Characterization and potential environmental risks of leachate from shredded rubber mulches

Cocktail effects of tire wear particles leachates on diverse biological models: A multilevel analysis

Tire wear particles (TWP) stand out as a major contributor to microplastic pollution, yet their environmental impact remains inadequately understood. This study delves into the cocktail effects of TWP leachates, employing molecular, cellular, and organismal assessments on diverse biological models. Extracted in artificial seawater and analyzed for metals and organic compounds, TWP leachates revealed the presence of polyaromatic hydrocarbons and 4-tert-octylphenol. Exposure to TWP leachates (1.5 to 1000 mg peq L-1) inhibited algae growth and induced zebrafish embryotoxicity, pigment alterations, and behavioral changes. Cell painting uncovered pro-apoptotic changes, while mechanism-specific gene-reporter assays highlighted endocrine-disrupting potential, particularly antiandrogenic effects. Although heavy metals like zinc have been suggested as major players in TWP leachate toxicity, this study emphasizes water-leachable organic compounds as the primary causative agents of observed acute toxicity. The findings underscore the need to reduce TWP pollution in aquatic systems and enhance regulations governing highly toxic tire additives.

Hazard assessment study on organic compounds and heavy metals from using artificial turf

Introduction

Artificial turf or synthetic grass releases hazardous substances such as heavy metals, polycyclic aromatic hydrocarbons (PAHs), and volatile organic compounds (VOCs).

Objective

The current study aimed to evaluate the concentration levels of hazardous substances that are emitted from artificial turf as a result of sunlight effect; and to assess the expected exposure risks to such emitted substances during various activities.The current study aimed to evaluate the concentration levels of hazardous substances that are emitted from artificial turf as a result of the effect of sunlight. And to assess the expected risks of exposure to these substances emitted during the various activities.

Study design

VOCs emitted from artificial turf samples were monitored and collected in the ambient air of three football fields, the ambient air around a piece of new artificial turf that has not yet been used on playing fields, but has been exposed to sunlight within one year and in the indoor air around a piece of new artificial turf. Which has not yet been used on the playgrounds and was placed at room temperature and away from sunlight.

Results

The current study shows that average afternoon morning VOCs levels were 277, 333, 405 and 509 mg/m³ in winter, autumn, spring and summer, respectively. The most predominant PAHs compounds present in the samples were compounds with 3-rings and 4-rings.The average daily intake (ADI) for three exposure routes (ingestion, inhalation, and dermal contact) was calculated for different age categories (3-6, 7-15, 16-18, 19-22, 23-55, and 56-70 year). Non-Carcinogenic exposure risk as hazard quotient (HQ) and hazard index (HI) were detected.

Conclusion

All HI values were <1, indicating that there is no potential adverse health effects occur as a result of a chemical exposure. Total carcinogenic risk (R) values for the different age categories were higher than 1E-04 for three football artificial grass fields, which indicated a high cancer risk development probability. HI and R probability increased in the age group of 7-15 year > 3-6 years.

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.

Environmental impacts and leachate analysis of waste rubber incorporated in construction and road materials: A review

In recent years, the recycling of waste tyre rubber in construction and road materials has emerged as a potential innovative solution to the growing waste rubber tyre dilemma. However, to determine the feasibility of any recycling method, it is crucial to assess the potential environmental implications of the proposed method. The environmental conditions waste tyre rubber products are exposed to are often not accurately simulated in leachate studies, leading to incomplete findings. The Toxicity Characteristics Leaching Procedure (TCLP) (1997) and Australian Bottle Leaching Procedure (ABLP) (1992), which have been used in most leachate studies in the past, have been criticised for inadequate replication of site conditions when applied to assess the leachability of modified materials. The objective of this study is to (1) review standard leachate testing methods and subsequently investigate the adequacy of these methods, (2) review all available major research focusing on the leaching characteristics and environmental and health implications of products recycled with waste tyre rubber, (3) prepare recommendations for the improvement of future leachate studies and testing based on the assessment of existing research. The existing leachate analysis studies that assess the environmental implications of different applications of waste tyre rubber have demonstrated that considerable knowledge gaps exist in the current body of knowledge. It was found leachate studies involving the recently published ABLP (2019) and Leaching Environmental Assessment Framework (LEAF) (2017) appeared to better replicate local environmental conditions and yield results of higher integrity and precision due to improved testing procedures. This study recommends that the ABLP and LEAF testing methods be applied to assess the leachability of heavy metals and organic materials (on which minimal research has been conducted) of all currently available products incorporated with waste tyre rubber, as well as in future leachate studies of waste tyre rubber.

Acute toxicity of tire wear particles, leachates and toxicity identification evaluation of leachates to the marine copepod, Tigriopus japonicus

Tire wear particles (TWPs) have been characterized as microplastics in recent years, and many of these TWPs will be eventually deposited in coastal areas, leading to adverse effects to marine organisms. Results of the acute toxicity test in this study showed that the 96-h LC50 values of the particles and leachate were 771.4 mg/L (95% CI = 684.4-869.6 mg/L) and 5.34 g/L (95% CI = 4.75-6.07 g/L), respectively. The chemical constituents of TWP and the leachate are very complex, and little research has been conducted to determine which of these constituents contribute to the toxicity of TWP leachate to marine organisms. Therefore, the composition of the TWP and leachate was analyzed, and a variety of chemicals were identified, including metals (Mn, Zn, etc.) and organic compounds (cyclohexanthiol, 4-ethyl-1,2-dimethylbenzene, benzothiazole, stearic acid, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, etc.). In addition, the marine copepod Tigriopus japonicus was applied as a model species in the toxicity identification evaluation study to characterize, identify and confirm the toxicity-causing substances in the TWP leachate. Zn was identified and confirmed as the main toxicant contributing to the toxicity. Furthermore, Zn concentrations in the leachate over time were investigated. The release of Zn from TWPs to the aquatic environment was slow, and conformed to a parabolic model with a release constant k of 2.06. The organic component, benzothiazole, exhibited an antagonistic effect with zinc in the acute toxicity of the TWP leachate.

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.

Release of Zinc and Polycyclic Aromatic Hydrocarbons From Tire Crumb Rubber and Toxicity of Leachate to Daphnia magna: Effects of Tire Source and Photoaging

Tire crumb rubber (TCR) has been widely used in artificial turf fields, however, the potential environmental risk of TCR and the effect of sunlight exposure are scarcely studied. Here, we evaluated leachability of Zn and polycyclic aromatic hydrocarbons (PAHs) in four types of TCRs and acute toxicity of leachates to Daphnia magna. The results showed that all types of TCRs tested released Zn (0.20-1.3 μg/g) and PAHs (9.4-17 μg/g) but only two were lethal to D. magna (mortality 73%). Notably, ultraviolet (UV) irradiation induced TCR to generate acidic leachate (pH ~ 4.8), which contained 24- and 1.2-fold higher concentrations of Zn and PAHs and therefore was more toxic to D. magna than that in the absence of UV treatment. These findings demonstrate source-dependent toxicity of TCR and highlight the need to consider the effect of photoaging when evaluating the environmental risks of TCR.

Crumb Rubber in Concrete—The Barriers for Application in the Construction Industry

This state-of-the-art review was aimed to conduct a comprehensive literature survey to summarize experiences of crumb rubber (CR) application in concrete within the last 30 years. It shows that certain gaps prevent obtaining a coherent overview of both mechanical behaviour and environmental impact of crumb rubber concrete (CRC) to object to the stereotypes which prevent to use of CR in concrete in the construction industry. Currently, four major barriers can be distinguished for a successful CR application in the concrete industry: (1) the cost of CR recycling, (2) mechanical properties reduction, (3) insufficient research about leaching criteria and ecotoxicological risks and (4) recyclability of CRC. The application of CR in concrete has certainly its advantages and in general cannot be ignored by the construction industry. CR can be applied, for example, as an alternative material to replace natural aggregates and CRC can be used as recycled concrete aggregates (RCA) in the future. A certain diversity for the CR application can be introduced in a more efficient way when surface treatment and concrete mix design optimization are properly developed for each type of CR application in concrete for possible field applications. The role of CRC should not be limited to structures that are less dependent on strength.

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.

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.

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.

Artificial Turf Infill: A Comparative Assessment of Chemical Contents

Concerns have been raised regarding toxic chemicals found in tire crumb used as infill in artificial turf and other play surfaces. A hazard-based analysis was conducted, comparing tire crumb with other materials marketed as alternative infills. These include other synthetic polymers as well as plant- and mineral-based materials. The comparison focused on the presence, absence, number, and concentration of chemicals of concern. No infill material was clearly free of concerns, but several are likely to be somewhat safer than tire crumb. Some alternative materials contain some of the same chemicals of concern as those found in tire crumb; however, they may contain a smaller number of these chemicals, and the chemicals may be present in lower quantities. Communities making choices about playing surfaces are encouraged to examine the full range of options, including the option of organically managed natural grass.

Artificial turf: chemical flux and development of silicone wristband partitioning coefficients

This work provides the first quantitative measure of in situ flux of semi-volatile contaminants on artificial turf fields. Passive samplers were used to identify gas-phase PAHs and OPAHs not previously reported associated with artificial turf. Utilizing a broad and targeted screen, we assess both artificial turf and from crumb rubber for 1,529 chemicals, including several with known health effects including benzo[c]fluorene. We also report the presence of 25 chemicals that have not yet been reported in artificial turf literature, including some with known effects on human health. This is the first report of bioavailable gas-phase PAH and OPAH concentrations on an outdoor field, to date gas-phase concentrations have only been reported from indoor facilities. Turf air and air were highly correlated at all three sites, and particularly at the recently-installed indoor site. Finally, thermal extraction and silicone passive samplers are highly suitable for larger-scale sampling campaigns that aim for less solvent and sample processing. We demonstrate for the first time that silicone passive samplers can be used to quantify volatile and semi-volatile organic chemicals from artificial turf. Co-deploying silicone passive samplers and conventional low density polyethylene, we develop partitioning coefficients that can be used for silicone passive air sampling environmental assessment.

Reduced zinc leaching from scrap tire during pavement applications

Large quantities of scrap tires have been generated and accumulated over the years. However, a significant amount of them are stocked due to the lack of environmentally-friendly methods for disposing of, or reusing them. Because tires contain approximately 1-2% zinc by weight, leaching of zinc from scrap tires could be an environmental concern. In this research, we investigated the leaching of zinc from tire particles that are used with asphalt for pavement applications. The effects of tire particle size and pH on zinc leaching were also examined. Our results indicated that asphalt treatment significantly reduced zinc leaching from tires, and that it was also reduced by increasing the tire particle size and pH. The leaching of zinc was quantified by using a speciation-based modeling approach. The model parameters, namely, the total leachable zinc mass and the adsorption constant, can be used to predict the leaching of zinc under different conditions. The reduction in zinc leaching from asphalt-treated tire particles was due to the physical blocking of the tire surface by the asphalt. Results also indicated that, while the leaching of zinc and other selected toxic elements from untreated tire particles using simulated acid rain was not significant compared to the drinking water regulations, asphalt treatment during the pavement application further improved the environmental performance of the tire particles.

Physical and chemical characterization of representative samples of recycled rubber from end-of-life tires

A large number of end-of-life tires (ELTs) were sampled and classified by type, age and origin to obtain recycled rubber samples representative of the materials placed on the Italian market. The selected recycled tire rubber samples were physically and chemically characterized and a chemometric approach was used to determine correlations. The polycyclic aromatic hydrocarbons (PAHs) content was correlated to the aromaticity index and a model was built to establish the H-Bay aromaticity index (H-Bay) from the PAH concentrations. ELT of different origin and age produced in non-European countries generally had higher PAH content and a higher H-Bay index. H-Bay values of all the samples were lower than the REACH limits and old tires had higher aromatic content than recent ones, possibly due to the replacement of aromatic oils in tire production.

Use of nuclear receptor luciferase-based bioassays to detect endocrine active chemicals in a biosolids-biochar amended soil

Biosolids are a potentially valuable source of carbon and nutrients for agricultural soils; however, potential unintended impacts on human health and the environment must be considered. Virtually all biosolids contain trace amounts endocrine-disrupting chemicals derived from human use of pharmaceuticals and personal care products (PPCPs). One potential way to reduce the bioavailability of PPCPs is to co-apply biosolids with biochar to soil, because biochar's chemical (e.g., aromaticity) and physical properties (e.g., surface area) give it a high affinity to bind many organic chemicals in the environment. We developed a soil-specific extraction method and utilized a luciferase-based bioassay (CALUX) to detect endocrine active chemicals in a biosolids-biochar co-amendment soil greenhouse study. Both biochar (walnut shell, 900 °C) and biosolids had positive impacts on carrot and lettuce biomass accumulation over our study period. However, the walnut shell biochar stimulated aryl hydrocarbon receptor activity, suggesting the presence of potential endocrine active chemicals in the biochar. Since the biochar rate tested (100 t ha^-1) is above the average agronomic rate (10-20 t ha^-1), endocrine effects would not be expected in most environmental applications. The effect of high temperature biochars on endocrine system pathways must be explored further, using both quantitative analytical tools to identify potential endocrine active chemicals and highly sensitive bioanalytical assays such as CALUX to measure the resulting biological activity of such compounds.

Evidence for New Light-Independent Pathways for Generation of the Endogenous Aryl Hydrocarbon Receptor Agonist FICZ

Activation of the aryl hydrocarbon receptor (AhR), a conserved transcription factor best known as a target for highly toxic halogenated substances such as dioxin, under normal xenobiotic-free conditions is of considerable scientific interest. We have demonstrated previously that a photoproduct of tryptophan, 6-formylindolo[3,2-b]carbazole (FICZ), fulfills the criteria for an endogenous ligand for this receptor and proposed that this compound is the enigmatic mediator of the physiological functions of AhR. Here, we describe novel light-independent pathways by which FICZ can be formed. The oxidant H2O2 was shown to convert tryptophan to FICZ on its own in the absence of light. The enzymatic deamination of tryptamine yielded indole-3-acetaldehyde (I3A), which then rearranged to FICZ and its oxidation product, indolo[3,2-b]carbazole-6-carboxylic acid (CICZ). Indole-3-pyruvate (I3P) also produced I3A, FICZ, and CICZ. Malassezia yeast species, which constitute a part of the normal skin microbiota, produce a number of AhR activators from tryptophan. We identified both FICZ and CICZ among those products. Formation of FICZ from tryptophan or I3P produces a complex mixture of indole derivatives, some of which are CYP1A1 inhibitors. These can hinder the cellular clearance of FICZ and thereby increase its power as an AhR agonist. We present a general molecular mechanism involving dehydrogenations and oxidative coupling for the formation of FICZ in which I3A is the important precursor. In conclusion, our results suggest that FICZ is likely to be formed systemically.

Experimental methodology for assessing the environmental fate of organic chemicals in polymer matrices using column leaching studies and OECD 308 water/sediment systems: Application to tire and road wear particles

Automobile tires require functional rubber additives including curing agents and antioxidants, which are potentially environmentally available from tire and road wear particles (TRWP) deposited in soil and sediment. A novel methodology was employed to evaluate the environmental fate of three commonly-used tire chemicals (N-cyclohexylbenzothiazole-2-sulfenamide (CBS), N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine (6-PPD) and 1,3-diphenylguanidine (DPG)), using a road simulator, an artificial weathering chamber, column leaching tests, and OECD 308 sediment/water incubator studies. Environmental release factors were quantified for curing (f(C)), tire wear (f(W)), terrestrial weathering (f(S)), leaching from TRWP (f(L)), and environmental availability from TRWP (f(A)) by liquid chromatography-tandem mass spectroscopy (LC/MS/MS) analyses. Cumulative fractions representing total environmental availability (F(T)) and release to water (FR) were calculated for the tire chemicals and 13 transformation products. F(T) for CBS, DPG and 6-PPD inclusive of transformation products for an accelerated terrestrial aging time in soil of 0.1 years was 0.08, 0.1, and 0.06, respectively (equivalent to 6 to 10% of formulated mass). In contrast, a wider range of 5.5×10(-4) (6-PPD) to 0.06 (CBS) was observed for F(R) at an accelerated age of 0.1 years, reflecting the importance of hydrophobicity and solubility for determining the release to the water phase. Significant differences (p<0.05) in the weathering factor, f(S), were observed when chemicals were categorized by boiling point or hydrolysis rate constant. A significant difference in the leaching factor, f(L), and environmental availability factor, f(A), was also observed when chemicals were categorized by log K(ow). Our methodology should be useful for lifecycle analysis of other functional polymer chemicals.

Effects of leachate from crumb rubber and zinc in green roofs on the survival, growth, and resistance characteristics of Salmonella enterica subsp. enterica serovar Typhimurium

The use of green roofs is a growing practice worldwide, particularly in densely populated areas. In an attempt to find new methods for recycling crumb rubber, incorporation of crumb rubber into artificial medium for plant growth in green roofs and similar engineered environments has become an attractive option for the recycling of waste tires. Though this approach decreases waste in landfills, there are concerns about the leaching of zinc and other heavy metals, as well as nutrient and organic compounds, into the environment. The present study analyzed the impact of leachate from crumb rubber and zinc on the growth and viability of Salmonella enterica subsp. enterica serovar Typhimurium. Zinc was chosen for further studies since it has been previously implicated with other biological functions, including biofilm formation, motility, and possible cross-resistance to antimicrobial agents. The study showed that Salmonella can colonize crumb rubber and that crumb rubber extract may provide nutrients that are usable by this bacterium. Salmonella strains with reduced susceptibility (SRS) to zinc were obtained after subculturing in increasing concentrations of zinc. The SRS exhibited differences in gene expression of flux pump genes zntA and znuA compared to that of the parent when exposed to 20 mM added zinc. In biofilm formation studies, the SRS formed less biofilm but was more motile than the parental strain.

Detection of organic compounds with whole-cell bioluminescent bioassays

Natural and manmade organic chemicals are widely deposited across a diverse range of ecosystems including air, surface water, groundwater, wastewater, soil, sediment, and marine environments. Some organic compounds, despite their industrial values, are toxic to living organisms and pose significant health risks to humans and wildlife. Detection and monitoring of these organic pollutants in environmental matrices therefore is of great interest and need for remediation and health risk assessment. Although these detections have traditionally been performed using analytical chemical approaches that offer highly sensitive and specific identification of target compounds, these methods require specialized equipment and trained operators, and fail to describe potential bioavailable effects on living organisms. Alternatively, the integration of bioluminescent systems into whole-cell bioreporters presents a new capacity for organic compound detection. These bioreporters are constructed by incorporating reporter genes into catabolic or signaling pathways that are present within living cells and emit a bioluminescent signal that can be detected upon exposure to target chemicals. Although relatively less specific compared to analytical methods, bioluminescent bioassays are more cost-effective, more rapid, can be scaled to higher throughput, and can be designed to report not only the presence but also the bioavailability of target substances. This chapter reviews available bacterial and eukaryotic whole-cell bioreporters for sensing organic pollutants and their applications in a variety of sample matrices.

Dissolution of copper and iron from automotive brake pad wear debris enhances growth and accumulation by the invasive macrophyte Salvinia molesta Mitchell

Automotive vehicles release particulate matter into the environment when their brakes are applied. The environmental effects of this automotive brake pad wear debris (BPWD) on the environment is a matter of growing debate yet the effects on plants have been largely untested. In this study, the effect of BPWD on the growth of the aquatic invasive Salvinia molesta Mitchell was examined. Salvinia molesta, plants were grown hydroponically in distilled water or in a distilled water extract containing BPWD. Growth of floating leaves, submerged leaves, and leaf nodes were measured over 20 d at 4-d intervals. At the conclusion of the study the amount of BPWD present in solutions and plant tissues was quantified using atomic absorption spectrometry (AAS). Cultivation of S. molesta in the water containing BPWD resulted in greater dissolution of Cu and Fe than occurred in the absence of plants. The tissue Cu and Fe concentrations of plants cultivated in the BPWD were significantly higher than plants grown in the absence of BPWD. Growth of S. molesta significantly increased when cultivated in the BPWD solutions in comparison to the distilled water. The results suggest that S. molesta and similar aquatic plants may be capable of increasing the dissolution of metal micronutrients from BPWD and utilizing those micronutrients to increase growth. Such growth responses could indicate that BPWD may interact with invasive floating macrophytes to more rapidly degrade the quality and stability of aquatic communities.

Hazardous organic chemicals in rubber recycled tire playgrounds and pavers

In this study, the presence of hazardous organic chemicals in surfaces containing recycled rubber tires is investigated. Direct material analyses using solvent extraction, as well as SPME analysis of the vapour phase above the sample, were carried out. Twenty-one rubber mulch samples were collected from nine different playgrounds. In addition, seven commercial samples of recycled rubber pavers were acquired in a local store of a multinational company. All samples were extracted by ultrasound energy, followed by analysis of the extract by GC-MS. The analysis confirmed the presence of a large number of hazardous substances including PAHs, phthalates, antioxidants (e.g. BHT, phenols), benzothiazole and derivatives, among other chemicals. The study evidences the high content of toxic chemicals in these recycled materials. The concentration of PAHs in the commercial pavers was extremely high, reaching values up to 1%. In addition, SPME studies of the vapour phase above the samples confirm the volatilisation of many of those organic compounds. Uses of recycled rubber tires, especially those targeting play areas and other facilities for children, should be a matter of regulatory concern.

Artificial turf football fields: environmental and mutagenicity assessment

The public has recently raised concerns regarding potential human health and environmental risks associated with tire crumb constituents in the artificial turf of football fields. The aim of the present study was to develop an environmental analysis drawing a comparison between artificial turf football fields and urban areas relative to concentrations of particles (PM10 and PM2.5) and related polycyclic aromatic hydrocarbons (PAHs), aromatic hydrocarbons (BTXs), and mutagenicity of organic extracts from PM10 and PM2.5. No significant differences were found between PM10 concentrations at an urban site and on a turf football field, both during warm and in cold seasons, either with or without on-field activity. PM2.5 concentrations were significantly greater at the urban site in the cold season as was the ratio of PM2.5 to PM10. BTXs were significantly greater at urban sites than on turf football fields on both on warm and cold days. The ratio of toluene to benzene (T/B ratio) was always comparable with that of normal urban conditions. The concentration of PAHs on the monitored football fields was comparable with urban levels during the two different sampling periods, and the contribution of PAHs released from the granular material was negligible. PM10 organic extract mutagenicity for artificial turf football fields was greater, whereas PM2.5 organic extract mutagenicity was lower, compared with the urban site studied. However, both organic extract mutagenicity values were comparable with the organic extract mutagenicity reported in the literature for urban sites. On the basis of environmental monitoring, artificial turf football fields present no more exposure risks than the rest of the city.

Zinc leaching from tire crumb rubber

Because tires contain approximately 1-2% zinc by weight, zinc leaching is an environmental concern associated with civil engineering applications of tire crumb rubber. An assessment of zinc leaching data from 14 studies in the published literature indicates that increasing zinc leaching is associated with lower pH and longer leaching times, but the data display a wide range of zinc concentrations, and do not address the effect of crumb rubber size or the dynamics of zinc leaching during flow through porous crumb rubber. The present study was undertaken to investigate the effect of crumb rubber size using the synthetic precipitation leaching procedure (SPLP), the effect of exposure time using quiescent batch leaching tests, and the dynamics of zinc leaching using column tests. Results indicate that zinc leaching from tire crumb rubber increases with smaller crumb rubber and longer exposure time. Results from SPLP and quiescent batch leaching tests are interpreted with a single-parameter leaching model that predicts a constant rate of zinc leaching up to 96 h. Breakthrough curves from column tests displayed an initial pulse of elevated zinc concentration (~3 mg/L) before settling down to a steady-state value (~0.2 mg/L), and were modeled with the software package HYDRUS-1D. Washing crumb rubber reduces this initial pulse but does not change the steady-state value. No leaching experiment significantly reduced the reservoir of zinc in the crumb rubber.

Inhibition of cytochrome P4501-dependent clearance of the endogenous agonist FICZ as a mechanism for activation of the aryl hydrocarbon receptor

Altered systemic levels of 6-formylindolo[3,2-b]carbazole (FICZ), an enigmatic endogenous ligand for the aryl hydrocarbon receptor (AHR), may explain adverse physiological responses evoked by small natural and anthropogenic molecules as well as by oxidative stress and light. We demonstrate here that several different chemical compounds can inhibit the metabolism of FICZ, thereby disrupting the autoregulatory feedback control of cytochrome P4501 systems and other proteins whose expression is regulated by AHR. FICZ is both the most tightly bound endogenous agonist for the AHR and an ideal substrate for cytochrome CYP1A1/1A2 and 1B1, thereby also participating in an autoregulatory loop that keeps its own steady-state concentration low. At very low concentrations FICZ influences circadian rhythms, responses to UV light, homeostasis associated with pro- and anti-inflammatory processes, and genomic stability. Here, we demonstrate that, if its metabolic clearance is compromised, femtomolar background levels of this compound in cell-culture medium are sufficient to up-regulate CYP1A1 mRNA and enzyme activity. The oxidants UVB irradiation and hydrogen peroxide and the model AHR antagonist 3'-methoxy-4'-nitroflavone all inhibited induction of CYP1A1 enzyme activity by FICZ or 2,3,7,8-tetrachlorodibenzo-p-dioxin, thereby subsequently elevating intracellular levels of FICZ and activating AHR. Taken together, these findings support an indirect mechanism of AHR activation, indicating that AHR activation by molecules with low affinity actually may reflect inhibition of FICZ metabolism and raising questions about the reported promiscuity of the AHR. Accordingly, we propose that prolonged induction of AHR activity through inhibition of CYP1 disturbs feedback regulation of FICZ levels, with potential detrimental consequences.

Leaching of zinc from tire wear particles under simulated estuarine conditions

Tire wear particles (TWP) abraded from end-of-life passenger car tires have been added at a concentration of 1 g L⁻¹ to river water, sea water and mixtures thereof in order to examine the chemical controls on the leaching of Zn from the rubber matrix. Results of time-dependent experiments conducted over a period of 5 days were consistent with a diffusion controlled leaching mechanism with rate constants of about 0.04 mg L⁻¹ h⁻½ in river water and between about 0.02 and 0.03 mg L⁻¹ h⁻½ in sea water. Additional experiments revealed a reduction in Zn dissolution with both increasing salinity and pH and enhancement of leaching in the presence of fluorescent light compared with dark conditions. In corresponding experiments conducted in the presence of a fixed quantity (0.8 g L⁻¹) of clean, fractionated estuarine sediment, aqueous Zn concentrations were reduced by at least an order of magnitude. Increasing the quantity of sediment resulted in a progressive reduction in Zn concentration until an apparent equilibrium was achieved, with partition coefficients defining the sediment-water distribution of Zn of about 550 mL g⁻¹ and 270 mL g⁻¹ in river water and sea water, respectively. Results are interpreted in terms of the dissolution of ZnO and other residual complexes from the matrix and the subsequent, rapid adsorption of Zn²⁺ ions to coexistent estuarine sediment. The findings of the study are discussed in terms of their implications for the transport, fate and effects of TWP Zn in aquatic environments that are likely to receive urban runoff.

Characterization of substances released from crumb rubber material used on artificial turf fields

Crumb rubber material (CRM) used as infill on artificial turf fields can be the source of a variety of substances released to the environment and to living organisms in the vicinity of the CRM. To assess potential risks of major volatilized and leached substances derived from CRM, methods were developed to identify organic compounds and elements, either in the vapor phase and/or the leachate from CRM. A qualitative method based on solid phase micro-extraction (SPME) coupled with gas chromatography/mass spectrometry (GC-MS) was developed to identify the major volatile and semi-volatile organic compounds out-gassing from CRM samples under defined laboratory conditions. Direct vapor phase injection into the GC-MS was applied for the quantitative analysis. Ten organic compounds were identified in the vapor phase by the SPME method. Volatile benzothiazole (BT) was detected at the highest level in all commercial CRM samples, in the range 8.2-69 ng g(-1) CRM. Other volatile PAHs and antioxidants were quantified in the vapor phase as well. A decrease of volatile compounds was noted in the headspace over CRM samples from 2-years-old fields when compared with the virgin CRM used at installation. An outdoor experiment under natural weathering conditions showed a significant reduction of out-gassing organic compounds from the CRM in the first 14 d; thereafter, values remained consistent up to 70 d of observation. Zinc was the most abundant element in the acidified leachate (220-13000 microg g(-1)), while leachable BT was detected at relatively low amounts.