Low-level lead exposure and elevations in blood pressure during pregnancy

The Causal Association Between Blood Lead and Sleep Disorders: Evidence from National Health and Nutrition Examination Survey and Mendelian Randomization Analysis

BACKGROUND

Poor sleep quality is a global public health concern. This study aimed to identify the risk factors for sleep disorders and clarify their causal effects.

METHODS

Data were obtained from the National Health and Nutrition Examination Survey (NHANES) and Mendelian randomization (MR)-Base databases. Baseline characteristics of individuals with and without sleep disorders were compared. A multivariate logistic regression analysis was performed to calculate the effects of each variable on sleep disorders. Causal effects of blood lead levels and hypertension on sleep disorders were assessed using MR analysis.

RESULTS

In total, 3660 individuals were enrolled in the study. The prevalence of self-reported sleep disorders was 26.21%. Serum lead level, serum mercury level, serum retinol level, prevalence of hypertension, and daily vigorous work duration were significantly higher for those in the sleep disorders group than the control group. After adjusting for various covariates, the effects of serum lead and hypertension on sleep disorders were stable from logistic regression models 1-4. MR analysis showed that blood lead levels were causally related to the risk of sleep disorders (odds ratio (OR) = 1.09, 95% confidence interval (CI) 1.01-1.17, P = 0.030). There was no causal link between elevated blood pressure and sleep disorders (OR = 0.99, 95% CI 0.94-1.04, P = 0.757). Goodness-of-fit tests and sensitivity analyses were used to verify the reliability of the results.

CONCLUSIONS

Blood lead is positively and causally associated with an increased risk of sleep disorders. These findings provide a novel perspective regarding sleep protection. Taking effective measures to reduce lead exposure may significantly improve sleep health.

Contribution of serum elements to blood pressure during pregnancy by impacting gut microbiota: A prospective cohort study

Exposure to environmental elements can alter gut microbiota, further affecting host health. Exploring the interrelationships among element exposure, gut microbiota and blood pressure (BP) during pregnancy, as well as the mediating roles of gut microbiota, is warranted, which holds implications for maternal and offspring health. In a prospective cohort study between 2017-2018, 733 pregnant women were included. The serum elements and gut microbiota during the second trimester were assessed, and BP was collected during the second and third trimester and before delivery. Fourteen associations were identified between serum elements and BP, including positive associations of zinc (Zn) and thallium (Tl) with systolic BP during the second trimester. Rubidium (Rb) showed a positive association with Pielou's evenness. Serum elements, such as Tl and Rb, were significantly associated with the relative abundance of bacteria and co-abundance groups (CAGs). Alpha diversity was negatively associated with BP levels and trajectories. Moreover, 15 associations between gut microbiota and BP were shown. Finally, mediation analysis confirmed that CAG2 and Pielou's evenness mediated the associations of Tl and Rb with BP, respectively. We concluded that serum elements can contribute to BP changes during pregnancy through gut microbiota, suggesting gut microbiota-targeted approach as a potential intervention.

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 prenatal multiple plasma metal exposure and newborn telomere length: Effect modification by maternal age and infant sex

Exposure to metals during pregnancy may affect maternal and infant health. However, studies on the combined effects of metals on the telomere length (TL) of newborns are limited. A prospective cohort study was conducted among 1313 mother-newborn pairs in the Guangxi Zhuang Birth Cohort. The concentrations of metals in maternal plasma during the first trimester were measured using inductively coupled plasma-mass spectrometry. We explored the associations between nine plasma metals and newborn TL using generalized linear models (GLMs), principal component analysis (PCA), quantile g-computation (qgcomp), and Bayesian kernel machine regression (BKMR). The GLMs revealed the inverse association between plasma arsenic (percent change, -5.56%; 95% CI: -7.69%, -3.38%) and barium concentrations (-9.84%; 95% CI: -13.81%, -5.68%) and newborn TL. Lead levels were related to significant decreases in newborn TL only in females. The PCA revealed a negative association between the PC3 and newborn TL (-4.52%; 95% CI: -6.34%, -2.68%). In the BKMR, the joint effect of metals was negatively associated with newborn TL. Qgcomp indicated that each one-tertile increase in metal mixture levels was associated with shorter newborn TL (-9.39%; 95% CI: -14.32%, -4.18%). The single and joint effects of multiple metals were more pronounced among pregnant women carrying female fetuses and among pregnant women <28 years of age. The finding suggests that prenatal exposure to arsenic, barium, antimony, and lead and mixed metals may shorten newborn TLs. The relationship between metal exposures and newborn TL may exhibit heterogeneities according to infant sex and maternal age.

Blood Lead Levels among Non-Occupationally Exposed Pregnant Women in Southern Thailand

Lead (Pb) is a heavy metal that is toxic to humans, especially children and pregnant women. In Thailand, guidelines exist to minimize lead exposure in pregnant women working in lead-related occupations. However, no guidelines exist for pregnant women who are not employed in these economic sectors. This cross-sectional study aimed to examine blood lead levels (BLLs) and related risk factors among 80 non-occupationally exposed pregnant women from the general population living in Nakhon Si Thammarat province, Southern Thailand. BLLs were determined by graphite furnace atomic absorption spectrophotometry. A validated questionnaire was adopted to interview participants which included demographic, consumer goods, supplement intake, and health factors. The mean BLL was 4.68 ± 1.55 µg/dL (95% CI 4.33-5.02) and 42.50% had BLLs ≥ 5 µg/dL. Higher education was the only demographic factor associated with BLLs ≥ 5 µg/dL (aOR 0.16, 95% CI 0.03-0.80, p = 0.027). Systolic blood pressure was also associated with BLLs ≥ 5 µg/dL (aOR 5.00, 95% CI 1.23-17.16, p = 0.023). However, consumer goods and supplement intake were not associated with BLLs. Our results indicate that pregnant women from the general population who were not in the risk exposure group had lead in their bodies. Except for education, demographics were not associated with pregnant women with BLLs. However, with health factors, even low BLLs had a small effect on systolic blood pressure. These data suggest a need for promoting health education and health interventions to prevent the dangers of lead exposure, especially for pregnant women and children.

Association of blood lead levels with preeclampsia: A cohort study in China

BACKGROUND

Preeclampsia is the main cause of maternal and perinatal death, especially in developing countries. Multiple studies suggest that blood lead levels in pregnancy are a risk factor for preeclampsia, even with low levels of blood lead. But less knows the dose-effect relationship of preeclampsia in low blood lead levels.

OBJECTIVES

This study aims to assess the association between blood lead levels and preeclampsia and to explore its dose-effect relationship between low blood lead levels and preeclampsia.

METHODS

The retrospective cohort study was consecutively conducted in a comprehensive tertiary hospital in Foshan city of Guangdong Province, China, from August 1, 2019, to November 30, 2019. Blood lead levels were measured in maternal whole blood in 12-27 (+6) weeks of pregnancy, using atomic absorption spectrometer. Preeclampsia diagnosis was ascertained from the electronic medical records system. The risk of preeclampsia was estimated by multivariable logical regression analysis, and a two-stage linear regression model was established to find out the dose-effect.

RESULTS

A total of 2174 people were included in this study, and 59 (2.7%) women developed preeclampsia. The dose-effect analysis revealed a non-linear association between blood lead levels and the risk of preeclampsia, with a cut-off point at 4.2 μg/dl. When blood lead levels were over 4.2 μg/dl, the risk of preeclampsia increased significantly with an increase in blood lead levels (OR = 2.05, 95%CI: 1.50, 2.81). In the multivariate regression models, per 1 μg/dl increment in blood lead levels was associated with 43% higher risk of developing preeclampsia (OR = 1.43,95%CI:1.17,1.74). Moreover, the association between blood lead levels and preeclampsia was stable in different subgroups.

CONCLUSIONS

Low levels of lead exposure had a dose-effect relationship of preeclampsia, with a cut-off point at 4.2 μg/dl. Blood lead levels had a non-linear association with preeclampsia. When the blood lead levels were higher than 4.2 μg/dl, the risk of preeclampsia increases by 105% for every 1 μg/dl increase in blood lead levels.

Association of blood metal exposure with testosterone and hemoglobin: A cross-sectional study in Hangzhou Birth Cohort Study

BACKGROUND

Few epidemiological studies have investigated associations of exposure to multiple metals with testosterone homeostasis and erythropoiesis, especially for the pregnant women.

METHODS

Among all the 1644 participants enrolled in Hangzhou Birth Cohort Study (HBCS) at baseline, a total of 918 pregnant women with complete data of interest were analyzed. The whole blood metals levels were examined by inductively coupled plasma mass spectrometry (ICP-MS), and serum testosterone level was evaluated by chemiluminescent microparticle immunoassay (CMIA), and erythropoietic parameters values were extracted from medical record. Multivariable linear regression models were applied to estimate the relationships between metals levels and testosterone level, and between metals levels and erythropoietic parameters, and potential confounders were adjusted.

RESULTS

Single metal model analysis revealed a significant association of blood As, Mn and Pb level with serum testosterone level. After controlling for multiple testing, the dose-response trend with statistical significance (FDR-adjusted p trend <0.05) was observed across tertiles of Pb with testosterone. This association, when by stratified by gender, remained in pregnant women with a male fetus but did not reach significant in those with a female fetus. Furthermore, blood Pb level was positively associated with red blood cell counts, hemoglobin level and hematocrit. Serum testosterone level was positively associated with red blood cell counts, hemoglobin level and hematocrit. Mediation analyses indicated that testosterone might act as a mediator in the association between Pb exposure and erythropoietic parameters.

CONCLUSIONS

Serum testosterone level and hemoglobin level was positively related to blood Pb level among Chinese pregnant women, and testosterone might mediate the effect of Pb exposure on hemoglobin. Additional prospective studies are warranted to confirm the causality.

Prenatal exposure to tobacco smoke leads to increased mitochondrial DNA content in umbilical cord serum associated to reduced gestational age

We investigated if prenatal exposures to tobacco smoke lead to changes in mitochondrial DNA content (mtDNA) in cord serum and adversely affect newborns' health. Umbilical cord serum cotinine levels were used to determine in utero exposure to smoking. Cord serum mtDNA was measured by quantitative polymerase chain reaction analysis of the genes coding for cytochrome c oxidase1 (MT-CO1) and cytochrome c oxidase2 (MT-CO2). Log transformed levels of mtDNA coding for MT-CO1 and MT-CO2 were significantly higher among infants of active smokers with higher serum level of cotinine (p < 0.05) and inversely associated with gestational age (p = 0.08; p = 0.02). Structural equation modeling results confirmed a positive association between cotinine and MT-CO1 and2 (p < 0.01) and inverse associations with gestational age (p = 0.02) and IGF-1 (p < 0.01). We identified a dose-dependent increase in the level of MT-CO1 and MT-CO2 associated to increased cord serum cotinine and decreased gestational age.

The relationship between blood lead levels and occupational exposure in a pregnant population

Background

Pregnant women exposed to lead are at risk of suffering reproductive damages, such as miscarriage, preeclampsia, premature delivery and low birth weight. Despite that the workplace offers the greatest potential for lead exposure, there is relatively little information about occupational exposure to lead during pregnancy. This study aims to assess the association between blood lead levels and occupational exposure in pregnant women from Durango, Mexico.

Methods

A cross-sectional study was carried out in a population of 299 pregnant women. Blood lead was measured in 31 women who worked in jobs where lead is used (exposed group) and 268 who did not work in those places (control group). Chi-square test was applied to compare exposed and control groups with regard to blood lead levels. Odds ratio (OR) and 95% confidence intervals (CI) were calculated. Multivariable regression analysis was applied to determine significant predictors of blood lead concentrations in the exposed group.

Results

Exposed women had higher blood lead levels than those in the control group (4.00 ± 4.08 μg/dL vs 2.65 ± 1.75 μg/dL, p = 0.002). Furthermore, women in the exposed group had 3.82 times higher probability of having blood lead levels ≥ 5 μg/dL than those in the control group. Wearing of special workwear, changing clothes after work, living near a painting store, printing office, junkyard or rubbish dump, and washing the workwear together with other clothes resulted as significant predictors of elevated blood lead levels in the exposed group.

Conclusions

Pregnant working women may be at risk of lead poisoning because of occupational and environmental exposure. The risk increases if they do not improve the use of protective equipment and their personal hygiene.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-016-3902-3) contains supplementary material, which is available to authorized users.

Environmental influences on reproductive health: the importance of chemical exposures

Chemical exposures during pregnancy can have a profound and life-long impact on human health. Because of the omnipresence of chemicals in our daily life, there is continuous contact with chemicals in food, water, air, and consumer products. Consequently, human biomonitoring studies show that pregnant women around the globe are exposed to a variety of chemicals. In this review we provide a summary of current data on maternal and fetal exposure, as well as health consequences from these exposures. We review several chemical classes, including polychlorinated biphenyls, perfluoroalkyl substances, polybrominated diphenyl ethers, phenols, phthalates, pesticides, and metals. Additionally, we discuss environmental disparities and vulnerable populations, and future research directions. We conclude by providing some recommendations for prevention of chemical exposure and its adverse reproductive health consequences.

Effectiveness of introducing point of care capillary testing and linking screening with routine appointments for increasing blood lead screening rates of young children: a before-after study

Background

Lead has significant neuro-toxic effects, particularly for young children. Voluntary screening of pre-school aged children for elevated blood lead levels has been an important part of the lead management program in the mining town of Broken Hill (NSW, Australia) since 1991, where lead remains a significant public health issue for young children despite average blood lead levels having fallen by two-thirds. The annual proportion of children screened declined to 0.39 in 2008. The objective of this study was to determine the impact of changing to capillary screening and linking screening with existing routine health programs on participation in blood lead screening by young children in the community.

Methods

We used a before-after study. Screening rates were determined from routinely collected service data and analysed using cross-sectional and cohort analyses.

Results

The proportion of children screened annually increased from 0.39 in 2008 to 0.75 in 2012, with the greatest increases among 11–23 and 48–59 month old children. The proportion of children screened at least once by 24 months increased from 0.63 for children born in 2007 to 0.98 for children born in 2010. Attendance stabilized after capillary screening was introduced, and increased markedly after screening was offered at immunization.

Conclusons

Changing from venous to capillary screening stabilized attendance and improving convenience was associated with dramatically increased screening. Linking screening with well-accepted mainstream child health programs is an effective strategy to improve participation in blood lead screening programs. The findings have implications for improving participation in other health screening programs.

Delivery Blood Pressure and Other First Pregnancy Risk Factors in Relation to Hypertensive Disorders in Second Pregnancies

BACKGROUND

First pregnancy characteristics and blood pressure (BP) measures may be associated with second pregnancy hypertensive disorder risk. We examined the association between first pregnancy risk factors and second pregnancy hypertensive disorders.

METHODS

Electronic medical records of nulliparas (n = 26,787) delivering at least twice in Utah (2002-2010) were used. Polychotomous logistic regression models estimated the association of first pregnancy risk factors with second pregnancy hypertensive disorders (gestational hypertension, preeclampsia, or chronic hypertension) stratified by first pregnancy hypertensive status and adjusted for second characteristics.

RESULTS

Among normotensive women in their first pregnancy, preterm birth (<34 weeks) and elevated BP at delivery admission in the first pregnancy increased odds of all incident hypertensive disorders in the second. Even borderline admission BP (either systolic or diastolic BP: 130-139 or 85-89 mm Hg, respectively) was associated with a doubling of hypertensive disorder risk in a subsequent pregnancy. First pregnancy BP was also associated with recurrence risks for hypertensive disorders, but the relation was stronger for women with gestational hypertension in their first pregnancy with more than 2-fold elevated risk across all BP categories (odds ratios range: 2.32-12.6). However, the majority of women (75%) with a hypertensive disorder in the first pregnancy do not repeat this outcome in the second pregnancy.

CONCLUSION

Delivery admission BP of a first pregnancy was strongly related to hypertensive disorder incidence and recurrence in the subsequent pregnancy. Although crude, these measures may prove useful as a predictor of long-term maternal health and future pregnancy risk.

Association of selenium and copper with lipids in umbilical cord blood

Altered levels of selenium and copper have been linked with altered cardiovascular disease risk factors including changes in blood triglyceride and cholesterol levels. However, it is unclear whether this can be observed prenatally. This cross-sectional study includes 274 singleton births from 2004 to 2005 in Baltimore, Maryland. We measured umbilical cord serum selenium and copper using inductively coupled plasma mass spectrometry. We evaluated exposure levels vis-à-vis umbilical cord serum triglyceride and total cholesterol concentrations in multivariable regression models adjusted for gestational age, birth weight, maternal age, race, parity, smoking, prepregnancy body mass index, n-3 fatty acids and methyl mercury. The percent difference in triglycerides comparing those in the highest v. lowest quartile of selenium was 22.3% (95% confidence interval (CI): 7.1, 39.7). For copper this was 43.8% (95% CI: 25.9, 64.3). In multivariable models including both copper and selenium as covariates, copper, but not selenium, maintained a statistically significant association with increased triglycerides (percent difference: 40.7%, 95% CI: 22.1, 62.1). There was limited evidence of a relationship of increasing selenium with increasing total cholesterol. Our findings provide evidence that higher serum copper levels are associated with higher serum triglycerides in newborns, but should be confirmed in larger studies.

Effect modification by vitamin D receptor genetic polymorphisms in the association between cumulative lead exposure and pulse pressure: a longitudinal study

BACKGROUND

Although the association between lead and cardiovascular disease is well established, potential mechanisms are still poorly understood. Calcium metabolism plays a role in lead toxicity and thus, vitamin D receptor (VDR) polymorphisms have been suggested to modulate the association between lead and health outcomes. We investigated effect modification by VDR genetic polymorphisms in the association between cumulative lead exposure and pulse pressure, a marker of arterial stiffness.

METHODS

We examined 727 participants (3,100 observations from follow-ups from 1991 to 2011) from the Normative Aging Study (NAS), a longitudinal study of aging. Tibia and patella bone lead levels were measured using K-x-ray fluorescence. Four single nucleotide polymorphisms (SNPs) in the VDR gene, Bsm1, Taq1, Apa1, and Fok1, were genotyped. Linear mixed effects models with random intercepts were implemented to take into account repeated measurements.

RESULTS

Adjusting for potential confounders, pulse pressure was 2.5 mmHg (95% CI: 0.4-4.7) and 1.9 mmHg (95% CI: 0.1-3.8) greater per interquartile range (IQR) increase in tibia lead (15 μg/g) and patella lead (20 μg/g), respectively, in those with at least one minor frequency allele in Bsm1 compared with those with major frequency allele homozygotes. The observed interaction effect between bone lead and the Bsm1 genotype persists over time during the follow-up. Similar results were observed in effect modification by Taq1.

CONCLUSIONS

This study suggests that subjects with the minor frequency alleles of VDR Bsm1 or Taq1 may be more susceptible to cumulative lead exposure-related elevated pulse pressure.

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.

A protocol for a systematic review of the effectiveness of interventions to reduce exposure to lead through consumer products and drinking water

BACKGROUND

The toxic heavy metal lead continues to be a leading environmental risk factor, with the number of attributable deaths having doubled between 1990 and 2010. Although major sources of lead exposure, in particular lead in petrol, have been significantly reduced in recent decades, lead is still used in a wide range of processes and objects, with developing countries disproportionally affected. The objective of this systematic review is to assess the effectiveness of regulatory, environmental and educational interventions for reducing blood lead levels and associated health outcomes in children, pregnant women and the general population.

METHODS/DESIGN

The databases MEDLINE, Embase and the Global Health Library (GHL) will be searched using a sensitive search strategy. Studies in English, German, French, Spanish, Italian or Afrikaans will be screened according to predefined inclusion and exclusion criteria. We will consider randomized and non-randomized studies accepted by the Cochrane Effective Practice and Organization of Care (EPOC) Group, as well as additional non-randomized studies. Screening of titles and abstracts will be performed by one author. Full texts of potentially relevant studies will be independently assessed for eligibility by two authors. A single author will extract data, with a second reviewer checking the extraction form. Risk of bias will be assessed by two researchers using the Graphical Appraisal Tool for Epidemiological studies, as modified by the Centre for Public Health at the UK National Institute for Health and Care Excellence. Any inconsistencies in the assessment of eligibility, data extraction or quality appraisal will be resolved through discussion. Where two or more studies report the primary outcome blood lead levels within the same population group, intervention category and source of lead exposure, data will be pooled using random effects meta-analysis. In parallel, harvest plots as a graphical method of evidence synthesis will be used to present findings for blood lead levels and secondary outcomes.

DISCUSSION

This systematic review will fill an important evidence gap with respect to the effectiveness of interventions to reduce lead in consumer products and drinking water in the context of new WHO guidelines for the prevention and management of lead poisoning. It will also contribute to setting a future research agenda.

Distribution of cadmium, mercury, and lead in different body parts of Baltic herring (Clupea harengus) and perch (Perca fluviatilis): implications for environmental status assessments

For heavy metals, quality standards indicating good environmental status are designed to evaluate concentrations in the whole fish body, whereas monitoring of metals is often conducted using muscle or liver tissue. As most metals accumulate at different rates in different parts of fish, data should be adjusted to reflect whole fish body concentrations; however, this requires knowledge on distribution of metal concentrations within fish. Here, concentrations of cadmium, mercury, and lead were analyzed in the liver, muscle and whole fish of herring and perch to create conversion factors for transformation of heavy metal concentrations between these tissues. Species-specific accumulation of metals between muscle, liver, and whole fish were observed. Relationships between different tissues were used to recalculate data from monitoring programs in the Baltic Sea region. Based on whole fish concentrations, environmental status for cadmium and mercury in herring improved compared to assessments based on muscle or liver concentrations alone.

Tobacco smoke exposure during pregnancy increases maternal blood lead levels affecting neonate birth weight

To assess the effect of lead exposure from cigarette smoke on fetal growth, blood lead concentrations were measured using inductively coupled plasma mass spectrometry in 150 healthy pregnant women. Mean lead concentrations in plasma and whole blood were significantly higher in the smoking group compared with the nonsmoking group in each trimester of pregnancy (p < 0.001). Logistic regression analysis showed the highest impact of the number of cigarettes smoked per day for serum lead concentration (β = 0.238; p < 0.05), while in whole blood, it was duration of smoking before conception (β = 0.297; p < 0.001). Birth weight of the smoking mothers' infants was significantly lower (mean ± SEM, 3,192 ± 50.8 and 3,569 ± 49.6 g, respectively; p < 0.001) and negatively correlated with lead levels in plasma (r = -0.38; p < 0.001) and in whole blood (r = -0.27; p < 0.001). Therefore, it is suggested that smoking during pregnancy increases lead concentrations in maternal blood. Fetal exposure to low doses of lead in utero may be a serious risk factor causing lower birth weight.

Environmental factors predicting blood lead levels in pregnant women in the UK: the ALSPAC study

Background

Lead is a widespread environmental toxin. The behaviour and academic performance of children can be adversely affected even at low blood lead levels (BLL) of 5–10 µg/dl. An important contribution to the infant's lead load is provided by maternal transfer during pregnancy.

Objectives

Our aim was to determine BLL in a large cohort of pregnant women in the UK and to identify the factors that contribute to BLL in pregnant women.

Methods

Pregnant women resident in the Avon area of the UK were enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC) in 1991–1992. Whole blood samples were collected at median gestational age of 11 weeks and analysed by inductively coupled plasma dynamic reaction cell mass spectrometry (n = 4285). Self-completion postal questionnaires were used to collect data during pregnancy on lifestyle, diet and other environmental exposures. Statistical analysis was carried out with SPSS v19.

Results

The mean±SD BLL was 3.67±1.47 (median 3.41, range 0.41–19.14) µg/dl. Higher educational qualification was found to be one of the strongest independent predictor of BLL in an adjusted backwards stepwise logistic regression to predict maternal BLL <5 or ≥5 µg/dl (odds ratio 1.26, 95% confidence interval 1.12–1.42; p<0.001). Other predictive factors included cigarette smoking, alcohol and coffee drinking, and heating the home with a coal fire, with some evidence for iron and calcium intake having protective effects.

Conclusion

The mean BLL in this group of pregnant women is higher than has been found in similar populations in developed countries. The finding that high education attainment was independently associated with higher BLL was unexpected and currently unexplained. Reduction in maternal lead levels can best be undertaken by reducing intake of the social drugs cigarettes, alcohol and caffeine, although further investigation of the effect of calcium on lead levels is needed.

The effects of low-level prenatal lead exposure on birth outcomes

Exposure to lead early in life may be a risk factor for fetal growth, but little is known about the effects of low-level prenatal lead exposure on birth outcomes. We measured maternal and cord blood lead levels and examined their associations with birth outcomes. Mother-infant pairs (n = 252) were recruited from a rural area located on the south coast of Laizhou Bay between 2010 and 2011. The median levels of maternal and cord blood lead were 3.20 and 2.52 μg/dL, respectively. Increasing maternal blood lead exposure was associated with decreasing birth weight (β = -148.99; 95% CI, -286.33 to -11.66), and a significant negative relationship was found between cord blood lead levels and birth length (β = -0.84; 95% CI, -1.52 to -0.16). Low-level prenatal lead exposure may adversely affect fetal growth. These results may be important for public health and have implications regarding the recommended blood lead levels.

Prohypertensive effect of gestational personal exposure to fine particulate matter. Prospective cohort study in non-smoking and non-obese pregnant women

Exposure to fine particulate matter (PM) is a recognized risk factor for elevated blood pressure (BP) and cardiovascular disease in adults, and this prospective cohort study was undertaken to evaluate whether gestational exposure to PM_2.5 has a prohypertensive effect. We measured personal exposure to fine particulate matter (PM_2.5) by personal air monitoring in the second trimester of pregnancy among 431 women, and BP values in the third trimester were obtained from medical records of prenatal care clinics. In the general estimating equation model, the effect of PM_2.5 on BP was adjusted for relevant covariates such as maternal age, education, parity, gestational weight gain (GWG), prepregnancy BMI, environmental tobacco smoke (ETS), and blood lead level. Systolic blood pressure (SBP) increased in a linear fashion across a dosage of PM_2.5 and on average augmented by 6.1 mm Hg (95% CI, 0.6–11.6) with log unit of PM_2.5 concentration. Effects of age, maternal education, prepregnancy BMI, blood lead level, and ETS were insignificant. Women with excessive gestational weight gain (>18 kg) had higher mean SBP parameters by 5.5 mmHg (95% CI, 2.7–8.3). In contrast, multiparous women had significantly lower SBP values (coeff. = −4.2 mm Hg; 95% CI, −6.8 to −1.6). Similar analysis performed for diastolic blood pressure (DBP) has demonstrated that PM_2.5 also affected DBP parameters (coeff. = 4.1; 95% CI, −0.02 to 8.2), but at the border significance level. DBP values were positively associated with the excessive GWG (coeff. = 2.3; 95% CI, 0.3–4.4) but were inversely related to parity (coeff. = −2.7; 95% CI, −4.6 to −0.73). In the observed cohort, the exposure to fine particulate matter during pregnancy was associated with increased maternal blood pressure.

The protean toxicities of lead: new chapters in a familiar story

Many times in the history of lead toxicology the view that "the problem" has been solved and is no longer a major health concern has prevailed, only to have further research demonstrate the prematurity of this judgment. In the last decade, an extraordinary amount of new research on lead has illustrated, all too clearly, that "the problem" has not disappeared, and that, in fact, it has dimensions never before considered. Recent risk assessments have concluded that research has yet to identify a threshold level below which lead can be considered "safe." Although children's intelligence has traditionally been considered to be the most sensitive endpoint, and used as the basis for risk assessment and standard setting, increased lead exposure has been associated with a wide variety of other morbidities both in children and adults, in some cases at biomarker levels comparable to those associated with IQ deficits in children. In adults, these endpoints include all-cause mortality and dysfunctions in the renal, cardiovascular, reproductive, central nervous systems. In children, IQ deficits are observed at blood lead levels well below 10 μg/dL, and the dose-effect relationship appears to be supra-linear. Other health endpoints associated with greater early-life lead exposure in children include ADHD, conduct disorder, aggression and delinquency, impaired dental health, and delayed sexual maturation. Studies employing neuroimaging modalities such as volumetric, diffusion tensor, and functional MRI are providing insights into the neural bases of the cognitive impairments associated with greater lead exposure.