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Background: Research, mainly conducted in Europe and North America, has shown an inequitable burden of internalising mental health problems among adolescents from poorer households. We investigated whether these mental health inequalities differ across a diverse range of countries and multiple measures of economic circumstances., Methods: In this longitudinal observational cohort study, we analysed data from studies conducted in eight countries (Australia, Ethiopia, India, Mexico, Peru, South Africa, the UK, and Viet Nam) across five global regions. All studies had self-reported measures of internalising symptoms using a validated scale at two timepoints in adolescence; a measure of household income, household consumption expenditure, or subjective wealth; and data collected between 2000 and 2019. Household income (measured in four countries), consumption expenditure (six countries), and adolescents' subjective assessment of household wealth (five countries) were measured in mid-adolescence (14-17 years). The primary outcome (internalising symptoms, characterised by negative mood, affect, and anxiety) was measured later in adolescence between age 17 and 19 years. Analyses were linear regression models with adjustment. Effect estimates were added to random-effects meta-analyses to aid understanding of cross-country differences., Findings: The overall pooled sample of eight studies featured 18 910 adolescents (9568 [50·6%] female and 9342 [49·4%] male). Household income had a small or null association with adolescents' internalising symptoms. Heterogeneity (I 2 statistic) was 71·04%, falling to 39·71% after adjusting for baseline symptoms. Household consumption expenditure had a stronger association with internalising symptoms (decreases of 0·075 SD in Peru [95% CI -0·136 to -0·013], 0·034 SD in South Africa [-0·061 to -0·006], and 0·141 SD in Viet Nam [-0·202 to -0·081] as household consumption expenditure doubled). The I 2 statistic was 74·24%, remaining similar at 74·83% after adjusting for baseline symptoms. Adolescents' subjective wealth was associated with internalising symptoms in four of the five countries where it was measured. The I 2 statistic was 57·09% and remained similar after adjusting for baseline symptoms (53·25%). We found evidence for cross-country differences in economic inequalities in adolescents' internalising symptoms, most prominently for inequalities according to household consumption expenditure. Subjective wealth explained greater variance in symptoms compared with the objective measures., Interpretation: Our study suggests that economic inequalities in adolescents' mental health are prevalent in many but not all countries and vary by the economic measure considered. Variation in the magnitude of inequalities suggests that the wider context within countries plays an important role in the development of these inequalities., Funding: Wellcome Trust., Competing Interests: Declaration of interests SE-L reports grants from the UK Medical Research Council, the National Institute for Health and Care Research, and the Economic and Social Research Council. KR-C reports support through a UK Research and Innovation Future Leaders Fellowship; grants from UK Research and Innovation and WHO; and previous membership on the Global Alliance for Chronic Disease expert advisory panel. All other authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.)

Nickel (Ni) ecotoxicity is dictated by water chemistry characteristics such as pH, water hardness, and amount of dissolved organic carbon. Bioavailability models have been developed to predict Ni toxicity and validated for European, Australian, and US natural waters. In this study, chronic toxicity tests in Ni-spiked Japanese river waters were conducted on a strain of Daphnia magna to test whether the chronic toxicity differs among Japanese natural waters with different water chemistries. Based on the results of chronic Ni toxicity tests, we assessed the performance of existing D. magna bioavailability models, which were developed in artificial waters (Model 1) and calibrated in European natural waters (Model 2), in terms of the accuracy and the bias of model predictions. Furthermore, we also calibrated the two models by using toxicity test results to develop a bioavailability model for Ni chronic toxicity to the strain of D. magna in Japanese river waters. The 10%, 20%, and 50% effect concentrations (EC 10 , EC 20 , and EC 50 ) of dissolved Ni on reproduction of the D. magna strain were within ranges from 8.1 to 44.9 μg/L, 9.0 to 57.1 μg/L, and 10.9 to 86.1 μg/L, respectively. Results indicate that differences in water chemistry among Japanese river waters influenced chronic Ni toxicity to the model organism. Model 1predicted 43% of the observed EC 10 , EC 20 , and EC 50 values within a factor of 2 and 100%, 100%, and 43% within a factor of 3, respectively. Model 2 predicted 14%, 14%, and 29% of the observed EC 10 , EC 20 , and EC 50 values within a factor of 2 and 43% within a factor of 3. The values of model bias based on the geometric mean of ratios of EC 10 , EC 20 and EC 50 values predicted by each of the two models and observed EC 10 , EC 20 , and EC 50 values were 0.71, 0.65, and 0.62 for Model 1 and 0.27, 0.26, and 0.29 for Model 2, respectively. After calibrating two models using the results of toxicity tests, refined Model 1 predicted 71%, 57%, and 57% of observed EC 10 , EC 20 , and EC 50 values within a factor of 2 and 100%, 86%, and 100% within a factor of 3; refined Model 2 predicted 71% of observed EC 10 , EC 20 , and EC 50 values within a factor 2 and 100%, 86%, and 86% within a factor of 3, respectively. Our results indicate that calibrating the Ni bioavailability models in Japanese natural waters increased their predictive capacity by a factor of up to approximately five., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

There has been an increased emphasis on incorporating bioavailability-based approaches into freshwater guideline value derivations for metals in the Australian and New Zealand water quality guidelines. Four bioavailability models were compared: the existing European biotic ligand model (European Union BLM) and a softwater BLM, together with 2 newly developed multiple linear regressions (MLRs)-a trophic level-specific MLR and a pooled MLR. Each of the 4 models was used to normalize a nickel ecotoxicity dataset (combined tropical and temperate data) to an index condition of pH 7.5, 6 mg Ca/L, 4 mg Mg/L, (i.e., approximately 30 mg CaCO 3 /L hardness), and 0.5 mg DOC/L. The trophic level-specific MLR outperformed the other 3 models, with 79% of the predicted 10% effect concentration (EC10) values within a factor of 2 of the observed EC10 values. All 4 models gave similar normalized species sensitivity distributions and similar estimates of protective concentrations (PCs). Based on the index condition water chemistry proposed as the basis of the national guideline value, a protective concentration for 95% of species (PC95) of 3 µg Ni/L was derived. This guideline value can be adjusted up and down to account for site-specific water chemistries. Predictions of PC95 values for 20 different typical water chemistries for Australia and New Zealand varied by >40-fold, which confirmed that correction for nickel bioavailability is critical for the derivation of site-specific guideline values. Environ Toxicol Chem 2021;40:100-112. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC., (© 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.)

Bioavailability-based approaches have been developed for the regulation of metals in freshwaters in several countries. Empirical multiple linear regression (MLR) models have been developed for nickel that can be applied to aquatic organisms. The MLR models have been compared against the use of previously developed biotic ligand models (BLMs) for the normalization of an ecotoxicity dataset compiled for the derivation of a water quality guideline value that could be applied in Australia and New Zealand. The MLR models were developed from data for a number of specific species and were validated independently to confirm their reliability. An MLR modeling approach using different models for algae, plants, invertebrates, and vertebrates performed better than either a pooled MLR model for all taxa or the BLMs, in terms of its ability to correctly predict the results of the tests in the ecotoxicity database based on their water chemistry and a fitted species-specific sensitivity parameter. The present study demonstrates that MLR approaches can be developed and validated to predict chronic nickel toxicity to freshwater ecosystems from existing datasets. The MLR approaches provide a viable alternative to the use of BLMs for taking account of nickel bioavailability in freshwaters for regulatory purposes. Environ Toxicol Chem 2021;40:113-126. © 2020 SETAC., (© 2020 SETAC.)