Comprehensive Identification and Ubiquitous Occurrence of Eight Classes of Rubber-Derived Vulcanization Accelerators in Urban Dusts.

Vulcanization accelerators (VAs) serve as crucial additives in synthetic rubber on a global scale. Despite their widespread use, the environmental presence, distribution, and associated exposure risks of VAs remain poorly understood. This study compiled a target list and conducted a screening for eight classes encompassing 42 VAs in diverse urban dust samples from South China. A total of 40 of the 42 target VAs were detectable across all four studied regions, among which 30 were identified for the first time in the environment. Among the eight structure-classified VA classes, xanthates exhibited the highest concentrations (median: 3810-81,300 ng/g), followed by thiazoles, guanidines, sulfenamides, dithiocarbamates, thiurams, thioureas, and others. The median total concentrations of all target VAs (∑VAs) were determined to be 5060 ng/g in road dust, 5730 ng/g in parking lot dust, 29,200 ng/g in vehicle repair plant dust, and 84,300 ng/g in household dust, indicating the widespread presence of numerous rubber-derived VAs in various urban environments. This study marked the first systematic effort to identify a wide range of emerging rubber-derived VAs prevalent in urban environments. The findings call for increased attention to these widely utilized but less well-evaluated chemicals in future research and environmental management efforts.

First Evidence of Hindered Amine Light Stabilizers As Abundant, Ubiquitous, Emerging Pollutants in Dust and Air Particles: A New Concern for Human Health.

Hindered amine light stabilizers (HALSs) represent a crucial class of polymer additives that are extensively used in plastics and other polymeric materials. However, their environmental presence and related exposure risks have until now remained unexplored. This study addressed this critical knowledge by examining dust and air particles collected in South China, utilizing a comprehensive analytical approach to identify and quantify nine monomeric HALSs. A total of seven of the nine studied HALSs were detected in the samples, with bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate (Tinuvin 770) and methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate (HS-508) identified as the most abundant and widespread pollutants. Median total concentrations of HALSs ranged from 417 to 8,830 ng/g in urban dust samples and from 28.6 to 70.9 pg/m3 in urban air particles. Notably, dust concentrations of HALSs significantly exceeded those of traditional well-known light stabilizers such as UV absorbers. Human exposure assessment indicated that in contrast to air inhalation dust ingestion represented a more substantial exposure pathway owing to the relatively low volatility of these newly identified chemicals. Predictive modeling suggests that many of the examined HALSs exhibited characteristics of persistence, high toxicity, or strong potential for long-range transport, underscoring their hazardous nature. This study represents the first comprehensive investigation into the prevalence of HALSs as a class of emerging pollutants widespread in the environment, necessitating heightened attention and further research in the future.

A review of liquid crystal monomers: Environmental occurrence, degradation, toxicity, and human exposure of an emerging class of E-waste pollutants.

Liquid crystal monomers (LCMs) are a class of organic compounds with diphenyl or dicyclohexane as the skeleton structure, which are widely used in the manufacturing of liquid crystal displays. They are recognized as novel organic compounds with persistence, bioaccumulation, toxicity, and potential for long-range transport. LCMs are inevitably released into the environment throughout the life cycle of electronic products, and their presence has been found in various abiotic matrixes (air, dust, sediment, leachate, soil) and biotic matrixes (aquatic organisms, human serum, and human skin wipe). Given that studies on LCMs are still in their infancy, this review comprehensively summarizes the extensive literature data on LCMs and identifies key knowledge gaps and future research needs. The physicochemical properties, production, and usage of LCMs are described. Their environmental distribution, degradation, toxicity, and human exposure are also discussed based on the available data and results. Existing data show that LCMs have large-scale environmental pollution and may pose potential ecological and health risks, but it is still insufficient to accurately assess their risks due to the lack of knowledge on LCMs in many areas, such as global contamination trend, environmental behavior, toxic effects, and human exposure assessment. We believe that future studies of LCMs need to investigate LCMs pollution on a large geographic scale, explore their sources, behavior, and fate in the environment, and assess their potential health hazards to organisms and humans.

Nationwide Occurrence and Unexpected Severe Pollution of Fluorescent Brighteners in the Sludge of China: An Emerging Anthropogenic Marker.

Fluorescent brighteners (FBs) are a group of mass-produced dyestuff chemicals that have been extensively used for decades. However, knowledge of their occurrence in municipal wastewater treatment plants on a large geographical scale remains unknown. Herein, we implemented the first nationwide survey for wastewater-derived FBs in sludge across major cities in China. All 25 target FBs were detected in the nationwide sludge. Ionic FBs exhibited much higher concentrations than nonionic FBs. The total sludge concentrations of 25 FBs (∑25FBs) ranged from 7300 to 1,520,000 ng/g, with a median of 35,300 ng/g. A clear geographical distribution of significantly higher concentrations of FBs was found in East and Central China than in West China (p < 0.05). The sludge concentrations of ∑25FBs were correlated well with the gross domestic product (GDP) and population size at the provincial level in China (p < 0.05), demonstrating the significance of anthropogenic impacts on FB levels in urban sludge. The nationwide annual emission of total FBs into sludge in China is estimated to be 835 tons/year, of which 134 tons/year is directly released into sludge-applied soils. Our work highlights another new class of chemicals that significantly contribute to the chemical mixtures in urban sludge and thus require immediate attention.

Development of an in vitro model to simulate migration of organic contaminants from pad products to human sweat and enhance dermal exposure risk assessment.

Dermal sorption is an important route for human exposure to organic chemicals embedded in consumer products, but the related chemical migration from consumer products to sweats was often overlooked in assessing skin exposure risk. To address this issue, the present study selected polycyclic aromatic hydrocarbons (PAHs), phthalic acid esters (PAEs), and benzothiazoles (BTs) as the target compounds and developed an in vitro simulation model with two artificial sweats (i.e., acidic and alkaline), a sorbent, and a PVC standard material. An appropriate biological inhibitor (ampicillin) and incubation time of 20 d for assessing the maximum migration efficiency of chemicals were selected. The mass balance of the target compounds during the in vitro incubation was verified. The established in vitro simulation model was used to determine the migration ratios of PAEs and BTs in three types of mouse pads. The maximum migration ratios of DBP, DIBP, DEHP, and BT from leather pad to both sweats were less than those for silicone and rubber pads. Key controlling parameters in migration ratios should be examined in subsequent investigations. Risk assessment showed that the daily exposure doses of PAEs and BTs in mouse pads were higher than the literature data. The hazard index of PAEs in leather pad exceed 1, indicating that PAEs could induce non-carcinogenic effects to human health through hand contact. Overall, the established in vitro simulation model provides a feasible alternative for assessing the potential risk for dermal exposure to consumer products.

Prevalence of phthalate alternatives and monoesters alongside traditional phthalates in indoor dust from a typical e-waste recycling area: Source elucidation and co-exposure risk.

This study first discovered the prevalence of phthalate (PAE) alternatives and PAE monoesters alongside traditional PAEs with elevated concentrations in indoor dust from typical e-waste recycling industrial park and adjacent communities. Among nine PAEs, high-molecular-weight (HMW) PAEs dominated over low-molecular-weight (LMW) PAEs in e-waste dust, with total concentrations (∑9PAEs) ranging from 170 to 5300 µg g-1. The diisononyl phthalate (DiNP) was identified as the most abundant PAE in e-waste dust, with over 10 times higher median concentration than that measured in home dust. Total concentrations of three PAE alternatives ranged from 20 to 1600 µg g-1 in e-waste dust, which were 3-10 times higher than the measured levels in home dust. A total of 13 monoesters were all identified in all samples with total concentrations of 4.7-59 µg g-1, and biodegradation of diesters was recognized as the major source of monoesters present in indoor dust. Significant correlations between the concentrations of PAE alternatives and the HMW PAEs were observed (p < 0.05), indicating that they are being simultaneously used in electronic and electrical products. The occupationally high co-exposure of e-waste dismantling workers to multiple PAEs and PAE alternatives as well as their monoesters should be of concern.

Blood partitioning and whole-blood-based maternal transfer assessment of chlorinated paraffins in mother-infant pairs from South China.

As a new group of persistent organic pollutants of concern, chlorinated paraffins (CPs) have been widely detected in the environment and biota, but their occurrence, partitioning, and transfer in humans have been not well documented. In this study, 32 pairs of maternal blood, cord blood, and placenta samples were collected from pregnant women in South China, and the blood was further separated into plasma and red blood cells (RBCs) for blood partitioning study. Short- and medium-chain CPs (SCCPs and MCCPs, respectively) were detected in all the five human biological matrices, suggesting prevalent exposure and maternal transfer of CPs in the pregnant women. Discrepant congener group profiles of CPs were observed in different human biological matrices. Significant differences in the plasma-RBC partitioning of CPs in the maternal and cord bloods were identified (p < 0.001). CP partitioning to plasma was stronger than that to RBCs in maternal blood, but the converse was true for cord blood. Mass fractions in plasma (Fp) for SCCPs (mean, 0.78) and MCCPs (0.74) in maternal blood were significantly higher than the values in cord blood. Transplacental transfer efficiencies (TTEs) were evaluated based on the whole blood concentrations of CPs in the maternal and cord bloods, and the TTEs ranged from 0.50 to 0.69 (first to third quartiles) for SCCPs and MCCPs, indicating that the placenta can partially restrict maternal transfer. The extent of CP retention in the placenta was assessed by the concentration ratio (RPM) of matched placenta and maternal blood, and interestingly, a U-shaped trend for placental retention (RPM) with increasing chain length was observed for individual congener groups. Significant relationships of the CP concentrations among the maternal blood, cord blood, and placenta were observed (p < 0.001). To our knowledge, this is the first study to report the plasma-RBC partitioning of CPs in human maternal and cord bloods, as well as the first study to evaluate TTEs based on whole blood concentrations. Our study confirmed that whole blood is the preferred matrix for accurately assessing human internal exposure and transplacental transfer of CPs.

Oxidative Oligomerization of Phenolic Endocrine Disrupting Chemicals Mediated by Mn(III)-L Complexes and the Role of Phenoxyl Radicals in the Enhanced Removal: Experimental and Theoretical Studies.

Soluble manganese(III), stabilized by ligands as Mn(III)-L complexes, are ubiquitous in natural waters and wastewaters and can potentially serve as both the oxidant and reductant in one-electron transfer reactions with organic contaminants. In this study, the oxidative transformations of 14 phenolic endocrine disrupting chemicals (EDCs) by in situ-formed Mn(III)-L complexes, generated from irradiated water containing Mn(II) and humic acid, were investigated. The pseudo-first-order rate constants (kobs, h-1) of these phenols varied from 1.0 × 10-4 to 5.9 × 10-2. A quantitative structure-activity relationship model was developed, which suggests that the electron-donating ability (EHOMO) of phenolic chemicals was the most important molecular characteristic for the Mn(III)-L-mediated oxidative transformation. Phenol transformation was initiated by the generation of a phenoxyl radical through electron transfer to Mn(III)-L. Subsequent self-coupling reactions between phenoxyl radicals resulted in the formation of self-coupling dimers and trimers. With the addition of simple phenol as a cosubstrate, enhanced transformations of these phenolic EDCs were clearly observed, and cross-coupling products of simple phenol and the substrates were also detected. In addition, a reaction activation energy calculation based on the transition-state theory indicated that the cross-coupling reaction was more likely than the self-coupling reaction to occur in the presence of phenol. This work provides new insights into the environmental fate of phenolic compounds.

Emissions and Occupational Exposure Risk of Halogenated Flame Retardants from Primitive Recycling of E-Waste.

The production and usage of non-polybrominated diphenyl ether (PBDE) halogenated flame retardants (HFRs) have substantially increased after the ban of several PBDEs. This has resulted in widespread environmental occurrence of non-PBDE HFRs, further amplified by emissions from primitive recycling of obsolete electronics (e-waste). The present study conducted chamber experiments to characterize 15 HFRs (∑15HFR) from thermal treatment and open burning of typical e-waste. Emission factors of ∑15HFR from thermal treatment were 2.6 × 104-3.9 × 105 ng g-1, slightly higher than those from open burning (8.8 × 103-1.0 × 105 ng g-1). Greater output over input mass ratios of ∑15HFR were obtained in thermal treatment than in open burning. Particulate and gaseous HFRs dominated the emissions in thermal treatment and open burning, respectively, largely because of the different temperatures used in the two processes. Particulate HFRs were primarily affiliated with fine particles (Dp < 1.8 µm) peaking at 0.56-1.0 or 0.32-0.56 µm in both thermal treatment and open burning. Occupational exposure to most FRs was relatively low, but several PBDEs may pose potential health risk to workers in e-waste home-workshops. Potentially accruing emissions and health risks of non-PBDE HFRs from primitive recycling of e-waste remain a great concern.

Occurrence of two novel triazine-based flame retardants in an E-waste recycling area in South China: Implication for human exposure.

The recent increase in the use of alternative flame retardants (FRs) in consumer products has led to emerging contaminants in the environment. Identification of novel FRs is urgently needed because the potential threat posed by these chemicals has provoked considerable attention, but the details of the threat are not yet widely understood. In this study, two novel triazine-based FRs, tris(2,3-dibromopropyl) isocyanurate (TDBP-TAZTO) and 2,4,6-tris(2,4,6-tribromophenoxy)-1,3,5-triazine (TTBP-TAZ), were identified in dust samples from an e-waste recycling area in China. Two legacy FRs, namely, tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCDD), were also analyzed for comparison. The mean level of TDBP-TAZTO in the e-waste dust samples was found to be much higher (2060 ng g-1) than that of HBCDD (526 ng g-1), while the mean level of TTBP-TAZ in residential dust samples was moderately higher (119 ng g-1) than that of HBCDD (35.7 ng g-1). A comparison of the TDBP-TAZTO and TTBP-TAZ concentrations with those of other alternative and legacy FRs indicated that TDBP-TAZTO is a major FR that is currently used in China. The estimated daily intake of TDBP-TAZTO via dust ingestion for occupational workers was much higher than that of HBCDD and was also much higher than for local adults and children. Exposure to TDBP-TAZTO poses a potentially high risk to the health of the local population, especially for the occupational workers, when the multicomponent chemical 'cocktail' effects are taken into account. More investigations on the environmental behaviors and risk factors of TDBP-TAZTO and TTBP-TAZ in various environmental matrices, as well as their toxicological effects, should be performed in the future.

Altitude-dependent accumulation of short chain chlorinated paraffins in fish from alpine lakes and Lhasa river on the Tibetan Plateau.

High mountain cold-trapping effects can play important roles in the global long-range transport of persistent organic pollutants (POPs). Short chain chlorinated paraffins (SCCPs) have recently been included into the Stockholm Convention as a new class of POPs. However, the long-range transport behavior and environmental fate of SCCPs still remain largely unknown in high-altitude mountain areas. In this study, a total of 51 fish samples were collected from five high-altitude mountain lakes and Lasha river across the Tibetan Plateau. SCCPs were positively detected in all fish samples, and the concentrations ranged from 3.9 to 107 ng g-1 dry weight (dw) with an average of 26.6 ng g-1 dw. Compared to aquatic organisms from the Artic and Antarctica, the SCCP levels found in alpine fish from the Tibetan Plateau were lower. A significant increasing trend in accumulation levels of SCCPs in alpine fish with the increasing altitude was found on the Tibetan Plateau (r = 0.98, p < 0.001). Shorter chain congener group C10 showed a significant increase in percentage contribution to total SCCPs with increasing altitude, but a contrary tendency was found for longer chain congener group C13. The widespread occurrence of SCCPs in Tibetan fish was mainly sourced from the long-range atmospheric transport, and the altitude-dependent distribution of SCCPs was due to the mountain cold-trapping effects and potential susceptibility to bioaccumulation. To our knowledge, this is the first report regarding the altitude-dependent accumulation of SCCPs in biota in the polar environment.

Photochemical behavior of benzophenone sunscreens induced by nitrate in aquatic environments.

Benzophenones (BPs), which are widely used UV filters, have aroused considerable public concern owing to their potential endocrine-disrupting activities. Herein, we systematically investigated their photochemical behavior and fate, which is mediated by nitrate in aquatic environments. The results showed that 10 µM of 3 BPs can be completely degraded within 4 h of simulated sunlight irradiation in a 10 mM nitrate solution at pH 8.0, and 2,4-dihydroxybenzophenone (BP-1) has a 31.6% mineralization rate after 12 h irradiation. Their photolytic rates (kobs) presented a significant linear correlation with the logarithmic values of the nitrate concentration for 0.1-10 mM (R2 > 0.98), and in three actual waters, the rates of BP-1 were also positively related to the intrinsic nitrate concentration. Furthermore, higher transformation rates under alkaline condition were observed, especially for BP-1, with its kobs at pH 10 being 8.3-fold higher than that at pH 6.0. Moreover, dissolved oxygen (DO) also has an impact on the reaction kinetics to some degree. According to the quenching experiments, we found that three reactive oxygen species (ROS), namely, •OH, •NO, and •NO2, participated in this photolysis of BPs, and the contribution of •OH accounted for 32.1%. Furthermore, we selected BP-1 as the model molecule to study the transformation pathways and toxicity changes in this system. Four main transformation pathways including hydroxylation, nitrosylation, nitration, and dimerization were proposed, based on liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS) analysis and density functional theory (DFT). According to the toxicity test, the formed intermediates were more toxic to Photobacterium phosphoreum than the parent BP-1. Therefore, these results can help reveal primary phototransformation mechanisms and evaluate the potential ecological risks of BPs in aquatic environments.

Ozonation of pentabromophenol in aqueous basic medium: Kinetics, pathways, mechanism, dimerization and toxicity assessment.

Ozonation has been identified effective technique to degrade phenolic compounds, and production of intermediate dimers are major threat. In this study, we systematically investigated the degradation of Pentabromophenol (PBP) in an aqueous medium by using two different ozone generators (sources: air and water). We studied various factors that influenced the degradation kinetics of PBP, including the pH (7.0, 8.0, and 9.0), humic acid (HA) and anions (Cl-, SO42-, NO3-, and HCO3-). PBP was efficiently degraded within 5 min (O3 source: water) and 45 min (O3 source: air) at pH 8.0 maintained by phosphate buffer. Reaction kinetics revealed 17 b y-products with five possible pathways, including dimers with their isomers and lower bromophenols. Furthermore, the frontier molecular orbital theory was employed to confirm the proposed ozonation pathways, including the breakage of the CO bond at C5 and C4 positions, and the cleavage of the CC bond at C3 and C6 position. Product P5, P14 (hydroxyl-nonabromophenyl ether) and P15 (dihydroxyl-octabromophenyl ether) were identified with isomers. Ecological Structure Activity Relationships toxicity assessment resulted into the conversion of highly toxic PBP (acute toxicity: LC50 = 0.11 mg L-1 for fish, LC50 = 0.124 mg L-1 for daphnia, and EC50 = 0.118 mg L-1 for green algae) to less harmful products aside from dimers. P14 (acute toxicity: LC50 = 1.04 × 105) found to be more toxic as compare to PBP. From these findings, we concluded that ozonation is an effective and ideal process for PBP degradation.

Enhanced Removal of Chlorophene and 17ß-estradiol by Mn(III) in a Mixture Solution with Humic Acid: Investigation of Reaction Kinetics and Formation of Co-oligomerization Products.

Reaction with soluble Mn(II) has been considered as a main decay pathway for superoxide in natural waters, accompanied by an important Mn redox cycling. In this study, the interaction of Mn(II) and humic acid (HA) was investigated in visible light irradiated water. Our results indicate that HA may play a dual role to act as a photosensitizer to produce superoxide anions (O2-) and as a strong ligand to stabilize the Mn(III), forming soluble Mn(III)L species for substrate transformation. Furthermore, the reaction kinetics, products, and mechanisms of chlorophene (CP) and estradiol (E2) mixture in the Mn(II)/HA/visible light reaction systems were assessed. The removal of CP and E2 was enhanced by 24.3% and 13.2%, respectively, in mixture solution at initial concentration of 1.0 µM for each target contaminant, as compared to the case of single-compound degradation. Product identification and density functional theory calculations indicated that cross-coupling reaction of CP and E2 radicals was more likely to occur than the self-coupling reaction in mixture solution. In addition, estrogenic activities of initial reaction solution were also effectively decreased during the transformation process. These findings provide new insights into Mn(III)-mediated reactions to better understand the environmental fate of organic contaminant mixture in waters.

Degradation of aqueous 2,4,4'-Trihydroxybenzophenone by persulfate activated with nitrogen doped carbonaceous materials and the formation of dimer products.

In this work, we systematically investigated the persulfate (PS) activation potential of a series of nitrogen doped carbonaceous materials for the degradation of 2,4,4'-trihydroxybenzophenone (2,4,4'-HBP), an additive in polyvinyl acetate films and personal care products. Nitrogen originating from urea, NH4NO3, indole and polyaniline was doped into carbonaceous materials, including hydroxylated multi-walled carbon nanotubes (CNT-OH), large-inner thin-walled carboxylated carbon nanotubes (CNT-COOH) and graphite oxide (GO), to examine the catalytic effect. The NH4NO3-CNT-OH catalyst, which showed the best catalytic performance in 2,4,4'-HBP removal, was characterized by SEM, TEM, FT-IR, Raman, BET surface area, XRD and XPS, and pyrrolic nitrogen was found to play a highly important role in the activation of PS. Under the conditions of [2,4,4'-HBP]0: [PS]0 = 1: 500, T = 25 °C, pH0 = 7.0, concentration of catalyst = 100 mg L-1, 43.48 µM 2,4,4'-HBP was completely removed in 2 h. According to electron paramagnetic resonance (EPR) spectra and radical quenching experiments, hydroxyl and sulfate radicals on the surface of the catalyst contributed to the substrate oxidation. Cleavage of C-C bridge bond, hydroxylation and polymerization were mainly involved in the oxidation process, leading to the formation of 10 intermediates (e.g., dimers), as detected by the MS/MS spectra. To the best of our knowledge, this report is the first to describe the transformation mechanism of 2,4,4'-HBP in nitrogen doped carbonaceous materials catalyzed PS system.

Degradation kinetics and transformation products of chlorophene by aqueous permanganate.

This paper evaluates the oxidation of an antibacterial agent, chlorophene (4-chloro-2-(phenylmethyl)phenol, CP), by permanganate (Mn(VII)) in water. Second-order rate constant (k) for the reaction between Mn(VII) and CP was measured as (2.05 ±â€¯0.05) × 101 M-1 s-1 at pH 7.0 for an initial CP concentration of 20.0 µM and Mn(VII) concentration of 60.0 µM. The value of k decreased with increasing pH in the pH range of 5.0-7.0, and then increased with an increase in solution pH from 7.0 to 10.0. The presence of MnO2 and Fe3+ in water generally enhanced the removal of CP, while the effect of humic acid was not obvious. Fourteen oxidation products of CP were identified by an electrospray time-of-flight mass spectrometer, and direct oxidation, ring-opening, and decarboxylation were mainly observed in the reaction process. The initial reaction sites of CP by Mn(VII) oxidation were rationalized by density functional theory calculations. Toxicity changes of the reaction solutions were assessed by the luminescent bacteria P. phosphoreum, and the intermediate products posed a relatively low ecological risk during the degradation process. The efficient removal of CP in secondary clarifier effluent and river water demonstrated the potential application of this Mn(VII) oxidation method in water treatment.

Leaf and root glucosinolate profiles of Chinese cabbage (Brassica rapa ssp. pekinensis) as a systemic response to methyl jasmonate and salicylic acid elicitation.

Glucosinolates (GSs) are an important group of defensive phytochemicals mainly found in Brassicaceae. Plant hormones jasmonic acid (JA) and salicylic acid (SA) are major regulators of plant response to pathogen attack. However, there is little information about the interactive effect of both elicitors on inducing GS biosynthesis in Chinese cabbage (Brassica rapa ssp. pekinensis). In this study, we applied different concentrations of methyl jasmonate (MeJA) and/or SA onto the leaf and root of Chinese cabbage to investigate the time-course interactive profiles of GSs. Regardless of the site of the elicitation and the concentrations of the elicitors, the roots accumulated much more GSs and were more sensitive and more rapidly responsive to the elicitors than leaves. Irrespective of the elicitation site, MeJA had a greater inducing and longer lasting effect on GS accumulation than SA. All three components of indole GS (IGS) were detected along with aliphatic and aromatic GSs. However, IGS was a major component of total GSs that accumulated rapidly in both root and leaf tissues in response to MeJA and SA elicitation. Neoglucobrassicin (neoGBC) did not respond to SA but to MeJA in leaf tissue, while it responded to both SA and MeJA in root tissue. Conversion of glucobrassicin (GBC) to neoGBC occurred at a steady rate over 3 d of elicitation. Increased accumulation of 4-methoxy glucobrassicin (4-MGBC) occurred only in the root irrespective of the type of elicitors and the site of elicitation. Thus, accumulation of IGS is a major metabolic hallmark of SA- and MeJA-mediated systemic response systems. SA exerted an antagonistic effect on the MeJA-induced root GSs irrespective of the site of elicitation. However, SA showed synergistic and antagonistic effects on the MeJA-induced leaf GSs when roots and leaves are elicitated for 3 d, respectively.