Publications by authors named "Shoji Nakayama"

Environmental exposure to heavy metals is ubiquitous. However, its relationship with steroid hormone levels is not well understood, particularly in pregnant women. This study investigated the association between prenatal heavy metal exposure and steroid hormone levels in an e-waste disposal area in China.

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Article Synopsis
  • In 2022, the International Society of Exposure Science launched the HB2GV Dashboard, a free online tool that compiles approximately 600 human biomonitoring guidance values for over 150 chemicals to assist risk assessors and managers.
  • The Dashboard includes various types of guidance values, primarily focusing on Biomonitoring Equivalents and Human Biomonitoring values, but new users may struggle to understand how to interpret these values effectively.
  • A case study on di-(2-ethylhexyl) phthalate (DEHP) is presented to highlight the differences in derivation methods, quality, and confident interpretation of guidance values, emphasizing the importance of selecting appropriate HB2GVs for informed health-based decisions.
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Objective: To quantify the association between a combination of modifiable prepregnancy lifestyle factors and the risk of adverse pregnancy outcomes (APOs).

Design: Prospective cohort study.

Setting: The Japan Environment and Children's Study.

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Background: Long-term exposure to inorganic arsenic (InAs) through arsenic (As)-contaminated drinking water poses serious health risks. However, epidemiological studies focusing on low-level dietary exposure to InAs are lacking. Furthermore, although toenail clippings are used as biomarkers for assessing As exposure in areas with contaminated drinking water, to date, no method has been developed for using toenails as a biomarker of long-term InAs exposure in individuals with lower exposure levels, e.

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  • Exposure to low doses of neonicotinoid insecticides during pregnancy may negatively affect children's neurodevelopment, prompting researchers to investigate urinary biomarkers of exposure in pregnant women.
  • The study involved collecting urine samples from 30 non-smoking pregnant women in Japan over a two-week period, measuring concentrations of neonicotinoid metabolites using advanced mass spectrometry techniques.
  • Results indicated that while certain metabolites like N-desmethyl-acetamiprid showed moderate reproducibility as exposure biomarkers, other neonicotinoids displayed poor reproducibility, suggesting that multiple urine samples are needed for accurate assessments of overall exposure.
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Background: Dioxin is an environmental pollutant as well as an endocrine disruptor in humans. Our longitudinal study wants to clarify the relationship between dioxin exposure and endocrine disorders in children living in the Vietnamese dioxin hotspot.

Method: Seventeen congeners of polychlorinated dibenzo-p-dioxins/polychlorinated dibenzo-furans (PCDDs/PCDFs) in maternal breast milk and seven serum steroid hormones in children of 43 and 46 mothers and their 9-year-old children from the non-exposure and the hotspot areas were measured, respectively.

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Despite numerous studies, the associations between per- and polyfluoroalkyl substances (PFAS) exposure and various lipid levels in pregnant women remain ambiguous, especially concerning the association with cord blood lipids. This analysis included 20,960 pregnant women enrolled in the Japan Environment and Children's Study, recruited between 2011 and 2014. Non-fasting plasma samples collected before 22 weeks of gestation were examined for PFAS concentrations.

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  • Maternal exposure to per- and polyfluoroalkyl substances (PFAS) during pregnancy may increase the risk of chromosomal abnormalities in offspring, based on recent experimental and epidemiological evidence.
  • A study using data from the Japan Environment and Children's Study found 44 cases of chromosomal abnormalities in over 24,000 births, with certain PFAS like PFNA and PFOS showing strong associations with these abnormalities.
  • The analysis indicated that a doubling of PFAS concentrations, particularly PFOS, was significantly linked to chromosomal issues, highlighting concerns about environmental exposure implications for fetal health.
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Background: Little is known about the relationship of healthy diets, which are widely recommended to prevent diseases in general populations, with the risk of hypertensive disorders of pregnancy (HDP), particular among non-Western populations with different dietary habits. We aimed to investigate the association between periconceptional diet quality and the risk of HDP among pregnant Japanese women.

Methods And Results: Dietary intake over 1 year before the first trimester of pregnancy was assessed using a validated, self-administered food frequency questionnaire among 81 113 pregnant Japanese women who participated in a prospective cohort of the Japan Environment and Children's Study.

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Per- and poly-fluoroalkyl substances (PFAS), which are long-lasting environmental contaminants that are released into the environment during the e-waste disassembly process, pose a threat to human health. Human milk is a complex and dynamic mixture of endogenous and exogenous substances, including steroid hormones and PFAS. Therefore, in this study, we aimed to investigate the association between PFAS and steroid hormones in human milk from women living close to an e-waste disassembly area.

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Background: High low-density lipoprotein cholesterol levels (LDL-C) during pregnancy have been associated with adverse pregnancy and offspring outcomes. While previous studies have suggested a potential link between organophosphate pesticide (OPP) exposure and higher LDL-C in the general population and agricultural workers, the relationship in pregnant women and the effect of body mass index on this relationship remain unclear. We examined the association between the urinary concentrations of OPP metabolites (dialkylphosphates) and blood lipid levels in pregnant women.

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Background: The developing brains are sensitive to methylmercury (MeHg). However, the exposure to MeHg in baby foods and toddler meals remains unknown. This study aimed to determine MeHg intake from baby food or toddler meals, and to investigate the relationship with child hair total mercury (THg).

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Humans are exposed to various bisphenols, alkylphenols and nitrophenols through dietary intake, food packaging and container materials, indoor and outdoor air/dust. This study aimed to evaluate exposure of Japanese pregnant women to environmental phenols by measuring target compounds in urine samples. From a cohort of the Japan Environment and Children's Study, 4577 pregnant women were selected.

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Environmental phenols are widely distributed in the environment and human samples, suggesting potential exposure to these chemicals. We designed an intervention trial with 30 participants over 6 days to assess the urinary concentrations and half-lives of environmental phenols in Japanese young people. The target environmental phenols include three parabens (methyl paraben, ethyl paraben, and propyl paraben), two benzophenones (benzophenone 1 and 3), two bisphenols (bisphenol F and bisphenol S), and triclosan.

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Article Synopsis
  • - Kawasaki disease (KD) is a common pediatric condition linked to future heart issues, but its causes are still unclear and may be related to PFAS, harmful substances found in various products.
  • - The study drew from a large birth cohort in Japan, monitoring over 25,000 children exposed to 28 types of PFAS during pregnancy to see if these chemicals affected KD risk by analyzing health outcomes until the children turned four.
  • - Results showed no significant relationship between PFAS exposure and KD incidence, with statistical analyses indicating a negative correlation between the PFAS mixture and KD occurrence, suggesting that PFAS may not increase KD risk.
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Electronic waste that has not been properly treated can lead to environmental contamination including of heavy metals, which can pose risks to human health. Infants, a sensitive group, are highly susceptible to heavy metals exposure. The aim of this study was to investigate the association between prenatal heavy metal exposure and infant birth outcomes in an e-waste recycling area in China.

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The effects of early-life exposure to per- and polyfluoroalkyl substances (PFAS) on the onset of asthma in children have been unclear. We examined the association between prenatal PFAS exposure and wheezing and asthma symptoms among 4-year-old children in a total of 17,856 mother-child pairs from the Japan Environment and Children's Study. Maternal first-trimester serum concentrations of six PFAS were used for the exposure assessment.

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Background: Recent studies have reported the effect of neonicotinoid (NEO) exposures on development in human. However, information about the risk of childhood development delays due to NEO exposures is limited.

Objectives: The study aimed to examine the association between NEO exposure and child development up to 4 years of age using data of the Japan Environment and Children's Study.

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Background: The role of prenatal diet on childhood wheezing and subsequent risk of asthma is inconclusive, which may be partly due to the heterogeneity in wheezing phenotypes. We aimed to identify wheeze trajectories in early childhood and to examine their associations with periconceptional maternal diet quality.

Methods: Data from 70,530 mother-child pairs of liveborn singletons from the Japan Environment and Children's Study were analysed.

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Seasonal variations of chemical compounds in indoor air and outdoor air and personal exposure to these chemicals were continuously monitored for 6 years using four types of passive sampling devices: PSD-BPE/DNPH packed with 2,4-dinitrophenylhydrazine and trans-1,2-bis(2-pyridyl)ethylene coated silica for ozone and carbonyls; PSD-VOC packed with Carboxen 572 or Active Carbon Beads particles for volatile organic compounds; PSD-TEA packed with triethanolamine impregnated silica for acid gases; and PSD-TEA packed with phosphoric acid impregnated silica for basic gases. Many chemical compounds except for nitrogen dioxide, formic acid, and benzene showed seasonal variations with high concentrations in summer and low concentrations in winter. In particular, formaldehyde, nonanal, 2-ethyl-1-hexanol, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, and ammonia concentrations showed remarkable seasonal variation.

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Background: Numerous studies suggest that sex steroids might play a role in sex disparity observed in allergic diseases in adults. However, whether sex hormones influence allergic diseases in children remains unclear. The aim of the present study was to examine the association of sex steroid hormones with allergic disease in Japanese children.

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As 3,3',5-triiodothyroacetic acid (TRIAC), a metabolite of thyroid hormones (THs), was previously detected in sewage effluent, we aimed to investigate exogenous TRIAC's potential for endocrine disruption. We administered either TRIAC or 3,3',5-triiodo-L-thyronine (LT3) to euthyroid mice and 6-propyl-2-thiouracil-induced hypothyroid mice. In hypothyroid mice, TRIAC administration suppressed the hypothalamus-pituitary-thyroid (HPT) axis and upregulated TH-responsive genes in the pituitary gland, the liver, and the heart.

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Article Synopsis
  • Prenatal exposure to heavy metals, especially mercury (Hg), may disrupt neurodevelopment and affect hormone levels in children, highlighting a risk in areas near electronic waste recycling in China.* -
  • The study analyzed human milk and serum steroid hormones in children at age four, finding a significant association between higher Hg levels and increased dehydroepiandrosterone (DHEA) concentrations.* -
  • Results suggest that while Hg may influence hormone levels, the effect is complex due to exposure to multiple metals, emphasizing the need for regulatory measures to mitigate heavy metal exposure.*
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A simultaneous, high-throughput and sensitive method for analysing nine neonicotinoid pesticides (NEOs) and four metabolites (NEOms) in urine using a liquid chromatography-tandem mass spectrometry (LC-MSMS) was developed. The method detection limit (MDL) and lowest concentration minimum reporting limit (LCMRL) of the nine NEOs were 0.0013-0.

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