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Mercury (Hg) is a ubiquitous heavy metal that originates from both natural and anthropogenic sources and is transformed in the environment to its most toxicant form, methylmercury (MeHg). Recent studies suggest that MeHg exposure can alter epigenetic modifications during embryogenesis. In this study, we examined associations between prenatal MeHg exposure and levels of cord blood DNA methylation (DNAm) by meta-analysis in up to seven independent studies (n = 1462) as well as persistence of those relationships in blood from 7 to 8 year-old children (n = 794). In cord blood, we found limited evidence of differential DNAm at cg24184221 in MED31 (β = 2.28 × 10-4, p-value = 5.87 × 10-5) in relation to prenatal MeHg exposure. In child blood, we identified differential DNAm at cg15288800 (β = 0.004, p-value = 4.97 × 10-5), also located in MED31. This repeated link to MED31, a gene involved in lipid metabolism and RNA Polymerase II transcription function, may suggest a DNAm perturbation related to MeHg exposure that persists into early childhood. Further, we found evidence for association between prenatal MeHg exposure and child blood DNAm levels at two additional CpGs: cg12204245 (β = 0.002, p-value = 4.81 × 10-7) in GRK1 and cg02212000 (β = -0.001, p-value = 8.13 × 10-7) in GGH. Prenatal MeHg exposure was associated with DNAm modifications that may influence health outcomes, such as cognitive or anthropometric development, in different populations. INMA: Main funding of the epigenetic studies in INMA were grants from Instituto de Salud Carlos III (Red INMA G03/176, CB06/02/0041), Spanish Ministry of Health (FIS-PI04/1436, FIS-PI08/1151 including FEDER funds, FIS-PI11/00610, FIS-FEDER-PI06/0867, FIS-FEDER-PI03–1615, FIS-FEDER PI16/1288, FIS-FEDER PI19/1338; Miguel Servet FEDER 15/0025 and 20/0006; FIS-FSE: 17/00260), Generalitat de Catalunya-CIRIT 1999SGR 00241, Generalitat Valenciana BEST/2020/059, Fundacio ́ La Marato ́ de TV3 (090,430), EU Commission (261357-MeDALL: Mechanisms of the Development of ALLergy), and European Research Council (268479-BREATHE: Brain dEvelopment and Air polluTion ultrafine particles in school childrEn). Korean exposome study: This study was supported by the Korean Environment Industry & Technology Institute (KEITI) through “the Environmental Health Action Program”, funded by Korea Ministry of Environment (2017001360005). MoBa: The Norwegian Mother, Father and Child Cohort Study is supported by the Norwegian Ministry of Health and Care Services and the Ministry of Education and Research, NIH/NIEHS (contract no N01-ES-75558), NIH/NINDS (grant no.1 UO1 NS 047537–01 and grant no.2 UO1 NS 047537–06A1). MoBa1 and MoBa 2 are supported by the Intramural Research Program of the NIH, National Institute of Environmental Health Sciences (Z01-ES-49019) and Norwegian Research Council/BIOBANK (grant no 221097). The work in MoBa3 was supported in part by a Postdoctoral Fellowship grant from the Ulleval Hospitals Research Council (now under Oslo University Hospital) and travel grants from the Unger-Vetlesens foundation and the Norwegian American Womens Club, all to M.C.M.K. MoBa3 epigenomics data analyses were funded by INCA/Plan Cancer-EVA-INSERM, France, and the International Childhood Cancer Cohort Consortium (I4C), and performed by the Epigenetics Group at the International Agency for Research on Cancer (IARC, Lyon, France), A.G. was supported by the grant from INCA/Plan Cancer-EVA-INSERM (France, 2015) to Z.H. and also by the IARC Postdoctoral Fellowship, partially supported by the EC FP7 Marie Curie Actions-People-Co-funding of regional, national and international programmes (COFUND). Project Viva: The Project Viva cohort is funded by NIH grants R01HL111108, R01NR013945, and R37 HD034568. RHEA: The Rhea project was financially supported by European projects, and the Greek Ministry of Health (Program of Prevention of Obesity and Neurodevelopmental Disorders in Preschool Children, in Heraklion district, Crete, Greece: 2011–2014; ‘Rhea Plus': Primary Prevention Program of Environmental Risk Factors for Reproductive Health, and Child Health: 2012–2015). The work was also supported by MICINN (MTM2015-68140-R), Centro Nacional de Genotipado-CEGEN-PRB2-ISCIII, the H2020-EU.3.1.2. - Preventing Disease Programme (grant agreement no 874583) (ATHLETE project), and from the European Union's Horizon 2020 research and innovation programme (grant Agreement number: 733206) (Early Life stressors and Lifecycle Health (LIFECYCLE)).

Background Prenatal arsenic (As) exposure could negatively affect child neuropsychological development, but the current evidence is inconclusive. Objectives To explore the relationship between prenatal urinary total As (TAs) concentrations, the As species and the methylation efficiency, and child neuropsychological development in a Spanish birth cohort. We also studied the effect modification produced by sex and several nutrients and elements. Materials and methods Study subjects were 807 mother–child pairs participating in the INMA (Childhood and Environment) Project. Urinary TAs and its metabolites, monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), inorganic As (iAs) and arsenobetaine were measured in the first trimester of pregnancy. Methylation efficiency was determined through the percentages of the metabolites and using principal component analysis. Children's neuropsychological development was assessed at the age of 4–5 years using the McCarthy Scales of Children's Abilities (MSCA). Multivariable linear regression models were built to assess the association between TAs, the As species and the maternal methylation efficiency, and the neuropsychological scores. We explored effect modification by sex, iron status, maternal nutrients status (serum manganese and selenium, and urinary zinc), and maternal vitamins intake (folate, and vitamins B12 and B6). Results The geometric mean (95%CI) of ∑As (sum of DMA, MMA and iAs) was 7.78 (7.41, 8.17) μg/g creatinine. MMA concentrations were inversely associated with the scores for the general, verbal, quantitative, memory, executive function and working memory scales (i.e. β [CI95%] = −1.37 [-2.33, −0.41] for the general scale). An inverse association between %MMA and the memory scores was found. Children whose mothers had lower manganese, zinc and ferritin concentrations obtained lower scores on several MSCA scales with decreasing As methylation efficiency. Discussion An inverse association was observed between MMA concentrations and children's neuropsychological development. Maternal levels of manganese, zinc and ferritin affected the association between As methylation efficiency and MSCA scores.

Background: Arsenic (As) is considered to be toxic for humans, the main routes of exposure being through drinking water and the diet. Once ingested, inorganic arsenic can be methylated sequentially to monomethyl and dimethyl arsenicals. Several factors can affect both As exposure and methylation efficiency. Objectives: To describe the urinary concentrations of the different As species and evaluate the methylation effi-ciency during pregnancy, as well as their associated factors in a birth cohort of pregnant Spanish women. Methods: Participants in this cross-sectional study were 1017 pregnant women from two areas of Spain who had taken part in the INMA (Environment and Childhood) project (2003 & ndash;2008). Total As (organic and inorganic compounds) and its main metabolites (monomethylarsonic acid, [MMA], dimethylarsinic acid, [DMA], inorganic As [iAs]) and arsenobetaine [AB]) were measured in urine samples collected during the first trimester. Socio-demographic and dietary information was collected through questionnaires. Multivariate linear regression models were used to explore the association between As species concentrations and covariates. Arsenic methylation efficiency was determined through the percentages of the metabolites and using As methylation phenotypes, obtained from principal component analysis. Results: Median urine concentrations were 33.0, 21.6, 6.5, 0.35 and 0.33 lig/g creatinine for total As, AB, DMA, MMA and iAs, respectively. Daily consumption of rice and seafood during the first trimester of pregnancy were positively associated with the concentration of As species (i.e., beta [CI95%] = 0.36 [0.09, 0.64] for rice and iAs, and 1.06 [0.68, 1.44] for seafood and AB). TAs, AB and iAs concentrations, and DMA and MMA concentrations were associated with legume and vegetable consumption, respectively. The medians of the percentage of As metabolites were 89.7 for %DMA, 5.1 for %MMA and 4.7 for %iAs. Non-smoker women and those with higher body mass index presented a higher methylation efficiency (denoted by a higher %DMA and lower %MMA). Discussion: Certain dietary, lifestyle, and environmental factors were observed to have an influence on both As species concentrations and methylation efficiency in our population. Further birth cohort studies in low exposure areas are necessary to improve knowledge about arsenic exposure, especially to inorganic forms, and its potential health impact during childhood. This study was supported by grants from Instituto de Salud Carlos III, Spain [FIS-FEDER: 07/0314; FIS 11/01007, 13/1944, 16/1288, 19/1338; Miguel Servet-FEDER: CP15/0025, CPII20/00006; FIS-FSE: 17/00260; Miguel Servet-FSE: MS15/0025, MS20/0006; PI06/0867 and FIS-PI18/01142 incl. FEDER funds] , Generalitat Valenciana, Spain BEST/2020/059, Department of Health of the Basque Government, Spain (2005111093) , Provincial Government of Gipuzkoa (DFG06/002) , and annual agreements with the municipalities in the study area (Zumarraga, Urretxu, Legazpi, Azkoitia, Azpeitia and Beasain) .

This study was funded by grants from Spanish Institute of Health Carlos III-Ministry of Economy and Competitiveness (INMA Network G03/176, CB06/02/0041, and FIS-FEDER: PI03/1615, PI04/1436, PI08/1151, PI04/2018, PI04/1509, PI04/1112, PI04/1931, PI05/1079, PI05/1052, PI06/1213, PI06/0867, PI07/0314, PI09/02647, PS09/00090, PI09/02311, MS11/0178, PI13/1944, PI13/2032, PI14/00891, PI16/1288, and PI17/00663). Miguel Servet-FEDER: MSII16/ 00051, CP14/00108 & PI16/00261 (Co-funded by European Regional Development Fund “A way to make Europe”), FEDER funds, MS13/00054. Generalitat de Catalunya-CIRIT 1999SGR 00241, JCI2011–09771–MICINN, Generalitat Valenciana (Conselleria de Sanitat048/2010 and 060/2010 and FISABIO-UGP 15-230, 15-244, and 15-249). Generalitat de Catalunya-CIRIT 1999SGR 00241, and Fundació La Marató de TV3 (090430). Alicia Koplowitz Foundation (2017). Universidad de Oviedo. FISS-PI13/2429. Fundación CajasturLiberbank. Department of Health of the Basque Government (2005111093 and 2009111069). The Provincial Government of Gipuzkoa (DFG06/004 and DFG08/001). The Fundación Roger Torné. ISGlobal is a member of the CERCA Programme, Generalitat de Catalunya. Mònica Guxens is funded by a Miguel Servet fellowship (MS13/00054) awarded by the Spanish Institute of Health Carlos III (Ministry of Economy and Competitiveness). Antonio J. Signes-Pastor and Margaret R. Karagas are funded by the following projects P01ES022832, RD 83544201, R25CA134286 and P42ES007373., Signes-Pastor, A.J., Vioque, J., Navarrete-Muñoz, E.M., Carey, M., García-Villarino, M., Fernández-Somoano, A., Tardón, A., Santa-Marina, L., Irizar, A., Casas, M., Guxens, M., Llop, S., Soler-Blasco, R., García-de-la-Hera, M., Karagas, M.R., Meharg, A.A.

Introduction Manganese (Mn) is an essential element, diet being its main source. Some epidemiological studies have found that a prenatal excess of Mn could negatively affect neuropsychological development during infancy, but the evidence is inconclusive. The aim of this study was to explore the relationship between maternal serum Mn concentrations and child neuropsychological development assessed at 1 year of age. Methods study subjects were 1179 mother–child pairs from two Spanish cohorts (Valencia and Gipuzkoa) of the INMA (Environment and Childhood) Project. Mn was measured in serum samples collected during the first trimester of pregnancy. Child neuropsychological development was assessed using the Bayley Scales of Infant Development, composed of both mental and psychomotor scales. Sociodemographic, lifestyle and dietary information was collected through questionnaires during pregnancy and during the child's first year of life. Serum Mn was log-2 transformed. Multivariable linear regression models were built. Generalized additive models were used to assess the shape of the relation between prenatal exposure to Mn and the neuropsychological test scores. Results geometric mean and 95% confidence interval (95% CI) of maternal serum Mn was 1.50 (1.48–1.53) μg/L. Levels of Mn were higher among non-working mothers and in those with a higher consumption of nuts. The association between maternal Mn levels and child neuropsychological development was negative in the multivariable models for the mental (β [95% CI] = −0.39 [-2.73, 1.95]) and psychomotor scales (β [95% CI] = −0.92 [-3.48, 1.65]), although the coefficients were not statistically significant. The best shape describing the relationship between Mn and the Bayley scales was linear in both cases. Conclusion This study shows a null association between maternal prenatal levels of Mn and neuropsychological development at one year after birth in two cohorts within the INMA study.

We assessed whether prenatal selenium (Se) exposure is associated with anthropometry at birth, placental weight and gestational age. Study subjects were 1249 mother-child pairs from the Valencia and Gipuzkoa cohorts of the Spanish Childhood and Environment Project (INMA, 2003–2008). Se was determined in serum samples taken at the first trimester of pregnancy. Socio-demographic and dietary characteristics were also collected by questionnaires. Mean (SD) serum Se concentration was 79.57 (9.64) μg/L. Se showed weak associations with both head circumference and gestational age. The association between serum Se concentration and birth weight and length was negative, and direct for placental weight and probability of preterm birth, although the coefficients did not reach statistical significance. Individuals with total mercury (THg) levels >15 μg/L reversed the serum Se concentration effect on head circumference. Significant interactions were found between sex and both gestational age and prematurity. Spontaneous birth gestational ages were estimated to be lower for males and their probability of prematurity was higher. In conclusion, prenatal Se exposure may be associated with lower head circumference and lower gestational ages at spontaneous birth. Interactions with THg exposure and gender should be considered when assessing these relationships.

The objective of this study was to describe the postnatal exposure to Hg and to evaluate its association with neuropsychological development among preschool children. The study population are 4–5 years old children (n = 1252) participant in the Spanish INMA Project. Total Hg was measured in cord blood and in hair samples taken at 4 years of age (2008–2012). Neuropsychological development was assessed using the McCarthy Scales of Children’s Abilities (MSCA). Information on covariates and possible confounders was obtained by questionnaires during pregnancy and childhood. Generalized additive and linear regression models were built in order to assess the relationship between MSCA scores and Hg exposure. We also evaluated the magnitude of the possible bias generated from measurement error in seafood intake estimate from questionnaire and Hg determination. The geometric mean of hair Hg was 0.98 μg/g [95% confidence interval (CI) 0.94, 1.03]. In the regression analysis, the association between Hg and the MSCA scores was positive for all the scales and statistically significant for the verbal (β = 0.89; 95%CI 0.38, 1.39), memory (β = 0.42; 95%CI 0.09, 0.76) and general cognitive scales (β = 1.35; 95%CI 0.45, 2.25). However, these associations were clearly attenuated when we adjusted by the children’s fish intake variables or when took into account theoretical scenarios of low precision in fish intake and Hg measurements. Hg levels in this Spanish population were high in comparison with other European countries; however, we did not observe adverse effects on child neuropsychological development associated with this postnatal exposure to Hg.

Background The excess of manganese (Mn) causes severe deleterious effects in the central nervous system, and the developing brain is especially sensitive to Mn overload. However, results of prospective studies regarding Mn neurodevelopmental effects remain inconclusive. The present study aims at studying the association of prenatal Mn exposure and neurodevelopment at 4–5 years of age. Methods: Mn serum concentration was measured in 1465 pregnant women from the INMA (INfancia y MedioAmbiente, Environment and Childhood) Project. Neurodevelopment was assessed using a standardized version of the McCarthy Scales of Children's Abilities (MSCA). Multivariate regression models were used for data analysis. Results: No association was found between Mn levels in serum and any of the McCarthy scales. However, the stratification by sex showed a positive and beneficial association of prenatal Mn levels and the verbal, quantitative and general-cognitive scales in girls (β (95%CI): 4 (0.03, 7.96), 4.5 (0.43, 8.57) and 4.32 (0.6, 8.05), respectively). Conclusions: A beneficial association was found for the first time between prenatal Mn levels measured in serum and neurodevelopment of female offspring at 4 years of age, which could have implications on public health policies, specifically on the establishment of policies promoting prenatal health related to dietary deficits of micronutrients such as Mn.

Early iron status plays an important role in prenatal neurodevelopment. Iron deficiency and high iron status have been related to alterations in child cognitive development, however, there are no data about iron intake during pregnancy with other environmental factors in relation to long term cognitive functioning of children. The aim of this study is to assess the relationship between maternal iron status and iron intake during pregnancy and child neuropsychological outcomes at 7 years of age. We used data from the INMA Cohort population-based study. Iron status during pregnancy was assessed according to serum ferritin levels, and iron intake was assessed with food frequency questionnaires. Working memory, attention, and executive function were assessed in children at 7 years old with the N-Back task, Attention Network Task, and the Trail Making Test, respectively. The results show that, after controlling for potential confounders, normal maternal serum ferritin levels (from 12 mg/L to 60 mg/L) and iron intake (from 14.5 mg/day to 30.0 mg/day), respectively, were related to better scores in working memory and executive functioning in offspring. Since these functions have been associated with better academic performance and adaptation to the environment, maintaining a good state of maternal iron from the beginning of pregnancy could be a valuable strategy for the community.

Introduction: Copper (Cu) is an essential element involved in biological processes; however, excessive Cu could be harmful because of its reactive nature. Very few studies have evaluated its potential neurotoxic effects. We aimed to evaluate the association between maternal Cu levels and children's neuropsychological development. Methods: Study subjects were mother-child pairs from the Spanish INMA (i.e. Childhood and Environment) Project. Cu was measured by inductively coupled plasma mass spectrometry in serum samples taken at the first trimester of pregnancy (2003-2005). Neuropsychological development was assessed using the Bayley Scales of Infant Development (BSID) at 12 months (n = 651) and the McCarthy Scales of Children's Abilities (MSCA) at 5 years of age (n = 490). Covariates were obtained by questionnaires during pregnancy and childhood. Multivariate linear and non-linear models were built in order to study the association between maternal Cu and child neuropsychological development.Results: The mean ± standard deviation of maternal Cu concentrations was 1606 ± 272 μg/L. In the multivariate analysis, a negative linear association was found between maternal Cu concentrations and both the BSID mental scale (beta = −0.051; 95% confidence intervals [CI]: −0.102, −0.001) and the MSCA verbal scale (beta = −0.044; 95%CI:-0.094, 0.006). Boys obtained poorer scores than girls, with increasing Cu at 12 months (interaction p-value = 0.040 for the mental scale and 0.074 for the psychomotor scale). This effect modification disappeared at 5 years of age. The association between Cu and the MSCA scores (verbal, perceptive performance, global memory and motor, general cognitive, and executive function scales) was negative for those children with lowest maternal iron concentrations (< 938μg/L).Conclusion: The Cu concentrations observed in our study were within the reference range established for healthy pregnant women in previous studies. The results of this study contribute to the body of scientific knowledge with important information on the possible neurotoxic capability of Cu during pregnancy.

The purpose of this study was to examine if the short semi-quantitative food frequency questionnaire (FFQ) is a reliable and valid tool to assess the diet of Spanish children aged 7&ndash, 9 years. We collected data from 156 children of the birth cohort INMA (Infancia y Medio Ambiente (Environment and Childhood)). Children&rsquo, s parents or care-givers completed a 46-item FFQ on two occasions over a 9&ndash, 12-month period about the children&rsquo, s diet. To explore the reproducibility of the FFQ, the nutrient and food group intake collected from the both FFQs were compared, while validity was examined by contrasting the nutrient values from the FFQs and the average of three 24-hour dietary recalls (24hDRs) taken in this period, and also with the concentration of several vitamins in the blood (carotenoids, vitamin D and &alpha, tocopherol). Pearson and de-attenuated correlation coefficients were calculated. The average correlation coefficients for nutrient intake&rsquo, s reproducibility was 0.41, ranging from 0.25 (calcium) to 0.65 (&beta, carotene), and for food group intake was 0.45, ranging from 0.18 (cereals) to 0.68 (sweetened beverages). Correlation coefficients slightly improved when we compared energy-adjusted intakes. The average correlation coefficients for validity against 24hDRs was 0.34 for energy-adjusted intakes, and 0.39 when de-attenuation coefficients were used. The validity coefficients against the blood concentrations of vitamins were 0.38 for &beta, cryptoxanthin, 0.26 for lycopene, 0,23 for &alpha, carotene and 0.15 for &beta, carotene, all of them statistically significant (p &lt, 0.05). This study suggests that our brief FFQ is a suitable tool for the dietary assessment of a wide range of nutrients and food groups in children 7&ndash, 9 years, despite the low to moderate reproducibility and validity observed for some nutrients.