Effect of pregnancy on the levels of urinary metals for females aged 17-39 years old: data from National Health and Nutrition Examination Survey 2003-2010

Exposure to heavy metals and trace elements among pregnant women with twins: levels and association with twin growth discordance

Background

Twin growth discordance is one of the leading causes of perinatal mortality in twin pregnancies. Whether prenatal exposure to heavy metals and trace elements is associated with twin growth discordance has not been studied yet.

Objective

To evaluate the prenatal level of heavy metals and trace elements in twin pregnancy and its relationship with twin growth discordance.

Methods

This study involving 60 twin pairs and their mothers was conducted in Zhejiang Province, China, in 2020-2021. The concentration of heavy metals and trace elements in maternal blood, umbilical cord, and placenta were collected at delivery and measured by inductively coupled plasma tandem mass spectrometer. The association of prenatal level with twin growth discordance was evaluated using conditional logistic regression.

Results

High levels of heavy metal elements (thallium in maternal blood and umbilical cord blood of larger twins, vanadium in the placenta of larger twins) and trace elements (iodine in the placenta of larger twins) during pregnancy, as well as low levels of heavy metal elements (strontium in the umbilical cord blood of larger twins, strontium and chromium in the umbilical cord blood of smaller twins, strontium in the placenta of larger twins, molybdenum and lead in the placenta of smaller twins and difference of molybdenum in the placenta of twins), are associated with intertwin birthweight discordance. Univariate regression analyses showed a significant effect of gestational age at delivery and eleven trace element data on intertwin birthweight discordance. Multivariable logistic regression analysis with transformed variables as dichotomous risk factors combined with baseline demographic characteristics showed Tl in maternal blood as an independent risk factor. The model constructed by combining Tl in maternal blood (OR = 54.833, 95% CI, 3.839-83.156) with the gestational week (OR = 0.618, 95% CI, 0.463-0.824) had good predictive power for intertwin birthweight discordance (AUC = 0.871). The sensitivity analysis results indicate that the effect of maternal blood thallium on intertwin birthweight discordance is stable and reliable.

Conclusion

To our knowledge, ours is the first case-control study to investigate the association between elevated maternal thallium levels before delivery and twin growth discordance.

Biomonitoring of inorganic arsenic species in pregnancy

Exposure assessment of inorganic arsenic is challenging due to the existence of multiple species, complexity of arsenic metabolism, and variety of exposure sources. Exposure assessment of arsenic during pregnancy is further complicated by the physiological changes that occur to support fetal growth. Given the well-established toxicity of inorganic arsenic at high concentrations, continued research into the potential health effects of low-level exposure on maternal and fetal health is necessary. Our objectives were to review the value of and challenges inherent in measuring inorganic arsenic species in pregnancy and highlight related research priorities. We discussed how the physiological changes of pregnancy influence arsenic metabolism and necessitate the need for pregnancy-specific data. We reviewed the biomonitoring challenges according to common and novel biological matrices and discussed how each matrix differs according to half-life, bioavailability, availability of laboratory methods, and interpretation within pregnancy. Exposure assessment in both established and novel matrices that accounts for the physiological changes of pregnancy and complexity of speciation is a research priority. Standardization of laboratory method for novel matrices will help address these data gaps. Research is particularly lacking in contemporary populations of pregnant women without naturally elevated arsenic drinking water concentrations (i.e. <10 µg/l).

Urinary fluoride levels and metal co-exposures among pregnant women in Los Angeles, California

BACKGROUND

Fluoride is ubiquitous in the United States (US); however, data on biomarkers and patterns of fluoride exposure among US pregnant women are scarce. We examined specific gravity adjusted maternal urinary fluoride (MUFsg) in relation to sociodemographic variables and metal co-exposures among pregnant women in Los Angeles, California.

METHODS

Participants were from the Maternal and Developmental Risks from Environmental and Social Stressors (MADRES) cohort. There were 293 and 490 women with MUFsg measured during first and third trimesters, respectively. An intra-class correlation coefficient examined consistency of MUFsg between trimesters. Kruskal-Wallis and Mann-Whitney U tests examined associations of MUFsg with sociodemographic variables. Covariate adjusted linear regression examined associations of MUFsg with blood metals and specific gravity adjusted urine metals among a subsample of participants within and between trimesters. A False Discovery Rate (FDR) correction accounted for multiple comparisons.

RESULTS

Median (IQR) MUFsg was 0.65 (0.5) mg/L and 0.8 (0.59) mg/L, during trimesters one and three respectively. During both trimesters, MUFsg was higher among older participants, those with higher income, and White, non-Hispanic participants than Hispanic participants. MUFsg was also higher for White, non-Hispanic participants than for Black, non-Hispanic participants in trimester three, and for those with graduate training in trimester one. MUFsg was negatively associated with blood mercury in trimester one and positively associated with blood lead in trimester three. MUFsg was positively associated with various urinary metals, including antimony, barium, cadmium, cobalt, copper, lead, nickel, tin, and zinc in trimesters one and/or three.

CONCLUSIONS

MUFsg levels observed were comparable to those found in pregnant women in Mexico and Canada that have been associated with poorer neurodevelopmental outcomes. Lower urinary fluoride levels among Hispanic and non-Hispanic Black participants in MADRES compared to non-Hispanic White participants may reflect lower tap water consumption or lower fluoride exposure from other sources. Additional research is needed to examine whether MUFsg levels observed among pregnant women in the US are associated with neurodevelopmental outcomes.

Effect of maternal thallium exposure in early pregnancy on the risk of preterm birth

Human activities have significantly increased the release of thallium (Tl) to the environment. However, the study of the relationship between maternal Tl exposure during pregnancy and the risk of preterm birth (PTB) is scarce so far. We aimed to investigate the association between Tl exposure in early pregnancy and the risk of PTB. A total of 2104 pregnant women from the Tongji Maternal and Child Health Cohort (TMCHC) in Wuhan, China were enrolled in the analysis. We collected the urine samples in early pregnancy (< 20 weeks) and inductively coupled plasma mass spectrometry (ICP-MS) was used to detect urinary Tl levels. The association between Tl levels and the risk of PTB was evaluated by an unconditional logistic regression. The median and geometric mean values of Tl levels were 0.35 μg/L (0.47 μg/g creatinine) and 0.33 μg/L (0.47 μg/g creatinine), respectively. Compared with the lowest tertile of Tl levels (≤ 0.37 μg/g creatinine), the highest tertile (> 0.57 μg/g creatinine) was associated with an increased risk of PTB with an adjusted odds ratio (OR) of 2.11 (95% confidence interval (CI): 1.08, 4.12). Stratified analyses showed an elevated risk of PTB related to the highest tertile of Tl levels for male newborns. After excluding women with miss covariate information, gestational diabetes mellitus, pregnancy-induced hypertension, reporting fish intake, or exposed to smoke, the association remained stable. Our results suggested that maternal Tl exposure during early pregnancy was positively associated with the risk of PTB, and Tl exposure may have a sex-specific effect on PTB.

Exposure to metals and metalloids among pregnant women from Spain: Levels and associated factors

BACKGROUND

Humans are regularly exposed to metals and metalloids present in air, water, food, soil and domestic materials. Most of them can cross the placental barrier and cause adverse impacts on the developing foetus.

OBJECTIVES

To describe the prenatal concentrations of metals and metalloids and to study the associated sociodemographic, environmental and dietary factors in pregnant Spanish women.

METHODS

Subjects were 1346 pregnant women of the INMA Project, for whom the following metals arsenic (As), cadmium (Cd), cobalt (Co), copper (Cu), molybdenum (Mo), nickel (Ni), lead (Pb), antimony (Sb), selenium (Se), thallium (Tl) and zinc (Zn) were determined in urine, at both the first and the third trimesters of gestation. Sociodemographic, dietary and environmental information was collected through questionnaires during pregnancy. Multiple linear mixed models were built in order to study the association between each metal and metalloid concentrations and the sociodemographic, environmental and dietary factors.

RESULTS

The most detected compounds were As, Co, Mo, Sb, Se and Zn at both trimesters. Zn was the element found in the highest concentrations at both trimesters and Tl was detected in the lowest concentrations. We observed significant associations between As, Cd, Cu, Sb, Tl and Zn concentrations and working situation, social class and age. Seafood, meat, fruits, nuts, vegetables and alcohol intake affected the levels of all the metals but Cd and Cu. Proximity to industrial areas, fields and air pollution were related to all metals except Cd, Sb and Se.

CONCLUSIONS

This is the first large prospective longitudinal study on the exposure to metals and metalloids during pregnancy and associated factors to include several cohorts in Spain. The present study shows that some modifiable lifestyles, food intakes and environmental factors could be associated with prenatal exposure to metal(loid)s, which may be considered in further studies to assess their relationship with neonatal health outcomes.

Health Risk Assessment of Exposure to 15 Essential and Toxic Elements in Spanish Women of Reproductive Age: A Case Study

This case study investigates the exposure of 119 Spanish women of reproductive age to 5 essential (Co, Cu, Mn, V, Zn) and 10 toxic (Ba, Be, Cs, Ni, Pb, Pt, Sb, Th, Al, U) elements and assesses their risk. The essential elements (Co, Cu, Mn, V, and Zn) showed average concentrations (GM: geometric mean) of 0.8, 35, 0.5, 0.2, and 347 μg/L, respectively. Five of the toxic elements (Ba, Cs, Ni, Al, U) exhibited detection frequencies of 100%. The GM concentrations of the novel toxic elements were 12 μg/L (Al), 0.01 μg/L (Pt), 0.02 μg/L (U), 0.12 μg/L (Th), 0.009 μg/L (Be) and 4 μg/L (Cs). The urine analysis was combined with a survey to assess any variations between subgroups and potential predictors of exposure to elements in the female population. Significant differences were obtained between the rural and urban areas studied for the toxic element Cs, with higher levels found in mothers living in urban areas. In relation to diet, statistically significantly higher levels of essential (Cu) and toxic (Ba) elements were detected in women with a high consumption of fish, while mothers who consumed a large quantity of legumes presented higher levels of the toxic element Ni (p = 0.0134). In a risk-assessment context, hazard quotients (HQs) greater than 1 were only observed for the essential elements Zn and Cu in P95. No deficiency was found regarding the only essential element for which a biomonitoring equivalent for nutritional deficit is available (Zn). For the less-studied toxic elements (Al, Pt, U, Th, Be, and Cs), HQs were lower than 1, and thus, the health risk due to exposure to these elements is expected to be low for the female population under study.

The Mediating Role of Placental Weight Change in the Association Between Prenatal Exposure to Thallium and Birth Weight: A Prospective Birth Cohort Study

Background: Previous studies have demonstrated the embryotoxicity and fetotoxicity of thallium (Tl). However, the effects of prenatal exposure to Tl on birth weight and placental weight and the mediating role of placental weight in the association of Tl with birth weight remain unclear.

Methods: We recruited 2,748 participants from the ongoing Prenatal Environment and Offspring Health Cohort (PEOH Cohort) study, which was initiated in 2016 in Guangzhou, China. The Tl concentrations in maternal urine samples collected during the first and third trimester were determined by inductively coupled plasma mass spectrometry. Birth weight and placental weight were extracted from maternal medical records.

Results: Pregnant women exposed to the highest tertile of Tl in the first trimester (β = −42.7 g, 95% CI: −82.3, −3.1 g) and third trimester (β = −50.6 g, 95% CI: −99.0, −2.3 g) had babies with lower birth weights than those exposed to the lowest tertile. We also found significant negative associations of exposure to Tl concentrations in the first and third trimester with placental weight. Mediation analyses showed that 50.3% (95% CI: 15.9, 79.2%) and 33.5% (95% CI: 1.3, 80.3%) of the effects of Tl exposure in the first and third trimester on birth weight were mediated by decreased placental weight.

Conclusion: Our results suggest that prenatal exposure to Tl is negatively associated with birth weight and that this association may be mediated by decreased placental weight.

Exposure and Risk Assessment of Hg, Cd, As, Tl, Se, and Mo in Women of Reproductive Age Using Urinary Biomonitoring

The present study analyzed the exposure and risk assessment of 4 toxic (Hg, Cd, As, Tl) and 2 essential (Se, Mo) elements in 119 Spanish women of reproductive age. The focus was on the elements for which risk-based benchmark, biomonitoring equivalents, or health-related human biomonitoring values have already been established. All elements presented frequencies of detection of 100% (greater than the limit of detection), except for Cd (99%). The 95th percentile concentrations were, for the toxic metals, 358.37 µg/L (total As), 1.10 µg/L (Cd), 0.41 µg/L (Tl), and 3.03 µg/L (total Hg) and, for the essential elements, 68.95 µg/L (total Se) and 154.67 (Mo). We examined sociodemographic factors and dietary habits of women as predictors of urinary metal concentrations. Arsenic was positively associated with fish, shellfish, and canned fish consumption, whereas Mo was found to be associated with the consumption of cereals and pastry products. Maternal urine levels of As were negatively correlated with gestational age. In a risk-assessment context, hazard quotients (HQs) using the 95th percentile ranged from 0.08 (Tl) to 15.1 (urinary speciated As), with Cd presenting an HQ of 1.1 (95th percentile). None of the essential metals presented concentrations higher than their upper intake level; however, 3% of the mothers showed lower levels of Se than the estimated average requirement (EAR) biomonitoring equivalent, and 20% of the mothers were found to have lower levels of Mo than the EAR biomonitoring equivalent, suggesting a nutritionally inadequate diet. Environ Toxicol Chem 2021;40:1477-1490. © 2021 SETAC.

Exposure to uranium and co-occurring metals among pregnant Navajo women

Navajo Nation residents are at risk for exposure to uranium and other co-occurring metals found in abandoned mine waste. The Navajo Birth Cohort Study (NBCS) was initiated in 2010 to address community concerns regarding the impact of chronic environmental exposure to metals on pregnancy and birth outcomes. The objectives of this paper were to 1) evaluate maternal urine concentrations of key metals at enrollment and delivery from a pregnancy cohort; and 2) compare the NBCS to the US general population by comparing representative summary statistical values. Pregnant Navajo women (N = 783, age range 14-45 years) were recruited from hospital facilities on the Navajo Nation during prenatal visits and urine samples were collected by trained staff in pre-screened containers. The U.S. Centers for Disease Control and Prevention (CDC), National Center for Environmental Health's (NCEH) Division of Laboratory Sciences (DLS) analyzed urine samples for metals. Creatinine-corrected urine concentrations of cadmium decreased between enrollment (1st or 2nd trimester) and delivery (3rd trimester) while urine uranium concentrations were not observed to change. Median and 95th percentile values of maternal NBCS urine concentrations of uranium, manganese, cadmium, and lead exceeded respective percentiles for National Health and Nutrition Evaluation Survey (NHANES) percentiles for women (ages 14-45 either pregnant or not pregnant.) Median NBCS maternal urine uranium concentrations were 2.67 (enrollment) and 2.8 (delivery) times greater than the NHANES median concentration, indicating that pregnant Navajo women are exposed to metal mixtures and have higher uranium exposure compared to NHANES data for women. This demonstrates support for community concerns about uranium exposure and suggests a need for additional analyses to evaluate the impact of maternal metal mixtures exposure on birth outcomes.

Identifying a critical window of maternal metal exposure for maternal and neonatal thyroid function in China: A cohort study

BACKGROUND

China, a developing country, has a particularly serious problem with metal pollution. We evaluated the association of metal exposure during pregnancy with maternal and neonatal thyroid function, and identified the critical window for maternal metal exposure effects on maternal and neonatal thyroid functions.

METHODS

The maternal urinary concentrations of mercury (Hg), cadmium (Cd), arsenic (As) and cesium (Cs) were determined in pregnant women during their first (n = 389) or third (n = 257) trimesters in a prospective cohort from 2014 to 2015 in Nanjing, China, using an inductively coupled plasma mass spectrometry (ICP-MS) instrument. Maternal serum-free thyroxine (FT4) and thyroid-stimulating hormone (TSH) were measured by electrochemiluminescent microparticle immunoassays in the second and third trimesters. Neonatal TSH levels were detected 72 h after birth.

RESULTS

Hg (>0.162 µg/L), Cd (>0.084 µg/L), As (>0.348 µg/L) and Cs (>0.093 µg/L) were detectable in 76.9%, 90.1%, 100% and 100% of maternal urine samples from women in the first trimester of pregnancy. In the multiple adjusted linear regression models, maternal exposures to Hg and Cd in the first trimester were positively associated with maternal TSH levels in the second trimester (P < 0.01, P = 0.02). Moreover, maternal exposures to Cd and Cs in the first trimester were positively associated with neonatal TSH levels (P = 0.04, P = 0.02). In the Bayesian kernel machine regression (BKMR) model, the results were stable and consistent with the linear regression model.

CONCLUSIONS

Maternal exposure to Hg, Cd and Cs in the first trimester was related to TSH levels in mothers and newborns. Efforts to identify maternal and neonatal thyroid disruptors should carefully consider the effects of exposure to these metals.

Repeated measures of prenatal thallium exposure and placental inflammatory cytokine mRNA expression: The Ma'anshan birth cohort (MABC) study

Thallium (Tl), a ubiquitous environmental toxicant, can cross the placental barrier during pregnancy. However, the effects of prenatal Tl exposure on placental function are currently unclear. Based on the Ma'anshan Birth Cohort study, we examined whether long-term prenatal Tl exposure was associated with placental inflammation. Tl concentrations were quantified in serum samples (n = 7050) from 2515 pregnancy during each trimester, placental inflammatory cytokine mRNA expression was assessed in 2519 placenta tissues. Geometric mean values of serum Tl concentrations were 63.57, 63.63 and 48.71 ng/L for the first, second and third trimesters, respectively. After adjustment for potential confounders, serum Tl concentration was positively associated with CD68 (β: 0.30; 95% CI: 0.05, 0.56) in the first trimester and TNF-α (β: 0.12; 95% CI: 0.01, 0.23), IL-6 (β: 0.15; 95% CI: 0.05, 0.25) and CD68 (β: 0.25; 95% CI: 0.10, 0.39) in the third trimester, however was negatively associated with IL-4 (β: -0.21; 95% CI: -0.41, -0.01) and CD206 (β: -0.23; 95% CI: -0.45, -0.02) in the first trimester. Repeated measures analysis showed that TNF-α, IL-6 and CD68 increased by 0.11 (95% CI: 0.01, 0.21), 0.12 (0.15, 95% CI: 0.05, 0.25), 0.22 (95% CI: 0.10, 0.39), respectively, with each 1ln-transformed Tl increase in total samples. Gender-specific analyses revealed that these associations were largely driven by male offspring. In addition, immunohistochemistry revealed that nuclear NF-κB p65 expression increased in placenta tissue. The results of this prospective cohort study provide longitudinal evidence that prenatal Tl exposure induces a placental inflammatory response in the Chinese population.

Association of adverse birth outcomes with prenatal uranium exposure: A population-based cohort study

Uranium (U) is a well-recognized hazardous heavy metal with embryotoxicity and fetotoxicity. However, little is known about its association with adverse birth outcomes. We aimed to investigate the potential correlation between prenatal U exposure and birth outcomes. Urine samples of 8500 women were collected before delivery from a birth cohort in Wuhan, China. Concentrations of urinary U and other metals were measured by inductively coupled plasma mass spectrometry. We used multivariable logistic regressions to evaluate the associations between urinary U concentrations and adverse birth outcomes, such as preterm birth (PTB), low birth weight (LBW) and small for gestational age (SGA). Associations of urinary U concentrations with gestational age, birth weight, and birth length were investigated by linear regressions. The geometric mean of U concentration was 0.03 μg/L. After adjustment for potential confounders, we found each Log₂-unit increase in U concentration was associated with a significant decrease in gestational age [adjusted β = -0.32 day; 95% confidence interval (CI): -0.44, -0.20] and a significant increased likelihood of PTB (adjusted OR = 1.18, 95% CI: 1.07, 1.29). This birth cohort uncovered an association of maternal exposure to U during pregnancy with decreased gestational age and increased risk of PTB. Our findings reveal an association of maternal exposure to U during pregnancy with decreased gestational age and increased risk of PTB.

Effect on the offspring of pregnant females CD-1 mice treated with a single thallium(I) application

Thallium (Tl) is a highly toxic metal for human beings; higher amounts found in diverse fluids of pregnant women are associated with low birth weight and preterm birth. However, experimental data concerning their effects on the embryonic development of mammalian organisms are limited. Hence, in the present work, TI(I) acetate of 0, 4.6, 9.2, or 18.5 mg/kg body weight were administered by intraperitoneal injection to groups of 10 pregnant CD-1 mice on the 7th gestational day, and animals were sacrificed on day 18 of gestation. The fetuses obtained showed some variations, such as trunk bent over (18.5 mg/kg), tail variations (all doses), forelimbs malrotation and hind limbs (all doses). Skeletal examination of the fetuses showed a delay in the ossification of skull bones, ribs, and limbs (all doses). In conclusion, the Intraperitoneal injection of Tl(I) acetate to pregnant mice induced morphological variations and a delay of the fetus ossification.

Prenatal exposure to thallium is associated with decreased mitochondrial DNA copy number in newborns: Evidence from a birth cohort study

BACKGROUND

Prenatal exposure to thallium is related to adverse birth outcomes. However, little is known about the effects of prenatal exposure to thallium on the mitochondrial DNA copy number (mtDNAcn) in newborns; such knowledge might reveal a potential mechanism linking maternal thallium exposure and adverse birth outcomes.

OBJECTIVE

To investigate the trimester-specific associations of maternal thallium exposure with cord blood leukocyte mtDNAcn.

METHODS

A total of 746 pregnant women with trimester-specific urinary samples and cord blood samples were recruited from Wuhan Children Hospital between November 2013 and March 2015 in Wuhan City, China. The concentration of thallium in maternal urine was quantified using inductively coupled plasma mass spectrometry (ICP-MS). Cord blood leukocyte mtDNAcn was measured by real-time quantitative polymerase chain reaction (qPCR). Trimester-specific associations of specific gravity (SG)-adjusted urinary thallium concentrations with mtDNAcn were estimated using a multiple informant model.

RESULTS

The geometric mean value of maternal urinary thallium was 0.34 μg/L, 0.36 μg/L, and 0.34 μg/L for the first, second, and third trimesters, respectively. Prenatal exposure to thallium during the first trimester, rather than during the second or the third trimester, was identified as negatively related to mtDNAcn. The multiple informant model showed a 10.4% lower level of mtDNAcn with each doubling increase of thallium levels (95% CI, -16.4%, -3.9%; P = 0.002). The observed associations were stronger among female newborns and among newborns born to older mothers.

CONCLUSIONS

The present study revealed a significant negative association between maternal thallium exposure during early pregnancy and cord blood leukocyte mtDNAcn in Chinese newborns, pointing to the important role of mitochondria as a target of thallium toxicity in early pregnancy.

Prenatal thallium exposure and poor growth in early childhood: A prospective birth cohort study

BACKGROUND

Thallium (Tl) exposure remains a public health problem with potential impacts on humans. Studies have suggested that prenatal exposure to thallium may be associated with fetal growth, but no studies are known have explored its association with early childhood anthropometry.

OBJECTIVE

To investigate the effects of prenatal Tl exposures on early child growth and development aged 0-2 years in a prospective birth cohort study.

METHODS

3080 pregnant women and their children participated in the study, which were recruited from a birth cohort in China. Serum samples collected in the first and second trimester of pregnant subjects and umbilical cord blood of infants were analyzed for Tl exposure assessment. Infant length or standing height and weight were obtained from medical records and 2 years planned visits. We used length/height and weight to calculate z-scores for weight-for-age (WAZ), height-for-age (HAZ), weight-for-height (WHZ), and body mass index-for-age (zBMI) based on World Health Organization standards. Linear mixed model was used to investigate the association between serum concentrations of Tl and the children's anthropometric characteristics (WAZ, HAZ, WHZ, and zBMI), and stratification analysis by sex was also examined.

RESULTS

The median (P₂₅-P₇₅) of Tl levels in the first trimester, second trimester and umbilical cord serum were 61.7 (50.7-77.0), 60.1 (50.9-74.8) and 38.4 (33.6-43.9) ng/L, respectively. Paired Mann-Whitney tests found Tl concentrations in umbilical cord serum were significantly less than that in maternal serum during the first and second trimesters (all p < 0.01). Using adjusted linear mixed model, no significant relationships were observed between maternal Tl exposure and child growth parameters. However, the umbilical cord serum Tl levels may contributed to decreased WAZ (β = -0.382, 95% confidence interval (CI): -0.670, -0.095) and HAZ (β = -0.427, 95% CI: -0.702, -0.152). When stratified by sex, the umbilical cord serum Tl levels were negatively related to WAZ (β = -0.450, 95% CI: -0.853, -0.048) and HAZ (β = -0.775, 95% CI: -1.160, -0.391) for girls. Among boys, overall Tl exposures were not significantly associated with early children anthropometric outcomes.

CONCLUSIONS

In the present study, our results suggested that prenatal Tl exposures may have a sex specific effect on child anthropometric measurements in the first 2 years of life. Umbilical cord serum Tl levels tended to be reduced child's stature and weight in young girls.

Placental concentrations of essential, toxic, and understudied metals and relationships with birth outcomes in Chattanooga, TN

BACKGROUND

Comprehensive examinations of placental metal concentrations and correlations with infant parameters are under-investigated. Chattanooga, Tennessee's consistently high incidence of low birth weight and potential for metal exposure provides an ideal opportunity to investigate potential correlations.

OBJECTIVES

To investigate the associations between a wide variety of metals in placental tissue and multiple infant parameters.

METHODS

A total of 31 elements were screened via ICP-MS in 374 individual placental samples. Of those, 14 were quantifiable in > 86% of the samples. We examined correlations between metal concentrations and infant parameters (birth weight, gestational age, birth weight centile, placental weight, birth length and head circumference). We fit multivariable regression models to estimate the covariate-adjusted associations of birth weight with ln-transformed concentrations of each of the 14 metals and used generalized additive models to examine nonlinear relationships.

RESULTS

Some of the strongest relationships with infant parameters came from several lesser-studied metals. Placental rhodium concentrations were negatively correlated with almost all infant parameters. In the fully adjusted regression model, birth weight was significantly associated with several metals. On an IQR (25th to the 75th percentile) basis, estimated changes in birthweight were: for cobalt (82.5 g, IQR=6.05 µg/kg, p = 0.006), iron (-51.5 g, IQR = 171800 µg/kg, p = 0.030), manganese (-27.2 g, IQR=152.1 µg/kg, p = 0.017), lead (-72.7 g, IQR=16.55 µg/kg, p = 0.004) and rhodium (-1365.5 g, IQR = 0.33 µg/kg, p < 0.001). Finally, a generalized additive model showed significant nonlinear relationships between birth weight and concentrations of Co and Rh.

CONCLUSIONS

Our comprehensive examination of placental metals illustrate many strong associations between lesser-studied metals and infant parameters. These data, in combination with our correlations of well-studied metals, illustrate a need to consider in utero exposure to a broad array of metals when considering fetal development.

Maternal lead exposure and premature rupture of membranes: a birth cohort study in China

OBJECTIVES

Maternal exposure to lead (Pb) has been suggested to correlate with adverse birth outcomes, but evidence supporting an association between Pb exposure and premature rupture of membranes (PROM) is limited. The aim of our study was to investigate whether maternal Pb exposure was associated with PROM and preterm PROM.

DESIGN

Cross-sectional cohort study.

STUDY POPULATION

The present study involved 7290 pregnant women from the Healthy Baby Cohort in Wuhan, China, during 2012-2014.

MAIN OUTCOME MEASURES

PROM was defined as spontaneous rupture of amniotic membranes before the onset of labour and was determined with a pH ≥6.5 for vaginal fluid. Maternal urinary Pb level was adjusted by creatinine concentration, and its relationship with PROM was analysed by logistic regression.

RESULTS

The IQR of maternal urinary Pb concentrations of the study population was 2.30-5.64 µg/g creatinine with a median of 3.44 µg/g creatinine. Increased risk of PROM was significantly associated with elevated levels of Pb in maternal urine (adjusted OR 1.23, 95% CI 1.0 to 1.47 for the medium tertile; adjusted OR 1.51, 95% CI 1.27 to 1.80 for the highest tertile). The risk of preterm PROM associated with Pb levels was significantly higher when compared with the lowest tertile (adjusted OR 1.24, 95% CI 0.80 to 1.92 for the medium tertile; adjusted OR 1.73, 95% CI 1.15 to 2.60 for the highest tertile). In addition, the relationship between Pb and PROM was more pronounced among primiparous women than multiparous women (p for interaction <0.01).

CONCLUSIONS

Our study found that higher levels of maternal Pb exposure was associated with increased risk of PROM, indicating that exposure to Pb during pregnancy may be an important risk factor for PROM.

Predictors of thallium exposure and its relation with preterm birth

Thallium (Tl) is a well-recognized hazardous toxic heavy metal that has been reported to have embryotoxicity and fetotoxicity. However, little is known about its association with preterm birth (PTB) in humans. We aimed to evaluate the predictors of Tl exposure and assessed its relation with PTB. The study population included 7173 mother-infant pairs from a birth cohort in Wuhan, China. Predictors of Tl concentrations were explored using linear regression analyses, and associations of Tl exposure with risk of PTB or gestational age at birth were estimated using logistic regression or generalized linear models. The geometric mean and median values of urinary Tl concentrations were 0.28 μg/L (0.55 μg/g creatinine) and 0.29 μg/L (0.53 μg/g creatinine). We found that maternal urinary Tl concentrations varied by gestational weight gain, educational attainment, multivitamin and iron supplementations. Women with Tl concentrations higher than 0.80 μg/g creatinine were at higher risk of giving birth prematurely versus those with Tl concentrations lower than 0.36 μg/g creatinine [adjusted odds ratio (95% confidence interval (CI)): 1.55 (1.05, 2.27)], and the association was more pronounced in PTB with premature rupture of membranes (PROM) rather than in PTB without PROM. About 3-fold increase in creatinine-corrected Tl concentrations were associated with 0.99-day decrease in gestational length (95% CI: -1.36, -0.63). This is the first report on the associations between maternal Tl exposure and the risk of PTB.

Determine Multiple Elements Simultaneously in the Sera of Umbilical Cord Blood Samples-a Very Simple Method

Analyzing the concentrations of heavy metals in the sera of umbilical cord blood samples can provide useful information about prenatal exposure to environmental agents. An analytical method based on ICP-MS to simultaneously determine multiple elements in umbilical cord blood samples was developed for assessing the in utero exposure to metallic and metalloid elements. The method only required as little as 100 μL of serum diluted 1:25 for direct analysis. Matrix-matched protocol was used to eliminate mass matrix interference and kinetic energy discrimination mode was used to eliminate the polyatomic ion interference. The assay was completed on average within 4 min with the detection limits ranging from 0.0002 to 44.4 μg/L for all the targeted elements. The detection rates for most of elements were 100 % other than cadmium (Cd), lead (Pb), and mercury (Hg). The testing results of the certified reference materials were ideal. The method is simple and sensitive, so it is suitable for the monitoring of large quantities of samples.

Dietary predictors of urinary cadmium among pregnant women and children

BACKGROUND

Cadmium is a toxic metal with modifiable exposure sources including diet. In pregnant women and children, unique dietary habits may contribute to DCd, and the relationship of diet to overall cadmium exposure can depend on specific factors during these transitional time periods.

OBJECTIVES

This study aimed to identify and quantify food sources of DCd, describe the distribution of UCd, and determine the relationship of DCd and intake of specific foods with UCd, stratified by maternal smoking history, among pregnant women and children in a well-characterized Mexico City birth cohort.

METHODS

Our sample included 192 pregnant women (third trimester) and 223 children (7-15years). DCd was calculated using FFQ and the U.S. TDS. We also measured UCd, maternal history of smoking, and additional covariates.

RESULTS

Pregnant women and children had geometric mean UCd concentrations of 0.19±0.78μg/L and 0.14±0.60μg/L, respectively. On average, estimated daily DCd intake was 9.3±3.5μg for women and 12.2±5.4μg for children. Adjusted linear regression models showed a positive association between DCd and UCd among women (p=0.03) and children (p=0.03) without a maternal history of smoking. Intake of fruit and vegetables among women and potato consumption among children were positively associated with UCd.

CONCLUSIONS

Pregnant women and their children are exposed to cadmium at dietary and urinary levels similar to those previously reported. Higher estimated DCd for children than for women could be attributed to the different FFQs or related to dietary pattern changes between age groups. DCd contributed to UCd in those without a maternal smoking history.

Biomarkers of exposure to environmental contaminants in French pregnant women from the Elfe cohort in 2011

BACKGROUND

As part of the perinatal component of the French Human Biomonitoring (HBM) program, biomarkers levels of various chemicals have been described among pregnant women having given birth in continental France in 2011 and who have been enrolled in the Elfe cohort (French Longitudinal Study since Childhood). This paper describes the design of the study and provides main descriptive results regarding exposure biomarkers levels.

METHODS

Exposure biomarkers were measured in biological samples collected at delivery from pregnant women randomly selected among the participants in the clinical and biological component of the Elfe cohort (n=4145). The geometric mean and percentiles of the levels distribution were estimated for each biomarker. The sampling design was taken into account in order to obtain estimates representative of the French pregnant women in 2011.

RESULTS

Results provide a nation-wide representative description of biomarker levels for important environmental contaminants among pregnant women who gave birth in France in 2011. Bisphenol A (BPA), and some metabolites of phthalates, pesticides (mainly pyrethroids), dioxins, furans, polychlorobiphenyls (PCBs), brominated flame retardants (BFRs), perfluorinated compounds (PFCs) and metals (except uranium) were quantified in almost 100% of the pregnant women. Some compounds showed a downward trend compared to previous studies (lead, mercury), but others did not (pyrethroids) and should be further monitored.

CONCLUSION AND PERSPECTIVES

The present results show that French pregnant women are exposed to a wide variety of pollutants, including some that have been banned or restricted in France.

Levels of dialkylphosphate metabolites in urine among general U.S. population

Data from National Health and Nutrition Examination Survey for years 2003-2008 were used to study the factors that affect urinary levels of dialkylphosphate (DAP) metabolites in urine. Separate regression models were fitted for children aged 6-11 years, adolescents aged 12-19 years, and adults aged ≥20 years. Specifically, DAP metabolites that were analyzed were: dimethylphosphate (DMP), diethylphosphate (DEP), dimethylthiophosphate (DMTP), and diethylthiophosphate (DETP). Males had statistically significantly lower adjusted levels than females for DMP for adolescents, for DEP for adults, for DMTP for both adolescents and adults, and for DETP for both children and adults. Nonsmokers had statistically significantly higher adjusted levels than smokers for DMTP for adolescents and for DMP and DMTP for adults. Exposure to second hand smoke at home was associated with relatively higher levels of DMP among children (p=0.01) but the reverse was found to be true for DMTP (p<0.01) among adolescents as well as adults (p=0.02). Children had higher levels of DMTP than both adolescents and adults (p<0.01) and higher levels of DETP than adolescents (p=0.02). Age was found to be negatively associated with the levels of DMTP (p=0.01) among children and positively associated (p<0.01) with the levels of all four metabolites among adults.

Impact of Pregnancy on the Levels of Parabens and Bisphenol A: Data from NHANES 2005–2010

Using data from the National Health and Nutrition Examination Survey, regression models were fitted to assess the relationship between the levels of bisphenol A and selected parabens and pregnancy status among females 20–44 years old with adjustments made for factors that may affect the levels of these chemicals. Pregnancy did not affect the levels of bisphenol A, ethyl paraben, methyl paraben, and propyl paraben, but the pregnancy was found to be associated with increased levels of butyl paraben. Also, the levels of bisphenol A and butyl, ethyl, and methyl parabens increased as pregnancy progressed from the first trimester to the third trimester. The increasing levels of bisphenol A and parabens during pregnancy are of concern and need further clinical explanation.

A Case-Control Study of Prenatal Thallium Exposure and Low Birth Weight in China

BACKGROUND

Thallium (Tl) is a highly toxic heavy metal widely present in the environment. Case reports have suggested that maternal exposure to high levels of Tl during pregnancy is associated with low birth weight (LBW), but epidemiological data are limited.

OBJECTIVES

This study was designed to evaluate whether prenatal Tl exposure is associated with an increased risk of LBW.

METHODS

This case-control study involving 816 study participants (204 LBW cases and 612 matched controls) was conducted in Hubei Province, China, in 2012-2014. Tl concentrations were measured in maternal urine collected at delivery, and associations with LBW were evaluated using conditional logistic regression.

RESULTS

Higher maternal urinary Tl levels were significantly associated with increased risk of LBW [crude odds ratio (OR) = 1.52; 95% CI: 1.00, 2.30 for the highest vs. lowest tertile], and the association was similarly elevated after adjustment for potential confounders (adjusted OR = 1.90; 95% CI: 1.01, 3.58 for the highest vs. lowest tertile). Stratified analyses showed slightly higher risk estimates for LBW associated with higher Tl levels for mothers < 28 years old and for mothers with lower household income; however, there was no statistical evidence of heterogeneity in risk according to maternal age (p for heterogeneity = 0.18) or household income (p for heterogeneity = 0.28).

CONCLUSION

To our knowledge, ours is the first case-control study to investigate the association between prenatal Tl exposure and LBW. The results suggest that prenatal exposure to high levels of Tl may be associated with an increased risk of LBW.

CITATION

Xia W, Du X, Zheng T, Zhang B, Li Y, Bassig BA, Zhou A, Wang Y, Xiong C, Li Z, Yao Y, Hu J, Zhou Y, Liu J, Xue W, Ma Y, Pan X, Peng Y, Xu S. 2016. A case-control study of prenatal thallium exposure and low birth weight in China. Environ Health Perspect 124:164-169; http://dx.doi.org/10.1289/ehp.1409202.

Prenatal exposure to lead in relation to risk of preterm low birth weight: A matched case-control study in China

We investigated the association between prenatal exposure to lead (Pb) and the risk of preterm low birth weight (PLBW). Pb concentrations in maternal urine collected at birth from 408 subjects (102 cases and 306 matched controls) were analyzed and adjusted by creatinine. The median Pb concentration in the PLBW cases (10.60μgPb/g creatinine) was higher than that of the controls (7.28μgPb/g creatinine). An adjusted odds ratio (OR) of 2.96 (95% CI=1.49-5.87) for PLBW was observed when the highest tertile was compared to the lowest tertile of Pb levels. The association was more pronounced among female infants (adjusted OR=3.67 for the highest tertile; 95% CI=1.35-9.93) than male infants (adjusted OR=1.91 for the highest tertile; 95% CI=0.74-4.95). Our study suggests that prenatal exposure to levels of Pb encountered today in China is associated with an elevated risk of PLBW.

An update to the toxicological profile for water-soluble and sparingly soluble tungsten substances

Tungsten is a relatively rare metal with numerous applications, most notably in machine tools, catalysts, and superalloys. In 2003, tungsten was nominated for study under the National Toxicology Program, and in 2011, it was nominated for human health assessment under the US Environmental Protection Agency's (EPA) Integrated Risk Information System. In 2005, the Agency for Toxic Substances and Disease Registry (ATSDR) issued a toxicological profile for tungsten, identifying several data gaps in the hazard assessment of tungsten. By filling the data gaps identified by the ATSDR, this review serves as an update to the toxicological profile for tungsten and tungsten substances. A PubMed literature search was conducted to identify reports published during the period 2004-2014, in order to gather relevant information related to tungsten toxicity. Additional information was also obtained directly from unpublished studies from within the tungsten industry. A systematic approach to evaluate the quality of data was conducted according to published criteria. This comprehensive review has gathered new toxicokinetic information and summarizes the details of acute and repeated-exposure studies that include reproductive, developmental, neurotoxicological, and immunotoxicological endpoints. Such new evidence involves several relevant studies that must be considered when regulators estimate and propose a tungsten reference or concentration dose.

Mercury in the gold mining district of San Martin de Loba, South of Bolivar (Colombia)

Gold mining is responsible for most Hg pollution in developing countries. The aims of this study were to assess the levels of total Hg (T-Hg) in human hair, fish, water, macrophyte, and sediment samples in the gold mining district of San Martin de Loba, Colombia, as well as to determine fish consumption-based risks for T-Hg ingestion. T-Hg levels were measured by electrothermal atomization and atomic absorption spectroscopy. The overall mean T-Hg level in hair for humans in the mining district of San Martin de Loba was 2.12 μg/g, whereas for the reference site, Chimichagua, Cesar, it was 0.58 μg/g. Mean T-Hg levels were not different when considered within localities belonging to the mining district but differed when the comparison included Chimichagua. T-Hg levels in examined locations were weakly but significantly associated with age and height, as well as with fish consumption, except in San Martin de Loba. High T-Hg concentrations in fish were detected in Pseudoplatystoma magdaleniatum, Caquetaia kraussii, Ageneiosus pardalis, Cyrtocharax magdalenae, and Triportheus magdalenae, whereas the lowest appeared in Prochilodus magdalenae and Hemiancistrus wilsoni. In terms of Hg exposure due to fish consumption, only these last two species offer some guarantee of low risk for Hg-related health problems. Water, floating macrophytes, and sediments from effluents near mining sites also had high Hg values. In mines of San Martin de Loba and Hatillo de Loba, for instance, the geoaccumulation index (I(geo)) for sediments reached values greater than 6, indicating extreme pollution. In short, these data support the presence of a high Hg-polluted environment in this mining district, with direct risk for deleterious effects on the health of the mining communities.

Levels of caffeine and its metabolites among U.S. smokers and nonsmokers

Data from National Health and Nutrition Examination Survey for the years 2009-2010 were used to estimate the levels of caffeine and 14 of its metabolite among U.S. smokers and nonsmokers after adjustments were made for other factors that affect observed caffeine levels. In this study, when adjusted for daily caffeine intake, adjusted levels (AGM) of caffeine and its metabolites were not found to be statistically significantly different between smokers and nonsmokers. AGMs for caffeine and all of its metabolites were found to be statistically significantly higher (p < 0.01) among females aged ≥ 12 years than males. For caffeine, 1,3-dimethylxanthine, and 1,7-dimethylxanthine, those aged ≥ 20 years had statistically significantly higher (p < 0.01) AGM than those aged 12-19 years but the reverse was true for 7-methylxanthine and 3,7-dimethylxanthine (p ≤ 0.02). The order of the AGMs by race/ethnicity was non-Hispanic whites > Hispanics > non-Hispanic blacks and most of the differences were statistically significant, at least between non-Hispanic whites and non-Hispanic blacks (p < 0.01). In general, there was a statistically significant positive association between the levels of caffeine and its metabolites and body mass index as well as daily caffeine intake. However, the levels of 7-methylxanthine were negatively associated with body mass index.

Kidney biomarkers associated with blood lead, mercury, and cadmium in premenopausal women: a prospective cohort study

Certain metals are harmful to the kidney and liver at high levels, but associations with functional biomarkers at low exposure levels among premenopausal women apparently has not been evaluated. Healthy, regularly menstruating women (n = 259) were followed for up to 2 menstrual cycles with up to 16 visits. Renal and liver biomarkers were measured in serum at each clinic visit. Cadmium (Cd), lead (Pb), and mercury (Hg) were measured in whole blood at baseline. Linear mixed models were adjusted for age, body mass index (BMI), race, average calories, alcohol intake, smoking, and cycle day. Median levels of Cd, Pb, and Hg were 0.31 μg/L, 0.88 μg/dl, and 1.1 μg/L, respectively. One-third of women had diminished glomerular filtration rate (eGFR) (<90 ml/min/1.73 m(2)). Each twofold increase in Cd was associated with a negative 4.9% change in blood urea nitrogen (BUN) and bilirubin. Each twofold rise in Pb was associated with decreased eGFR and increased creatinine. A twofold elevation in Hg was associated with higher protein and reduced alkaline phosphatase. In healthy, predominantly nonsmoking women, low levels of Cd, Pb, and Hg were associated with changes in select biomarkers of kidney and liver function.

Effects of environmental temperature change on mercury absorption in aquatic organisms with respect to climate warming

Because of global warming, the quantity of naturally generated mercury (Hg) will increase, subsequently methylation of Hg existing in seawater may be enhanced, and the content of metal in marine products rise which consequently results in harm to human health. Studies of the effects of temperatures on Hg absorption have not been adequate. In this study, in order to observe the effects of temperature changes on Hg absorption, inorganic Hg or methylmercury (MeHg) was added to water tanks containing loaches. Loach survival rates decreased with rising temperatures, duration, and exposure concentrations in individuals exposed to inorganic Hg and MeHg. The MeHg-treated group died sooner than the inorganic Hg-exposed group. The total Hg and MeHg content significantly increased with temperature and time in both metal-exposed groups. The MeHg-treated group had higher metal absorption rates than inorganic Hg-treated loaches. The correlation coefficients for temperature elevation and absorption were significant in both groups. The results of this study may be used as basic data for assessing in vivo hazards from environmental changes such as climate warming.

Elevated mercury levels in pregnant woman linked to skin cream from Mexico

Mercury exposure during pregnancy can have serious health effects for a developing fetus including impacting the child's neurologic and cognitive development. Through biomonitoring in a low-income Latina population in California, we identified a patient with high levels of mercury and traced the source to face creams purchased in a pharmacy in Mexico.