Nuclear m(6)A Reader YTHDC1 Regulates mRNA Splicing.

The regulatory role of N(6)-methyladenosine (m(6)A) and its nuclear binding protein YTHDC1 in pre-mRNA splicing remains an enigma. Here we show that YTHDC1 promotes exon inclusion in targeted mRNAs through recruiting pre-mRNA splicing factor SRSF3 (SRp20) while blocking SRSF10 (SRp38) mRNA binding. Transcriptome assay with PAR-CLIP-seq analysis revealed that YTHDC1-regulated exon-inclusion patterns were similar to those of SRSF3 but opposite of SRSF10. In vitro pull-down assay illustrated a competitive binding of SRSF3 and SRSF10 to YTHDC1. Moreover, YTHDC1 facilitates SRSF3 but represses SRSF10 in their nuclear speckle localization, RNA-binding affinity, and associated splicing events, dysregulation of which, as the result of YTHDC1 depletion, can be restored by reconstitution with wild-type, but not m(6)A-binding-defective, YTHDC1. Our findings provide the direct evidence that m(6)A reader YTHDC1 regulates mRNA splicing through recruiting and modulating pre-mRNA splicing factors for their access to the binding regions of targeted mRNAs.

METTL3-mediated m6A modification is required for cerebellar development.

N6-methyladenosine (m6A) RNA methylation is the most abundant modification on mRNAs and plays important roles in various biological processes. The formation of m6A is catalyzed by a methyltransferase complex including methyltransferase-like 3 (METTL3) as a key factor. However, the in vivo functions of METTL3 and m6A modification in mammalian development remain unclear. Here, we show that specific inactivation of Mettl3 in mouse nervous system causes severe developmental defects in the brain. Mettl3 conditional knockout (cKO) mice manifest cerebellar hypoplasia caused by drastically enhanced apoptosis of newborn cerebellar granule cells (CGCs) in the external granular layer (EGL). METTL3 depletion-induced loss of m6A modification causes extended RNA half-lives and aberrant splicing events, consequently leading to dysregulation of transcriptome-wide gene expression and premature CGC death. Our findings reveal a critical role of METTL3-mediated m6A in regulating the development of mammalian cerebellum.

An Integrated Model for Input and Migration of Mercury in Chinese Coastal Sediments.

Coastal sediments are a major sink of the global mercury (Hg) biogeochemical cycle, bridging terrestrial Hg migration to the open ocean. It is thus of substantial interest to quantify the Hg contributors to coastal sediments and the extents to which the Hg sequestered into coastal sediments affects the ocean. Here, we measured concentrations and isotope compositions of Hg in Chinese coastal sediments and found that estuary sediments had distinctly higher δ202Hg and lower Δ199Hg values than marine sediments. Hg isotope compositions of marine sediments followed a latitudinal trend where δ202Hg decreases and Δ199Hg increases from north to south. An integrated model was developed based on a Hg isotope mixing model and urban distance factor (UDF), which revealed a significant difference in Hg source contributions among the estuary and marine sediments and a gradual change of dominant Hg sources from terrestrial inputs (riverine and industrial wastewater discharges) to atmospheric deposition with a decrease in urban impact. A UDF value of 306 ± 217 was established as the critical point where dominant Hg sources started to change from terrestrial inputs to atmospheric deposition. Our study helps explain the input and migration of Hg in Chinese marginal seas and provides critical insights for targeted environmental management.

Mercury isotopic compositions of mosses, conifer needles, and surface soils: Implications for mercury distribution and sources in Shergyla Mountain, Tibetan Plateau.

Understanding the distribution and sources of mercury (Hg) in the Tibetan Plateau is of great value to study the long-range transport of Hg. Herein, the total Hg (THg) concentrations and the isotopic compositions of mosses, conifer needles, and surface soils collected from both slopes of the Shergyla Mountain of Tibetan Plateau were analyzed. The contents of THg in samples (except mosses on the eastern slope) were significantly positively correlated with altitude in both the western and eastern slopes, possibly caused by topographic factors. In contrast, Δ199Hg in samples was significantly negatively correlated with altitude. On the basis of Hg isotopic compositions, atmospheric Hg0 uptake was indicated as the primary accumulation pathway of Hg in mosses (Δ199Hg: -0.12 ±â€¯0.09‰, -0.26 - 0.00‰, 1 SD, n = 10) and conifer needles (Δ199Hg: -0.21 ±â€¯0.08‰, -0.36 - -0.11‰, 1 SD, n = 9). Moreover, the contributing fractions of atmospheric Hg0 to Hg in surface soils (Δ199Hg: -0.20 ±â€¯0.07‰, -0.31 - -0.06‰, 1 SD, n = 17) increased with altitude and accounted for an average of 87 ± 9% in atmospheric sources. Due to the special geographic positions and environmental conditions of the Tibetan Plateau, the results of this study were essential for further understanding the long-range transport and global cycling of Hg.

Tracing aquatic bioavailable Hg in three different regions of China using fish Hg isotopes.

To trace the most concerned bioavailable mercury (Hg) in aquatic environment, fish samples were collected from three typical regions in China, including 3 rivers and 1 lake in the Tibetan Plateau (TP, a high altitude background region with strong solar radiation), the Three Gorges Reservoir (TGR, the largest artificial freshwater reservoir in China), and the Chinese Bohai Sea (CBS, a heavily human-impacted semi-enclosed sea). The Hg isotopic compositions in fish muscles were analyzed. The results showed that anthropogenic emissions were the main sources of Hg in fish from TGR and CBS because of the observed negative δ202Hg and positive Δ199Hg in these two regions (TGR, δ202Hg: - 0.72 to - 0.29‰, Δ199Hg: 0.15 - 0.52‰; CBS, δ202Hg: - 2.09 to - 0.86‰, Δ199Hg: 0.07 - 0.52‰). The relatively higher δ202Hg and Δ199Hg (δ202Hg: - 0.37 - 0.08‰, Δ199Hg: 0.50 - 1.89‰) in fish from TP suggested the insignificant disturbance from local anthropogenic activities. The larger slopes of Δ199Hg/Δ201Hg in fish from TGR (1.29 ± 0.14, 1SD) and TP (1.25 ± 0.06, 1SD) indicated methylmercury (MeHg) was produced and photo-reduced in the water column before incorporation into the fish. In contrast, the photoreduction of Hg2+ was the main process in CBS (slope of Δ199Hg/Δ201Hg: 1.06 ± 0.06, 1SD). According to the fingerprint data of Hg isotopes, the most important source for aquatic bioavailable Hg in TP should be the long-range transported Hg, contrasting to the anthropogenic originated MeHg from surface sediments and runoffs in TGR and inorganic Hg from continental inputs in CBS. Therefore, the isotopic signatures of Hg in fish can provide novel clues in tracing sources and behaviors of bioavailable Hg in aquatic systems, which are critical for further understanding the biogeochemical cycling of Hg.

Mutual detoxification of mercury and selenium in unicellular Tetrahymena.

Selenium (Se) is commonly recognized as a protective element with an antagonistic effect against mercury (Hg) toxicity. However, the mechanisms of this Hg-Se antagonism are complex and remain controversial. To gain insight into the Hg-Se antagonism, a type of unicellular eukaryotic protozoa (Tetrahymena malaccensis, T. malaccensis) was selected and individually or jointly exposed to two Hg and three Se species. We found that Se species showed different toxic effects on the proliferation of T. malaccensis with the toxicity following the order: selenite (Se(IV))>selenomethionine (SeMeth)>selenate (Se(VI)). The Hg-Se antagonism in Tetrahymena was observed because the joint toxicity significantly decreased under co-exposure to highly toxic dosages of Hg and Se versus individual toxicity. Unlike Se(IV) and Se(VI), non-toxic dosage of SeMeth significantly decreased the Hg toxicity, revealing the influence of the Se species and dosages on the Hg-Se antagonism. Unexpectedly, inorganic divalent Hg (Hg2+) and monomethylmercury (MeHg) also displayed detoxification towards extremely highly toxic dosages of Se, although their detoxifying efficiency was discrepant. These results suggested mutual Hg-Se detoxification in T. malaccensis, which was highly dependent on the dosages and species of both elements. As compared to other species, SeMeth and MeHg promoted the Hg-Se joint effects to a higher degree. Additionally, the Hg contents decreased for all the Hg-Se co-exposed groups, revealing a sequestering effect of Se towards Hg in T. malaccensis.

Elemental Mass Size Distribution for Characterization, Quantification and Identification of Trace Nanoparticles in Serum and Environmental Waters.

Accurate characterization, quantification, and identification of nanoparticles (NPs) are essential to fully understand the environmental processes and effects of NPs. Herein, the elemental mass size distribution (EMSD), which measures particle size, mass, and composition, is proposed for the direct size characterization, mass quantification, and composition identification of trace NPs in complex matrixes. A one-step method for the rapid measurement of EMSDs in 8 min was developed through the online coupling of size-exclusion chromatography (SEC) with inductively coupled plasma mass spectrometry (ICP-MS). The use of a mobile phase with a relatively high ionic strength (a mixture of 2% FL-70 and 2 mM Na2S2O3) ensured the complete elution of different-sized NPs from the column and, therefore, a size-independent response. After application of a correction for instrumental broadening by a method developed in this study, the size distribution of NPs by EMSD determination agreed closely with that obtained from transmission electron microscopy (TEM) analysis. Compared with TEM, EMSD allows a more rapid determination with a higher mass sensitivity (1 pg for gold and silver NPs) and comparable size discrimination (0.27 nm). The proposed EMSD-based method was capable of identifying trace Ag2S NPs and core-shell nanocomposite Au@Ag, as well as quantitatively tracking the dissolution and size transformation of silver nanoparticles in serum and environmental waters.

Tracking the Transformation of Nanoparticulate and Ionic Silver at Environmentally Relevant Concentration Levels by Hollow Fiber Flow Field-Flow Fractionation Coupled to ICPMS.

It is a great challenge to monitor the physical and chemical transformation of nanoparticles at environmentally relevant concentration levels, mainly because the commonly used techniques like dynamic light scattering and transmission electron microscopy are unable to characterize and quantify trace level nanoparticles in complex matrices. Herein, we demonstrate the on-line coupled system of hollow fiber flow field-flow fractionation (HF5), minicolumn concentration, and inductively coupled plasma mass spectrometry (ICPMS) detection as an efficient approach to study the aggregation and chemical transformation of silver nanoparticles (AgNPs) and ionic Ag species in the aqueous environment at ng/mL levels. Taking advantage of the in-line dialysis of HF5, the selective capture of Ag(I) species by the resin in minicolumn, and the high selectivity and sensitivity of ICPMS detection, we recorded the aggregation of 10 ng/mL AgNPs in complex matrices (e.g., NOM, Na+/Ca2+), revealing an interesting tiny AgNPs formation process of photoreduction of trace level Ag(I) that is different from larger AgNPs generated at high concentration of Ag(I) by accurate characterization and respectively identifying and quantifying new thiol-complexed Ag(I) and residual Ag(I) in the intertransformation of Ag(I) and AgNPs in domestic wastewater by simultaneously detecting the S and Ag signals via ICPMS.

Characterization and speciation of mercury in mosses and lichens from the high-altitude Tibetan Plateau.

The accumulation and species of mercury (Hg) in mosses and lichens collected from high-altitude Tibetan Plateau were studied. The altitudes of the sampling sites spanned from 1983 to 5147 m, and a total of 130 mosses and 52 lichens were analyzed. The total mercury (THg) contents in mosses and lichens were in the ranges of 13.1-273.0 and 20.2-345.9 ng/g, respectively. The average ratios of methylmercury (MeHg) in THg in mosses and lichens were 2.4 % (0.3-11.1 %) and 2.7 % (0.4-9.6 %), respectively, which were higher than those values reported in other regions. The contents of THg in both mosses and lichens were not correlated with the THg in soils (p > 0.05). The lipid contents displayed a significantly positive correlation with concentrations of MeHg in mosses (r = 0.461, p < 0.01, n = 90), but not in lichens. The correlations between Hg contents in mosses and the altitudes, latitudes and longitudes of sampling sites indicated the mountain trapping and spatial deposition of Hg in the Tibetan Plateau.

Tetrabromobisphenol-A/S and Nine Novel Analogs in Biological Samples from the Chinese Bohai Sea: Implications for Trophic Transfer.

Tetrabromobisphenol-A/S (TBBPA/S) analogs have raised substantial concern because of their adverse effects and potential bioaccumulative properties, such as TBBPA bis(allyl ether) (TBBPA-BAE) and TBBPA bis(2,3-dibromopropyl ether) (TBBPA-BDBPE). In this study, a comprehensive method for simultaneous determination of TBBPA/S and nine novel analogs, including TBBPA-BAE, TBBPA-BDBPE, TBBPS-BDBPE, TBBPA mono(allyl ether) (TBBPA-MAE), TBBPA mono(2-bromoallyl ether) (TBBPA-MBAE), TBBPA mono(2,3-dibromopropyl ether) (TBBPA-MDBPE), TBBPS-MAE, TBBPS-MBAE, and TBBPS-MDBPE in biological samples was developed. The distribution patterns and trophic transfer properties of TBBPA/S and analogs in various biological samples collected from the Chinese Bohai Sea were then studied in detail. For the first time, TBBPA-MBAE and TBBPS-BDBPE were detected in biological samples and TBBPA-MBAE was identified as a byproduct. The concentrations of TBBPA and analogs ranged from ND (not detected or below the method detection limit) to 2782.8 ng/g lipid weight (lw), and for TBBPS and analogs ranged from ND to 927.8 ng/g lw. High detection frequencies (>86%) for TBBPA, TBBPS and TBBPA-MAE, TBBPA-MDBPE, TBBPS-MAE, TBBPS-MBAE, and TBBPS-MDBPE were obtained. Meanwhile, TBBPA, TBBPS, and these five analogs displayed trophic dilution tendencies due to significantly negative correlations between trophic levels and lipid-corrected concentrations together with the trophic magnification factors (from 0.31 to 0.55). The results also indicated the novel TBBPA-MAE, TBBPA-MBAE, TBBPA-MDBPE, TBBPS-MAE, TBBPS-MBAE, and TBBPS-MDBPE could be generated not only as byproducts, but also as the probable transformation products of commercial TBBPA/S derivatives.

Toward full spectrum speciation of silver nanoparticles and ionic silver by on-line coupling of hollow fiber flow field-flow fractionation and minicolumn concentration with multiple detectors.

The intertransformation of silver nanoparticles (AgNPs) and ionic silver (Ag(I)) in the environment determines their transport, uptake, and toxicity, demanding methods to simultaneously separate and quantify AgNPs and Ag(I). For the first time, hollow fiber flow field-flow fractionation (HF5) and minicolumn concentration were on-line coupled together with multiple detectors (including UV-vis spectrometry, dynamic light scattering, and inductively coupled plasma mass spectrometry) for full spectrum separation, characterization, and quantification of various Ag(I) species (i.e., free Ag(I), weak and strong Ag(I) complexes) and differently sized AgNPs. While HF5 was employed for filtration and fractionation of AgNPs (>2 nm), the minicolumn packed with Amberlite IR120 resin functioned to trap free Ag(I) or weak Ag(I) complexes coming from the radial flow of HF5 together with the strong Ag(I) complexes and tiny AgNPs (<2 nm), which were further discriminated in a second run of focusing by oxidizing >90% of tiny AgNPs to free Ag(I) and trapped in the minicolumn. The excellent performance was verified by the good agreement of the characterization results of AgNPs determined by this method with that by transmission electron microscopy, and the satisfactory recoveries (70.7-108%) for seven Ag species, including Ag(I), the adduct of Ag(I) and cysteine, and five AgNPs with nominal diameters of 1.4 nm, 10 nm, 20 nm, 40 nm, and 60 nm in surface water samples.

[Synthetic phenolic compounds perturb lipid metabolism and induce obesogenic effects].

Given continuous development in society and the economy, obesity has become a global epidemic, arousing great concern. In addition to genetic and dietary factors, exposure to environmental chemicals is associated with the occurrence and development of obesity. Current research has indicated that some chemicals with endocrine-disrupting effects can affect lipid metabolism in vivo, causing elevated lipid storage. These chemicals are called "environmental obesogens". Synthetic phenolic compounds (SPCs) are widely used in industrial and daily products, such as plastic products, disinfectants, pesticides, food additives, and so on. The exposure routes of SPCs to the human body may include food and water consumption, direct skin contact, etc. Their unintended exposure could cause harmful effects on human health. As a type of endocrine disruptor, SPCs interfere with adipogenesis and lipid metabolism, exhibiting the characteristics of environmental obesogens. Because SPCs have similar phenolic structures, gathering information on their influences on lipid metabolism would be helpful to understand their structure-related effects. In this review, three commonly used research methods for screening environmental obesogens, including in vitro testing for molecular interactions, cell adipogenic differentiation models, and in vivo studies on lipid metabolism, are summarized, and the advantages and disadvantages of these methods are compared and discussed. Based on both in vitro and in vivo data, three types of SPCs, including bisphenol A (BPA) and its analogues, alkylphenols (APs), and synthetic phenolic antioxidants (SPAs), are systematically discussed in terms of their ability to disrupt adipogenesis and lipid metabolism by focusing on adipose and hepatic tissues, among others. Common findings on the effects of these SPCs on adipocyte differentiation, lipid storage, hepatic lipid accumulation, and liver steatosis are described. The underlying toxicological mechanisms are also discussed from the aspects of nuclear receptor transactivation, inflammation and oxidative stress regulation, intestinal microenvironment alteration, epigenetic modification, and some other signaling pathways. Future research to increase public knowledge on the obesogenic effects of emerging chemicals of concern is encouraged.

Time-resolved fluoroimmunoassay as an advantageous analytical method for assessing the total concentration and environmental risk of fluoroquinolones in surface waters.

Due to the widespread occurrence in the environment and potential risk toward organisms of fluoroquinolones (FQs), it is of importance to develop high efficient methods for assessing their occurrence and environmental risk. A monoclonal antibody (Mab) with broad cross-reactivity to FQs was produced by immunizing BALB/c mice with a synthesized immunogen prepared by conjugating ciprofloxacin with bovine serum albumin. This developed Mab (C2F3C2) showed broad and high cross-reactivity (40.3-116%) to 12 out of the 13 studied FQs. Using this Mab and norfloxacin conjugated with carrier protein ovalbumin as coating antigen, a time-resolved fluoroimmunoassay (TRFIA) method was developed for determining the total concentration of at least 12 FQs in environmental waters. The respective detection limit (LOD) and IC(50) calculated from the standard curve were 0.053 µg/L and 1.83 µg/L for enrofloxacin (ENR). The LODs of the other FQs, estimated based on the corresponding cross-reactivity and the LOD of ENR, were in the range of 0.051-0.10 µg/L. The developed TRFIA method showed good tolerance to various interfering substances present in environmental matrix at relevant levels, such as humic acids (0-10 mg/L DOC), water hardness (0-2% Ca(2+) and Mg(2+), w/v), and heavy metals (0-1 mg/L). The spiked recoveries estimated by spiking 0.5, 1, and 2 µg/L of five representative FQs into various water samples including paddy water, tap water, pond water, and river water were in the range of 63-120%. The measured total FQ concentration by TRFIA agreed well with that of liquid chromatography-tandem mass spectrometry and was applied to directly evaluate the occurrence and environmental risk of FQs in the surface water of a case area. TRFIA showed high efficiency and great potential in environmental risk assessment as it measures directly the total concentration of a class of pollutants.

Quantification of the uptake of silver nanoparticles and ions to HepG2 cells.

The toxic mechanism of silver nanoparticles (AgNPs) is still debating, partially because of the common co-occurrence and the lack of methods for separation of AgNPs and Ag(+) in biological matrices. For the first time, Triton-X 114-based cloud point extraction (CPE) was proposed to separate AgNPs and Ag(+) in the cell lysates of exposed HepG2 cells. Cell lysates were subjected to CPE after adding Na2S2O3, which facilitated the transfer of AgNPs into the nether Triton X-114-rich phase by salt effect and the preserve of Ag(+) in the upper aqueous phase through the formation of hydrophilic complex. Then the AgNP and Ag(+) contents in the exposed cells were determined by ICP-MS after microwave digestion of the two phases, respectively. Under the optimized conditions, over 67% of AgNPs in cell lysates were extracted into the Triton X-114-rich phase while 94% of Ag(+) remained in the aqueous phase, and the limits of detection for AgNPs and Ag(+) were 2.94 µg/L and 2.40 µg/L, respectively. This developed analytical method was applied to quantify the uptake of AgNPs to the HepG2 cells. After exposure to 10 mg/L AgNPs for 24 h, about 67.8 ng Ag were assimilated per 10(4) cells, in which about 10.3% silver existed as Ag(+). Compared to the pristine AgNPs (with 5.2% Ag(+)) for exposure, the higher ratio of Ag(+) to AgNPs in the exposed cells (10.3% Ag(+)) suggests the transformation of AgNPs into Ag(+) in the cells and/or the higher uptake rate of Ag(+) than that of AgNPs. Given that the toxicity of Ag(+) is much higher than that of AgNPs, the substantial content of Ag(+) in the exposed cells suggests that the contribution of Ag(+) should be taken into account in evaluating the toxicity of AgNPs to organisms, and previous results obtained by regarding the total Ag content in organisms as AgNPs should be reconsidered.

Cysteine modified small ligament Au nanoporous film: an easy fabricating and highly efficient surface-assisted laser desorption/ionization substrate.

Au nanoporous films (NPFs) with different surface modification and morphology were fabricated and utilized as substrates for the analysis of a series of compounds, including amino acids, drug, cyclodextrins, peptides, and polyethylene glycols, using surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF MS). It was found that the size and interconnection state of the NPF ligament as well as the surface modification are key parameters that affect the laser desorption/ionization performance. Compared with 2,5-dihydroxybenzoic acid, pristine NPF, and aminobenzenethiol or 3-mercaptopropanoic acid modified Au NPFs, cysteine modified Au NPF generated intense and background-suppressing mass spectra. Regarding the effect of Au NPF morphology, the Au NPF with nanopores in the range of 10-30 nm, ligament size of 5 nm, and electrochemistry surface area of 26.1 m(2)/g exhibited the highest performance as a substrate. This high-performance NPFs can be easily fabricated by capping agent replacement induced self-organization of ultrathin nanowires, followed by self-assembling of a monolayer (SAM) of cysteine. The good thermal/electroconductivity and uniformity of Au NPFs avoided the fragmentation of analytes, eliminated the intrinsic matrix ions interference, and provided good reproducibility (RSD ≤ 10%). Additionally, the fabricated NPFs can be easy divided into microarrays (a ~4 × 4 array from a 1 cm × 1 cm NPF). This work provides a simple and cost-effective route for acquiring an Au nanostructure as a SALDI substrate, which offers a new technique for high-speed analysis of low-molecular weight compounds.

Fabrication of a Au nanoporous film by self-organization of networked ultrathin nanowires and its application as a surface-enhanced Raman scattering substrate for single-molecule detection.

Due to its demonstrated usefulness in fields such as trace analysis, biodiagnosis, and in vivo study, surface-enhanced Raman scattering (SERS) has received renewed interest in recent years. Development of SERS substrates is of great importance as the SERS intensity and reproducibility depend strongly on the SERS substrates. In this paper we report the fabrication of Au nanoporous film (NPFs) by self-organization of networked ultrathin Au nanowires for use as SERS substrates. The acquired Au NPFs display controllable thickness, low relative density, and considerable specific surface area. Furthermore, this self-organization of nanowires not only provides abundant junctions between nanowires, 5-20 nm nanopores, and three-dimensional nanowells, but also makes nanopores/nanogaps down to 1-2 nm. These nanoscale characteristics result in a high spatial density of hotspots with Raman enhancement factors up to 10(9). Combined with the uniformity and high purity, our Au NPF provides high-quality substrates for SERS sensing.

Sorption to dissolved humic acid and its impacts on the toxicity of imidazolium based ionic liquids.

Two typical ionic liquids (ILs), 1-butyl-3-methylimidazolium chloride ([C4MIM]Cl) and 1-octyl-3-methylimidazolium chloride ([C8MIM]Cl), are demonstrated to associate strongly with dissolved organic matter (DOM) with distribution coefficients (KDOC) in the range of 10(4.2) to 10(4.6) for Aldrich humic acid (used as model DOM). With the increase of humic acid concentration to 11 µg/mL DOC (dissolved organic carbon), the free fraction (ratio of freely dissolved to total concentration) of [C4MIM]Cl and [C8MIM]Cl reduced to about 0.85 and 0.79, respectively. This reduction of freely dissolved concentration gave rise to remarkable reduction of bioavailability and toxicity of the two ILs. MTT assay with HepG2 cell lines showed that the EC50 values were 459 µmol/L for [C4MIM]Cl and 12 µmol/L for [C8MIM]Cl, respectively, and the cell viability increased about 50% in the presence of trace amount of humic acid (1 µg/mL DOC). The SOS/umu test indicated mutagenicity for [C4MIM]Cl at levels above 664 µmol/L, and the genotoxicity was diminished with the addition of trace humic acid (0.00000374-0.374 µg/mL DOC). The studied ILs showed acute toxicity toward model fish medaka with a 96 h median lethal concentration (LC50) of 2254 µmol/L for [C4MIM]Cl and 366 µmol/L for [C8MIM]Cl. The addition of humic acid (5.49 µg/mL DOC for [C8MIM]Cl, 1.37 µg/mL DOC for [C4MIM]Cl) to IL solutions reduced the death rate of medaka to a minimum value of ∼25% of that at zero DOC. Our results suggest that DOM may play an important role in determining the environmental fate and toxicity of imidazolium-based ILs, and its effects should be taken into account in assessing the environmental risk of ILs.

Excretion of PFOA and PFOS in male rats during a subchronic exposure.

Perfluorinated compounds (PFCs), a class of synthetic surfactants that are widely used, have become global environmental contaminants because of their high persistence and bioaccumulation. An increasing number of studies have described the pharmacokinetics of PFCs following in vivo exposure, however, few papers have focused on the excretion of these compounds during a period of consecutive exposure. In this study, the excretions of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in male Sprague-Dawley rats gavaged consecutively for 28 days were investigated and compared. The faster elimination rate in urine compared to feces indicated that urinary excretion is the primary clearance route in rats for either PFOA or PFOS. During the first 24 h after administration of PFOA (5 and 20 mg/kg body weight/day), about 24.7-29.6% of the oral dose was excreted through urine and feces, while for PFOS, the excretion amounts were only 2.6-2.8% of the total gavaged doses (5 and 20 mg/kg body weight/day). The excretion rates of both PFCs increased with increasing exposure doses. The higher elimination rate of PFOA through excretion indicated its lower accumulation in rats, thus inducing possible lower toxicities compared to PFOS.

Investigations on boron levels in drinking water sources in China.

To evaluate boron contamination of public drinking water in China, both dissolved and total boron contents in 98 public drinking water sources from 49 cities, 42 brands of bottled water samples from supermarkets in several cities, and 58 water samples from boron industrial area were measured by inductively coupled plasma-mass spectrometry (ICP-MS). Our experimental results showed that boron existed in public drinking water sources mainly in dissolved status with total concentrations ranging from 0.003 to 0.337 mg/L (mean = 0.046 mg/L). The mean boron concentrations in mineral and pure bottled water were 0.052 and 0.028 mg/L, respectively. The results obtained in this work showed that there was no health risk on view of boron in public drinking water sources and bottled water. In boron industrial area, boron concentrations in surface water and ground water were 1.28 mg/L (range = 0.007-3.8 mg/L) and 18.3 mg/L (range = 0.015-140 mg/L), respectively, which indicated that boron industry caused boron pollution in local water system.

A typical derivative and byproduct of tetrabromobisphenol A: Development of novel high-throughput immunoassays and systematic investigation of their distributions in Taizhou, an e-waste recycling area in eastern China.

Environmental distribution and concentration of tetrabromobisphenol A bis- (2-hydroxyethyl) ether (TBBPA-DHEE) and tetrabromobisphenol A mono- (hydroxyethyl) ether (TBBPA-MHEE), are obscure due to the lack of available analytical methods. Here two novel immunoassays were established to systematically investigate their distributions in Taizhou, Eastern China. Five monoclonal antibodies against pollutants were generated with two designed haptens through animal immunization. After matched with different coating antigens/antibodies, ELISAs were established (LOD for TBBPA-DHEE, 0.12 ng/mL, based on OVA-M3/mAb-D4G6; LOD for TBBPA-MHEE, 0.79 ng/mL, based on OVA-M3/mAb-D2G6) and applied for investigation of their occurrences at a typical e-waste recycling area after 2-year samples collection, where the total 33 water, 32 soil and 16 biological samples were collected with the highest concentrations of 3.46 ng/mL, 2.76 ng/g (dry weight, dw) and 5.01 ng/g (dw), respectively. Meanwhile, our study also indicated that at the centralizing e-waste recycling sites the serious pollution for both chemicals still existed despite of various efforts. Besides, obvious improvements were observed at an abandoned e-waste recycling region treated and remedied for many years by the local Chinese government. These findings highlight the importance of policy decisions in treatment of pollutants to reduce organic pollutant-related health risks.