The Mothers and Children's Environmental Health (MOCEH) study

Association of maternal ultra-processed food consumption during pregnancy with atopic dermatitis in infancy: Korean Mothers and Children's Environmental Health (MOCEH) study

BACKGROUND

Maternal diet during pregnancy might influence the development of childhood allergic disorders. There are few studies on the association between processed food intake and infant atopic dermatitis (AD) during pregnancy. The aim of the present study was to investigate the association of ultra-processed food (UPF) intake during pregnancy with infantile AD.

METHODS

This study involved 861 pairs of pregnant women and their offspring from the Mothers' and Children's Environmental Health (MOCEH) study, a multi-center birth cohort project conducted in Korea. Dietary intake was estimated using a 24-h recall method at 12-28 weeks gestation. The NOVA classification was used to identify UPF, and UPF intake was calculated as the percentage of total energy consumption and categorized into quartiles. Infantile AD was assessed based on medical history and the criteria of the International Study of Asthma and Allergies in Childhood (ISAAC). Associations were assessed by logistic regression with adjustment for confounding factors.

RESULTS

Children born to mothers in the highest quartile of UPF consumption (15.5% or more of the total energy) compared to the lowest quartile (6.8% or less) showed a higher risk of AD within 12 months [odds ratio (OR) = 1.69; 95% confidence interval (CI): 1.07-2.66, P for trend 0.0436]. After adjustment for the confounding factors under study, the association was strengthened; the adjusted OR between extreme quartiles was 2.19 (95% CI: 1.11-4.32, P for trend = 0.0418). This association was maintained even after an additional adjustment based on the Korean Healthy Eating Index (KHEI), an indicator of diet quality.

CONCLUSIONS

Higher maternal consumption of UPF during pregnancy was associated with a greater risk of infantile AD within the first year of life.

Infantile allergic diseases: a cohort study prenatal fish intake and mercury exposure context

BACKGROUND

Allergic diseases (ADs) have been increasingly reported in infants and children over the last decade. Diet, especially the inclusion of fish intake, may help to lower the risk of ADs. However, fish also, can bioaccumulate environmental contaminants such as mercury. Hence, our study aims to determine what effects the type and frequency of fish intake have on ADs in six-month-old infants, independently and jointly with mercury exposure.

METHODS

This study is part of the prospective birth cohort: Mothers and Children's Environmental Health (MOCEH) study in South Korea. Data was collected on prenatal fish intake, prenatal mercury concentration and ADs for infants aged six months for 590 eligible mother-infant pairs. Logistic regression analysis was conducted to evaluate the risk of prenatal fish intake and mercury concentration on ADs in infants. Finally, interaction between fish intake and mercury concentration affecting ADs in infants was evaluated. Hazard ratios of prenatal fish intake on ADs in 6 month old infants were calculated by prenatal mercury exposure.

RESULTS

Logistic regression analysis showed that white fish (OR: 0.53; 95% CI 0.30-0.94; P < 0.05) intake frequency, once a week significantly decreased the risk of ADs in infants. Stratification analysis showed that consuming white fish once a week significantly reduced the hazard of ADs (HR: 0.44; 95% CI 0.21-0.92; P < 0.05) in infants in the high-mercury (≥ 50th percentile) exposure group.

CONCLUSION

The result indicates that prenatal white fish intake at least once a week reduces the risk of ADs in infants, especially in the group with high prenatal mercury exposure.

Association of postnatal exposure to mixture of bisphenol A, Di-n-butyl phthalate and Di-(2-ethylhexyl) phthalate with Children's IQ at 5 Years of age: Mothers and Children's environmental health (MOCEH) study

Early childhood is important for neurodevelopment, and exposure to endocrine disruptors such as bisphenol A (BPA) and phthalates in this period may cause neurodevelopmental disorders and delays. The present study examined the association between exposure to mixtures of BPA and three metabolites of phthalates in early childhood and IQ at 5 years of age. The Mother and Children's Environmental Health (MOCEH) study is a prospective birth cohort study conducted in Korea with 1751 pregnant women enrolled from 2006 to 2010. After excluding those without relevant data, 47 children were included in the final analysis. We measured children's urinary concentrations of metabolites of endocrine-disrupting chemicals (Bisphenol A, mono-(2-ethyl-5-oxohexyl) phthalate, mono-(2-ethyl-5-hydroxyhexyl) phthalate and mono-(2-ethyl-5-butyl) phthalate) at ages of 24 and 36 months. We evaluated the children's IQ with the Korean Wechsler Intelligence Test at the age of 5 years. After adjusting for potential confounders, a multiple linear regression was conducted to examine the associations between individual endocrine-disrupting chemicals and the IQ of the children. Weighted Quantile Sum (WQS) regression and quantile-based g-computation were used to assess the association between IQ at age 5 and exposure to mixtures of BPA and phthalates. In the single-chemical analyses, mono-(2-ethyl-5-butyl) phthalate exposure at 36 months was adversely associated with children's IQ (β = -4.93, 95% confidence interval (CI): -9.22, -0.64). In the WQS regression and quantile-based g-computation analyses, exposure to the mixture of BPA and phthalates was associated with lower IQ [β = -9.13 (P-value = 0.05) and β = -9.18 (P-value = 0.05), respectively]. The largest contributor to the overall association was exposure to mono-(2-ethyl-5-butyl) phthalate at 36 months. In the present study, postnatal exposure to mixtures of BPA and three metabolites of phthalates was associated with decreased IQ of children at age 5.

Effect of PM concentration on anemia blood indicators reduced by air purifiers

Housewives perform daily household chores, which directly expose them to indoor particulate matter (PM). Indoor PM exposure is a potential factor that increases systemic inflammation and affects hematopoietic action. This study investigated the decrease in indoor PM concentration by air purifiers on indicators of anemia, such as hemoglobin, mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC). We analyzed the data of 40 housewives who were subjected to an air purifier intervention in Seoul and Ulsan, Republic of Korea. Indoor exposure levels of PM2.5 and PM10 were analyzed with sensor adjusted and gravimetric measurement. We also investigated the same anemia indicators before and after the installation of an air purifier for three months (short-term: one month, long-term: three months). Statistical analysis was performed by a multiple linear model and a linear mixed model. The indoor PM exposure levels and air purifier use were related to anemia indicators (hemoglobin and MCHC). The increase in indoor PM2.5 level was associated with a decrease in MCHC (β: 0.034, P = 0.031) and hemoglobin (β: 0.013, P = 0.04). The decrease in indoor PM2.5 concentration by air purifier was associated with an increase in MCHC (β: 0.204, P = 0.087) and hemoglobin (β: 0.190, P = 0.039). In particular, after air purifier intervention, the amounts of MCHC and hemoglobin significantly increased. Our results suggest that indoor air purifier use could decrease indoor PM level and the risk of anemia to housewives. Because the effect on anemia is subacute, it was confirmed three months after air purifier operation. In conclusion, anemia indicators can be improved by PM reduction management.

Prenatal phthalate exposure and cord blood DNA methylation

Exposure to phthalates has been shown to impede the human endocrine system, resulting in deleterious effects on pregnant women and their children. Phthalates modify DNA methylation patterns in infant cord blood. We examined the association between prenatal phthalate exposure and DNA methylation patterns in cord blood in a Korean birth cohort. Phthalate levels were measured in 274 maternal urine samples obtained during late pregnancy and 102 neonatal urine samples obtained at birth, and DNA methylation levels were measured in cord blood samples. For each infant in the cohort, associations between CpG methylation and both maternal and neonate phthalate levels were analyzed using linear mixed models. The results were combined with those from a meta-analysis of the levels of phthalates in maternal and neonatal urine samples, which were also analyzed for MEOHP, MEHHP, MnBP, and DEHP. This meta-analysis revealed significant associations between the methylation levels of CpG sites near the CHN2 and CUL3 genes, which were also associated with MEOHP and MnBP in neonatal urine. When the data were stratified by the sex of the infant, MnBP concentration was found to be associated with one CpG site near the OR2A2 and MEGF11 genes in female infants. In contrast, the concentrations of the three maternal phthalates showed no significant association with CpG site methylation. Furthermore, the data identified distinct differentially methylated regions in maternal and neonatal urine samples following exposure to phthalates. The CpGs with methylation levels that were positively associated with phthalate levels (particularly MEOHP and MnBP) were found to be enriched genes and related pathways. These results indicate that prenatal phthalate exposure is significantly associated with DNA methylation at multiple CpG sites. These alterations in DNA methylation may serve as biomarkers of maternal exposure to phthalates in infants and are potential candidates for investigating the mechanisms by which phthalates impact maternal and neonatal health.

Association of paternal cadmium and other heavy metal exposure to birth outcomes using propensity score matching

BACKGROUND

Human exposure to cadmium has various effects on health, especially on male reproductive organs. Although it is widely known that prenatal maternal cadmium exposure can affect birth outcomes, the effect of paternal exposure to cadmium remains unclear.

OBJECTIVES

This study aimed to evaluate the effect of paternal cadmium exposure on fetal growth by considering maternal cadmium exposure and exposure to other heavy metals, namely mercury and lead.

METHODS

The Mothers and Children's Environmental Health (MOCEH) study is a prospective birth cohort study in Korea. Overall, 1313 families (father-mother-child triple) without child abnormalities and who completed paternal whole blood cadmium assessments were included in this study. Families were divided into two subgroups based on the blood sampling periods, namely early and late pregnancy. Subjects were selected as follows: one family triple with a high level of paternal cadmium and two triples with low levels of paternal cadmium, using the method of propensity score matching. And linear regression analyses were performed.

RESULTS

The group with high paternal cadmium exposure (80% or more; 1.93 μg/L) had lower birth weight infants compared to the group with low cadmium concentrations (β(se) = -0.21(0.10); p-value = 0.0283). After stratification by infant sex, prenatal paternal cadmium exposure significantly reduced the birth weight of females in subgroups of different sampling times, namely early pregnancy (β(se) = -0.52 (0.22); p-value = 0.0170) and late pregnancy (β(se) = -0.43 (0.18); p-value = 0.0160). Finally, after performing propensity score matching in the early pregnancy measurement group, it was found that the prenatal exposure of father to cadmium significantly reduced birth weight in females (β(se) = -0.72(0.25); p-value = 0.0047).

CONCLUSION

This study assessed the effect of paternal cadmium exposure on birth outcomes in family units consisting of a father, mother, and child. Prenatal paternal cadmium exposure negatively affected birth weight, especially that of female, considering covariates and other heavy metals exposure, namely mercury and lead.

Association between prenatal cadmium exposure and cord blood DNA methylation

Prenatal cadmium exposure is known to affect infant growth and organ development. Nonetheless, the role of DNA methylation in cadmium-related health effects has yet to be determined. To this end, we investigated the relationship between prenatal cadmium exposure and cord blood DNA methylation in Korean infants through an epigenome-wide association study. Cadmium concentrations in maternal blood during early and late pregnancy and in cord blood collected from newborns were measured using atomic adsorption spectrometry and DNA methylation analysis was conducted using HumanMethylationEPIC BeadChip kits. After adjusting for infant sex, maternal pregnancy body mass index, smoking status, and estimated leukocyte composition, we analyzed the association between CpG methylation and cadmium concentration in 364 samples. Among 835,252 CpG sites, maternal blood cadmium concentration in early pregnancy was significantly associated with two differentially methylated CpG sites, cg05537752 and cg24904393, which were annotated ATP9A and no gene, respectively. The study findings indicate that prenatal cadmium exposure is significantly associated with methylation statuses of several CpG sites and regions in Korean infants, especially during early pregnancy.

Gene-environment interactions related to maternal exposure to environmental and lifestyle-related chemicals during pregnancy and the resulting adverse fetal growth: a review

Background

There are only limited numbers of reviews on the association of maternal-child genetic polymorphisms and environmental and lifestyle-related chemical exposure during pregnancy with adverse fetal growth. Thus, this article aims to review: (1) the effect of associations between the above highlighted factors on adverse fetal growth and (2) recent birth cohort studies regarding environmental health risks.

Methods

Based on a search of the PubMed database through August 2021, 68 epidemiological studies on gene-environment interactions, focusing on the association between environmental and lifestyle-related chemical exposure and adverse fetal growth was identified. Moreover, we also reviewed recent worldwide birth cohort studies regarding environmental health risks.

Results

Thirty studies examined gene-smoking associations with adverse fetal growth. Sixteen maternal genes significantly modified the association between maternal smoking and adverse fetal growth. Two genes significantly related with this association were detected in infants. Moreover, the maternal genes that significantly interacted with maternal smoking during pregnancy were cytochrome P450 1A1 (CYP1A1), X-ray repair cross-complementing protein 3 (XRCC3), interleukin 6 (IL6), interleukin 1 beta (IL1B), human leukocyte antigen (HLA) DQ alpha 1 (HLA-DQA1), HLA DQ beta 1 (HLA-DQB1), and nicotinic acetylcholine receptor. Fetal genes that had significant interactions with maternal smoking during pregnancy were glutathione S-transferase theta 1 (GSTT1) and fat mass and obesity-associated protein (FTO). Thirty-eight studies examined the association between chemical exposures and adverse fetal growth. In 62 of the 68 epidemiological studies (91.2%), a significant association was found with adverse fetal growth. Across the studies, there was a wide variation in the analytical methods used, especially with respect to the genetic polymorphisms of interest, environmental and lifestyle-related chemicals examined, and the study design used to estimate the gene-environment interactions. It was also found that a consistently increasing number of European and worldwide large-scale birth cohort studies on environmental health risks have been conducted since approximately 1996.

Conclusion

There is some evidence to suggest the importance of gene-environment interactions on adverse fetal growth. The current knowledge on gene-environment interactions will help guide future studies on the combined effects of maternal-child genetic polymorphisms and exposure to environmental and lifestyle-related chemicals during pregnancy.

Supplementary information

The online version contains supplementary material available at https://doi.org/10.1265/ehpm.21-00033.

The continuing evolution of birth cohort studies: achievements and challenges

Well-designed birth cohorts are able to estimate prevalence/distribution of various health events/outcomes, and to link early-life origins with adult health and function. The past two decades have seen a surge in the establishment of new birth cohorts and their accompanying research. We discussed distinct designs of current birth cohort studies, reviewed their achievements, and highlighted insights obtained from birth cohort studies, as well as challenges we are facing. Birth cohort studies are providing increasing opportunities to identify determining factors for short- and long-term health, yielding substantial evidence to uncover biological mechanisms of diseases and phenotypes, and providing further insights for public health. Dynamic monitoring, accurate measurements, long-term follow-ups and collaborative efforts are warranted in new birth cohorts to elucidate the nature of life course relationships in contemporary generation.

Comparison of the exposure assessment of di(2-ethylhexyl) phthalate between the PBPK model-based reverse dosimetry and scenario-based analysis: A Korean general population study

Di (2-ethylhexyl) phthalate (DEHP), classified as a reproductive toxicant, is a ubiquitous pollutant in foodstuffs, dust, and commercial products. In this study, to provide a useful cross-check on the accuracy of the exposure assessment, the estimated daily intake of DEHP was compared using reverse dosimetry with a physiologically-based pharmacokinetic (PBPK) model and a scenario-based probabilistic estimation model for six subpopulations in Korea. For reverse dosimetry analysis, the concentrations of urinary DEHP metabolites, namely mono (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and mono (2-ethyl-5-oxohexyl)phthalate (MEOHP), from three human biomonitoring program datasets were used. For the scenario-based model, we evaluated the various exposure sources of DEHP, including diet, air, indoor dust, soil, and personal care products (PCPs), and also determined its levels based on the literature review and measurements of indoor dust. The DEHP exposure doses using both exposure assessment approaches were similar in all cases, except for the 95th percentile exposure doses in toddlers (1-2 years) and young children (3-6 years). The PBPK-reverse dosimetry estimated daily intakes at the 95th percentile ranged between 22.53 and 29.90 μg/kg/day for toddlers and young children. These exceeded the reference dose (RfD) of 20 μg/kg bw/day of the US Environmental Protection Agency (EPA) based on the increased relative liver weight. Although, food was considered the primary source of DEHP, contributing to a total exposure of 50.8-75.1%, the effect of exposure to indoor dust should not be overlooked. The occurrence of high levels of DEHP in indoor dust collected from Korean homes suggests the use of a wide variety of consumer products containing DEHP. Furthermore, more attention should be paid to the high exposure levels of DEHP, especially in young children. Therefore, it is necessary to perform continuous monitoring of the indoor dust, consumer products, and the body burden of children.

Pre- and postnatal exposure to multiple ambient air pollutants and child behavioral problems at five years of age

Ambient air pollution is emerging as a risk factor for adverse neurological symptoms and early childhood diseases. This study aimed to evaluate the association between pre- and postnatal exposure to air pollutants and childhood behavior by using MOCEH prospective birth cohort data. In total, 353 mother-child pairs at birth, who completed child behavioral assessments using the Korean version of the Child Behavior Checklist at five years of age, were included in the study. Multivariate linear regression (MLR) for single pollutant and Bayesian kernel machine regression (BKMR) for multiple pollutants were conducted. MLR analysis showed that air pollutant exposures during the first trimester were significantly associated with the internalizing problems score after adjusting for covariates. The estimates were 0.19 (0.05-0.32) per 1 μg/m³ increase in PM_2.5, 0.13 (0.04-0.22) per 1 μg/m³ increase in PM₁₀, and 0.20 (0.02-0.37) per 1 ppb increase in NO₂. The BKMR model analysis revealed that the overall effects of multiple air pollutants during the first trimester of pregnancy and 0-6 months of the infantile period were significantly associated with behavioral problems. Boys showed a stronger associations than girls. Taken together, these results showed that the first trimester of pregnancy and 0-6 months of the infantile period were important for air pollutant exposure because exposure at these periods was associated with behavioral problems in 5-year-old children. Future efforts are required to control air pollution levels and reduce the health burden of vulnerable populations, including pregnant women and children.

Prenatal Exposure to Traffic-Related Air Pollution and the DNA Methylation in Cord Blood Cells: MOCEH Study

Particulate matter with a diameter of ≤10 µm (PM₁₀) and nitrogen dioxide (NO₂) affect the DNA methylation in the fetus, but epigenetic studies regarding prenatal exposure to air pollution in Asia are lacking. Therefore, this study aimed to assess whether there is any association between the ambient concentrations of PM₁₀ and NO₂ and CpG methylation in the cord blood DNA by using a Korean birth cohort. The concentrations of the air pollutants were incorporated into the final LUR model by using the maternal address data. The methylation level was determined using HumanMethylationEPIC BeadChip and a linear regression analysis model. A multipollutant model including both PM₁₀ and NO₂ and models with single pollutants were used for each trimester exposure. The number of differentially methylated positions was the largest for midpregnancy exposure in both the single pollutant models and the multipollutant regression analysis. Additionally, gene-set analysis regarding midpregnancy exposure revealed four gene ontology terms (cellular response to staurosporine, positive regulation of cytoskeleton organization, neurotransmitter transport, and execution phase of apoptosis). In conclusion, these findings show an association between prenatal PM₁₀ and NO₂ exposure and DNA methylation in several CpG sites in cord blood cells, especially for midpregnancy exposure.

Association of maternal dietary patterns during pregnancy with small-for-gestational-age infants: Korean Mothers and Children's Environmental Health (MOCEH) study

BACKGROUND

Nutrients that support the desired growth and development of the fetus (i.e., micronutrients like folate, iron, and zinc) have been associated with birth outcomes, such as gestational age at delivery and birth weight.

OBJECTIVES

We characterized the maternal dietary patterns that explain the maximum variation in folate, iron, and zinc intakes in pregnant Korean women using reduced-rank regression (RRR) and investigated the association of these patterns with small-for-gestational-age (SGA) risk.

METHODS

A total of 1158 pregnant Korean women at 12-28 weeks of gestation and their newborns were recruited for the Mothers and Children's Environmental Health (MOCEH) study between 2006 and 2010. A semiquantitative FFQ was collected from the women, and RRR was used to derive their dietary patterns. Log-transformed maternal intakes of folate, iron, and zinc were selected as the intermediate response variables to extract dietary patterns. Infant birth outcome measurements were obtained from hospital records. Associations were assessed by logistic regression with adjustment for confounding factors.

RESULTS

Three dietary patterns were identified. Pattern 1, characterized by high intakes of grains, green/yellow and light-colored vegetables, kimchi, legumes, fruits, meat, eggs, fish, seaweeds, tofu/soymilk, yogurt, and nuts, was associated with a lower risk of SGA in the highest quartile than in the lowest quartile (OR: 0.36; 95% CI: 0.14, 0.94). Especially, maternal dietary pattern 1 was negatively related to high-sensitivity C-reactive protein in the blood and malondialdehyde concentrations in the urine. No association was observed between other dietary patterns and SGA.

CONCLUSION

Among pregnant Korean women, adherence to a dietary pattern characterized by high intakes of grains, green/yellow and light-colored vegetables, kimchi, legumes, fruits, meat, eggs, fish, seaweeds, tofu/soymilk, yogurt, and nuts is associated with a lower risk of delivering SGA infants.

Sample management: a primary critical starting point for successful omics studies

Biological samples collected from cohort studies are widely utilized in molecular genetic studies and are typically stored long term for future applications, such as omics analyses. The extent of sample availability is determined by proper sample handling, and it is of primary importance for successful omics studies. However, questions on whether samples in long-term storage are properly available for omics experiments has been raised, because the quality and availability of such samples remain unknown until their actual utilization. In that perspective, several guidelines for proper sample management have been suggested. In addition, several researchers assessed how improper management damages sample using mock sample and suggested a set of requirements for sample handling. In this review, we present several considerations for sample handling eligible for omics studies. Focusing on birth cohorts, we describe the types of samples collected from which omics data were generated. This review ultimately aims to provide proper guidelines for sample handling for successful human omics studies.

Direct and Indirect Effects of Indoor Particulate Matter on Blood Indicators Related to Anemia

Exposure to indoor particulate matter (PM) is a potential risk factor that increases systemic inflammation and affects erythropoiesis. This study investigated the association between exposure to indoor PM and blood indicators related to anemia (BIRA) in housewives. Indoor PM and blood folate status are important factors in the risk of anemia. This was a housewife cohort study; we recruited 284 housewives in Seoul and Ulsan, Republic of Korea. Indoor exposure to PM2.5 and PM10 was measured by gravimetric analysis and sensors. We investigated the BIRA, such as hemoglobin (Hb), hematocrit, mean corpuscular volume (MCV), mean corpuscular Hb (MCH), and mean corpuscular Hb concentration (MCHC). Statistical analysis was performed by multiple linear regression model and mediation analysis. The association between BIRA and PM was assessed by multiple linear regression models fitted by mediation analyses. The increase in the level of indoor PM2.5 was associated with a decrease in MCV (Beta coefficient (B): −0.069, Standard error (SE): 0.022) and MCH (B: −0.019, SE: 0.009) in gravimetric measurements. The increase in the level of indoor PM2.5 was associated with a decrease in Hb (B: −0.024, SE: 0.011), hematocrit (B: −0.059, SE: 0.033), and MCV (B: −0.081, SE: 0.037) and MCH (B: −0.037, SE: 0.012) in sensor measurements (PM2.5-Lag10). Further, we identified a serum folate-mediated PM effect. The indoor PM exposure was significantly associated with decreased Hb, MCV, and MCH in housewives. Taken together, our data show that exposure to indoor PM is a risk factor for anemia in housewives. Blood folate concentration can be a mediating factor in the effect of indoor PM on BIRA. Therefore, folate intake should be recommended to prevent anemia in housewives. Moreover, indoor PM exposure should be managed.

Joint association of prenatal bisphenol-A and phthalates exposure with risk of atopic dermatitis in 6-month-old infants

BACKGROUND

Prenatal exposure to bisphenol A (BPA) and phthalates could trigger immune response. Few studies have investigated the association between prenatal BPA and phthalate exposure and atopic dermatitis (AD) in infants.

OBJECTIVE

We aimed to clarify the joint association of prenatal exposure to BPA and phthalate metabolites with AD incidence in 6-month-old infants.

METHODS

We included 413 mother-child pairs from the Mothers and Children's Environmental Health (MOCEH) in a prospective birth cohort study. Maternal urinary BPA, mono-2-ethyl-5-hydroxyhexyl phthalate (MEHHP), mono-2-ethyl-5-oxohexyl phthalate (MEOHP), and mono-n-butyl phthalate (MnBP) concentrations were measured during early and late pregnancy. We applied the Bayesian kernel machine regression (BKMR) with probit regression to estimate the association of BPA and phthalate metabolites with AD incidence after adjusting for potential confounders. Individual association was estimated by differences in predicted probabilities comparing each individual chemical concentration at 75th versus 25th percentiles, while other chemicals were set at their median. Overall joint effect was estimated by differences in predicted probabilities comparing all chemical concentrations at 75th versus 25th percentiles.

RESULTS

Individual effect of MEHHP in late pregnancy was strongly associated with incident AD [Difference: 0.244 (95% credible interval: -0.066, 0.554)] in the model including both early and late exposures. Furthermore, we confirmed overall joint association of urinary BPA and phthalate metabolites during pregnancy with a higher risk of AD [0.347 (0.168, 0.526) for late pregnancy exposure, and 0.307 (0.094, 0.521) for both early and late pregnancy]. Additionally, the joint association was more prominent among girls than that in boys.

CONCLUSIONS

The joint association of prenatal exposure to BPA and phthalates could be associated with the incident AD in 6-month-old infants. Further studies are needed to confirm the synergistic effect of BPA and phthalate exposures on AD in children.

Maternal Nutritional Status and Development of Atopic Dermatitis in Their Offspring

Atopic dermatitis (AD) is the leading chronic skin inflammatory disease and the initial manifestation of atopic march. Available evidence supports the notion that primary prevention early in life leads to a decreased incidence of AD, thus possibly decreasing the subsequent occurrence of atopic march. Nutritional status is essential to a proper functioning immune system and is valued for its important role in AD. Essential nutrients, which include carbohydrates, proteins, lipids, vitamins, and minerals, are transferred from the mother to the fetus through the placenta during gestation. Various nutrients, such as polyunsaturated fatty acids (PUFAs) and vitamin D, were studied in relation to maternal status and offspring allergy. However, no strong evidence indicates that a single nutrient or food in mothers' diet significantly affects the risk of childhood AD. In the light of current evidence, mothers should not either increase nor avoid consuming these nutrients to prevent or ameliorate allergic diseases in their offspring. Each essential nutrient has an important role in fetal development, and current government recommendations suggest specific intake amounts for pregnant women. This review discusses evidence on how various nutrients, including lipids (monounsaturated fatty acids, PUFAs, saturated fatty acids, and short-chain fatty acids), carbohydrates (oligosaccharides and polysaccharides), proteins, vitamins (A, B, C, D, and E), and trace minerals (magnesium, iron, zinc, copper, selenium, and strontium) in maternal status are associated with the development of AD and their possible mechanisms.

Prenatal lead exposure and cord blood DNA methylation in the Korean Exposome Study

BACKGROUND

Prenatal lead exposure has been reported to affect infant growth and nervous system development, as well as to influence DNA methylation. We conducted an epigenome-wide association study to identify associations between prenatal lead exposure and cord blood DNA methylation in Korean infants.

METHODS

Cord blood samples were assayed with the Illumina HumanMethylationEPIC BeadChip kits, and maternal blood lead levels during early and late pregnancy, as well as cord blood lead level, were measured. The association between CpG methylation and lead level was analyzed using the limma package, with adjusting for infant sex, maternal pre-pregnancy body mass index, and estimated leukocyte composition.

RESULTS

Among 364 blood samples (182 males and 182 females), those for which maternal and cord blood lead concentrations during early and later pregnancy was known were used for analysis. Maternal lead concentration in blood during early pregnancy was significantly associated with the methylation status of specific positions. After data stratification by infant sex, we found that, in males, the level of maternal blood lead was associated with 18 CpG sites during early pregnancy, and with one CpG site near the NBAS gene, during late pregnancy. In female samples, there was no significant association between DNA methylation and lead concentrations.

CONCLUSIONS

Prenatal lead exposure was associated with altered, gender-specific patterns of DNA methylation in Korean infants.

Prenatal heavy metal exposures and atopic dermatitis with gender difference in 6-month-old infants using multipollutant analysis

BACKGROUND

Prenatal exposure to heavy metals during critical developmental phases has been implicated in allergic phenotypes. However, few studies have been conducted on the gender-specific association of prenatal heavy metal exposure with atopic dermatitis (AD) in infants.

OBJECTIVE

To examine the gender-specific association of prenatal exposure to multiple heavy metals with AD incidence in 6-month-old infants using data from the Mothers and Children's Environmental Health (MOCEH).

METHODS

We evaluated 738 mother-child pairs from the MOCEH study, an ongoing prospective birth cohort. The concentrations of three heavy metals (lead, mercury and cadmium) in maternal blood samples were measured during early and late pregnancy. Each quartile of heavy metal concentration was used to consider the possible nonlinear association with AD. For assessing the multi-pollutant model, we constructed the multivariate regression model including all three heavy metals at both early and late pregnancy. Further, the group Lasso model was used to perform the variable selection with categorized exposures and assess the effect of multiple pollutants including their pairwise interactions.

RESULTS

A total of 200 incident cases of AD were diagnosed in 6-month-old infants. In the multivariate regression model of the boy group, adjusted odds ratios comparing the second, third and fourth quartile of lead exposure in boys with the first quartile were 1.83 (95% CI: 1.00, 3.38), 1.04 (0.91, 3.32) and 2.40 (1.18, 4.90), respectively. However, the only second quartile of lead exposure compared to first quartile was significantly associated with AD in girls. In addition, the results of the group Lasso model were similar with the results of multivariate regression model.

CONCLUSION

The results suggest that lead exposure in late pregnancy increases risk of AD in 6-month-old boys although the strength of association is weak. Further studies are needed to confirm the susceptibility window and gender differences in lead-induced AD.

Adverse effects of prenatal mercury exposure on neurodevelopment during the first 3 years of life modified by early growth velocity and prenatal maternal folate level

BACKGROUND AND AIMS

Previous studies have suggested that mercury exposure and folate levels during pregnancy may influence early childhood neurodevelopment. Rapid catch-up growth in children is associated with an increased risk of pathological nervous system development. We evaluated whether the association between prenatal folate and mercury-related neuropsychological dysfunction was modified by growth velocity during childhood.

METHODS

The Mothers and Children's Environmental Health (MOCEH) birth cohort study began in 2006 and by 2010, 1751 women had been enrolled before the second trimester of their pregnancy along with their partners. Participants visited the research center at birth and 6, 12, 24, and 36 months. We measured mercury levels in maternal and cord blood and folate in maternal serum. Questionnaires to evaluate the environment and health of their child were administered and anthropometric factors including body weight and height were measured. Certified investigators used the Bayley test to measure neurobehavioral outcomes. We calculated postnatal growth change as the change in infant weight for-age z-score between birth and 3 years. Multiple linear regression and mixed models were used to examine the association between mercury exposure and children's neurodevelopment as well as the modifying effects of folate and growth velocity.

RESULTS

A total of 30.6% of children experienced rapid growth during the first 3 years of life. Median values of mercury in the low folate group were significantly higher in rapid growers (3.41 μg/L in maternal blood and 5.63 μg/L in cord blood) than in average/slow growers (3.05 μg/L in maternal blood and 5.19 μg/L in cord blood). Rapid growers were also significantly associated with decreased psychomotor development scores during the first 3 years of life and with having mothers who had low prenatal folate levels, even after adjusting for potential confounders.

CONCLUSION

Prenatal mercury exposure adversely affects infant neurodevelopment and is associated with rapid growth during the first 3 years of life. This effect was limited to children whose mothers had low prenatal folate levels, suggesting a protective effect of folate against developmental neurotoxicity due to mercury exposure and rapid catch-up growth.

Metal mixtures in pregnant women and umbilical cord blood at urban populations-Rio de Janeiro, Brazil

This study aims to assess interrelationships between serum lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) concentrations in pregnant women in their third trimester and umbilical cord blood, while inter-metal correlations were also determined. This study is part of the PIPA project (Childhood and Environmental Pollutant Project), whose pilot study was carried out from October 2017 to August 2018 and will be presented here. Blood samples were obtained from 117 mother-umbilical cord pairs and analyzed concerning metal concentrations. A positive correlation was found between metal concentrations in mother and cord blood (R > 0.7, p < 0.001). The results indicate that mother metal concentrations are able to determine child metal concentrations (p < 0.001). The correlations between maternal blood metal concentrations were positive for all assessed metals except for As and Hg. The strongest correlations in this matrix were observed between Cd and Pb (R = 0.471 p = 0.000), Cd and Hg (R = 0.425 p = 0.000), and Pb and Hg (R = 0.427 p = 0.000). Umbilical cord correlations were lower compared to mother blood correlations. In general, the four analyzed metals displayed significant correlations to serum concentrations in both maternal and cord blood.

The Association Between Mercury Exposure and Atopic Dermatitis in Early Childhood: A Mothers and Children's Environmental Health Study

BACKGROUND

Atopic dermatitis is a chronic and relapsing inflammatory skin disease. Although mercury has been suggested as a risk factor, the underlying mechanism and the relationship between mercury and atopic dermatitis remains unclear. The objective of the present study was to investigate the relationship between mercury exposure and the presence of atopic dermatitis in early childhood.

METHODS

This study is part of the prospective Mothers and Children's Environmental Health cohort study. A total of 1,751 pregnant women were enrolled in Mothers and Children's Environmental Health. After delivery, children were followed up. Blood samples were collected and mothers were asked about the presence of atopic dermatitis in their children via a questionnaire at 6, 12, 24, 36, and 60 months of age.

RESULTS

After excluding participants who did not meet the inclusion criteria, a total of 1,061 mother-children pairs were included in the analysis. The geometric mean of mercury concentrations in cord blood was 5.1 µg/L. In adjusted models, cord blood mercury exposure (odds ratio [OR] = 1.1; 95% confidence interval [CI] = 1.0, 1.2 at 12-24 months) and postnatal mercury exposure (OR = 1.2; 95% CI = 1.0, 1.5 at 24-36 months, OR = 1.4; 95% CI = 1.1, 1.8 at 48-60 months) were associated with the presence of atopic dermatitis in children.

CONCLUSIONS

Postnatal mercury exposure at 24 months of age increases the risk of atopic dermatitis in children.

Environmental pollutants affecting children's growth and development: Collective results from the MOCEH study, a multi-centric prospective birth cohort in Korea

BACKGROUND

The Mothers and Children's Environmental Health study (MOCEH) is a multi-centric prospective birth cohort study investigating effects of various environmental pollutants like heavy metals, endocrine disruptors, air pollutants, nutrition and lifestyle on birth outcomes, growth and development, health and disease of children. In this study, we report all the outcomes from the MOCEH study describing the different environmental pollutants affecting children's health and disease.

METHODS

In MOCEH study, 1,751 pregnant women in their first trimester were recruited at 3 centers from 2006 to 2010 in South Korea. The children were followed from birth up to 6 years. Information on health outcomes of children including birth parameters, demographic characteristics, medical and child-rearing history, and nutritional status, were repeatedly obtained through the follow-ups by questionnaires administration, clinical evaluation, and biological specimen collection and measurements. Prenatal and postnatal measurement in biospecimen, i.e., lead, mercury, cadmium, manganese, 1-hydroxypyrene, 2-naphthol, malonadialdehyde, hippuric acid, bisphenol A and phthalate metabolites, and measurement in air samples, i.e., particulate matter, nitrogen dioxide, and total volatile organic compounds were performed.

RESULTS

The results show the adverse effect of prenatal exposure to heavy metals like mercury, lead and cadmium on children's physical, cognitive and neurobehavioral development. Exposure to endocrine disruptors, air pollution, second hand smoke, and mother's lifestyle during pregnancy affects children's growth and development. We also identified specific window periods of exposure of pollutants significantly related to children's health outcomes.

CONCLUSION

The collective results from MOCEH study provide strong scientific evidence that exposures to prenatal and postnatal environmental pollutants have a negative effect on growth and development of children, which will be useful in implementing effective national policy to improve children's environmental health.

Prenatal exposure to mixtures of heavy metals and neurodevelopment in infants at 6 months

BACKGROUND

Exposure to mixture of neurotoxic metals such as lead, mercury and cadmium occurs at a specific point of time. When exposed to metal mixtures, one metal may act as an agonist or antagonist to another metal. Thus, it is important to study the effects of exposure to a combination of metals on children's development using advance statistical methods.

OBJECTIVES

In this study, we explored the effects of prenatal metal exposure including lead, mercury and cadmium in early pregnancy (12-20 weeks), late pregnancy (>28 weeks), and at birth on neurodevelopment of infants at 6 months of age.

METHODS

We included 523 eligible mother-child pairs from the mothers and children environmental health (MOCEH) study, a prospective birth cohort study in Korea. We used linear regression, Bayesian kernel machine regression (BKMR) and generalized additive models (GAM), to evaluate the effects of exposure to metal mixtures on neurodevelopment of infants aged 6 months. The Korean version of Bayley scale of infant and toddler development-II was used to measure the child's neurodevelopment.

RESULTS

Linear regression models showed a significant negative effect of lead exposure during late pregnancy on the mental development index (MDI) [β = -2.51 (-4.92, -0.10)] scores of infants aged 6 months following co-exposure to mercury. Further, linear regression analysis showed a significant interaction between late pregnancy lead and mercury concentrations. BKMR analysis showed similar results as those obtained in linear regression models. These results were also replicated in the GAM. Stratification analysis showed that greater than 50 percentile concentration of mercury in late pregnancy potentiated the adverse effects of lead in late pregnancy on MDI [β = -4.33 (-7.66, -1.00)] and psychomotor development index (PDI) [β = -5.30 (-9.13, -1.46)] at 6 months of age. Prenatal cadmium exposure did not show a significant association with MDI and PDI at 6 months in the linear regression or BKMR analysis.

CONCLUSION

Based on all the statistical methods used, we demonstrated the effect of combined exposure to metals on the neurodevelopment of infants aged 6 months, with significant interaction between lead and mercury.

Combined effects of multiple prenatal exposure to pollutants on birth weight: The Mothers and Children's Environmental Health (MOCEH) study

BACKGROUND

Increasing evidence shows that prenatal environmental exposures is a risk factor for restricted intrauterine growth. However, only a few studies have examined the effects of multiple environmental exposures on fetal growth.

OBJECTIVE

To investigate the effects of prenatal exposure on multiple environmental pollutants (heavy metals, bisphenol, phthalates, and air pollutants) on birth weight.

METHODS

The Mothers and Children's Environmental Health study is a prospective birth cohort comprising a total of 719 mother-child pairs, including 466 pairs undergoing early pregnancy exposure and 542 pairs of late pregnancy exposure. The concentrations of three heavy metals (mercury, lead, and cadmium) in the maternal blood samples were measured. The concentrations of three phthalate metabolites [mono(2-ethyl-5-hydroxyhexyl) phthalate, mono(2-ethyl-5-oxohexyl) phthalate, and mono-n-butyl phthalate] and bisphenol A in maternal urine samples were measured. Daily exposure to ambient particulate matter (PM10) and nitrogen dioxide (NO2) exposure was estimated based on residence and averaged by gestational age. To assess the combined effect of multiple pollutants, principal components analysis (PCA) and supervised principal components analysis (SCPA) were conducted.

RESULTS

Based on PCA, the components representing PM10 and NO2 exposure during early pregnancy were significantly associated with birth weight of -32.68 g (95% CI: -64.45 g to -0.91 g) per unit increase of the corresponding component. In SCPA model, the components representing NO2 exposure during early pregnancy and the combined exposure to mercury and lead during late pregnancy were negatively associated with birth weight of -46.63 g (95% CI: -90.65 g to -2.62 g) and -55.32 g (95% CI: -99.01 g to -11.64 g), respectively, per unit increase of the corresponding component.

CONCLUSION

Based on our multi-pollutant model, PM10 and NO2 exposure in early pregnancy and the combined effect of Pb and Hg in late pregnancy were associated with reduced birth weight. Our results suggest that exposure to various pollutants during pregnancy has a significant cumulative effect on birth weight, even if each pollutant is at a level below the concentration required for direct effect.

Health effect research on Hebei Spirit Oil Spill (HEROS) in Korea: a cohort profile

PURPOSE

The Hebei Spirit Oil Spill occurred on 7 December 2007 and resulted in the spillage of 12 547 kl of crude oil on the coastline near Taean. Historically, this was the largest oil spill in Korean water. The health effect research on Hebei Spirit Oil Spill (HEROS) is a prospective cohort study that aimed to evaluate the long-term health effects of oil spill exposure on residents in the affected community.

PARTICIPANTS

The Taean Environmental Health Center initially enrolled adults, adolescents and children living in Taean in 2009 and 2010. Follow-up surveys of participating adults and children were conducted every other year. By 2017, a total of 9585 adults and 2216 children and adolescents were enrolled. Of these, 294 adults and 102 children and adolescents were included in all subsequent surveys.

FINDINGS TO DATE

Children who lived closer to the oil spill site exhibited a lower level of pulmonary function and higher prevalence of allergic rhinitis, than those who lived further away from the oil spill site. Adults who lived in a highly exposed area or participated in clean-up work had higher urine levels of the oxidative stress biomarkers malondialdehyde and 8-hydroxydeoxyguanosine. Changes in haematological parameters during a 3-year period were observed in residents of both sexes in highly exposed areas, in addition to increases in respiratory diseases and mental health problems in female and male participants, respectively.

FUTURE PLANS

The findings of this study will better enable policy makers to develop environmental health policies intended to prevent adverse health effects in residents of communities affected by oil spills, as well as policies regarding the management of future oil accidents. The HEROS study will continue to follow participants in future and will be updated to enable an investigation of long-term health effects.

Associations of Maternal Cell-Phone Use During Pregnancy With Pregnancy Duration and Fetal Growth in 4 Birth Cohorts

Results from studies evaluating potential effects of prenatal exposure to radio-frequency electromagnetic fields from cell phones on birth outcomes have been inconsistent. Using data on 55,507 pregnant women and their children from Denmark (1996-2002), the Netherlands (2003-2004), Spain (2003-2008), and South Korea (2006-2011), we explored whether maternal cell-phone use was associated with pregnancy duration and fetal growth. On the basis of self-reported number of cell-phone calls per day, exposure was grouped as none, low (referent), intermediate, or high. We examined pregnancy duration (gestational age at birth, preterm/postterm birth), fetal growth (birth weight ratio, small/large size for gestational age), and birth weight variables (birth weight, low/high birth weight) and meta-analyzed cohort-specific estimates. The intermediate exposure group had a higher risk of giving birth at a lower gestational age (hazard ratio = 1.04, 95% confidence interval: 1.01, 1.07), and exposure-response relationships were found for shorter pregnancy duration (P < 0.001) and preterm birth (P = 0.003). We observed no association with fetal growth or birth weight. Maternal cell-phone use during pregnancy may be associated with shorter pregnancy duration and increased risk of preterm birth, but these results should be interpreted with caution, since they may reflect stress during pregnancy or other residual confounding rather than a direct effect of cell-phone exposure.

Cohort profile: Beyond birth cohort study - The Korean CHildren's ENvironmental health Study (Ko-CHENS)

The Korean CHildren's ENvironmental health Study (Ko-CHENS) is a nationwide prospective birth cohort showing the correlation between the environmental exposures and the health effects to prevent the environmental diseases in children, and it provides the guidelines for the environmental hazardous factors, applying the life-course approach to the environmental-health management system. The Ko-CHENS consists of 5000 Core and 65,000 Main Cohorts. The children in the Core Cohort are followed up at 6 months, every year before their admission into the elementary school, and every 3 years from the first year after this admission. The children in the Cohort will be followed up through the data links (Statistics Korea, National Health Insurance Service [NHIS], and Ministry of Education). The individual biospecimens will be analyzed for 19 substances. The long-term-storage biological samples will be used for the further substance analysis. The Ko-CHENS will investigate whether the environmental variables including the perinatal outdoor and indoor factors and the greenness contribute causally to the health outcomes in the children and adolescents. In addition to the individual surveys, the assessments of the outdoor exposures and health outcomes will use the national air-quality monitoring data and claim data of the NHIS, respectively. The two big-data forms of the Ko-CHENS are as follows: The Ko-CHENS data that can be linked with the nationally registered NHIS health-related database, including the medical utilization and the periodic health screening, and the birth/mortality database in the Statistics; the other is the Big-CHENS dataset that is based on the NHIS mother delivery code, for which the follow-up of almost 97% of the total birth population is expected. The Ko-CHENS is a very cost-effective study that fully exploits the existing national big-data systems with the data linkage.

Exposure to prenatal secondhand smoke and early neurodevelopment: Mothers and Children's Environmental Health (MOCEH) study

BACKGROUND

The association between exposure to secondhand smoke (SHS) during pregnancy and a child's neurodevelopment has not been established yet. We explored the association between prenatal exposure to SHS and neurodevelopment at 24 months of age considering genetic polymorphism and breastfeeding in 720 mothers and their offspring enrolled in the Korean multicenter birth cohort study (Mothers and Children Environmental Health, MOCEH).

METHODS

We quantified urine cotinine concentrations in mothers once from 12th to 20th gestational weeks and excluded those whose urine cotinine levels exceeded 42.7 ng/ml to represent SHS exposure in early pregnancy. Mental developmental index (MDI) and psychomotor developmental index (PDI) values were measured using the Korean version of the Bayley Scales of Infant Development II (K-BSID-II) at 24 months of age. A general linear model was used to assess the relationship between maternal urinary cotinine level and neurodevelopment.

RESULTS

MDI scores were inversely associated with cotinine [β = - 2.73; 95% confidence interval (CI): - 5.32 to - 0.15] in children whose mothers had early pregnancy urinary cotinine levels >1.90 ng/ml. No association was evident in children whose mothers had cotinine levels ≤1.90 ng/ml. This negative association was more pronounced in children whose mothers had both Glutathione S-transferases mu 1 (GSTM1) and theta 1 (GSTT1) null type [β = - 5.78; 95% CI: -10.69 to - 0.87], but not in children whose mothers had any present type of GSTM1/GSTT1 [β = - 1.64; 95% CI: -4.79 to 1.52]. The association was no longer significant when children received breast milk exclusively for up to 6 months [β = - 0.24; 95% CI: -4.69 to 4.20] compared to others [β = - 3.75; 95% CI: -7.51 to 0.00]. No significant association was found for PDI.

CONCLUSIONS

Maternal exposure to SHS during pregnancy may result in delayed MDI in early childhood. This effect might be modified by genetic polymorphism and breastfeeding behavior.

Maternal fruit and vegetable or vitamin C consumption during pregnancy is associated with fetal growth and infant growth up to 6 months: results from the Korean Mothers and Children's Environmental Health (MOCEH) cohort study

Background

Based on data obtained from pregnant women who participated in the Mothers and Children’s Environmental Health (MOCEH) study in South Korea, we aimed to determine whether maternal intake of fruits and vegetables or vitamin C is associated with fetal and infant growth.

Methods

A total of 1138 Korean pregnant women at 12–28 weeks gestation with their infants were recruited as study participants for the MOCEH. Intake of fruits and vegetables or vitamin C during pregnancy was assessed by a 1-day 24-h recall method. Fetal biometry was determined by ultrasonography at late pregnancy. Infant weight and length were measured at birth and 6 months.

Results

A multiple regression analysis after adjusting for covariates showed that maternal intake of fruits and vegetables was positively associated with the biparietal diameter of the fetus and infant’s weight from birth to 6 months. Also, maternal vitamin C intake was positively associated with the abdominal circumference of the fetus and infant birth length. In addition, there was a significant inverse relationship between consumption of fruits and vegetables (below the median compared to above the median of ≥519 g/d) and the risk of low growth (<25th percentile) of biparietal diameter (odds ratio (OR): 2.220; 95% confidence interval (CI): 1.153–4.274) and birth weight (OR: 1.434; 95% CI: 1.001–2.056). A significant inverse relationship also existed between vitamin C consumption (below vs above the estimated average requirement (EAR) of ≥85 mg/d) and the risk of low growth (<25th percentile) of birth weight (OR: 1.470; 95% CI: 1.011–2.139), weight from birth to 6 months (OR: 1.520; 95% CI: 1.066–2.165), and length at birth (OR: 1.579; 95% CI: 1.104–2.258).

Conclusions

An increased intake of fruits and vegetables or vitamin C at mid-pregnancy is associated with increased fetal growth and infant growth up to 6 months of age.

Maternal cell phone use during pregnancy and child cognition at age 5 years in 3 birth cohorts

BACKGROUND

There have been few studies of children's cognitive development in relation to mothers' cell phone use, and most were limited to outcomes at age 3 years or younger. We examined the relationship between maternal cell phone use during pregnancy and cognitive performance in 5-year old children.

METHODS

This study included data from 3 birth cohorts: the Danish National Birth Cohort (DNBC) (n = 1209), Spanish Environment and Childhood Project (INMA) (n = 1383), and Korean Mothers and Children's Environment Health Study (MOCEH) (n = 497). All cohorts collected information about maternal cell phone use during pregnancy and cognitive performance in children at age 5. We performed linear regression to compute mean differences (MD) and 95% confidence intervals (CI) in children's general, verbal, and non-verbal cognition scores comparing frequency of maternal prenatal cell phone use with adjustments for numerous potential confounding factors. Models were computed separately for each cohort and using pooled data in meta-analysis.

RESULTS

No associations were detected between frequency of prenatal cell phone use and children's cognition scores. Scores tended to be lower in the highest frequency of use category; MD (95% CI) in general cognition scores were 0.78 (-0.76, 2.33) for none, 0.11 (-0.81, 1.03) for medium, and -0.41 (-1.54, 0.73) for high compared to low frequency of use. This pattern was seen across all cognitive dimensions, but the results were imprecise overall.

CONCLUSION

We observed patterns of lower mean cognition scores among children in relation to high frequency maternal prenatal cell phone use. The causal nature and mechanism of this relationship remain unknown.

Occurrence of 44 elements in human cord blood and their association with growth indicators in newborns

There is growing concern about environmental pollution produced by elements, including "emerging" contaminants, such as rare earth elements (REE) and other trace elements (TE), which are extensively and increasingly employed in the manufacture of consumer electronics. Previous research has shown that prenatal exposure to some elements (mainly heavy metals) may be associated with decreased fetal growth and other adverse birth outcomes. Recent studies have also shown that environmental exposure to REE and TE may be related to adverse effects on human health. This cross-sectional study, which included nearly 92% of the births in 2016 in La Palma (Canary Islands, Spain; n = 471), aimed to evaluate the potential adverse health effects exerted by a wide range of elements on newborns. We quantified the levels of 44 elements (including 26 REE and TE) in their umbilical cord blood. Our results showed low or very low levels of most elements. We found an inverse association between antimony (Sb) and birth weight (Spearman's r = -0.106, p = 0.021). A similar trend was observed between nickel (Ni) and birth weight and between chromium (Cr) and birth length, although in this case the significance was borderline. Bismuth appeared as a risk factor for having a birth weight below the tenth percentile in the univariate (OR = 3.30; 95% CI = 1.25-8.78; p = 0.017) and multivariate analyses (OR = 5.20; 95% CI = 1.29-20.91; p = 0.020). When assessing the effect of element mixtures, the sum of Cr, Ni, and Sb appeared as a risk factor for having a birth weight below the tenth percentile in the univariate (OR = 2.41; 95% CI = 1.08-5.35; p = 0.031) and multivariate analyses (OR = 3.84; 95% CI = 1.42-10.39; p = 0.008). Our findings suggest that some inorganic elements-isolated or in mixture-are associated to a lower fetal growth. Additional research is needed to understand the role of inorganic pollutants on fetal development.

Assessment of radiofrequency electromagnetic field exposure from personal measurements considering the body shadowing effect in Korean children and parents

We aimed to assess the personal radiofrequency electromagnetic field (RF-EMF) exposure levels of children and adults through their activities, with consideration to the body shadowing effect. We recruited 50 child-adult pairs, living in Seoul, Cheonan, and Ulsan, South Korea. RF-EMF measurements were performed between September and December 2016, using a portable exposure meter tailored to capture 14 Korean radiofrequency (RF) bands ranging from 87.5 to 5875MHz. The participants carried the device for 48h and kept a time-activity diary using a smartphone application in flight mode. To enhance accuracy of the exposure assessment, the body shadowing effect was compensated during the statistical analysis with the measured RF-EMF exposure. The compensation was conducted using the hybrid model that represents the decrease of the exposure level due to the body shadowing effect. A generalized linear mixed model was used to compare the RF-EMF exposure levels by subjects and activities. The arithmetic (geometric) means of the total power density were 174.9 (36.6) μW/m² for all participants, 226.9 (44.6) for fathers, 245.4 (44.8) for mothers, and 116.2 (30.1) for children. By compensating for the body shadowing effect, the total RF-EMF exposure increased marginally, approximately 1.4 times. Each frequency band contribution to total RF-EMF exposure consisted of 76.7%, 2.4%, 9.9%, 5.0%, 3.3%, and 2.6% for downlink, uplink, WiFi, FM Radio, TV, and WiBro bands, respectively. Among the three regions, total RF-EMF exposure was highest in Seoul, and among the activities, it was highest in the metro, followed by foot/bicycle, bus/car, and outside. The contribution of base-station exposure to total RF-EMF exposure was the highest both in parents and children. Total and base-station RF-EMF exposure levels in Korea were higher than those reported in European countries.

Birth Cohort Consortium of Asia: Current and Future Perspectives

BACKGROUND

The environmental health of children is one of the great global health concerns. Exposures in utero and throughout development can have major consequences on later health. However, environmental risks or disease burdens vary from region to region. Birth cohort studies are ideal for investigating different environmental risks.

METHODS

The principal investigators of three birth cohorts in Asia including the Taiwan Birth Panel Study (TBPS), the Mothers and Children's Environmental Health Study (MOCEH), and the Hokkaido Study on Environment and Children' Health (Hokkaido Study) coestablished the Birth Cohort Consortium of Asia (BiCCA) in 2011. Through a series of five PI meetings, the enrolment criteria, aim of the consortium, and a first-phase inventory were confirmed.

RESULTS

To date, 23 birth cohorts have been established in 10 Asian countries, consisting of approximately 70,000 study subjects in the BiCCA. This article provides the study framework, environmental exposure and health outcome assessments, as well as maternal and infant characteristics of the participating cohorts.

CONCLUSIONS

The BiCCA provides a unique and reliable source of birth cohort information in Asian countries. Further scientific cooperation is ongoing to identify specific regional environmental threats and improve the health of children in Asia.

Association of maternal omega-6 fatty acid intake with infant birth outcomes: Korean Mothers and Children's Environmental Health (MOCEH)

Background

Maternal fatty acids (FAs) intake has an effect on birth weight, birth length, and gestational age, as fetal development is entirely dependent on the maternal essential FA supply. This study aimed to identify the association between the maternal intake of FAs and birth outcomes among pregnant women who participated in the Mothers and Children’s Environmental Health (MOCEH) prospective cohort study in South Korea.

Methods

A total of 1407 pregnant women, aged 30.2 ± 3.7 years, at 12 to 28 weeks’ gestation were recruited between August 2006 and December 2010. Their dietary intake during pregnancy was investigated by the 1-day 24-h dietary recall method. The pregnancy outcome data—namely infant’s gestational age, birth weight, and birth length—were analyzed for their associations with their mothers’ intake of FAs.

Results

When adjusted for confounding factors, multiple regression analysis revealed adverse effects on birth weight (P = 0.031) and birth length (P = 0.025) with high maternal intake of omega-6 FAs. In the multiple logistic regression analysis, the odds ratio (OR) for the risk of being below the 10th percentile for birth weight was higher in the highest quintile (Q5) compared to the lowest quintile (Q1) of omega-6 FA intake levels (OR = 2.444; 95% CI = 1.038–5.751; P for trend = 0.010). Also, the OR for being above the 90th percentile of birth length was lower in the highest quintile (Q5) compared to that in the lowest quintile (Q1) of omega-6 FA intake (OR = 0.432; 95% CI = 0.211–0.884; P for trend = 0.020). However, the maternal intake of omega-3 FAs was not related to gestational age, birth weight, or birth length.

Conclusions

A high maternal omega-6 FA intake was negatively associated with birth weight and birth length.

Air pollution exposure during pregnancy and ultrasound and birth measures of fetal growth: A prospective cohort study in Korea

Few studies have examined the effects of air pollution on fetal growth based on ultrasound measures during pregnancy. More data is needed to evaluate the windows of special vulnerability. Our aim was to investigate the association of ambient air pollution during pregnancy with fetal and neonatal characteristics in a cohort of Korean women. Maternal exposure to particulate matter with an aerodynamic diameter<10μm (PM₁₀) and nitrogen dioxide (NO₂) was estimated using land-use regression models based on residential address. The biparietal diameter (BPD), abdominal circumference (AC), femur length (FL), and estimated fetal weight (EFW) were evaluated via ultrasonography, and birth weight (BW), birth length (BL), and head circumference at birth (BHC) were obtained from medical records. The multiple linear regression model was used to adjust for confounders, and the mixed-effect model was used to evaluate longitudinal effect. The negative effects for NO₂ and PM₁₀ were estimated; in the adjusted analyses the decreases of BPD were -0.26mm (95% confidence interval [CI]=-0.41 to -0.11, with a 10μg/m³ increase) in the second trimester for NO₂, and -0.30mm (95% CI=-0.59 to -0.03, with a 10μg/m³ increase) in the third trimester for PM₁₀. Both NO₂ and PM₁₀ levels (10μg/m³) during third trimester were inversely associated with BHC, and NO₂ level was inversely associated with BL in all exposure windows. No significant associations for AC, FL, and EFW were observed. The longitudinal analyses showed inverse association of NO₂ exposure with head and length growth (P<0.001). Our findings suggest that ambient air pollution is associated with impaired fetal head size from mid-gestation onwards.

Associations between prenatal lead exposure and birth outcomes: Modification by sex and GSTM1/GSTT1 polymorphism

Maternal lead exposure is associated with poor birth outcomes. However, modifying effects of polymorphism in glutathione S-transferases (GST) gene and infant sex remain unexplored. Our aim was to evaluate whether associations between prenatal lead and birth outcomes differed by maternal GST genes and infant sex. Prospective data of 782 mother-child pairs from Mothers and Children's Environmental Health (MOCEH) study were used. The genotyping of GST-mu 1 (GSTM1) and theta-1 (GSTT1) polymorphisms was carried out using polymerase chain reaction. Multivariable linear regression was used to examine whether the association between blood lead (BPb) level and birth outcomes (birthweight, length, and head circumference) varied by maternal GST genes and sex. We did not find a statistically significant association between prenatal BPb levels and birth outcomes; in stratified analyses, the association between higher BPb level during early pregnancy and lower birthweight (β=-224 per square root increase in BPb; 95% confidence interval (CI): -426, -21; false discovery rate p=0.036) was significant in males of mothers with GSTM1 null. Results were similar for head circumference model (β=-0.78 per square root increase in BPb; 95% CI: -1.69, 0.14, p=0.095), but the level of significance was borderline. Head circumference model showed a significant three-way interaction among BPb during early pregnancy, GSTM1, and sex (p=0.046). For combined analysis with GSTM1 and GSTT1, GSTM1 null and GSTT1 present group showed a significant inverse association of BPb with birthweight and head circumference in males. Our findings of the most evident effects of BPb on the reduced birthweight and head circumference in male born to the mother with GSTM1 null may suggest a biological interaction among lead, GST genes and sex in detoxification process during fetal development.

Sex-Dependent Effects of Developmental Lead Exposure on the Brain

The role of sex as an effect modifier of developmental lead (Pb) exposure has until recently received little attention. Lead exposure in early life can affect brain development with persisting influences on cognitive and behavioral functioning, as well as, elevated risks for developing a variety of diseases and disorders in later life. Although both sexes are affected by Pb exposure, the incidence, manifestation, and severity of outcomes appears to differ in males and females. Results from epidemiologic and animal studies indicate significant effect modification by sex, however, the results are not consistent across studies. Unfortunately, only a limited number of human epidemiological studies have included both sexes in independent outcome analyses limiting our ability to draw definitive conclusions regarding sex-differentiated outcomes. Additionally, due to various methodological differences across studies, there is still not a good mechanistic understanding of the molecular effects of lead on the brain and the factors that influence differential responses to Pb based on sex. In this review, focused on prenatal and postnatal Pb exposures in humans and animal models, we discuss current literature supporting sex differences in outcomes in response to Pb exposure and explore some of the ideas regarding potential molecular mechanisms that may contribute to sex-related differences in outcomes from developmental Pb exposure. The sex-dependent variability in outcomes from developmental Pb exposure may arise from a combination of complex factors, including, but not limited to, intrinsic sex-specific molecular/genetic mechanisms and external risk factors including sex-specific responses to environmental stressors which may act through shared epigenetic pathways to influence the genome and behavioral output.

Prenatal TVOCs exposure negatively influences postnatal neurobehavioral development

Prenatal exposure to volatile organic compounds may restrict fetal development and adversely influence infants' life. Therefore, we investigated the relationship between prenatal exposure to total volatile organic compounds (TVOC) and postnatal neurobehavioral development. A subsample of 383 pregnant participants was chosen from the prospective birth cohort study of Mother and Children's Environmental Health Study; MOCEH (N=1,751) from three regions of the Republic of Korea (Seoul, Cheon-an, and Ulsan). Participants were enrolled during their first trimester with informed consent. We investigated maternal characteristics including socio-economic and obstetrical history using questionnaires. An environmental hygienist measured participating mothers' personal TVOC exposure using passive samplers during pregnancy. Participants visited the research center at 6, 12, 24 and 36 months. At each visit, questionnaires about infantile environment and health conditions were answered and a neurobehavioral test (BSID-II) was conducted by certified investigators. We conducted multiple general linear and mixed model analyses to investigate the relationship between TVOC and infantile neurobehavioral development (SAS 9.3). Mean prenatal TVOC exposure was 284.2μg/m³. In longitudinal analyses on infantile neurobehavioral development, adjusted mean psychomotor development index and mental developmental index scores in high TVOC exposure group (cut off at Q3: 374.0 ug/m3) were 3 points lower than the low exposure group. Results suggested exposure to higher TVOC during the fetal period may adversely influence neurobehavioral development in the early life stage.

Prenatal mercury exposure, fish intake and neurocognitive development during first three years of life: Prospective cohort mothers and Children's environmental health (MOCEH) study

OBJECTIVES

In this prospective cohort study, the effects of prenatal Hg exposure on neurocognitive development during the first 3years of life were investigated.

METHODS

The maternal blood levels of Hg were assessed during pregnancy and in cord blood. Maternal fish intake was assessed by interviewing the weekly frequency of fish intake during pregnancy. Maternal n-3 and n-6 fatty acid intake was estimated based on 24h recall food intake interview. The mental (MDI) and psychomotor (PDI) development index scores were assessed using the Bayley Scales of Infant Development at 6, 12, 24, 36months of age.

RESULTS

The geometric mean of the maternal blood Hg concentration was 3.3μg/L (10th percentile=1.81; 90th=5.91) during the early pregnancy, 3.0μg/L (10th=1.68; 90th=5.57) during late pregnancy, and 5.1μg/L (10th=2.94; 90th=8.93) in cord blood. After adjusting for weekly frequency of fish intake, the blood Hg concentrations during early pregnancy showed association with the adjusted MDI (β=-0.408, p=0.048) and PDI scores (β=-0.550, p=0.031) at 6months. After further adjusting for n-3 and n-6 fatty acids estimated based on 24h recall of food intake, the blood Hg concentrations during early pregnancy showed association with the MDI (β=-0.489, p=0.026) and PDI (β=-0.664, p=0.015) at 6months.

CONCLUSION

These results show that prenatal Hg exposure during early pregnancy adversely associated with early neurodevelopment during infancy, after adjusting for fish and n-3, n-6 fatty acid intake. Consuming fish high in fatty acids and low in Hg during early pregnancy may be important to neurocognitive development at early infancy.

Gender difference in the effects of lead exposure at different time windows on neurobehavioral development in 5-year-old children

BACKGROUND

Although the association between lead exposure and children's neurodevelopment has been studied, gender differences remain to be investigated. We examined the effects of lead exposure on the neurobehavioral development of 5-year-old children to identify the vulnerable time window of exposure and potential gender difference.

METHOD

A total of 1751 pregnant women and children participated in the prospective birth cohort study, Mothers and Children's Environmental Health study, since 2006. Lead levels were measured in the maternal blood in early and late pregnancies, in cord blood at birth, and in 2-, 3-, and 5-year-old children's blood. The behavior of 575 children aged 5years were assessed using the Korean Child Behavior Checklist. The association between the blood lead level at each time window and behavior was examined using a generalized linear model adjusted for potential confounders and covariates.

RESULTS

Lead levels at late pregnancy were significantly associated with increased risk of behavioral problems in males. Lead levels in 2- and 5-year-old children's blood significantly increased behavioral risks in females: for a 1-μg/dL increase in blood lead levels, the score for total behavioral problems increased by 3.00 (95% confidence interval [CI]: 0.56-5.45) during the late pregnancy in males, whereas it increased by 3.82 (95% CI: 1.25-6.39) at 2years and by 5.72 (95% CI: 0.44-10.99) at 5years in females with a stronger effect in attention and sleep problems.

CONCLUSION

Effects of lead toxicity on children's neurobehavioral development showed gender differences. Males were more susceptible to prenatal exposure, while females were more susceptible to postnatal exposure with stronger effects in attention and sleep problems.

Birth cohorts in Asia: The importance, advantages, and disadvantages of different-sized cohorts

Asia contains half of the world's children, and the countries of Asia are the most rapidly industrializing nations on the globe. Environmental threats to the health of children in Asia are myriad. Several birth cohorts were started in Asia in early 2000, and currently more than 30 cohorts in 13 countries have been established for study. Cohorts can contain from approximately 100-200 to 20,000-30,000 participants. Furthermore, national cohorts targeting over 100,000 participants have been launched in Japan and Korea. The aim of this manuscript is to discuss the importance of Asian cohorts, and the advantages and disadvantages of different-sized cohorts. As for case, one small-sized (n=514) cohort indicate that even relatively low level exposure to dioxin in utero could alter birth size, neurodevelopment, and immune and hormonal functions. Several Asian cohorts focus prenatal exposure to perfluoroalkyo substances and reported associations with birth size, thyroid hormone levels, allergies and neurodevelopment. Inconsistent findings may possibly be explained by the differences in exposure levels and target chemicals, and by possible statistical errors. In a smaller cohort, novel hypotheses or preliminary examinations are more easily verifiable. In larger cohorts, the etiology of rare diseases, such as birth defects, can be analyzed; however, they require a large cost and significant human resources. Therefore, conducting studies in only one large cohort may not always be the best strategy. International collaborations, such as the Birth Cohort Consortium of Asia, would cover the inherent limitation of sample size in addition to heterogeneity of exposure, ethnicity, and socioeconomic conditions.

Prenatal Bisphenol-A exposure affects fetal length growth by maternal glutathione transferase polymorphisms, and neonatal exposure affects child volume growth by sex: From multiregional prospective birth cohort MOCEH study

We aimed to evaluate the effects of Bisphenol-A (BPA) exposure on fetal/child growth from the fetal period to 72months after birth. The MOCEH study is a prospective birth cohort study in Korea. A total of 788 mother-child pairs in the third trimester and 366 pairs in the neonatal period who completed BPA assessment and fetal/children growth outcomes were included. BPA assessments were conducted twice in the third trimester using maternal urines and the neonatal period using neonatal urines. Fetal femur length was measured with ultrasound, and estimated-fetal-weight was calculated. Child growth outcomes including three z-scores for age-specific length, weight-for-length (WFL) and weight were calculated. Analysis was performed according to infant sex and maternal glutathione transferases (GSTs) polymorphisms. When maternal urinary BPA concentration in the third trimester increased by 1 log-transformed unit of BPA/Cr, the third trimester femur length decreased 0.03(0.01)cm in the whole and 0.06(0.02)cm in the GSTM1/GSTT1 either null group. Then, maternal urinary BPA levels and birth outcomes were positively correlated. When the prenatal BPA concentration is increased by 1 log-transformed unit of BPA/Cr, the z-score for weight at birth increased 0.05(0.02) in whole and 0.06(0.03) in boys and the z-score for WFL at birth increased 0.05(0.02) in whole and 0.07(0.03) in girls. In linear mixed models, significant positive effects of the neonatal urinary BPA were found on WFL over the 72months period. When the neonatal BPA concentration is increased by 1 log-transformed unit of BPA concentration, the z-score for weight through 6-72months increased 0.09(0.03) in whole and 0.12(0.05) in girls. Our study suggests BPA exposure is negatively associated with intrauterine linear growth, but has a positive association with volume growth during childhood. Furthermore, intrauterine growth was affected by maternal GSTs polymorphism, and child growth was affected by sex.

Preventive Effect of Residential Green Space on Infantile Atopic Dermatitis Associated with Prenatal Air Pollution Exposure

Few birth cohort studies have examined the role of traffic-related air pollution (TRAP) in the development of infantile atopic dermatitis (AD), but none have investigated the role of preventive factors such as green spaces. The aim of this study was to investigate whether exposure to nitrogen dioxide (NO₂) and particulate matter with an aerodynamic diameter of <10 μm (PM₁₀) during pregnancy is associated with increased risk of development of AD in 6-month-old children and also to examine how this association changes with residential green space. This study used prospective data from 659 participants of the Mothers and Children's Environmental Health study. Subjects were geocoded to their residential addresses and matched with air pollution data modeled using land-use regression. Information on infantile AD was obtained by using a questionnaire administered to the parents or guardians of the children. The association between infantile AD and exposure to NO₂ and PM₁₀ was determined using logistic regression models. We assessed the effects of residential green spaces using stratified analyses and by entering product terms into the logistic regression models. The risk of infantile AD significantly increased with an increase in air pollution exposure during the first trimester of pregnancy. The adjusted odds ratio (OR) and 95% confidence interval (CI) were 1.219 (1.023-1.452) per 10 μg/m³ increase in PM₁₀ and 1.353 (1.027-1.782) per 10 ppb increase in NO₂. An increase in the green space within 200 m of residence was associated with a decreased risk of AD (OR = 0.996, 95% CI: 0.993-0.999). The stratified analysis of residential green space revealed stronger associations between infantile AD and PM₁₀ and NO₂ exposure during the first trimester in the areas in the lower tertiles of green space. This study indicated that exposure to TRAP during the first trimester of pregnancy is associated with infantile AD. Less residential green space may intensify the association between TRAP exposure and infantile AD.

Stability of cognitive development during the first five years of life in relation to heavy metal concentrations in umbilical cord blood: Mothers' and Children's Environmental Health (MOCEH) birth cohort study

The objective of this study was to investigate stability of cognitive development during the first five years of life in relation to heavy metal concentrations in umbilical cord blood in Korean children. This research is part of the Mothers' and Children's Environmental Health (MOCEH) study, a multi-center prospective birth cohort study of pregnant women in Korea who were recruited from 2006 to 2010. We analyzed the complete follow-up data of children who were 5years-old in 2016. We measured lead, mercury, and cadmium levels in the umbilical cord blood of 251 children, and analyzed them, for whom neurodevelopmental data were available. We determined stability of cognitive development scores using three methods. First, we used partial correlation analyses to examine the stability of cognitive development at each measurement time. Second, we used Cramer's V to investigate the magnitude and direction of changes in cognitive development scores at each follow-up period among three groups (high, medium, and low scores). The results showed that cognitive development scores measured at the closest times had the strongest correlations, and the stability of cognitive development scores increased with age, from 6 to 60months. Groups at the extreme ends of cognitive development (high or low scores) had more stable scores, and this tendency was also stronger in infants >24months-old. The stability of cognitive development was unrelated to the umbilical cord level of heavy metals, based on analysis with Fisher's transformation. In conclusion, the present study showed that the cognitive development scores in a cohort of infants (6 to 60months-old) were stable.

Path analysis of prenatal mercury levels and birth weights in Korean and Taiwanese birth cohorts

Prospective cohort studies of the effect of mercury (Hg) exposure on birth weight have shown conflicting results. We combined data from Taiwanese and Korean birth cohorts, and assessed the effects of Hg exposure on birth weight. The first cohort was drawn from the Mothers and Children's Environmental Health (MOCEH) study performed in Korea from 2006 to 2010. The second cohort was enrolled from 2004 to 2005 and included singleton term births from the Taiwan Birth Panel Study (TBPS). In total, 1147 pregnant women were included in this study. A pooled analysis was performed to obtain combined estimates of the association between prenatal total Hg exposure and birth weight. A significant negative association between maternal and cord blood Hg and birth weight in the high-Hg group (Hg level>25th percentile) was detected (maternal blood: β=-0.056; 95% CI, -0.100 to -0.013, cord blood: β=-0.075; 95% CI, -0.121 to -0.028). Hg level showed a negative coefficient in the path analysis, indicating an adverse effect on birth weight (total effects: β=-0.177, P=0.01 in MOCEH, β=-0.204, P=0.03 in TBPS), but fish consumption exhibited a strong positive coefficient. In addition, fish consumption exerted a significant indirect effect on birth weight through exposure to cord blood Hg. Exposure to hazardous contaminants and beneficial nutrients may be highly correlated in those who frequently consume fish. Moreover, Hg in cord blood may adversely affect birth weight.

Blood heavy metal concentrations in pregnant Korean women and their children up to age 5years: Mothers' and Children's Environmental Health (MOCEH) birth cohort study

The present study assessed the associations of heavy metal concentrations in pregnant women with the concentrations in their children during early childhood. This study is a part of the Mothers' and Children's Environmental Health (MOCEH) study, a Korean multi-center prospective birth cohort study of 1751 pregnant women who were recruited from 2006 to 2010. We completed the follow-up of children who were 5years-old in 2016. Lead, total mercury, and cadmium were measured in women during early and late pregnancy, in cord blood, and in children who were 2, 3, and 5years-old. Lead concentration was lowest in cord blood, highest in 24month-old children, and then decreased with child age. Total mercury concentration was highest in cord blood, and gradually decreased with child age. Cadmium concentration was lowest in cord blood, and increased with child age. After adjusting for child sex, maternal age, and maternal education level, we found strong correlations between the levels of lead and total mercury in women during late pregnancy with the levels in cord blood; however, there were weak correlations between the levels of these metals in women during late pregnancy and cord blood with the levels in their children. In conclusion, maternal lead and mercury concentrations correlated with the levels in cord blood and in children up to age 60months. This correlation may be due to high trans-placental transmission of these metals and shared living environment such as environmental exposure, food consumption, and lifestyle.