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Aim: Left-behind children (LBC) now account for more than 1 in 5 Chinese children, and they often suffer from behavioural problems when their parents leave their rural homes to seek work in urban areas. The primary aim of this meta-analysis was to compare the incidence rates and factor scores of behavioural problems in LBC, who now account for more than one-fifth of Chinese children, and non-LBC.Methods: This systematic review and meta-analysis explored the children's characteristic behavioural problems using the Achenbach Child Behaviour Check List. A subgroup analysis was conducted to compare the different behavioural problems of LBC with different characteristics. The meta-analysis assessed 1405 papers and analysed 13 papers from 2007 to 2015, covering 10 264 LBC and 8909 non-LBC from 2 to 19 years of age.Results: The incidence rates of behavioural problems were higher in LBC than non-LBC. The highest risks were noted in boys aged between 6 and 11 years of age, who were more likely to be withdrawn and be affected by somatic complaints, schizophreniform disorder, compulsive behaviour and depression.Conclusion: Interventions and policies are urgently needed to tackle behavioural issues among LBC, especially high-risk males aged 6-11 years. [ABSTRACT FROM AUTHOR]

Inorganic divalent mercury complexes (Hg 2+ ) and monomethylmercury complexes (MeHg) are the main mercury species in aquatic systems and their toxicity to aquatic organisms is of great concern. Tetrahymena is a type of unicellular eukaryotic protozoa located at the bottom of food chain that plays a fundamental role in the biomagnification of mercury. In this work, the dynamic accumulation properties, toxicological characteristics and mechanisms of Hg 2+ and MeHg in five Tetrahymena species were evaluated in detail. The results showed that both Hg 2+ and MeHg were ingested and exhibited inhibitory effects on the proliferation or survival of Tetrahymena species. However, the ingestion rate of MeHg was significantly higher than that of Hg 2+ . The mechanisms responsible for the toxicity of MeHg and Hg 2+ were different, although both chemicals altered mitochondrial membrane potential (MMP). MeHg disrupted the integrity of membranes while Hg 2+ had detrimental effects on Tetrahymena as a result of the increased generation of reactive oxygen species (ROS). In addition, the five Tetrahymena species showed different capacities in accumulating Hg 2+ and MeHg, with T. corlissi exhibiting the highest accumulations. The study also found significant growth-promoting effect on T. corlissi under low concentration exposure (0.003 and 0.01μg Hg/mL (15 and 50nM)), suggesting different effect and mechanism that should be more closely examined when assessing the bioaccumulation and toxicity of mercury in aquatic ecosystems., (Copyright © 2017 Elsevier B.V. All rights reserved.)