from this study demonstrated UV/chlorine is likewise efficient for BZA and BTZ removal but the toxicity should be considered in the BTZ degradation.

Towards Next-Generation Sustainable Composites Made of Recycled Rubber, Cenospheres, and Biobinder

The utilisation of industrial residual products to develop new value-added materials and reduce their environmental footprint is one of the critical challenges of science and industry. Development of new multifunctional and bio-based composite materials is an excellent opportunity for the effective utilisation of residual industrial products and a right step in the Green Deal's direction as approved by the European Commission. Keeping the various issues in mind, we describe the manufacturing and characterisation of the three-component bio-based composites in this work. The key components are a bio-based binder made of peat, devulcanised crumb rubber (DCR) from used tyres, and part of the fly ash, i.e., the cenosphere (CS). The three-phase composites were prepared in the form of a block to investigate their mechanical properties and density, and in the form of granules for the determination of the sorption of water and oil products. We also investigated the properties' dependence on the DCR and CS fraction. It was found that the maximum compression strength (in block form) observed for the composition without CS and DCR addition was 79.3 MPa, while the second-highest value of compression strength was 11.2 MPa for the composition with 27.3 wt.% of CS. For compositions with a bio-binder content from 17.4 to 55.8 wt.%, and with DCR contents ranging from 11.0 to 62.0 wt.%, the compressive strength was in the range from 1.1 to 2.0 MPa. Liquid-sorption analysis (water and diesel) showed that the maximum saturation of liquids, in both cases, was set after 35 min and ranged from 1.05 to 1.4 g·g ^-1 for water, and 0.77 to 1.25 g·g^-1 for diesel. It was observed that 90% of the maximum saturation with diesel fuel came after 10 min and for water after 35 min.

Miniaturized active air sampling method for the analysis of tire rubber pollutants from indoor and outdoor places

An effective, quick, and sustainable air analysis method was developed to analyze 41 volatiles and semivolatile organic compounds present in tire rubber and crumb rubber materials. The proposed method, based on active sampling using a sorbent material followed by an ultrasound assisted extraction, was developed with the aim of obtaining a fast and simple procedure to determine polycyclic aromatic hydrocarbons, plasticizers, antioxidants, and vulcanization agents in air. A small amount of sorbent (25 mg) was used, and the analytes were recovered in only 1 mL of solvent. An experimental design was applied to study the influence of main factors such as type of sorbent and type of solvent, extraction technique (ultrasound-assisted extraction and vortex extraction), extraction time, as well as the factor interactions. Under optimal conditions, no breakthrough occurs in the studied interval (up to 4 m³ ). Linearity was demonstrated in a wide concentration range. Accuracy of the total sampling-extraction analysis was evaluated obtaining satisfactory recoveries as well as good precision. The method was successfully applied to different outdoor and indoor air environments, including a recycled rubber synthetic turf football pitch.

Hazardous compounds in recreational and urban recycled surfaces made from crumb rubber. Compliance with current regulation and future perspectives

Crumb rubber obtained from scrap tires is greatly employed for the construction of different facilities for sport, recreational and other uses. However, in recent years the concern about their safety and the related adult and children exposure to these surfaces is growing. This study aims a thorough chemical characterization encompassing 42 hazardous compounds, including polycyclic aromatic hydrocarbons (PAHs), phthalates, adipates, antioxidants and vulcanization agents in a wide range of crumb rubber from different surfaces. For the extraction of the target compounds, a method based on ultrasound-assisted extraction followed by gas chromatography-tandem mass spectrometry (UAE-GC-MS/MS) has been validated. Forty crumb rubber samples coming from synthetic turf football pitches, outdoor and indoor playgrounds, urban pavements, commercial tiles and granulates, and scrap tires, were analyzed. In addition, green alternative materials, such as sand and artificial turf based on cork granulate infill were included to compare the levels of the target compounds with those of crumb rubber. Most of the analyzed recycled surfaces meet the recent limits proposed by the European Commission for rubber granulates and mulches, although they exceed in several cases the maximum levels allowed for rubber consumer products. Besides, most of the other target compounds, including several of them considered as endocrine disruptors, were detected in the analyzed samples, reaching parts per million concentrations.

Tire wear particle and leachate exposures from a pristine and road-worn tire to Hyalella azteca: Comparison of chemical content and biological effects

Tire emissions have emerged as an environmental contaminant of concern. To fully understand their effects to biota, research is needed from different stages of a tire's lifecycle. In this study we exposed freshwater Hyalella azteca to tire wear particles (TWPs) as particle suspensions or their respective chemical leachates (the chemicals released from tire particles into water) from a pristine (P-TWP) and worn (W-TWP) tire of same make and model. Acute and long-term toxicity experiments on H. azteca showed that P-TWP suspensions were more toxic than W-TWP suspensions with estimated LC50 values of 364 ± 64 particles (0.19 ± 0.03 g L-1) and 3073 ± 211 particles (0.91 ± 0.06 g L-1), respectively. However, leachates from W- and P-TWPs appeared equally toxic, but did not conform to a sigmoidal dose-response pattern and LC50 values could not be derived. In long-term tests (21 d) P-TWP suspensions showed no significant effects on H. azteca mortality (p = 0.970) or reproduction (p = 0.123), but growth was significantly reduced (p = 0.003) at the highest concentration tested (250 particles mL-1 or 0.127 g L-1). Chemical analysis of both particle types and their leachates showed that four compounds, benzothiazole, 1-indanone, aluminum and zinc, consistently leached from TWPs into water. Analysis of the two TWPs showed a difference in the concentration of the various compounds. Specifically, P-TWPs contained significantly more 1-octanethiol, phenanthrene, anthracene and aluminum than W-TWPs, suggesting that they are possible candidates for the increased toxicity observed following P-TWP exposure.

Trends in the management of waste tyres and recent experimental approaches in the analysis of polycyclic aromatic hydrocarbons (PAHs) from rubber crumbs

The health and environmental consciousness of waste tires has increased tremendously over the years. This has motivated efforts to develop secondary applications that will utilize tire when they reach the end of their life cycle and limit their disposal in landfills. Among the applications of waste tires which are discussed in this review, the use of rubber crumbs in artificial turf fields has gained worldwide attention and is increasing annually. However, there are serious concerns regarding chemicals that are used in the manufacturing process of tires, which ultimately end up in rubber crumbs. Chemicals such as polycyclic aromatic hydrocarbons (PAH) and heavy metals which are found in rubber crumbs have been identified as harmful to human health and the environment. This review paper is intended to highlight some of the methods which have been used to manage waste tire; it also looks at chemicals/materials used in tire compounding which are identified as possible carcinogenic.

VOC Emission Analysis of Bitumen Using Proton-Transfer Reaction Time-Of-Flight Mass Spectrometry

Bitumen is one of the most important materials used in roads. During asphalt pavement construction, workers can be affected by emissions, such as volatile organic compounds (VOCs), when bitumen is heated. Therefore, it is crucial to correctly identify and measure VOCs. This paper presents a novel, promising method to determine VOC emissions. The proposed method offers a way to standardize routine measurements on a lab scale, enabling reliable comparison across bitumen types and their modifications or additives. A proton-transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) was used to monitor VOC emissions from commercial unmodified bitumen and crumb rubber modified bitumen (CRMB) with heating of up to 180 °C. Results confirmed that the temperature range of 160–180 °C is a highly influential factor for VOC emissions from heated commercial bitumen and particularly CRMB. A significant increase in alkane and aromatic emission was detected when the binders were heated to 180 °C. Sulfur-containing VOCs were almost nonexistent for the base bitumen fumes, while a significant increase was detected in the fumes when two different types of CR were added to the bitumen, even at 120 °C. The additional CR in the bituminous binder contributed to the potentially harmful VOC emission of benzothiazole, which belongs to the class of sulfur-containing compounds. The concentration of benzothiazole was 65%, 38%, and 35% higher for CR1 in comparison to CR2 at 140, 160, and 180 °C, respectively. It is clear from the results that this method allows different bitumen sources or modifications to be quickly analyzed and their VOC emissions cross-compared. If adopted and confirmed further, the method could offer the asphalt industry a viable solution to monitor VOC emissions by analyzing samples in real time at different steps of the production process.

Toxicological effects of micronized tire crumb rubber on mummichog (Fundulus heteroclitus) and fathead minnow (Pimephales promelas)

Recent studies on the distribution of microplastics in the Charleston Harbor, SC, USA revealed that a large part of the microplastic particles that are found in the intertidal sediments are tire wear particles. These particles originate from the wear of tire treads on roadways, and wash into the estuary during rain events. The abundance of these particles has raised questions about potential toxicity to aquatic organisms that ingest these particles. The synthetic rubber in car tires consists of a large variety of chemicals, which can vary between manufacturers, but usually contains styrene-butadiene rubber, carbon black and zinc. To investigate the potential toxicity of tire wear particles, both mummichogs (Fundulus heteroclitus) and fathead minnow (Pimephales promelas) were exposed to different concentrations of crumb rubber particles (38-355 µm) in a 7-day static renewal exposure. Dissection of the fish revealed that crumb rubber was ingested and accumulated in the intestinal tract. At the highest concentration tested (6 g/L) partial mortality was observed in the fathead minnow, which came close to the assumed LC₅₀. To investigate if polynuclear aromatic hydrocarbons (PAHs) were leaching from the particles, bile fluorescence was measured, together with potential induction of cytochrome P450-1A through the ethoxyresorufin-O-deethylase (EROD) assay. Elevated levels of 2-, 4-, and 5-, ring structures representative of PAHs were detected in the bile of exposed animals. Bile fluorescence indicated that 4-ring PAH compounds were the most bioavailable from the crumb rubber particles. Induction of EROD activity was observed in exposed animals at environmentally relevant concentrations of the crumb rubber particles (<1-2 g/L), and this elevated EROD activity indicated that PAH compounds from the crumb rubber particles were being metabolized in both mummichogs and fathead minnow.

Profiling and potential cancer risk assessment on children exposed to PAHs in playground dust/soil: a comparative study on poured rubber surfaced and classical soil playgrounds in Seoul

Children can get affected by polycyclic aromatic hydrocarbons (PAHs) while they interact with play area soil/rubber surfacing and exposed to PAHs by dermal contact, inhalation and hand-to-mouth activity. A comparative study has been conducted on PAHs profiling and probable cancer risk of children from PAHs present in uncovered playground surface soil and poured rubber surfaced playground dust. Surface soil and dust samples have been collected from 14 different children parks around the Korea University campus, Seoul, Republic of Korea. Concentrations of 16 PAHs in the soils/dust were found to be in a range of 2.82-57.93 μg g^-1. Profiling of the PAHs from the playground soils/dust reveals 3-ring PAHs are dominating with 79.9% of total PAHs content, on an average. The diagnostic ratio analysis confirms that vehicular exhaust and fossil fuel burning are likely the main sources of high molecular weight carcinogenic PAHs, whereas low molecular weight PAHs have pyrogenic origin. The probabilistic health risk assessment using Monte Carlo simulations for the estimation of the 95% cancer risk exposed to the PAHs from the surfaced playgrounds shows a little higher value than the USEPA safety standard (1.3 × 10^-5). Sensitivity analysis revealed exposure duration and relative skin adherence factor for soil as the most influential parameters of the assessment. Noticeably, cancer risk is approximately 10 times higher in poured rubber surfaced playgrounds than in uncovered soil playgrounds.

The pollution conveyed by urban runoff: A review of sources

Urban stormwater and snowmelt pollution contributes significantly to the deterioration of surface waters quality in many locations. Consequently, the sources of such pollution have been studied for the past 50 years, with the vehicular transportation sector and the atmospheric deposition identified early as the major pollution sources. In search for mitigation of this pollution, source controls, besides other measures, were recognised as effective pollution mitigation tools, whose successful implementation requires a good knowledge of pollution sources. Even though great research efforts have been exerted to document specific sources of urban runoff pollution, or specific groups of pollutants present in urban runoff, a comprehensive overview of all known contributing sources is still missing. This review contributes to closing this gap by compiling findings of previous research and critically synthesizing the current knowledge of various stormwater pollution sources. As the emphasis is placed on the sources, the related issues of implications for urban surface water quality and possible source controls for individual sources are touched upon just briefly, where required. The review showed that the atmospheric deposition, vehicular transportation-related activities and metallic building envelopes continue to be among the major pollution sources, which have been studied in a far greater detail than other sources. Furthermore, it was noted that because of the rapid advances in clean manufacturing and pollution control technologies, a large part of the body of data on stormwater quality available in the literature should be considered as historical data, which may no longer describe well the current conditions. Progressing historical data obsolescence, combined with continuing releases of new materials and chemicals, and, in some cases of new substances of potential concern, into the environment, suggests that the identification of important stormwater runoff/snowmelt pollution sources, and the associated pollutants, has been and will remain to be a work in progress.

Occurrence and risk assessment of benzothiazole, benzotriazole and benzenesulfonamide derivatives in airborne particulate matter from an industrial area in Spain

In this study we monitored benzothiazole (BTHs), benzotriazole (BTRs) and benzenesulfonamide (BSAs) derivatives in airborne particulate matter from four sampling sites near the port of Tarragona (Spain) over a one-year period. To do so, we developed a method based on ultrasound-assisted solvent extraction (USAE) followed by gas chromatography-mass spectrometry (GC-MS). We also studied concentrations of NO₂ and airborne particulate matter (PM_2.5 and PM_coarse) for a year. Our results showed NO₂ and PM_2.5 concentrations below the maximum average values established by the Europen Directive 2008/50/EC in the zone under study. Moreover, NO₂ values are directly proportional to changes in weather conditions and traffic emissions, while PM_coarse and PM_2.5 concentrations do not follow a clear trend as these may be generated from multiple sources (loading and unloading activities and traffic emissions). Regarding BTHs, BTRs and BSAs concentrations in particulate matter, the compounds found at the highest concentrations were 1-H-benzothiazole, 2-methylbenzothiazole, 2-chlorobenzothiazole, 1-H-benzotriazole, 4-methyl-1-H-benzotriazole, 2-(methylthio)-benzothiazole, 5-methyl-1-H-benzotriazole and bromobenzenesulfonamide with average concentrations ranging from 0.19 to 1.54 ng m^-3 in PM_coarse and from 0.09 to 0.61 ng m^-3 in PM_2.5. The remaining compounds were below the method quantification limits (MQLs) or were undetected in the samples analysed. Health risk values associated with the inhalation of the studied compounds were between 1.80 × 10^-3 and 1.27 × 10^-2 in the worst-exposure scenario.