Flake thickness is one of the defining properties of graphene-related 2D materials (GR2Ms), and therefore requires reliable, accurate, and reproducible measurements with well-understood uncertainties. This is needed regardless of the production method or manufacturer because it is important for all GR2M products to be globally comparable. An international interlaboratory comparison on thickness measurements of graphene oxide flakes using atomic force microscopy has been completed in technical working area 41 of versailles project on advanced materials and standards. Twelve laboratories participated in the comparison project, led by NIM, China, to improve the equivalence of thickness measurement for two-dimensional flakes. The measurement methods, uncertainty evaluation and a comparison of the results and analysis are reported in this manuscript. The data and results of this project will be directly used to support the development of an ISO standard.

OBJECTIVE: To analyze and evaluate the testing capability of arsenic in drinking water in the laboratories of the provincial and municipal centers for disease control and prevention across the country by implementing the interlaboratory comparison project.
METHODS: The preparation method of the secondary standard materials were used as the reference for the sample preparation in the interlaboratory comparison project. The homogeneity and stability of the samples and short-term stability for simulated transportation were tested by single factor analysis of variance(ANOVA) and linear regression and mean consistency test(t test). On top of using the kernel density estimation to test the distribution of laboratory test result, we adopted precision statistical method to analyze the laboratory test result and used Z-score to evaluate the testing ability of each participating laboratory.
RESULTS: A total of 411 laboratories throughout the country participated in the proficiency testing program.389 laboratories(94.6%) of participating laboratories, obtained satisfactory result. Results provided by 2 laboratories(0.5%) of total participating laboratories, were found suspicious in their capacities. Finally, there were 20 laboratories(4.9%) of total participating laboratories, with result found to be outliers.
CONCLUSIONS: The testing capability of arsenic in drinking water has been ranked as satisfactory in the laboratories of the provincial and municipal centers for disease control and prevention across the country, and the testing capability of a small number of laboratories requires further improvement.

OBJECTIVE: To analyze and evaluate the testing capability of cadmium in drinking water in the laboratories of the provincial and municipal centers for disease control and prevention across the country by implementing the interlaboratory comparison project.
METHODS: The preparation method of the secondary standard materials were used as the reference for the sample preparation in the interlaboratory comparison project. The homogeneity and stability of the samples and short-term stability for simulated transportation were tested by single factor analysis of variance(ANOVA) and linear regression and mean consistency test(t test). On top of using the kernel density estimation to test the distribution of laboratory test result, we adopted precision statistical method to analyze the laboratory test result and used Z-score to evaluate the testing ability of each participating laboratory.
RESULTS: A total of 409 laboratories throughout the country participated in the proficiency testing program.383 laboratories(93.6%) of participating laboratories, obtained satisfactory result. Results provided by 4 laboratories(1.0%) of total participating laboratories, were found suspicious in their capacities. Finally, there were 22 laboratories(5.4%) of total participating laboratories, with result found to be outliers.
CONCLUSIONS: The statistical result of the interlaboratory comparison project show that the testing capability of cadmium in drinking water has been ranked as satisfactory in the laboratories of the provincial and municipal centers for disease control and prevention across the country, and the testing capability of a small number of laboratories requires further improvement.

OBJECTIVE: To analyze and evaluate the testing capability of lead in drinking water in the laboratories of the provincial and municipal centers for disease control and prevention across the country by implementing the interlaboratory comparison project.
METHODS: The preparation method of the secondary standard materials were used as the reference for the sample preparation in the interlaboratory comparison project. The homogeneity and stability of the samples and short-term stability for simulated transportation were tested by single factor analysis of variance(ANOVA) and mean consistency test(t test). On top of using the kernel density estimation to test the distribution of laboratory test result, we adopted a robust statistical method to analyze the laboratory test result and used Z-score to evaluate the testing ability of each participating laboratory.
RESULTS: A total of 448 laboratories throughout the country participated in the proficiency testing program.341 laboratories(76.1%) of participating laboratories, obtained satisfactory result. Results provided by 28 laboratories(6.3%) of total participating laboratories, were found suspicious in their capacities. Finally, there were 79 laboratories(17.6%) of total participating laboratories, with result found to be outliers.
CONCLUSIONS: The statistical result of the interlaboratory comparison project show that the testing capability of lead in drinking water has been ranked as satisfactory in the laboratories of the provincial and municipal centers for disease control and prevention across the country, and the testing capability of a small number of laboratories requires further improvement.

The common duckweed (Lemna minor), a freshwater monocot that floats on the surfaces of slow-moving streams and ponds, is commonly used in toxicity testing. The novel Lemna root- regrowth test is a toxicity test performed in replicate test vessels (24-well plates), each containing 3 mL test solution and a 2-3 frond colony. Prior to exposure, roots are excised from the plant, and newly developed roots are measured after 3 days of regrowth. Compared to the three internationally standardized methods, this bioassay is faster (72 h), simpler, more convenient (requiring only a 3-mL) and cheaper. The sensitivity of root regrowth to 3,5-dichlorophenol was statistically the same as using the conventional ISO test method. The results of interlaboratory comparison tests conducted by 10 international institutes showed 21.3% repeatability and 27.2% reproducibility for CuSO4 and 21.28% repeatability and 18.6% reproducibility for wastewater. These validity criteria are well within the generally accepted levels of <30% to 40%, confirming that this test method is acceptable as a standardized biological test and can be used as a regulatory tool. The Lemna root regrowth test complements the lengthier conventional protocols and is suitable for rapid screening of wastewater and priority substances spikes in natural waters.

Thoron (220Rn) exhalation from building materials has become increasingly recognized as a potential source for radiation exposure in dwellings. However, contrary to radon (222Rn), limited information on thoron exposure is available. As a result no harmonized test procedures for determining thoron exhalation from building materials are available at present. This study is a first interlaboratory comparison of different test methods to determine the thoron exhalation and a pre-step to a harmonized standard. The purpose of this study is to compare the experimental findings from a set of three building materials that are tested, and to identify future challenges in the development of a harmonized standard.

Objective: To investigate the current status and real performance of the detection of RUNX1-RUNX1T1 fusion transcript levels and WT1 transcript levels in China through interlaboratory comparison. Methods: Peking University People\'s Hospital (PKUPH) prepared the samples for comparison. That is, the fresh RUNX1-RUNX1T1 positive (+) bone morrow nucleated cells were serially diluted with RUNX1-RUNX1T1 negative (-) nucleated cells from different patients. Totally 23 sets with 14 different samples per set were prepared. TRIzol reagent was added in each tube and thoroughly mixed with cells for homogenization. Each laboratory simultaneously tested RUNX1-RUNX1T1 and WT1 transcript levels of one set of samples by real-time quantitative PCR method. All transcript levels were reported as the percentage of RUNX1-RUNX1T1 or WT1 transcript copies/ABL copies. Spearman correlation coefficient between the reported transcript levels of each participated laboratory and those of PKUPH was calculated. Results: ①RUNX1-RUNX1T1 comparison: 9 samples were (+) and 5 were (-) , the false negative and positive rates of the 20 participated laboratories were 0 (0/180) and 5% (5/100) , respectively. The reported transcript levels of all 9 positive samples were different among laboratories. The median reported transcript levels of 9 positive samples were from 0.060% to 176.7%, which covered 3.5-log. The ratios of each sample\'s highest to the lowest reported transcript levels were from 5.5 to 12.3 (one result which obviously deviated from other laboratories\' results was not included) , 85% (17/20) of the laboratories had correlation coefficient ≥0.98. ②WT1 comparison: The median reported transcript levels of all 14 samples were from 0.17% to 67.6%, which covered 2.6-log. The ratios of each sample\'s highest to the lowest reported transcript levels were from 5.3-13.7, 62% (13/21) of the laboratories had correlation coefficient ≥0.98. ③ The relative relationship of the reported RUNX1-RUNX1T1 transcript levels between the participants and PKUPH was not always consistent with that of WT1 transcript levels. Both RUNX1-RUNX1T1 and WT1 transcript levels from 2 and 7 laboratories were individually lower than and higher than those of PKUPH, whereas for the rest 11 laboratories, one transcript level was higher than and the other was lower than that of PKUPH. Conclusion: The reported RUNX1-RUNX1T1 and WT1 transcript levels were different among laboratories for the same sample. Most of the participated laboratories reported highly consistent result with that of PKUPH. The relationship between laboratories of the different transcript levels may not be the same.
目的： 通过室间比对了解国内RUNX1-RUNX1T1融合转录本及WT1转录本检测现状和真实表现。 方法： 北京大学人民医院（简称PKUPH）制备比对样品，即用RUNX1-RUNX1T1（-）患者与RUNX1-RUNX1T1（+）患者新鲜骨髓/外周血有核细胞进行不同比例的稀释，制备出14种比对样本，每种样本各制备23份平行样本，加入TRIzol均质化后-70℃保存。各家中心采用RT-PCR技术同时检测各样本的RUNX1-RUNX1T1融合转录本及WT1转录本水平，统一以目的基因拷贝数/ABL拷贝数×100%的形式报告结果。通过Spearman相关分析计算各家中心与PKUPH检测结果之间的相关系数。 结果： ①RUNX1-RUNX1T1比对：9份为阳性、5份为阴性样本，参与的20家实验室的假阳性率为5%（5/100），假阴性率为0（0/180）。每份阳性样本各家检测值均不相同，9份阳性样本各家报告的结果中位值为0.060%~176.7%，共覆盖3.5个log的范围，各份样本最高与最低报告结果的比值为5.5~12.3（去除1份明显偏离的结果）。85%（17/20）的实验室与PKUPH结果之间的相关系数≥0.98。②WT1比对：14份样本各家报告结果均不相同，中位值为0.16%~67.6%，覆盖2.6个log的范围，各样本检测最高值与最低值的比值为5.3~13.7.62%（13/21）的实验室与PKUPH结果的相关系数≥0.98。③两个转录本每家与PKUPH报告结果的相对关系不一致，2家均低于、7家均高于PKUPH，另11家为1个高于另一个低于PKUPH。 结论： 同一样本各家中心报告的RUNX1-RUNX1T1及WT1转录本水平不同，大多数实验室与PKUPH报告的结果具有很高的一致性，实验室间不同转录本水平的相对关系不一定相同。.