Blood lead at currently acceptable levels may cause preterm labour

Associations of maternal blood metal concentrations with plasma eicosanoids among pregnant women in Puerto Rico

BACKGROUND/AIM

Heavy metals are known to induce oxidative stress and inflammation, and the association between metal exposure and adverse birth outcomes is well established. However, there lacks research on biomarker profiles linking metal exposures and adverse birth outcomes. Eicosanoids are lipid molecules that regulate inflammation in the body, and there is growing evidence that suggests associations between plasma eicosanoids and pregnancy outcomes. Eicosanoids may aid our understanding of etiologic birth pathways. Here, we assessed associations between maternal blood metal concentrations with eicosanoid profiles among 654 pregnant women in the Puerto Rico PROTECT birth cohort.

METHODS

We measured concentrations of 11 metals in whole blood collected at median 18 and 26 weeks of pregnancy, and eicosanoid profiles measured in plasma collected at median 26 weeks. Multivariable linear models were used to regress eicosanoids on metals concentrations. Effect modification by infant sex was explored using interaction terms.

RESULTS

A total of 55 eicosanoids were profiled. Notably, 12-oxoeicosatetraenoic acid (12-oxoETE) and 15-oxoeicosatetraenoic acid (15-oxoETE), both of which exert inflammatory activities, had the greatest number of significant associations with metal concentrations. These eicosanoids were associated with increased concentrations of Cu, Mn, and Zn, and decreased concentrations of Cd, Co, Ni, and Pb, with the strongest effect sizes observed for 12-oxoETE and Pb (β:-33.5,95 %CI:-42.9,-22.6) and 15-oxoETE and Sn (β:43.2,95 %CI:11.4,84.1). Also, we observed differences in metals-eicosanoid associations by infant sex. Particularly, Cs and Mn had the most infant sex-specific significant associations with eicosanoids, which were primarily driven by female fetuses. All significant sex-specific associations with Cs were inverse among females, while significant sex-specific associations with Mn among females were positive within the cyclooxygenase group but inverse among the lipoxygenase group.

CONCLUSION

Certain metals were significantly associated with eicosanoids that are responsible for regulating inflammatory responses. Eicosanoid-metal associations may suggest a role for eicosanoids in mediating metal-induced adverse birth outcomes.

Assessing lead exposure in U.S. pregnant women using biological and residential measurements

There is strong scientific evidence for multiple pathways of human exposure to lead (Pb) in residential settings, particularly for young children; however, less is known about maternal exposure during pregnancy and children's exposure during early lifestages. A robust, multi-faceted secondary analysis was conducted using data collected by the National Institute of Child Health and Human Development in the 2009-2014 National Children's Study Vanguard Studies. Descriptive statistics summarized Pb concentrations of maternal blood, maternal urine, and house dust vacuum samples collected during pregnancy and residence surface wipes collected both during pregnancy and six months post-partum. The maternal blood Pb level geometric mean was 0.44 μg/dL (n = 426), with no women having values ≥ 5 μg/dL; creatinine-adjusted maternal urinary Pb geometric mean was 0.43 μg/g (n = 366). These blood and urine concentrations are similar to those observed for females in the general U.S. population in the National Health and Nutrition Examination Survey 2010-2011 cycle. A modest correlation between maternal blood Pb and surface wipe measurements during pregnancy was observed (Spearman r = 0.35, p < 0.0001). Surface wipe Pb loadings obtained in mother's homes during pregnancy (n = 640) and from areas where children spent the most time at roughly 6 months of age (n = 99) ranged from 0.02 to 71.8 ng/cm2, with geometric means of 0.47 and 0.49 ng/cm2, respectively, which were relatively low compared to other national studies. Survey responses of demographic, lifestyle, and residence characteristics were assessed for associations with blood concentration and surface wipe loading. Demographic (e.g., race/ethnicity, income, education, marital status) and housing characteristics (e.g., year home built, paint condition, own or rent home, attached garage) were associated with both maternal blood and surface wipe loadings during pregnancy. The availability of residential environmental media and extensive survey data provided enhanced understanding of Pb exposure during pregnancy and early life.

Prenatal Lead Exposure, Genetic Factors, and Cognitive Developmental Delay

Importance

Although the effects of lead (Pb) exposure on neurocognition in children have been confirmed, the individual associations of prenatal Pb exposure and its interaction with genetic factors on cognitive developmental delay (CDD) in children remain unclear.

Objective

To investigate the association of prenatal Pb exposure and its interaction with genetic factors with CDD risk.

Design, Setting, and Participants

Women in Wuhan, China, who had an expected delivery date between March 2014 and December 2017, were recruited for this prospective cohort study. Children were assessed for cognitive development at approximately 2 years of age (March 2016 to December 2019). Maternal venous blood, cord blood, and venous blood from children were collected in a longitudinal follow-up. Data analysis was performed from March 2022 to February 2023.

Exposure

Prenatal Pb exposure, and genetic risk for cognitive ability evaluated by polygenic risk score constructed with 58 genetic variations.

Main Outcomes and Measures

Cognitive developmental delay of children aged approximately 2 years was assessed using the Chinese revision of the Bayley Scale of Infant Development. A series of multivariable logistic regressions was estimated to determine associations between prenatal Pb exposure and CDD among children with various genetic backgrounds, adjusting for confounding variables.

Results

This analysis included 2361 eligible mother-child pairs (1240 boys [52.5%] and 1121 girls [47.5%]; mean [SD] ages of mothers and children, 28.9 [3.6] years and 24.8 [1.0] months, respectively), with 292 children (12.4%) having CDD. Higher maternal Pb levels were significantly associated with increased risk of CDD (highest vs lowest tertile: odds ratio, 1.55; 95% CI, 1.13-2.13), adjusting for demographic confounders. The association of CDD with maternal Pb levels was more evident among children with higher genetic risk (highest vs lowest tertile: odds ratio, 2.59; 95% CI, 1.48-4.55), adjusting for demographic confounders.

Conclusions and Relevance

In this cohort study, prenatal Pb exposure was associated with an increased risk of CDD in children, especially in those with a high genetic risk. These findings suggest that prenatal Pb exposure and genetic background may jointly contribute to an increased risk of CDD for children and indicate the possibility for an integrated strategy to assess CDD risk and improve children's cognitive ability.

Refining risk estimates for lead in drinking water based on the impact of genetics and diet on blood lead levels using the Collaborative Cross mouse population

Blood lead (Pb) level (BLL) is a commonly used biomarker to evaluate associations with health effects. However, interventions to reduce the adverse effects of Pb require relating BLL to external exposure. Moreover, risk mitigation actions need to ensure protection of more susceptible individuals with a greater tendency to accumulate Pb. Because little data is available to quantify inter-individual variability in biokinetics of Pb, we investigated the influence of genetics and diet on BLL in the genetically diverse Collaborative Cross (CC) mouse population. Adult female mice from 49 CC strains received either a standard mouse chow or a chow mimicking the American diet while being provided water ad libitum with 1000 ppm Pb for 4 weeks. In both arms of the study, inter-strain variability was observed; however, in American diet-fed animals, the BLL was greater and more variable. Importantly, the degree of variation in BLL among strains on the American diet was greater (2.3) than the default variability estimate (1.6) used in setting the regulatory standards. Genetic analysis identified suggestive diet-associated haplotypes that were associated with variation in BLL, largely contributed by the PWK/PhJ strain. This study quantified the variation in BLL that is due to genetic background, diet, and their interactions, and observed that it may be greater than that assumed for current regulatory standards for Pb in drinking water. Moreover, this work highlights the need of characterizing inter-individual variation in BLL to ensure adequate public health interventions aimed at reducing human health risks from Pb.

Prenatal blood lead levels and Birth Weight: a Meta-analysis study

Purpose

Lead, a known toxic metal, causes several adverse reproductive effects, including low birth weight. Fortunately, the exposure level has sharply decreased during the recent decades, but a definitive safe level did not introduce for pregnant women yet. The current meta-analysis study aimed to conduct a quantitative estimation of maternal and umbilical cord blood lead effects on birth weight.

Methods

Two researchers have independently searched the scientific literature for retrieving related studies using the PRISMA criteria for data extraction. Twenty-one full-text articles were selected from primary 5006 titles, limited by the English language and published between 1991 and 2020 on humans.

Results

The pooled mean of maternal and umbilical cord blood lead levels were 6.85 µg/dL (95% CI: 3.36-10.34) and 5.41 µg/dL (95%CI: 3.43-7.40), respectively. The correlation coefficient analysis showed a significant inverse association between the mean maternal blood lead level and birth weight, which was confirmed by Fisher Z-Transformation analysis (-0.374, 95% CI: -0.382, -0.365, p < 0.01). In addition, a significantly lower birth weight (∆: 229 gr, p < 0.05) was found in the relatively high level of maternal blood lead than in low-level exposure (> 5 µg/dL vs. ≤ 5 µg/dL, respectively).

Conclusion

In short, the present study findings suggest an increasing maternal blood lead levels could be a potential risk factor for reducing birth weight. Thus, pregnant women should avoid lead exposure, as much as possible.

Supplementary information

The online version contains supplementary material available at 10.1007/s40201-022-00843-w.

Associations Between the Lead Level in Maternal Blood and Umbilical Cord Blood and Congenital Heart Diseases in Offspring

The incidence of congenital heart diseases (CHDs) shows an increasing trend and results in large health burdens in China. However, there have been inconsistent results of the relationship between lead (Pb) level and risk of CHDs. We performed a pair-matched case-control study and included 97 cases and 194 controls to investigate the association between pregnancy Pb exposure and the risk of CHDs in a birth cohort study conducted in Lanzhou, China. The results showed that compared to the lowest Pb tertile, both highest tertile levels of maternal blood and umbilical cord blood Pb were associated with an increased risk of CHDs. The similar significant results were found in cases with isolated CHDs. Compared to both lowest tertiles of Pb level in maternal blood and umbilical cord blood, the highest tertile was associated with an increased risk of CHDs, especially for isolated CHDs. Overall, our study suggests a significant association between pregnancy Pb exposure and risk of CHDs, especially for isolated CHDs. Future studies are needed to elucidate the underlying mechanism.

Exposure of preterm neonates to toxic metals during their stay in the Neonatal Intensive Care Unit and its impact on neurodevelopment at 2 months of age

BACKGROUND

Premature neonates might be exposed to toxic metals during their stay in the neonatal intensive care unit (NICU), which could adversely affect neurodevelopment; however, limited evidence is available. The present study was therefore designed to assess the exposure to mercury, lead, cadmium, arsenic, and manganese of preterm neonates who received total parenteral nutrition (TPN) and/or red blood cell (RBC) transfusions during their NICU stay and the risk of neurodevelopment delay at the age of 2 months.

METHODS

We recruited 33 preterm neonates who required TPN during their NICU admission. Blood samples were collected for metal analysis at two different time points (admission and before discharge). Metals in the daily TPN received by preterm neonates were analyzed. Neurodevelopment was assessed using the Ages and Stages Questionnaire Edition 3 (ASQ-3).

RESULTS

All samples of TPN had metal contamination: 96% exceeded the critical arsenic limit (0.3 μg/kg body weight/day); daily manganese intake from TPN for preterm neonates exceeded the recommended dose (1 µg/kg body weight) as it was added intentionally to TPN solutions, raising potential safety concerns. All samples of RBC transfusions exceeded the estimated intravenous reference dose for lead (0.19 µg/kg body weight). Levels of mercury, lead and manganese in preterm neonates at discharge decreased 0.867 µg/L (95% CI, 0.76, 0.988), 0.831 (95%CI, 0.779, 0.886) and 0.847 µg/L (95% CI, 0.775, 0.926), respectively. A decrease in ASQ-3-problem solving scores was associated with higher levels of blood lead in preterm neonates taken at admission (ß = -0.405, 95%CI = -0.655, -0.014), and with plasma manganese (ß = -0.562, 95%CI = -0.995, -0.172). We also observed an association between decreased personal social domain scores with higher blood lead levels of preterm neonates before discharge (ß = -0.537, 95%CI = -0.905, -0.045).

CONCLUSION

Our findings provide evidence to suggest negative impacts on the neurodevelopment at 2 months of preterm infants exposed to certain metals, possibly related to TPN intake and/or blood transfusions received during their NICU stay. Preterm neonates may be exposed to levels of metals in utero.

Association between toxic metals, vitamin D and preterm birth in the Maternal-Infant research on environmental chemicals study

BACKGROUND

Toxic metals, like lead, are risk factors for preterm birth (PTB), but few studies have examined low levels found in most Canadians. Vitamin D, which may have antioxidant activity, protects against PTB.

OBJECTIVES

In this study, we investigated the impact of toxic metals (lead, mercury, cadmium and arsenic) on PTB and examined if maternal plasma vitamin D concentrations modify these associations.

METHODS

We investigated whether concentrations of metals in whole blood measured in early and late pregnancy were associated with PTB (<37 weeks) and spontaneous PTB in 1851 live births from the Maternal-Infant Research on Environmental Chemicals Study using discrete time survival analysis. We also investigated whether the risk of PTB was modified by first-trimester plasma 25-hydroxyvitamin D (25OHD) concentrations.

RESULTS

Of 1851 live births, 6.1% (n = 113) were PTBs and 4.9% (n = 89) were spontaneous PTB. A 1 μg/dL increase in blood lead concentrations during pregnancy was associated with an increased risk of PTB (relative risk [RR] 1.48, 95% confidence interval [CI] 1.00, 2.20) and spontaneous PTB (RR 1.71, 95% CI 1.13, 2.60). The risk was higher in women with insufficient vitamin D concentrations (25OHD <50 nmol/L) for both PTB (RR 2.42, 95% CI 1.01, 5.79) and spontaneous PTB (RR 3.04, 95% CI 1.15, 8.04). However, an interaction on the additive scale was not present. Arsenic was associated with a higher risk of PTB (RR 1.10, 95% CI 1.02, 1.19) and spontaneous PTB (RR 1.11, 95% CI 1.03, 1.20) per 1 μg/L.

CONCLUSIONS

Gestational exposure to low levels of lead and arsenic may increase the risk of PTB and spontaneous PTB; individuals with insufficient vitamin D may be more susceptible to the adverse effects of lead. Given our relatively small number of cases, we encourage testing of this hypothesis in other cohorts, especially those with vitamin D-deficient populations.

Does short-term, airborne lead exposure during pregnancy affect birth outcomes? Quasi-experimental evidence from NASCAR's deleading policy

BACKGROUND

There is evidence of a weak placental-fetal barrier to lead, suggesting that maternal lead exposure could affect the fetus. The health consequences for newborns from in utero lead exposure are not well understood.

OBJECTIVES

We estimated the effects by trimester, of short-term (<1 week), airborne lead exposure during pregnancy on birth outcomes.

METHODS

We use quasi-experimental variation in airborne lead exposure during pregnancy, based on NASCAR's deleading of racing fuel in 2007, in a difference-in-differences model, to estimate the effect of deleading on the birth outcomes of all live births (n = 147,673) in the Charlotte-Concord-Gastonia Metropolitan Statistical Area between 2004 and 2009.

RESULTS

After deleading, children born to mothers residing <4000 m of Charlotte Motor Speedway (relative to those residing >10,000 m) experienced an average increase in birthweight (BW) of 102.50 g [P < 0.001]. The probability of low birthweight (LBW) declined by 0.045 [P = 0.001], preterm (PRE) births by 0.03 [P = 0.04], and small for gestational age (SGA) by 0.04 [P = 0.002]. We find that benefits accrue primarily in preterm LBW and SGA babies, and from decreased lead exposure in the first trimester.

CONCLUSIONS

Short-term exposure to airborne lead during pregnancy adversely affects birth outcomes. Reducing even very brief exposure to airborne lead during pregnancy may improve birth outcomes.

Trends of Blood Lead Levels in US Pregnant Women: The National Health and Nutrition Examination Survey (2001–2018)

Objectives

This study investigates the trends of blood lead levels in US pregnant women based on the National Health and Nutrition Examination Survey from 2001 to 2018.

Methods

A total of 1,230 pregnant women were included in this study. The weighted logistic regression was applied to analyze the association between sociodemographic characteristics with high blood levels. We computed the blood lead levels for each survey period from 2001–2002 to 2017–2018. Moreover, we used the adjusted linear regression model to investigate the time-related change in blood lead level. The odds ratio (OR) with a 95% confidence interval (CI) was calculated accordingly.

Results

The mean blood lead was 0.73 ± 0.03 ug/dL, and high blood lead was observed in 2.53% of individuals. The Mexican Americans were more associated with high blood lead than the non-Hispanic white (OR, 1.072; 95% CI, 1.032-1.112). The mean blood lead level has decreased from 0.97 ug/dL in 2001–2002 to 0.46 ug/dL in 2013–2014. Afterward, a slight increase was observed with the mean blood lead of 0.55 ug/dL in 2015–2016 and 0.53 ug/dL in 2017-2018. In the adjusted linear regression model, each year's increase would lead to a 0.029 ug/dL decrease in blood lead (P < 0.001). However, no significant change was observed in the 2017–2018 cycle compared with 2009–2010 (P = 0.218).

Conclusion

This study summarized the trend of blood lead levels in US pregnant women over 2001–2018. Continued effort is still required to control lead sources better and protect this population from lead exposure.

Prenatal lead exposure and childhood lung function: Influence of maternal cortisol and child sex

INTRODUCTION

Maternal hypothalamic-pituitary-adrenal (HPA) axis disruption in pregnancy may contribute to the programming of childhood respiratory disease and may modify the effect of chemical toxins, like lead (Pb), on lung development. Child sex may further modify these effects. We sought to prospectively examine associations between maternal HPA axis disruption, prenatal Pb and childhood lung function and explore potential effect modification by maternal cortisol and child sex on the association between prenatal Pb and lung function outcomes.

MATERIALS AND METHODS

Analyses included 222 mothers and children enrolled in a longitudinal birth cohort study in Mexico City. Maternal diurnal salivary cortisol was assessed in pregnancy; cortisol awakening response (CAR) and diurnal slope were calculated. Blood Pb was measured during the second trimester of pregnancy. Post-bronchodilator lung function was tested at ages 8-11 years. Associations were modeled using generalized linear models with interaction terms, adjusting for covariates.

RESULTS

A higher (flatter) diurnal slope was associated with lower FEV₁/FVC ratio (β: 0.433, 95%CI [-0.766, -0.101]). We did not find any main effect associations between prenatal Pb and lung function outcomes. We report an interaction between Pb and cortisol in relation to FEV₁/FVC and FEF_25-75% (p_interaction<0.05 for all). Higher prenatal Pb was associated with reduced FEV₁/FVC only in children whose mothers had a high CAR. Higher prenatal Pb was also associated with reduced FEV₁/FVC and FEF_25-75% in mothers with a flatter diurnal slope. A 3-way interaction between prenatal Pb, CAR and sex on FEV₁/FVC, indicated that boys born to women with high CAR and higher prenatal Pb levels had lower FEV₁/FVC ratios (p_interaction = 0.067).

CONCLUSIONS

Associations between prenatal Pb and childhood lung function were modified by disrupted maternal cortisol in pregnancy and child sex. These findings underscore the need to consider complex interactions to fully elucidate effects of prenatal Pb exposure on childhood lung function.

Neighborhood Poverty in Combination with Older Housing Is Associated with Adverse Birth Outcomes: A Study on Ubiquitous Lead Risk among 1 Million Births in Texas

The purpose of this study was to determine whether housing age in combination with neighborhood poverty, as a proxy for fetal exposure to heavy metal lead, is associated with adverse birth outcomes. We linked population-level birth certificate data for Black, Hispanic, White and Other women, stratified by nativity, from 2009-2011 in Texas (n = 1,040,642) to census the tract-level median housing age/poverty level from the American Community Survey, 2007-2011. Tracts with median housing age values before 1975 with a poverty level of 20% or more were considered to be neighborhoods with a high risk of exposure to deteriorating lead-based paint. We estimated multilevel models to examine the relationship between neighborhood housing age/poverty level and each dependent variable (preterm birth, low birth weight, small-for-gestational age). The odds of adverse birth outcomes were significantly higher for mothers living in high-poverty neighborhoods with median housing built before the lead-based paint ban. Increased awareness of-and improved methods of alleviating- ubiquitous lead-based paint exposure in Texas may be necessary interventions for positive developmental trajectories of children. Allocating federal funds for place-based interventions, including universal lead paint mitigation, in older, high-poverty neighborhoods may reduce the disproportionate risk of adverse birth outcomes.

Association of maternal lead exposure with the risk of preterm: a meta-analysis

BACKGROUND

The relationship between maternal lead level and risk of preterm birth (PTB) remained controversial. Therefore, herein we performed this meta-analysis to investigate the association of maternal blood, urine and cord blood lead level with the risk of PTB using observational studies.

METHODS

A systematic search was conducted in PubMed, EMBASE and Ovid Medline databases from inception to August 2019, and sixteen studies with 65600 participants investigating the association between maternal lead level and PTB were included in our meta-analysis. Odds ratios (ORs) and 95% confidence intervals (95% CI) were calculated for the highest versus lowest lead level by random-effects model.

RESULTS

Overall, the pooled OR of all included articles for the highest versus lowest PTB score was 1.29 (95% CI = 1.14-1.46; I2 = 80.4%, p < .001), and the results revealed a direct and significant relationship between second and third trimester blood lead level (BLL) and PTB (OR 2nd trimester= 1.61, 95% CI = 1.08-2.40, OR 3rd trimester= 1.57, 95% CI = 1.11-2.23).

CONCLUSION

Results of this meta-analysis showed that maternal BLL is directly associated with the risk of PTB.

Association of prenatal maternal blood lead levels with birth outcomes in the Japan Environment and Children's Study (JECS): a nationwide birth cohort study

BACKGROUND

Despite dramatic declines in prenatal maternal blood lead levels (BLLs) in most developed countries, little is known about the effects of extremely low-level (<1.0 µg/dL) lead exposure on fetal growth.

METHODS

We measured maternal BLL during the second or third trimester of pregnancy and assessed birth outcomes, including birthweight, preterm birth (<37 gestational weeks) risk, small for gestational age births (SGA; birthweight <10th percentile) and low birthweight (LBW; <2500 g). The association between birthweight and maternal BLL was estimated using linear and quadratic spline models. Multivariable logistic models were used to examine the risk of binary responses.

RESULTS

From 103 099 pregnant women, 20 000 blood samples were randomly selected for analysis. The maternal BLL range was 0.16-7.4 µg/dL, and the median was 0.63 µg/dL. After adjusting for covariates, the linear model showed that each 0.1 μg/dL increase in maternal BLL was associated with a 5.4 g decrease in mean birthweight [95% confidence interval (CI), 3.4 to 7.5 g]. The risk of SGA [adjusted odds ratio (aOR), 1.03; 95% CI, 1.02 to 1.05) and LBW (aOR, 1.03; 95% CI, 1.02 to 1.05) increased, whereas the risk of preterm delivery did not (aOR, 0.99; 95% CI, 0.97 to 1.02).

CONCLUSIONS

Even at a maternal BLL below 1.0 µg/dL, prenatal lead exposure was associated with decreased birthweight and increased risk of SGA and LBW, but not preterm delivery. The adverse effect estimates of prenatal lead exposure on birth outcomes were quantitatively small and clinically limited at this low level.

Prenatal blood levels of some toxic metals and the risk of spontaneous abortion

High-level toxic metal exposure has become rare in the recent years. Although, it has not known whether relatively lower exposure may adversely affect human reproductive system. Spontaneous abortion (SA) is a serious reproductive problem, which, in many cases, the cause(s) is not clearly understood. To assess the relationship between prenatal blood level of metals and SA risk, we compared blood concentration of some heavy metals in samples taken from mothers recruited in Tehran Environment and Neurodevelopmental Defects (TEND) study conducted on apparently healthy pregnant women in Tehran, Iran who subsequently experienced spontaneous abortion with mothers who their pregnancy ended to live births. During early gestation, 206 women were enrolled to the survey and followed up till fetal abortion or baby deliveries occur. Blood metal concentrations were measured using an inductively coupled plasma mass spectrometer. The mean blood levels of lead, antimony, and nickel were higher in SA than ongoing pregnancy; however, this difference was not statistically significant. When adjusted for covariates, the logistic regression analysis showed significant association between maternal age and the risk of SA in all models. Among toxic metals only antimony had a noticeable positive relation with the risk of SA (OR: 1.65, 95% CI:1.08-2.52, P value: 0.02). Pearson's correlation coefficient showed significant (P < 0.05) positive correlations among prenatal blood metals levels, except for nickel. Although the present study failed to provide strong evidence for the effects of toxic metals on the occurrence of SA at the relatively low-levels, these metals should be avoided in women who plan pregnancy and/or during the early stages of gestation to prevent the chance of adverse effects.

Placental chemical elements concentration in small fetuses and its relationship with Doppler markers of placental function

INTRODUCTION

In this study, we aimed at quantifying placental concentrations of 22 chemical elements in small fetuses (SGA) as compared with normally grown fetuses (AGA), and to assess the relationship with Doppler markers of placental function.

METHODS

Prospective cohort study, including 71 SGA fetuses (estimated fetal weight < 10th percentile) and 96 AGA fetuses (estimated fetal weight > 10th percentile), recruited in the third trimester of gestation. The placental concentration of 22 chemical elements was determined by inductively coupled plasma optical emission spectrophotometer (ICP-OES, ICAP 6500 Duo Thermo): aluminum (Al), beryllium (Be), bismuth (Bi), calcium (Ca), cadmium (Cd), cobalt (Co), chrome (Cr), copper (Cu), magnesium (Mg), manganese (Mn), molybdenum (Mo), nickel (Ni), phosphorus (P), lead (Pb), rubidium (Rb), sulfur (S), strontium (Sr), titanium (Ti), thallium (Tl), antimony (Sb), selenium (Se), and zinc (Zn). Placental function was assessed by measuring the following fetal-maternal parameters: Uterine artery Pulsatility Index (UtA PI), Umbilical artery Pulsatility Index (UA PI) and Middle Cerebral artery Pulsatility Index (MCA PI). The association between the chemical elements concentration and study group and the association with Doppler measures were evaluated.

RESULTS

SGA was associated with significantly (p < 0.05) lower concentrations of Al (AGA 21.14 vs SGA 0.51 mg/kg), Cr (AGA 0.17 vs SGA 0.12 mg/kg), Cu (AGA 0.89 vs SGA 0.81 mg/kg), Mg (AGA 0.007 vs SGA 0.006 g/100g), Mn (AGA 0.60 vs SGA 0.47 mg/kg), Rb (AGA 1.68 vs SGA 1.47 mg/kg), Se (AGA 0.02 vs SGA 0.01 mg/kg), Ti (AGA 0.75 vs SGA 0.05 mg/kg) and Zn (AGA 9.04 vs SGA 8.22 mg/kg). Lower placental concentrations of Al, Cr, Mn, Se, Ti were associated with abnormal UtA, UA and MCA Doppler.

DISCUSSION

Lower placental concentrations of Al, Cr, Cu, Mn, Rb, Se, Ti and Zn are associated with SGA fetuses and abnormal fetal-maternal Doppler results. Additional studies are required to further understand how chemical elements affect fetal growth and potentially find strategies to prevent SGA.

Blood lead level monitoring related to environmental exposure in the general Iranian population: a systematic review and meta-analysis

Exposure to lead can cause adverse health problems incorporating hypophosphatemia, heart and liver disease, cancers, neurological and cardiovascular diseases, central nervous disorders, and sensory disorders. This study investigated the blood lead level in the general Iranian population with environmental exposure to lead. In the presented systematic review and meta-analysis, the authors searched Iranian dataset, including Magiran, SID, Iranmedex, and Nopa, and the main dataset, comprising PubMed, Scopus, Embase, and Web of Science, all available articles until 12 January 2019, and extracting 55 studies (with 63 data for analysis) to a meta-analysis. A comprehensive meta-analysis software, pooled standard deviation, mean, sample size, and the utterly random effects model was analyzed in this study. The results showed that the overall mean BLL (95% CI) in total inquiries was 6.41 μg/dL (5.96 to 6.87). Besides, the results for gender and age subgroups were as follows: mean BLL, 6.47 μg/dL, 95% CI, 5.79, to 7.15, mean BLL, 6.44 μg/dL, 95% CI, 5.96, to 6.91, respectively. Conclusively the mean BLL in the Iranian population was higher than the recommended level by the US Centers for Disease Control and Prevention (CDC). Results indicated that the mean BLL in men and adults was more elevated than in women and children, respectively. Therefore, BLL monitoring and screening of the general Iranian population are is necessary to determine a reference value.

Lead Levels in Wild Boar Meat Sauce (Ragù) Sold on the Italian Market

Game meat is endowed with excellent nutritional value, but it may also be a possible source of harmful substances, such as mycotoxins and heavy metals. In particular, several studies showed that lead fragments from hunting ammunition are able to represent a residual contaminant in the meat of wild boars or deer, representing a possible source of lead absorption. Even though wild boar meat consumption in Italy is rather limited, this meat could also be present in very popular Italian recipes, such as the typical meat sauce called ragù. We evaluated the lead levels in 48 samples (three different batches for each of the 16 brands) of ready-to-eat wild boar meat ragù sold on the Italian market in food stores and online distribution with the inductively coupled plasma-mass spectrometry (ICP-MS) technique. A high variability was found in the lead levels detected in the samples, with a median lead level of 0.10 mg/kg (0.01–18.3 mg/kg) and some of the samples showing very high lead concentrations. Since no intake level of lead is considered completely safe, and maximum levels for game meat have so far not been established, a greater attention on the risks to consumers’ health related to the presence of this heavy metal in game meat is recommended.

Prenatal Environmental Metal Exposure and Preterm Birth: A Scoping Review

Preterm birth (PTB) and its complications are the leading causes of under-five year old child deaths, accounting worldwide for an estimated one million deaths annually. The etiology of PTB is complex and multifactorial. Exposures to environmental metals or metalloids are pervasive and prenatal exposures to them are considered important in the etiology of PTB. We conducted a scoping review to determine the extent of prenatal exposures to four metals/metalloids (lead, mercury, cadmium and arsenic) and their association with PTB. We reviewed original research studies published in PubMed, Embase, the Cochrane Library, Scopus, POPLINE and the WHO regional indexes from 2000 to 2019; 36 articles were retained for full text review. We documented a higher incidence of PTB with lead and cadmium exposures. The findings for mercury and arsenic exposures were inconclusive. Metal-induced oxidative stress in the placenta, epigenetic modification, inflammation, and endocrine disruptions are the most common pathways through which heavy metals and metalloids affect placental functions leading to PTB. Most of the studies were from the high-income countries, reflecting the need for additional data from low-middle-income countries, where PTB rates are higher and prenatal exposure to metals are likely to be just as high, if not higher.

Association between blood lead level during pregnancy and birth weight: A meta-analysis

BACKGROUND

We aimed to provide a quantitative summary of evidence for a relationship between prenatal lead (Pb) exposure and birth weight.

METHODS

PubMed and Web of Science databases were searched for eligible epidemiological studies. We transformed findings in eligible studies with different effect-size metrics to standardized regression coefficients, and used fixed-effects or random-effects models to assess the pooled effects of prenatal Pb exposure on birth weight.

RESULTS

There was a significant negative association between prenatal Pb exposure and birth weight. Birth weight reduction was associated with elevated lead levels in maternal blood (β = -0.094; 95% confidence interval [CI]: -0.157 to -0.030) and cord blood (β = -0.120; 95% CI: -0.239 to -0.001).

CONCLUSIONS

This meta-analysis is the first to provide a quantitative assessment of Pb exposure during pregnancy and an increased risk of lower birth weight.

Hair Metal Levels and Childhood Weight Gain

Background:

Exposure to toxic metals remains a public health problem with lifelong impacts on childhood growth and development. We aimed to investigate metals effects on preschool children’s anthropometric variables.

Methods:

The study was conducted in Tehran, Iran, from Jul 2013 to Mar 2016. We measured scalp hair metal concentrations (lead, cadmium, arsenic, zinc, manganese, and cobalt), using inductively coupled plasma mass spectrometry, in 207 preschool children’s (36 to 72 months old).

Results:

A significant negative correlation between children’s hair lead levels and children’s weight was found (r= −0.178, P<0.05). Linear regression analysis confirmed the relationship when adjusted for the confounders, including children’s age, sex, height, family income, and maternal education (β= −0.191; t= −3.426, P< 0.01). The ANOVA analysis showed a significant (P<0.01) difference between hair lead level and children’s weight-for-age percentiles. Totally and separately, in almost all weight percentiles, hair lead levels were higher in girls than boys.

Conclusion:

The present study on Iranian children showed the current levels of lead exposure might negatively influence on children growth, with higher risk for girls than boys.

Early exposure to food contaminants reshapes maturation of the human brain-gut-microbiota axis

Early childhood growth and development is conditioned by the consecutive events belonging to perinatal programming. This critical window of life will be very sensitive to any event altering programming of the main body functions. Programming of gut function, which is starting right after conception, relates to a very well-established series of cellular and molecular events associating all types of cells present in this organ, including neurons, endocrine and immune cells. At birth, this machinery continues to settle with the establishment of extra connection between enteric and other systemic systems and is partially under the control of gut microbiota activity, itself being under the densification and the diversification of microorganisms' population. As thus, any environmental factor interfering on this pre-established program may have a strong incidence on body functions. For all these reasons, pregnant women, fetuses and infants will be particularly susceptible to environmental factors and especially food contaminants. In this review, we will summarize the actual understanding of the consequences of repeated low-level exposure to major food contaminants on gut homeostasis settlement and on brain/gut axis communication considering the pivotal role played by the gut microbiota during the fetal and postnatal stages and the presumed consequences of these food toxicants on the individuals especially in relation with the risks of developing later in life non-communicable chronic diseases.

Blood lead levels in antenatal women and its association with iron deficiency anemia and adverse pregnancy outcomes

OBJECTIVES

Lead is one of the most toxic heavy metal prevalent in the environment, which affects almost all major organs including heart, brain, intestines, kidneys as well as reproductive organs. It has been known that serum iron deficiency is associated with increased serum lead levels as lead is a particularly pernicious element to iron metabolism. Lead is also known to freely cross the placenta too; hence, this study was planned to determine any association between antenatal iron deficiency anemia (IDA), raised blood lead levels (BPb), and adverse pregnancy outcomes.

MATERIALS AND METHODS

This was an observational study done on 99 antenatal women with IDA and 41 nonanemic antenatal women. Lead levels were assessed in these 140 antenatal women and they were followed for adverse pregnancy outcomes. Chi-square test was used to find a difference in quantitative variables and Pearson's correlation test was used to assess association between BPb and hemoglobin levels.

RESULTS

We found that in 11 out of 99 (11.11%) women with IDA, BPb levels were high as compared to high BPb levels in only 1 out of 41 (2.4%) women without IDA and the high BPb levels ranged from 4 μg/dl-16.9 μg/dl with a mean BPb of 8.1 μg/dl. The difference in BPb among anemic and nonanemic antenatal women was significant (P < 0.05) and there was a negative dose effect relationship between BPb levels and hemoglobin levels. This difference in antenatal outcomes among women with and without high BPb levels was also significant with increased incidence of pre-eclampsia, FGR, and preterm deliveries in women with raised BPb levels. The incidence of NICU admission was also higher in the neonates of mothers with high BPb levels.

CONCLUSIONS

We propose screening of high-risk women based on their social, occupational, environmental, and personal factors, with serum lead levels in the preconception period itself. All public and personal measures must be taken to reduce lead consumption and exposure in the preconception and antenatal period.

Regulation of Nrf2 and NF-κB during lead toxicity in bovine granulosa cells

Lead (Pb), one of the pervasive and protracted environmental heavy metals, is believed to affect the female reproductive system in many species. The Nrf2 and NF-κB are the two key transcriptional factors regulating cellular redox status and response against stress and inflammation respectively, showing an interaction between each other. The aim of this study is to investigate the effect of Pb on bovine granulosa cells (GCs) and its association with the regulation of Nrf2 and NF-κB pathways. For this, bovine GCs were cultured in vitro and exposed to different doses of Pb for 2 h. Cellular response to Pb insult was investigated 24 h post treatment. Results showed that exposure of GCs to Pb-induced ROS accumulation and protein carbonylation. Additionally, GCs exhibited reduction in cell viability and decrease in the expression of cell proliferation marker genes (CCND2 and PCNA). This was accompanied by cell cycle arrest at G0/G1 phase. Moreover, Pb downregulated both Nrf2 and NF-κB and their downstream genes. Lead increased the expression of endoplasmic reticulum (ER) stress marker genes (GRP78 and CHOP) and the proapoptotic gene (caspase-3) while the antiapoptotic gene (BCL-2) was reduced. Our findings suggest that Pb-driven oxidative stress affected GCs proliferation, enhances ER stress, induces cell cycle arrest and mediates apoptosis probably via disruption of Nrf2/NF-κB cross-talk. However, further functional analysis is required to explain different aspects of Nrf2 and NF-κB interactions under metal challenge.

Recommended acceptable levels of maternal serum typical toxic metals from the perspective of spontaneous preterm birth in Shanxi Province, China

Preterm birth is an important issue of public reproductive health worldwide. The effects of the toxic metals on the likelihood of spontaneous preterm birth (SPB) are still under discussion. Our study aimed to investigate the association between maternal exposure to the five typical toxic metals or metalloid (i.e. arsenic (As), cadmium (Cd), chromium (Cr), mercury (Hg), and lead (Pb)) and the SPB likelihood. The mothers delivering fetus with SPB (cases) and those with term healthy birth (controls) were chosen from a prospective birth cohort of 3201 women carried out in Shanxi Province, China. A total of 147 SPB cases and 381 controls were included in our nested case-control study. We collected maternal general information by questionnaire and collected their blood sample during recruitment. The serum concentrations of the five toxic metals were measured by inductively coupled-plasma mass spectrometry. We found that the demographic information between the cases and controls were well balanced. The participants in our study had relatively higher serum As concentration. For the other toxic metals (i.e. Cd, Cr, Hg, and Pb), their serum concentrations were overall in the middle range of those from general population. There were no significant associations of the serum concentrations of the five concerned toxic metals with the SPB likelihood. Our study results overall did not support that maternal exposure to As or Cd significantly contribute to the SPB risk in the current exposure level, as well as the other three toxic metals. We further proposed their upper concentration limits in maternal serum from the perspective of SPB likelihood during the early pregnant period, i.e. 18.2 ng/mL of As, 1.05 ng/mL of Cd, 0.96 ng/mL of Cr, 1.07 ng/mL of Hg, and 1.54 ng/mL of Pb.

Is the Concentration of Cadmium, Lead, Mercury, and Selenium Related to Preterm Birth?

Environmental pollution and exposure of people to heavy metals cause many bad obstetric outcomes. Our aim is to demonstrate the role of cadmium (Cd), lead (Pb), mercury (Hg), and selenium (Se) in preterm labor etiology with a case-control study. In this study, between November 2017 and April 2018, preterm delivery mothers and term delivery mothers were compared in Çorum, Turkey. All deliveries were performed with cesarean sections and there were 30 mothers in the control group and 20 in the study group. The maternal blood, maternal urine, umbilical cord blood, and heavy metal levels in the amnion fluid in both groups were studied. Graphite furnace atomic absorption spectrometry was used to determine the blood concentration of Cd, Pb, Hg, and Se. We found lower levels of selenium in blood and urine of preterm delivery mothers and umbilical cord and amnion fluids of preterm infants (p < 0.01). We found a statistically significant positive correlation at selenium levels between mother's blood and umbilical cord blood (r (50) = 0.896, p < 0.001) and between maternal urine and amniotic fluid (r (50) = 0.841, p < 0.001). We have not found a similar correlation between mother and fetus of other metals (p > 0.05). We found that selenium levels were lower in mothers who were preterm birth in the light of the data in our study. We could not determine the positive or negative correlation of Cd, Pb, and Hg levels in blood, urine, and amniotic fluid samples with preterm birth.

Altered cord blood mitochondrial DNA content and pregnancy lead exposure in the PROGRESS cohort

INTRODUCTION

Lead (Pb) crosses the placenta and can cause oxidative stress, reduced fetal growth and neurological problems. The principal source of oxidative stress in human cells is mitochondria. Therefore, disruption of normal mitochondrial function during pregnancy may represent a primary mechanism behind the adverse effects of lead. We sought to assess the association of Pb exposure during pregnancy with mitochondrial DNA (mtDNA) content, a sensitive marker of mitochondrial function, in cord blood.

MATERIALS AND METHODS

This study comprised mother-infant pairs from the Programming Research in Obesity, Growth, Environment and Social Stressors (PROGRESS) study, a prospective birth-cohort that enrolled 1050 pregnant women from Mexico City who were receiving prenatal care between December 2007 and July 2011. Quantitative PCR was used to calculate relative MtDNA content (mitochondrial-to-nuclear DNA ratio (mtDNA/nDNA)) in cord blood. Lead concentrations in both maternal blood (2nd and 3rd trimester and at delivery day) and in cord blood were measured by ICP-MS. Multivariable regression models adjusting for multiple confounders were fitted with 410 mother-infant pairs for whom complete data for mtDNA content, lead levels, and covariates were available.

RESULTS

Maternal blood Pb measured in the second (mean 3.79 μg/dL, SD 2.63; β = 0.059, 95% CI 0.008, 0.111) and third trimester (mean 3.90 μg/dL; SD 2.84; β = 0.054, 95% CI 0.002, 0.107) during pregnancy and PB in cord blood (mean 3.50 μg/dL, SD 2.59; β = 0.050, 95% CI 0.004; 0.096) were associated with increased cord blood mtDNA content (mean 1.46, SD 0.44). In two-way interaction analyses, cord blood Pb marginally interacted with gestational age leading to an increase in mtDNA content for pre-term births (Benjamini-Hochberg False Discovery Rate correction; BH-FDR = 0.08).

CONCLUSION

This study shows that lead exposure in pregnancy alters mtDNA content in cord blood; therefore, alteration of mtDNA content might be a mechanism underlying the toxicity of lead.

Lead and copper in hunted wild boars and radiographic evaluation of bullet fragmentation between ammunitions

The purpose of the present study was to evaluate the content of lead in carcasses of wild boars shot with lead bullets, in comparison with that of copper caused by lead-free ammunitions. Radiographic images of hunted boars were obtained in order to assess the degree of bullet fragmentation in the carcasses. Samples of meat were collected from different body areas at increasing distance from bullet trajectory, to be analysed by ICP-MS for lead and copper levels. In wild boars shot with lead ammunitions, a massive dispersion of bullet fragments and very high lead levels were detected. By contrast, in wild boars killed with copper ammunitions no radiographic signs of bullet fragmentation were observed. Copper ammunitions seem therefore a safer alternative to standard lead-core ones, due to their minimal fragmentation and the relatively low toxicity of this metal.

Placental metal concentrations and birth outcomes: The Environment and Childhood (INMA) project

OBJECTIVE

To examine the association of placental levels of arsenic (As), cadmium (Cd), mercury (Hg), lead (Pb), manganese (Mn), and chromium (Cr) with birth outcomes (birth weight, length, and head circumference, low birth weight [LBW], gestational age, preterm delivery, and small for gestational age [SGA]) in mother-child pairs from the Environment and Childhood (INMA) Project in Spain.

METHODS

Metal concentrations were measured in placenta tissue samples randomly selected from five INMA cohorts. Data on birth outcomes were obtained from medical records. Associations were assessed in a sub-sample of 327 mother-infant pairs by regression models adjusted for confounding factors and for all metals simultaneously. Effect modification by sex was also evaluated.

RESULTS

Elevated placental Cd levels (>5.79 vs. <3.30 ng/g) were associated with reduced birth weight (-111.8 g, 95%CI = -215.6; -8.06, p-trend = 0.01) and length (-0.62 cm, 95%CI = -1.20; -0.04, p-trend = 0.02), while a 10% increase in Cd was associated with 1.21-fold increased odds (95%CI = 1.01; 1.43) of LBW in the global sample but with 14% lower odds (95%CI = 0.78; 0.96) of preterm delivery in males (P_interaction = 0.10). Detected (vs. undetected) Hg was associated with reduced head circumference (-0.49 cm, 95%CI = -1.00; 0.03) in females (P_interaction = 0.03). A 10% increase in placental Mn was associated with slight increases in gestational age (0.04 weeks, 95%CI = 0.01; 0.07) in the global sample and in head circumference (0.05 cm, 95%CI = -0.01; 0.10) in females (P_interaction = 0.03). Elevated Cr levels (>99.6 vs. <56.1 ng/g) were associated with reduced birth length (-0.68 cm, 95%CI = -1.33; -0.04, p-trend = 0.02) and slightly increased gestational age (0.35 weeks, 95%CI = -0.07; 0.77, p-trend = 0.08) in the global sample. As and Pb were detected in few placentas (27% and 13%, respectively) and were not associated with any studied birth outcome.

CONCLUSIONS

Data suggest that in utero exposure to Cd, Hg, and Cr could adversely affect fetal growth, whereas Mn and Cr appear to have a positive effect on gestational age. Given the relatively small number of subjects, sex-specific associations should be interpreted with caution.

Blood Lead Levels in Women of Child-Bearing Age in Sub-Saharan Africa: A Systematic Review

This paper reported available studies on blood lead level of childbearing age in Sub-Saharan African women. PubMed and Google scholar databases were searched for original articles reporting blood lead levels of women of childbearing age in Sub-Saharan Africa. Searches were not limited to year of study but limited to studies published in English Language. Data were extracted and synthesized by estimating the weighted mean of the reported blood lead levels. Fifteen papers fulfilled the inclusion criteria. Mean blood lead levels of women in the studies ranged from 0.83 to 99 μg/dl. The overall weighted mean of blood lead levels was 24.73 μg/dl. The weighted mean from analyses of data on blood lead levels of pregnant women alone was 26.24 μg/dl. Identified sources of lead exposure included lead mine, informal lead-acid battery recycling, leaded gasoline and piped water. Elevated BLLs were associated with incidence of preeclampsia, hypertension, and malaria. Important contributing factors for elevated blood lead levels (BLL) in these women include poverty, high environmental lead burden, low awareness on lead exposure hazards and lack of regulation for lead in consumer products. BLLs of women of childbearing age in SSA are unacceptably high. There is need therefore, for aggressive programs to address lead exposure in this population.

Investigation of association between environmental and socioeconomic factors and preterm birth in California

BACKGROUND

Preterm birth (PTB),2 defined as birth at gestational age <37 weeks, is a major public health concern. Infants born prematurely, comprising of about 10% of the US newborns, have elevated risks of neonatal mortality and a wide array of health problems. Although numerous clinical, genetic, environmental and socioeconomic factors have been implicated in PTB, very few studies investigate the impacts of multiple pollutants and social factors on PTB using large scale datasets.

OBJECTIVES

To evaluate association between environmental and socioeconomic factors and PTB in California.

METHODS

We linked the birth cohort file maintained by the California Office of Statewide Health Planning and Development from 2009 to 2012 years across 1.8 million births and the CalEnviroScreen 3.0 dataset from California Communities Environmental Health Screening Tool at the census tract level for 56 California counties. CalEnviroScreen contains 7 exposure and 5 environmental effects variables that constitute the Pollution Burden variable, and 5 socioeconomic variables. We evaluated relationships between environmental exposures and the risk of PTB using hierarchical clustering analyses and GIS-based visualization. We also used logistic regression to evaluate the relationship between specific pollutant and exposure indicators and PTB, accounted for socio-demographic determinants such as maternal race/ethnicity, maternal age, maternal education and payment of delivery costs.

RESULTS

There exists geographic variability in PTB for groups of counties with similar environmental and social exposure profiles. We found an association between Pollution Burden, particulate matter ≤2.5 μm (PM2.5), and Drinking Water Scores and PTB (adjusted odds ratios were 1.03 (95% Confidence Interval (CI): 1.01, 1.04), 1.03 (95% CI: 1.02,1.04), and 1.04 (95% CI: 1.03,1.05), respectively). Additional findings suggest that certain drinking water contaminants such as arsenic and nitrate are associated with PTB in California.

CONCLUSIONS

CalEnviroScreen data combined with birth records offer great opportunity for revealing novel exposures and evaluating cumulative exposures related to PTB by providing useful environmental and social information. Certain drinking water contaminants such as arsenic and nitrate are potentially associated with PTB in California and should be investigated further. Small association signals may involve sizeable population impacts.

Blood lead levels in pregnant women referring to midwifery clinic in a referral center in Tehran

Background:

Lead effects on children and pregnant women are grave, and screening tests would be logical to detect high blood lead levels (BLLs) in early stages.

Materials and Methods:

Blood samples were taken from the pregnant mothers who referred to midwifery clinic with further phone interview postdelivery.

Results:

In 100 patients evaluated, the mean age was 29 ± 5 years (median interquartile range gestational age of 33 [24, 37] weeks). There was a significant correlation between polluted residential area and median BLL (P = 0.044) and substance exposure (P = 0.02). The median BLL was significantly lower in those without a history of lead toxicity in the family (P = 0.003). The only factor that could predict the BLL levels lower than 3.2 and 5 μg/dL was living in the nonindustrial area. All pregnant women delivered full-term live babies.

Conclusion:

Positive history of lead toxicity in the family and living in polluted areas may pose a higher BLL in pregnant women.

Environmental toxic metals in placenta and their effects on preterm delivery-current opinion

Preterm birth is a significant public reproductive health concern globally; Furthermore, preterm birth has long-lasting medical and pecuniary burdens on the society. Moreover, preterm birth is well-established as the underlying cause of low birth weight in infants as well as neonatal mortality. A growing body of literature suggests that the etiology of preterm delivery in women is elusive; however, countless environmental factors are considered responsible for preterm birth. Environmental contaminants that are toxic metals such as lead, cadmium, arsenic, and mercury are familiar confounding factors for preterm birth globally. Recent studies have indicated that these toxic heavy metals induce oxidative stress in the trophoblastic placental tissue by producing reactive oxygen species that alter the mechanism of antioxidants possibly leading to preterm birth. Moreover, no obvious mechanism underlying metal-induced oxidative stress in the placenta has been identified until date. Consequently, this review offers an outline of the currently existing scientific information on the association of toxic metals and redox status of the placental tissue with preterm birth. Furthermore, this study critically recognizes the gaps related to the deleterious effect of metals on the gestation period in scientific literature.

Data on the environmental exposure to lead in Iran

The data was obtained to present the environmental and occupational exposure to lead in Iranian populations based on the published articles. To acquire the data, online resources including Google Scholar, Magiran, SID, Iranmedex, PubMed, and Science Direct were searched and 104 articles were found out of which 70 that focused on the level of lead in blood, urine, milk, and hair of different Iranian populations were selected. Since the results of the studies were not homogenous, it was not possible to carry out a meta-analysis. The average blood lead level (BLL) among workers, ordinary people, patients with specific diseases, addicts, and pregnant women, women in labor, infants, and children are presented in this article. The average BLL was compared to the standards.

[Effects of Trace Environmental Chemicals on Child Health-Lead as an Example]

The low birthrate and aging population of Japan are entering a serious phase. As measures against the declining birthrate, improvement of the environment is promoted to support childbirth and child-rearing, but even if the birthrate increases in the future, it will take time before the effect is observed as an increase in the population. As the number of children and young people is decreasing, in order to maintain a wealthy and sustainable society, we should create an environment wherein each child can grow healthily and demonstrate sufficient abilities in participating in society. The authors have been studying the influence of exposure to environmental chemical substances on the development of children. Lead is especially considered to impair neurological development even at low concentrations of exposure. In this paper, using lead as an example, we discuss risk assessment and countermeasures for the health effects of trace chemical substances on a society with a declining birthrate. Substances that show neurotoxicity increase social costs even at low concentrations of exposure. To preserve and promote social vitality in Japan despite the declining birthrate and aging population, it is essential that measures are taken on the basis of scientifically reasonable cost/benefit assessment. For this purpose, we think that it is necessary to analyze costs and benefits in addition to the risk assessment of low concentrations of chemical substances.

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.

The effects of lead and aluminum exposure on congenital heart disease and the mechanism of oxidative stress

OBJECTIVES

This study aimed to analyze the association between fetal lead or aluminum exposure and congenital heart disease (CHD) occurrence as well as to explore the mechanism of oxidative stress in heart development.

METHODS

Lead and aluminum concentrations were measured by ICP-MS in umbilical serum. The oxidative stress statuses were analyzed by measuring SOD, GPx and MDA with colorimetric assays.

RESULTS

Higher concentrations of Al were seen in the CHD groups compared to the controls. The risk of CHD occurrence increased markedly in the highly elevated Al group (aOR 2.08, 95%CI 1.11-3.88). With increasing Al and Pb levels, the activity of SOD decreased, and the level of MDA increased. Significantly decreased activity of SOD and GPx were found in the CHD groups (P < 0.05).

CONCLUSION

Fetal aluminum exposure may contribute to CHD occurrence. Oxidative stress was related to the concentration of Pb and Al, which may be involved in the occurrence of CHD.

Selected maternal, fetal and placental trace element and heavy metal and maternal vitamin levels in preterm deliveries with or without preterm premature rupture of membranes

AIM

To compare maternal, fetal and placental trace element (magnesium, zinc and copper) and heavy metal (cadmium and lead) and maternal vitamin (retinol, α [alpha]-tocopherol, vitamin D₃ , 25-hydroxyvitamin D₃ and 1,25-dihydroxyvitamin D₃ ) levels in preterm deliveries with and without preterm premature rupture of membranes (PPROM).

METHODS

Sixty-eight patients giving birth preterm were grouped into preterm deliveries with PPROM (n = 35) and without PPROM (n = 33). Following delivery, maternal and umbilical cord blood sera and placental tissue samples were obtained. While magnesium, zinc, copper, cadmium and lead levels were measured in all samples, the levels of retinol, α-tocopherol, vitamin D₃ , 25-hydroxyvitamin D₃ and 1,25-dihydroxyvitamin D₃ were measured only in maternal serum.

RESULTS

While magnesium level in maternal serum and zinc levels in both maternal and umbilical cord sera were lower, placental magnesium level was higher in preterm deliveries with PPROM (P < 0.01). Umbilical cord serum magnesium, placental tissue zinc and maternal and umbilical cord sera and placental tissue copper, cadmium, and lead levels did not differ between the groups (P > 0.05). In preterm deliveries with PPROM, 25-hydroxyvitamin D₃ and retinol levels were higher, while vitamin D₃ and 1,25-dihydroxyvitamin D₃ levels were lower in maternal serum (P < 0.05). Maternal serum α-tocopherol levels were similar between the groups.

CONCLUSION

Compared to spontaneous preterm births, PPROM is associated with low maternal serum together with high placental tissue magnesium and low maternal and umbilical cord sera zinc levels. Higher retinol and 25-hydroxyvitamin D₃ and lower vitamin D₃ and 1,25-dihydroxyvitamin D₃ maternal serum levels are also evident in these patients.

Risk factors for premature birth in French Guiana: the importance of reducing health inequalities

OBJECTIVES

French Guiana has the highest birth rate in South America. This French territory also has the highest premature birth rate and perinatal mortality rate of all French territories. The objective was to determine the premature birth rate and to identify the prevalence of risk factors of premature birth in French Guiana.

METHODS

A retrospective study of all births in French Guiana was conducted between January 2013 and December 2014 using the computerized registry compiling all live births over 22 weeks of gestation on the territory.

RESULTS

During this period 12 983 live births were reported on the territory. 13.5% of newborns were born before 37 (1755/12 983). The study of the registry revealed that common sociodemographic risk factors of prematurity were present. In addition, past obstetrical history was also important: a scarred uterus increased the risk of prematurity adjusted odds ratio =1.4, 95%CI (1.2-1.6). Similarly, obstetrical surveillance, the absence of preparation for birth or of prenatal interview increased the risk of prematurity by 2.4 and 2.3, the excess fraction in the population was 69% and 72.2%, respectively.

CONCLUSIONS

Known classical risk factors are important. In the present study excess fractions were calculated in order to prioritize interventions to reduce the prematurity rate.

Association between Blood Lead Levels and Delta-Aminolevulinic Acid Dehydratase in Pregnant Women

Blood lead levels (BLLs) and delta-aminolevulinic acid dehydratase (ALAD) activity are considered biomarkers of lead exposure and lead toxicity, respectively. The present study was designed to investigate the association between BLLs and ALAD activity in pregnant women from Durango, Mexico. A total of 633 pregnant women aged 13–43 years participated in this study. Blood lead was measured by a graphite furnace atomic absorption spectrometer. ALAD activity was measured spectrophotometrically. Mean blood lead was 2.09 ± 2.34 µg/dL; and 26 women (4.1%) crossed the Centers for Disease Control (CDC) recommended level of 5 µg/dL. ALAD activity was significantly lower in women with levels of lead ≥5 µg/dL compared to those with BLLs < 5 µg/dL (p = 0.002). To reduce the influence of extreme values on the statistical analysis, BLLs were analyzed by quartiles. A significant negative correlation between blood lead and ALAD activity was observed in the fourth quartile of BLLs (r = −0.113; p < 0.01). Among women with blood lead concentrations ≥2.2 µg/dL ALAD activity was negatively correlated with BLLs (r = −0.413; p < 0.01). Multiple linear regression demonstrated that inhibition of ALAD in pregnant women may occur at levels of lead in blood above 2.2 µg/dL.

Environmental chemicals and preterm birth: Biological mechanisms and the state of the science

PURPOSE OF REVIEW

Preterm birth is a significant worldwide health problem of uncertain origins. The extant body of literature examining environmental contaminant exposures in relation to preterm birth is extensive but results remain ambiguous for most organic pollutants, metals and metalloids, and air pollutants. In the present review we examine recent epidemiologic studies investigating these associations, and identify recent advances and the state of the science. Additionally, we highlight biological mechanisms of action in the pathway between chemical exposures and preterm birth, including inflammation, oxidative stress, and endocrine disruption, that deserve more attention in this context.

RECENT FINDINGS

Important advances have been made in the study of the environment and preterm birth, particularly in regard to exposure assessment methods, exploration of effect modification by co-morbidities and exposures, and in identification of windows of vulnerability during gestation. There is strong evidence for an association between maternal exposure to some persistent pesticides, lead, and fine particulate matter, but data on other contaminants is sparse and only suggestive trends can be noted with the current data.

SUMMARY

Beyond replicating current findings, further work must be done to improve understanding of mechanisms underlying the associations observed between environmental chemical exposures and preterm birth. By examining windows of vulnerability, disaggregating preterm birth by phenotypes, and measuring biomarkers of mechanistic pathways in these epidemiologic studies we can improve our ability to detect associations with exposure, provide additional evidence for causality in an observational setting, and identify opportunities for intervention.

Low level lead exposure and pregnancy outcomes in an observational birth cohort study: dose-response relationships

Background

National and international guidelines on safe levels for blood Pb in pregnancy focus on a threshold above which exposure is of concern. However, it has recently been suggested that the decrease in birth weight per unit increase in blood Pb is actually greater at lower than at higher concentrations of Pb without evidence of a lower threshold of effect. Our aim was to investigate whether there was evidence for a differential effect of maternal Pb levels on birth outcomes and/or a threshold value for effects.

Methods

Blood samples from pregnant women enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC) were analysed. Data collected on the infants included anthropometric variables. We fitted adjusted multivariable fractional polynomial models for birth outcomes.

Results

Adjusted models that assumed a linear relationship between untransformed blood Pb and the outcomes provided the best fit: an increase of 1 µg/dl was associated with changes in birth weight of −9.93 (95 % CI −20.27, 0.41) g, head circumference −0.03 (95 % CI −0.06, 0.00) cm and crown–heel length −0.05 (95 % CI −0.10, 0.00) cm.

Conclusion

There was no evidence in this study to suggest a supralinear dose–response relationship or a lower threshold for the effect of maternal blood Pb on birth outcomes. This has implications for consideration of national and international guidelines on levels of concern in pregnancy. Exposure to Pb should be kept as low as possible during pregnancy to minimise adverse outcomes.

Maternal tea consumption and the risk of preterm delivery in urban China: a birth cohort study

BACKGROUND

Studies investigating the relationship between maternal tea drinking and risk of preterm birth have reached inconsistent results.

METHODS

The present study analyzed data from a birth cohort study including 10,179 women who delivered a singleton live birth were conducted in Lanzhou, China between 2010 and 2012.

RESULTS

Drinking tea (OR = 1.36, 95 % CI: 1.09-1.69), and specifically green (OR = 1.42, 95 % CI: 1.08-1.85) or scented tea (OR = 1.61, 95 % CI: 1.04-2.50), was associated with an increased risk of preterm birth. Drinking tea was associated with both moderate preterm (OR = 1.41, 95 % CI: 1.12-1.79) and spontaneous preterm birth (OR = 1.41, 95 % CI: 1.09-1.83). Risk of preterm birth increased with decreasing age of starting tea drinking (<20 years, OR = 1.60, 95 % CI: 1.17-2.20) and increasing duration (p for trend < 0.01). The relationship between tea drinking and preterm birth is modified by both maternal age (p < 0.05) and gestational weight gain (p < 0.05).

CONCLUSIONS

Despite conflicting findings in the previous literature, we saw a significant association with maternal tea drinking and risk of preterm birth in our cohort. More studies are needed both to confirm this finding and to elucidate the mechanism behind this association.

Is Prenatal Lead Exposure a Concern in Infancy? What Is the Evidence?

BACKGROUND

Exposure to unhealthy and unsafe environments cause 1 in 4 deaths in childhood each year. Early exposure to lead beginning prenatally and continuing throughout childhood is one of the mechanisms associated with unhealthy and unsafe environments, particularly in industrial countries and urban communities. Lead is a known heavy metal that crosses the placenta and blood-brain barrier depositing in fetal tissues.

PURPOSE

The purpose of this integrative review was to determine which maternal-fetal dyads were at high risk for elevated umbilical cord lead (Pb) levels and to examine the consequences associated with elevated umbilical cord Pb levels.

SEARCH STRATEGY

PubMed was searched to obtain English language publications from 2005 to March 2015 for studies examining the effects of prenatal lead exposure on infant outcomes using key terms "lead" combined with "infant." A total of 17 articles were retained for analysis.

FINDINGS

Infants with elevated umbilical cord blood lead levels were associated with maternal demographic factors and country of origin. Maternal-specific exposure to lead products prior to or during pregnancy was associated with elevated umbilical cord blood lead levels. The consequences of prenatal lead exposure to the infant at birth anthropometrically were mixed. The evidence on neurological consequences of prenatal exposure to lead appears to reflect changes in cognitive impairment; however, it needs further study.

IMPLICATIONS FOR PRACTICE

The major recommendation is primary prevention of lead exposure across the life span. Implementation of policies that reduce the availability of leaded products to reduce leaded products, especially ones aimed at children and women of childbearing age.

IMPLICATIONS FOR RESEARCH

Research needs to be focused in 2 directions: (1) prevention of lead exposure during pregnancy and (2) prevention of lead leaching from bones for all women of childbearing age.

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.

Adverse effects of maternal lead levels on birth outcomes in the ALSPAC study: a prospective birth cohort study

OBJECTIVE

To study the associations of prenatal blood lead levels (B-Pb) with pregnancy outcomes in a large cohort of mother-child pairs in the UK.

DESIGN

Prospective birth cohort study.

SETTING

Avon area of Bristol, UK.

POPULATION

Pregnant women enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC).

METHODS

Whole blood samples were collected and analysed by inductively coupled plasma dynamic reaction cell mass spectrometry (n = 4285). Data collected on the infants included anthropometric variables and gestational age at delivery. Linear regression models for continuous outcomes and logistic regression models for categorical outcomes were adjusted for covariates including maternal height, smoking, parity, sex of the baby and gestational age.

MAIN OUTCOME MEASURES

Birthweight, head circumference and crown-heel length, preterm delivery and low birthweight.

RESULTS

The mean blood lead level (B-Pb) was 3.67 ± 1.47 μg/dl. B-Pb ≥ 5 μg/dl significantly increased the risk of preterm delivery (adjusted odds ratio [OR] 2.00 95% confidence interval [95% CI] 1.35-3.00) but not of having a low birthweight baby (adjusted OR 1.37, 95% CI 0.86-2.18) in multivariable binary logistic models. Increasing B-Pb was significantly associated with reductions in birth weight (β -13.23, 95% CI -23.75 to -2.70), head circumference (β -0.04, 95% CI -0.07 to -0.06) and crown-heel length (β -0.05, 95% CI -0.10 to -0.00) in multivariable linear regression models.

CONCLUSIONS

There was evidence for adverse effects of maternal B-Pb on the incidence of preterm delivery, birthweight, head circumference and crown-heel length, but not on the incidence of low birthweight, in this group of women.

Maternal lead exposure and risk of congenital heart defects occurrence in offspring

Maternal lead exposure may be harmful to fetal development. However, sufficient evidence was lacked about the risk on cardiac development in offspring. To explore the association between maternal lead exposure and risks of congenital heart defects (CHDs) occurrence in fetuses, a case-control study was adopted during pregnant women making antenatal examinations. The maternal hair lead levels were measured by using inductively coupled plasma mass spectrometry (ICP-MS), and logistic regression analysis was used to calculate the odds ratio (OR). Three hundred and sixteen cases and 348 controls were eligible to the study. The median level of lead in maternal hair of case (0.670ng/mg) was significantly higher (AOR 3.07, 95% CI 2.00-4.72) than that of the control (0.461ng/mg), including the CHD cases with or without extracardiac malformations (AOR 3.55, 2.94, respectively). Maternal lead exposure is associated with the risk of some subtypes of CHDs occurrence in offspring. The potential dose-response relationship is also presented.