Screening and prioritization of nano- and microplastic particle toxicity studies for evaluating human health risks – development and application of a toxicity study assessment tool

Concern regarding the human health implications that exposure to nano- and microplastic particles (NMPs) potentially represents is increasing. While there have been several years of research reporting on the ecotoxicological effects of NMPs, human health toxicology studies have only recently emerged. The available human health hazard data are thus limited, with potential concern regarding the relevance and reliability for understanding the potential human health implications. In this study we develop and apply a NMP toxicity screening assessment tool (NMP-TSAT) for evaluating human health effects studies against a suite of quality assurance and quality control (QA/QC) criteria for both in vivo and in vitro studies. A total of 74 studies representing either inhalation or oral exposure pathways were identified and evaluated. Assessment categories include particle characterization, experimental design, and applicability for risk assessment; with critical and non-critical criteria organized to allow screening and prioritization. It is observed that the majority of studies evaluated using the NMP-TSAT have been performed on monodisperse particles, predominately spheres (≈60%), consisting of polystyrene (≈46%). The majority of studies have tested particles < 5 μm, with a minimal particle size of 10 nm and a maximum particle size of about 200 μm. The total assessment score (TAS) possible for in vivo studies is 52, whereas for in vitro studies it is 46, which is based on receiving a maximum score of 2 against 26 and 23 criteria, respectively. The evaluated TAS ranged from between 12 and 44 and 16–34, for in vivo and in vitro studies, respectively. Given the challenges associated with prioritizing studies based on ranking them according to their TAS we propose a Tiered approach, whereby studies are initially screened based on how they score against various critical criteria, which have been defined for their relevance for assessing the hazards and risks for human health. In this instance, studies that score a minimum of ‘1’ against each of the critical criteria, regardless of how they rank according to their TAS, are prioritized as part of a Tier 1 screening and prioritization phase, which would then be followed by an expert evaluation, representing a Tier 2 level of assessment. Using this approach we identify 10 oral ingestion and 2 inhalation studies that score at least 1 against all critical criteria. Lastly, several key observations for strengthening future effects studies are identified, these include a need for the generation and access to standard reference materials representative of human exposure to NMPs for use in toxicity test systems and/or the improved characterization and verification of test particle characteristics, and the adoption of study design guidance, such as recommended by OECD, when conducting either in vivo inhalation or oral ingestion toxicity tests.

Developing Qualitative Plasmid DNA Reference Materials to Detect Mechanisms of Quinolone and Fluoroquinolone Resistance in Foodborne Pathogens

The aim of this study was to develop homogeneous and stable plasmid DNA reference materials for detecting the mechanisms of resistance to quinolones and fluoroquinolones in foodborne pathogens. The DNA fragments of 11 target genes associated with quinolone and fluoroquinolone resistance were artificially synthesized, inserted into plasmid vectors, and transferred into recipient cells. PCR and sequencing of DNA were performed to assess the genetic stability of the target DNA in recombinant Escherichia coli DH5α cells during subculturing for 15 generations. The limit of detection (LOD) of the target DNA was determined using PCR and real-time qualitative PCR (qPCR). The homogeneity and storage stability of plasmid DNA reference materials were evaluated in terms of plasmid DNA quantity, PCR-measured gene expression, and qPCR threshold cycle. All 11 target DNAs were successfully synthesized and inserted into vectors to obtain recombinant plasmids. No nucleotide mutations were identified in the target DNA being stably inherited and detectable in the corresponding plasmids during subculturing of recombinant strains. When the target DNA was assessed using PCR and qPCR, the LOD was ≤1.77 × 105 and 3.26 × 104 copies/μL, respectively. Further, when the reference materials were stored at 37 °C for 13 days, 4 °C for 90 days, and −20 °C for 300 days, each target DNA was detectable by PCR, and no mutations were found. Although the threshold cycle values of qPCR varied with storage time, they were above the LOD, and no significant differences were found in the quantity of each plasmid DNA at different timepoints. Further, the homogeneity and stability of the materials were highly consistent with the requirements of standard reference materials. To summarize, considering that our plasmid DNA reference materials conformed to standard requirements, they can be used to detect the mechanisms of quinolone and fluoroquinolone resistance in foodborne pathogens.

PHƯƠNG PHÁP K-ZERO TRONG PHÂN TÍCH KÍCH HOẠT NEUTRON (k0 - NAA)

Phân tích kích hoạt neutron (NAA) là một phương pháp phân tích vật lí hạt nhân không hủy mẫu với độ nhạy và độ chính xác cao có khả năng giải quyết nhiều bài toán thực tế trong nghiên cứu địa chất, khảo cổ, nông – sinh – y, vật liệu, môi trường… Trong NAA, có 3 loại nguồn neutron thường được sử dụng: nguồn đồng vị, máy gia tốc và lò phản ứng. Sử dụng nguồn neutron từ lò phản ứng hạt nhân nghiên cứu có thông lượng neutron cao, vì vậy đây là nguồn neutron cho NAA có nhiều ưu điểm nhất trong 3 loại nguồn kể trên. NAA có các phương pháp chuẩn hoá khác nhau: tuyệt đối, tương đối, chuẩn đơn và k-zero, trong đó phương pháp k-zero của NAA (k0-NAA) được đánh giá là phương pháp ổn định (về mặt sai số hệ thống) có độ nhạy và độ chính xác cao, đặc biệt khi nghiên cứu một số đối tượng như bài toán môi trường, địa chất, khảo cổ… quan tâm đặc biệt đến mối tương quan giữa các nguyên tố cho nhiều mẫu nghiên cứu thì thể hiện sự ưu việt vượt trội của phương pháp. Chính vì vậy mà phương pháp k0-NAA đã được chọn và sử dụng ở nhiều nơi trên thế giới như một phương pháp chuẩn (tham khảo) dùng để phê chuẩn (validation) cho các mẫu chuẩn – tham khảo (standard reference materials) và cũng là phương pháp chính trong nhiều đối tượng nghiên cứu.

A standard addition method to quantify serum lithium by inductively coupled plasma mass spectrometry

Background Therapeutic monitoring of lithium (Li) is important because of its narrow therapeutic range and therapeutic index. Here, the authors present the evaluation of an accurate method for the determination of lithium in serum. Method Serum samples were diluted with 0.3% ultrapure nitric acid and were spiked with an internal standard germanium (Ge). The Li/Ge ratio was detected in He mode; we utilized standard addition method to quantify lithium in human serum. The new inductively coupled plasma mass spectrometry (ICP-MS) assay was characterized for linearity, specificity, imprecision, trueness, accuracy, and comparison. Results The correlation coefficients (r) of linearity were all > 0.9999. The specificity proved to be good. The total coefficients of variation (CV) were 1.11% and 0.49% for the two serum samples. The mean bias from target values of standard reference materials (SRM 956d) was −0.71% for Level I, −017% for Level II, and 2.20 for Level III. External Quality Assessment Scheme for Reference Laboratories in Laboratory Medicine (RELA) gave satisfied results for the new method. Comparison with the ion-selective electrode routine method got reasonable results. Conclusion This high accuracy method is an attractive alternative for lithium measurement and can be used as a candidate reference method to improve quality of serum lithium in China.

Determination Of Silver In Geological Samples Using Aerosol Dilution ICP-MS After Water-Bath Extraction With Inverse Aqua Regia

A valid method for trace silver (Ag) detection in geological samples was developed in this study using aerosol dilution inductively coupled plasma-mass spectrometry after extraction with inverse aqua regia. This was proposed primarily to reduce the interference from Nb and Zr during mass spectrometric measurements. Almost 93% of Nb and Zr was removed after the extraction. By mixing an appropriate amount of Ar with the sample aerosol using an aerosol dilution system prior to plasma, the residual Nb oxides and Zr oxides or hydroxides could be successfully removed. The relative yields of the interfering oxides and hydroxides were as low as 0.087% (NbO/Nb) and 0.013% (ZrOH/Zr), which were 3–5 times lower than those in the traditional mode without the addition of Ar. Moreover, the signal-to-noise ratio of Ag was five times higher than that in the traditional mode. The proposed method was applied to the determination of Ag in 68 standard reference materials (SRMs) of soil, sediment, and rock. The results for 47 of these geological SRMs were in good agreement with the reference values. The Ag levels in three SRMs (GSP-2 Granodiorite, STM-2, and SGR-1b) are being reported for the first time herein. For these SRMs, 10 separate aliquots of the sample were digested and analyzed over a period of three months, and analysis revealed that the determined values were reasonable. Thus, the proposed method shows significant potential for the accurate determination of trace Ag in various geological samples.

Development and Validation of a Liquid Chromatography Mass Spectrometry Method for Simultaneous Measurement of 25-OH D3, epi-25-OH D3, 25-OH D2, Vitamin A, α-Tocopherol, and γ-Tocopherol

Background Circulatory fat-soluble vitamin levels are commonly measured to identify deficiencies that may lead to rickets, osteomalacia, night blindness, and reversible motor and sensory neuropathies. We developed and validated a rapid and robust LC-MS/MS method that simultaneously measures 25-OH D3, epi-25-OH D3, 25-OH D2, vitamin A, α-tocopherol, and γ-tocopherol for clinical use. Method 100 µL of serum was mixed with isotope-labeled internal standard and extracted using a 96-well supported-liquid extraction plate with 1.5 mL of hexanes/isopropanol (90/10) (v/v). Dried eluate was reconstituted with 100 µL of methanol/water (90/10) (v/v) and analyzed by LC-MS/MS with a 10-minute gradient. Accuracy was assessed using NIST Standard Reference Materials SRM972a and SRM968f, patient comparison analysis with a LC-MS/MS method at a reference lab, and spike-recovery studies using patient sera and vitamin D-depleted serum. Analytical measurement range (AMR) was determined by spiking 6 analytes into vitamin D-depleted serum to give 7 specimens at varying concentrations. The lower limit of the measuring interval (LLMI) was assessed using 6 pooled specimens with varying low concentrations of each analyte over 20 days. Precision (repeatability and reproducibility) was assessed using quality control materials. Interference studies were performed using pooled patient specimens spiked with varying concentrations of hemoglobin, bilirubin, or intralipid. Matrix effect was assessed by post-column infusion and by matrix dilution with saline. Results The method was linear covering physiological concentrations with r2 &gt; 0.99. Repeatability and reproducibility were &lt;15% CV at all QC levels. LLMI for 25-OH D3, epi-25-OH D3, 25-OH D2, vitamin A, α-tocopherol, and γ-tocopherol were 4 ng/mL (15% CV), 4 ng/mL (15% CV), 4 ng/mL (18% CV), 1 µg/dL (20% CV), 0.2 µg/mL (20% CV), and 0.2 µg/mL (8% CV). Recoveries for NIST Standard Reference Materials were between 92 - 111% and between 81 - 122% for spike-recovery studies. Passing-Bablok analyses for vitamin D total, vitamin A, and α-tocopherol demonstrated slopes between 1.04 and 1.11 and r2 between 0.94 and 0.96. Minimal matrix effect was observed. Conclusions We have developed and validated a comprehensive and rapid LC-MS/MS method for the simultaneous measurement of 25-OH D3, epi-25-OH D3, 25-OH D2, vitamin A, α-tocopherol, and γ-tocopherol for clinical use.

Screening Coarse Airborne Dust for Lead-Rich Phase Occurrence during Characterisation of Particle Mineralogy, Chemistry and Provenance: Application to Deposits in the Vicinity of an Integrated Steelworks

A method has been developed to screen large numbers (~103–104 per sample) of coarse airborne dust particles for the occurrence of Pb-rich phases, together with quantification of the particles’ mineralogy, chemistry, and inferred provenance. Using SEM-EDS spectral imaging (SI) at 15 kV, and processing with the custom software PARC, screening of individual SI pixels is performed for Pb at the concentration level of ~10% at a length-scale of ~1 µm. The issue of overlapping Pb-Mα and S-Kα signal is resolved by exploiting peak shape criteria. The general efficacy of the method is demonstrated on a set of NIST particulate dust standard reference materials (SRMs 1649b, 2580, 2584 and 2587) with variable total Pb concentrations, and applied to a set of 31 dust samples taken in the municipalities surrounding the integrated steelworks of Tata Steel in IJmuiden, the Netherlands. The total abundances of Pb-rich pixels in the samples range from none to 0.094 area % of the (total) particle surfaces. Overall, out of ca. 92k screened particles, Pb was found in six discrete Pb-phase dominated particles and, more commonly, as superficial sub-particles (sub-micron to 10 µm) adhering to coarser particles of diverse and Pb-unrelated provenance. No relationship is apparent between the samples’ Pb-rich pixel abundance and their overall composition in terms of particle provenance.

Thallium: A Polluting Metal of New Generation. Its Voltammetric Determination in Herbal Medicines in Presence of Metal Interferences

The present paper reports a new application: the voltammetric determination in herbal medicines of ultra-trace thallium(I), in the presence of lead(II), tin(II) and antimony(III) as interfering metals, by square wave anodic stripping voltammetry (SWASV). A conventional three-electrodes voltammetric cell was employed with a stationary hanging mercury drop electrode (HMDE) as working electrode and a platinum electrode and an Ag|AgCl|KClsatd. electrode as auxiliary and reference electrodes, respectively. The supporting electrolyte was 0.5 mol L−1 ammonium citrate buffer pH 6.5 + 7.3·10−3 mol L−1 EDTA-Na2. The analytical procedure was verified by the analysis of the standard reference materials: spinach Leaves NIST-SRM 1570a and tomato leaves NIST-SRM 1573a from National Institute of Standards and Technology. Precision and trueness, expressed as relative standard deviation and relative error, respectively, were generally lower than 7% in all cases. Once set up on the standard reference materials, the analytical procedure was transferred and applied to herbal medicines samples—Taraxacun officinale weber, Eucalyptus globulus and Harpagophytum procumbens DC—sold on the market. A critical comparison with spectroscopic measurements is also discussed.

Application of instumetal neutron activation analysis method for determination of some trace elements in lichens around three sites in Algiers

Trace elements (TEs) constitute a major part of pollution, which can induce a detrimental impact on public health. A precise analysis of these elements in the environment is an important parameter in the evaluation of the population's quality of life. This work aims to quantify the concentration of some trace elments in enviromental samples using Istrumental Neutron Activation Analysis technique (INAA); also a comparative study between three sampling points (Draria, Baraki and Reghaia) were done. The Samples and standards were irradiated for 6 h at “NUR” research reactor with a thermal neutron flux of 1013 n cm−2 s−1, and analyzed by gamma ray spectrometry using HPGe detector. Seventeen elements were assessed: Ba, Br, Ce, Co, Cr, Hf, Fe, La, Nd, Rb, Sb, Sc, Se, Sm, Sr, Yb and Zn in this study. The accuracy of the method was evaluated by analyzing Certified Reference Materials (CRMs) and Standard Reference Materials (SRMs). The data obtained in this work may contribute to obtaining information about a possible rank of pollution and the different capabilities of elemental bioaccumulation by lichens.