Blood lead levels among pregnant women: historical versus contemporaneous exposures

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.

The association between lead exposure and crime: A systematic review

Prior research has demonstrated an association between lead exposure and criminal behavior at the population-level, however studies exploring the effect of lead exposure on criminal behavior at the individual-level have not been reviewed systematically. The intent of this study is to complete a systematic review of all studies assessing individual-level exposures to lead and the outcomes of crime and antisocial behavior traits. We included peer reviewed studies that were published prior to August 2022 and were classified as cohort, cross-sectional, or case-control. Studies measuring the outcomes of crime, delinquency, violence, or aggression were included. The following databases were searched using a standardized search strategy: ProQuest Environmental Science Database, PubMed, ToxNet and the Public Affairs Information Service (PAIS). Seventeen manuscripts met our inclusion criteria. Blood lead was measured in 12 studies, bone lead in 3 studies, and dentine lead levels in 2 studies. This systematic review identified a wide range of diverse outcomes between exposure to lead at multiple windows of development and later delinquent, criminal and antisocial behavior. A review of all potential confounding variables included within each study was made, with inclusion of relevant confounders into the risk of bias tool. There is limited data at the individual level on the effects of prenatal, childhood, and adolescent lead exposure and later criminal behavior and more evidence is necessary to evaluate the magnitude of the associations seen in this review. Our review, in conjunction with the available biological evidence, suggests that an excess risk for criminal behavior in adulthood exists when an individual is exposed to lead in utero or in the early years of childhood. The authors report no conflict of interest and no funding source. Clinical trial registration: PROSPERO ID: CRD42021268379.

Concentrations of per- and polyfluoroalkyl substances (PFAS) in human placental tissues and associations with birth outcomes

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous environmental contaminants commonly detected in human serum. Previous studies have observed associations between maternal serum PFAS and adverse pregnancy and birth outcomes such as lower birth weight or pre-eclampsia; however, few studies have explored these associations with birth outcomes and placental tissue PFAS concentration. The placenta is a vital contributor to a healthy pregnancy and may be involved in the mechanism of PFAS reproductive toxicity. Our goal was to measure placental PFAS concentrations and examine associations with birth outcomes (e.g., birth weight, gestational duration). Placenta samples (n = 120) were collected during delivery from women enrolled in the Healthy Pregnancy, Healthy Baby cohort (HPHB) in Durham, North Carolina. All placenta samples contained detectable PFAS, with perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorodecanoic acid (PFDA) being the most abundant and most frequently detected (all >96% detection frequency). While placental PFAS concentrations did not differ by infant sex, higher PFAS levels were observed in placenta from nulliparous women, suggesting that parity influences the accumulation of PFAS in the placenta. We used linear regression models to examine associations between placental PFAS and birth outcomes. After adjustment for parity, tobacco use, maternal age, and maternal race, we found that placental PFOS was associated with lower birth weight for gestational age in male infants and higher birth weight for gestational age in female infants. Similar findings were seen for PFNA for birth weight for gestational age. These differences in birth outcomes based on infant sex highlight a need to explore mechanistic differences in PFAS toxicity during gestation for male and female infants.

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.

Heavy Metal Mixture Exposure and Effects in Developing Nations: An Update

The drive for development and modernization has come at great cost. Various human activities in developed and developing countries, particularly in sub-Saharan Africa (SSA) have given rise to environmental safety concerns. Increased artisanal mining activities, illegal refining, use of leaded petrol, airborne dust, arbitrary discarding and burning of toxic waste, absorption of production industries in inhabited areas, inadequate environmental legislation, and weak implementation of policies, have given rise to the incomparable contamination and pollution associated with heavy metals in recent decades. This review evaluates the public health effects of heavy metals and their mixtures in SSA. This shows the extent and size of the problem posed by exposure to heavy metal mixtures in regard to public health.

Placental biomarkers of PAH exposure and glutathione-S-transferase biotransformation enzymes in an obstetric population from Tijuana, Baja California, Mexico

Environmental exposures along the US-Mexico border have the potential to adversely affect the maternal-fetal environment. The purpose of this study was to assess placental biomarkers of environmental exposures in an obstetric population at the California-Baja California border in relation to detoxifying enzymes in the placenta and nutritional status. This study was conducted on consenting, full-term, obstetric patients (n=54), delivering in a hospital in Tijuana, Baja California (BC), Mexico. Placental polyaromatic hydrocarbon (PAH)-DNA adducts were measured in addition to placental glutathione-S-transferase (GST) activity and genotype, maternal serum folate, and maternal and umbilical cord blood lead and cadmium levels. A questionnaire was administered to the mothers to determine maternal occupation in a maquiladora, other exposures, and obstetric indicators. In univariate analysis, maternal serum folate levels were inversely correlated with total PAH-DNA adducts (rho=-0.375, p=0.007); adduct #1 (rho=-0.388, p=0.005); and adduct #3 (rho =-0.430, p=0.002). Maternal lead levels were significantly positively correlated with cord blood lead levels (rho=0.512, p<0.001). Cadmium levels were generally very low but significantly higher in mothers exposed to environmental tobacco smoke (ETS) (either at work or at home, n=10). In multivariate analysis, only maternal serum folate levels remained as a significant negative predictor of total DNA-PAH adducts levels in placenta. These findings affirm that placental tissue is a valuable and readily available source of human tissue for biomonitoring; and indicate that further study of the role of nutrition in detoxification and mitigation of environmental exposures in pregnant women is warranted.

Environmental Remediation to Address Childhood Lead Poisoning Epidemic due to Artisanal Gold Mining in Zamfara, Nigeria

BACKGROUND

From 2010 through 2013, integrated health and environmental responses addressed an unprecedented epidemic lead poisoning in Zamfara State, northern Nigeria. Artisanal gold mining caused widespread contamination resulting in the deaths of > 400 children. Socioeconomic, logistic, and security challenges required remediation and medical protocols within the context of local resources, labor practices, and cultural traditions.

OBJECTIVES

Our aim was to implement emergency environmental remediation to abate exposures to 17,000 lead poisoned villagers, to facilitate chelation treatment of children ≤ 5 years old, and to establish local technical capacity and lead health advocacy programs to prevent future disasters.

METHODS

U.S. hazardous waste removal protocols were modified to accommodate local agricultural practices. Remediation was conducted over 4 years in three phases, progressing from an emergency response by international personnel to comprehensive cleanup funded and accomplished by the Nigerian government.

RESULTS

More than 27,000 m3 of contaminated soils and mining waste were removed from 820 residences and ore processing areas in eight villages, largely by hand labor, and disposed in constructed landfills. Excavated areas were capped with clean soils (≤ 25 mg/kg lead), decreasing soil lead concentrations by 89%, and 2,349 children received chelation treatment. Pre-chelation geometric mean blood lead levels for children ≤ 5 years old decreased from 149 μg/dL to 15 μg/dL over the 4-year remedial program.

CONCLUSIONS

The unprecedented outbreak and response demonstrate that, given sufficient political will and modest investment, the world's most challenging environmental health crises can be addressed by adapting proven response protocols to the capabilities of host countries.

CITATION

Tirima S, Bartrem C, von Lindern I, von Braun M, Lind D, Anka SM, Abdullahi A. 2016. Environmental remediation to address childhood lead poisoning epidemic due to artisanal gold mining in Zamfara, Nigeria. Environ Health Perspect 124:1471-1478; http://dx.doi.org/10.1289/ehp.1510145.

Concentrations of polybrominated diphenyl ethers (PBDEs) and 2,4,6-tribromophenol in human placental tissues

Legacy environmental contaminants such as polybrominated diphenyl ethers (PBDEs) are widely detected in human tissues. However, few studies have measured PBDEs in placental tissues, and there are no reported measurements of 2,4,6-tribromophenol (2,4,6-TBP) in placental tissues. Measurements of these contaminants are important for understanding potential fetal exposures, as these compounds have been shown to alter thyroid hormone regulation in vitro and in vivo. In this study, we measured a suite of PBDEs and 2,4,6-TBP in 102 human placental tissues collected between 2010 and 2011 in Durham County, North Carolina, USA. The most abundant PBDE congener detected was BDE-47, with a mean concentration of 5.09ng/g lipid (range: 0.12-141ng/g lipid; detection frequency 91%); however, 2,4,6-TBP was ubiquitously detected and present at higher concentrations with a mean concentration of 15.4ng/g lipid (range:1.31-316ng/g lipid; detection frequency 100%). BDE-209 was also detected in more than 50% of the samples, and was significantly associated with 2,4,6-TBP in placental tissues, suggesting they may have a similar source, or that 2,4,6-TBP may be a degradation product of BDE-209. Interestingly, BDE-209 and 2,4,6-TBP were negatively associated with age (rs=-0.16; p=0.10 and rs=-0.17; p=0.08, respectively). The results of this work indicate that PBDEs and 2,4,6-TBP bioaccumulate in human placenta tissue and likely contribute to prenatal exposures to these environmental contaminants. Future studies are needed to determine if these joint exposures are associated with any adverse health measures in infants and children.

Associations of birth outcomes with maternal polybrominated diphenyl ethers and thyroid hormones during pregnancy

BACKGROUND

Previous research has linked polybrominated diphenyl ether (PBDE) exposure to poor birth outcomes and altered thyroid hormone levels.

OBJECTIVES

We examined whether maternal PBDE serum levels were associated with infant birth weight (g), head circumference (cm), birth length (cm), and birth weight percentile for gestational age. We explored the potential for a mediating role of thyroid hormone levels.

METHODS

During 2008-2010, we recruited 140 pregnant women in their third trimester as part of a larger clinical obstetrics study known as Healthy Pregnancy, Healthy Baby. Blood samples were collected during a routine prenatal clinic visit. Serum was analyzed for PBDEs, phenolic metabolites, and thyroid hormones. Birth outcome information was abstracted from medical records.

RESULTS

In unadjusted models, a two-fold increase in maternal BDE 153 was associated with an average decrease in head circumference of 0.32cm (95% CI: -0.53, -0.12); however, this association was attenuated after control for maternal risk factors. BDE 47 and 99 were similarly negatively associated but with 95% confidence intervals crossing the null. Associations were unchanged in the presence of thyroid hormones.

CONCLUSIONS

Our data suggest a potential deleterious association between maternal PBDE levels and infant head circumference; however, confirmatory studies are needed in larger sample sizes. A mediating role of thyroid hormones was not apparent.

The effect of parity on maternal body mass index, plasma mineral element status and new-born anthropometrics

BACKGROUND

Adverse pregnancy outcome is an important public health problem that has been partly associated with increasing maternal parity.

AIM

To determine the effect of parity on maternal body mass index (BMI), mineral element status and newborn anthropometrics.

METHODS

Data for 349 pregnant women previously studied for the impacts of maternal plasma mineral element status on pregnancy and its outcomes was analysed. Obstetric and demographic data and 5mls of blood samples were obtained from each subject. Blood lead, plasma copper, iron and zinc were determined using atomic absorption spectrophotometer.

RESULTS

Maternal BMI increases with parity. Women with parity two had significantly higher plasma zinc but lower plasma copper with comparable levels of the elements in nulliparous and higher parity groups. Although plasma iron was comparable among the groups, blood lead was significantly higher in parity > three. Newborn birth length increases with parity with a positive correlation between parity and maternal BMI (r = 0.221; p = 0.001) and newborn birth length (r = 0.170; p = 0.002) while plasma copper was negatively correlated with newborn's head circumference (r = -0.115; p = 0.040).

CONCLUSION

It is plausible that parity affects maternal BMI and newborn anthropometrics through alterations in maternal plasma mineral element levels. While further studies are desired to confirm the present findings, there is need for pregnant and would-be pregnant women to diversify their diet to optimize their mineral element status.

Cadmium levels in a North Carolina cohort: Identifying risk factors for elevated levels during pregnancy

The objectives of this study were to examine cadmium (Cd) levels and relationships to demographics in an observational, prospective pregnancy cohort study in Durham County, North Carolina. Multivariable models were used to compare blood Cd levels across demographic characteristics. The relative risk of having a blood Cd level that exceeds the US national median (0.32 μg/l) was estimated. Overall, >60% of the women had an elevated (>0.32 μg/l) blood Cd level. Controlling for confounding variables, smoking was associated with 21% (95% CI: 15-28%) increased risk for an elevated blood Cd level. High Cd levels were also observed in non-smokers and motivated smoking status-stratified models. Race, age, education, relationship status, insurance status and cotinine level were not associated with risk of elevated Cd levels among smokers; however, older age and higher cotinine levels were associated with elevated Cd levels among non-smokers. Taken together, more than half of pregnant women in this cohort had elevated blood Cd levels. Additionally, among non-smokers, 53% of the women had elevated levels of Cd, highlighting other potential sources of exposure. This study expands on the limited data describing Cd levels in pregnant populations and highlights the importance of understanding Cd exposures among non-smokers. Given the latent health risks of both smoking and Cd exposure, this study further highlights the need to biomonitor for exposure to toxic metals during pregnancy among all women of child-bearing age.

Effect measure modification of blood lead-air lead slope factors

There is abundant literature finding that susceptibility factors, including race and ethnicity, age, and housing, directly influence blood lead levels. No study has explored how susceptibility factors influence the blood lead-air lead relationship nationally. The objective is to evaluate whether susceptibility factors act as effect measure modifiers on the blood lead-air lead relationship. Participant level blood lead data from the 1999 to 2008 National Health and Nutrition Examination Survey were merged with air lead data from the US Environmental Protection Agency. Linear mixed effects models were run with and without an air lead interaction term for age group, sex, housing age, or race/ethnicity to determine whether these factors are effect measure modifiers for all ages combined and for five age brackets. Age group and race/ethnicity were determined to be effect measure modifiers in the all-age model and for some age groups. Being a child (1-5, 6-11, and 12-19 years) or of Mexican-American ethnicity increased the effect estimate. Living in older housing (built before 1950) decreased the effect estimate for all models except for the 1-5-year group, where older housing was an effect measure modifier. These results are consistent with the peer-reviewed literature of time-activity patterns, ventilation, and toxicokinetics.

Maternal cadmium levels during pregnancy associated with lower birth weight in infants in a North Carolina cohort

Cadmium (Cd) is a ubiquitous environmental contaminant, a known carcinogen, and understudied as a developmental toxicant. In the present study, we examined the relationships between Cd levels during pregnancy and infant birth outcomes in a prospective pregnancy cohort in Durham, North Carolina. The study participants (n = 1027) had a mean Cd level of 0.46 µg/L with a range of <0.08 to 2.52 µg/L. Multivariable models were used to establish relationships between blood Cd tertiles and fetal growth parameters, namely birth weight, low birth weight, birth weight percentile by gestational age, small for gestational age, pre-term birth, length, and head circumference. In multivariable models, high maternal blood Cd levels (≥0.50 µg/L) during pregnancy were inversely associated with birth weight percentile by gestational age (p = 0.007) and associated with increased odds of infants being born small for gestational age (p<0.001). These observed effects were independent of cotinine-defined smoking status. The results from this study provide further evidence of health risks associated with early life exposure to Cd among a large pregnancy cohort.

Trace metals in blood and urine of newborn/mother pairs, adolescents and adults of the Flemish population (2007-2011)

The Flemish Centre for Environment and Health started with human biomonitoring in 2002 (FLEHS I: 2002-2006). The main goal of the second human biomonitoring cycle (FLEHS II: 2007-2011), was to determine mean values for a large number of pollutants in a representative sample of the general Flemish population. Values for Cd and Pb were updated, and a group of previously undetermined metals and metalloids (As, Mn, Cu and Tl) were included in some of the age groups. In this human biomonitoring program, three different age groups of the general Flemish population were monitored: 255 newborns and their mothers, 210 adolescents aged 14-15, and 204 adults between 20 and 40 years old. Trace elements were determined in cord blood and maternal blood of the mothers, in blood and urine of adolescents and in urine of adults. Determinants of life-style and personal factors were taken into account. The levels of trace elements in cord blood and maternal blood were for most elements at the lower end of the range found in literature. For Pb, As and Tl, a strong correlation (respectively r=0.43, 0.55 and 0.33; p<0.05) was found between levels in cord blood (respectively 8.6, 0.54 and 0.017 μg/L) and maternal blood (11.1, 0.64 and 0.028 μg/L), indicating that they are transported via the placenta from mother to fetus. The levels found in the adolescents and adults were compared with results from international biomonitoring studies, and were found to be in the same ranges. With the exception of Pb, all trace elements increased with increasing age group population. Finally, the results also showed that the levels of Cd and Pb in blood for this campaign (e.g. for Pb 8.6 and 14.8 μg/L in neonates and adolescents respectively) were lower compared to the first campaign (e.g. for Pb 14.7 and 21.7 μg/L in neonates and adolescents respectively), indicating a decrease over time. However, differences in sampling strategies might partially explain this observed trend.

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.

Differences in prenatal exposure to mercury in South African communities residing along the Indian Ocean

Mercury is a persistent environmental pollutant that has the potential to adversely affect human health, particularly, foetal neurodevelopment. The purpose of the study was to investigate prenatal mercury (Hg) exposure in the population in three sites along the South Africa coast. Study subjects included women (n=350) who were admitted for delivery at the local hospitals. Maternal and cord blood samples were collected to measure total mercury and each participant was required to answer a questionnaire. The 90th percentile of mercury levels in maternal and cord blood of the total population was 1.15 μg/l and 1.67 μg/l, respectively. Site 1 (Manguzi) participants had the highest maternal geometric mean (GM) values of 0.93 μg/l, which was significantly different from Site 2 (Port Shepstone) (0.49 μg/l) and Site 3 (Empangeni) (0.56 μg/l) (ANOVA test, p<0.001). Umbilical cord blood GM Hg level for Site 1 (1.45 μg/l) was more than double the GM Hg level in Site 2 (0.70 μg/l) and Site 3 (0.73 μg/l). Univariate analysis indicated that the following maternal characteristics were positive predictors for elevated umbilical cord Hg levels: maternal blood Hg levels, living with a partner, residing in Site 1, living in informal housing, using wood and gas for cooking, borehole water as a drinking source, and a member of the household being involved in fishing. Maternal dietary predictors of elevated Hg levels in umbilical cord blood included consuming fresh fish, tinned fish, fruit or dairy products, daily. This study provides baseline data and reveals that 2% of the study population were above the EPA's reference value (5.8 μg/l) suggesting low level exposure to mercury in pregnant women and the developing foetus in South Africa. Further research is required to explore the sources of elevated Hg levels in Site 1.

Blood lead concentrations in sub-Saharan African children below 6 years: systematic review

OBJECTIVE

To assess the geometric mean of blood lead levels in children aged below 6 years living in sub-Saharan Africa.

METHODS

Search strategies were developed in MEDLINE, Web of Science and Google scholar system, supplemented by screening of references from included papers and review articles. Studies including children younger than 6 years residing in sub-Saharan Africa (SSA) were eligible. The studies were assessed for quality of methods for blood collection, for participants' recruitment and for quality control for lead analyses. Data were extracted and synthetised by estimating the mean weighted by sample size.

RESULTS

A total of 11 148 published papers were identified with only 16 studies conducted in SSA. Only nine of them were relevant of inclusion criteria. The weighted mean of blood lead levels was 13.1 μg/dl. Five of included studies were classified as being less likely to present selection bias, having performed venipuncture and adequate quality control for lead analyses. The weighted mean from analyses involving only these studies was 16.2 μg/dl. Six of the included studies reported the prevalence of blood lead levels ≥10 μg/dl; levels ranged from 7.0% to 70.9%. Only one study reported the prevalence of blood lead levels ≥5 μg/dl (50%).

CONCLUSIONS

The geometric mean of blood lead levels in sub-Saharan African children is still elevated relative to the US children. The new standard from the Centers for Disease Control and Prevention (5 μg/dl) implies that important efforts should be directed towards the initiation (or reinforcement) of prevention programmes and thorough research studies in sub-Saharan Africa.

Blood Pb Levels in pregnant Nigerian women in Abakaliki, South-Eastern Nigeria

Environmental lead (Pb) exposure and toxicity have been recognised as public health problems of global importance, affecting both the developed and developing nations. In this work, blood Pb of pregnant women that were not exposed to lead by their occupation (n = 349), with mean ± SD age of 27.0 ± 4.8 years and gestational age of 21.8 ± 3.1 weeks at recruitment were determined using atomic absorption spectrophotometer. The results showed that 309 (88.5 %) of the women had a mean ± SD blood Pb of 40.0 ± 16.5 μg/dl, which is higher than the current US Centre for Disease Prevention and Control action limit (>10 μg/dl). The observed high prevalence of elevated blood Pb levels may be related to maternal low socioeconomic status. Health education is, therefore, urgently needed to sensitise the general public and the policy makers of the level of Pb exposure in Abakaliki environment and the inherent health implications. In addition to mandatory environmental lead monitoring, blood Pb screening for would-be mother is recommended, and those whose blood Pb are found elevated should be appropriately treated.

Child neurodevelopment in a Bolivian mining city

This study evaluates the neurodevelopment of children living near contaminated mining industries during their first year of life. Participants from the city of Oruro (Bolivia) were prospectively recruited during pregnancy. Follow-up occurred between May 2007 and November 2009. Information about the socioeconomic status and medical history of the pregnant women were collected using questionnaires. Neurodevelopment was evaluated for 246 children using the Bayley Scales of Infant Development (BSID) at 10.5-12.5 months of age. Exposure to trace elements (Pb, As, Cd, Sb, Cs, Zn, Fe, Cu, Se, Rb, and Sr) during prenatal life was evaluated by testing maternal blood concentrations before delivery. Almost all measured levels were lower than the control limits. The blood lead concentration of pregnant women was low, considering the contaminated environmental context. The geometric mean was 1.76 μg/dL (95% CI: 1.68-1.84), a level comparable with those observed in non-contaminated areas. The only element found to be relatively elevated was antimony, with a geometric mean of 1.03 μg/dL (95% CI: 0.96-1.11). Our results suggest that women from this mining area were not highly exposed. The Bayley Scales of Infant Development (BSID) did not reveal mental or psychomotor abnormalities. Surprisingly, at the observed low levels, lead was positively associated with the children's BSID performance.

Associations between polybrominated diphenyl ether (PBDE) flame retardants, phenolic metabolites, and thyroid hormones during pregnancy

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) are chemical additives used as flame retardants in commercial products. PBDEs are bioaccumulative and persistent and have been linked to several adverse health outcomes.

OBJECTIVES

This study leverages an ongoing pregnancy cohort to measure PBDEs and PBDE metabolites in serum collected from an understudied population of pregnant women late in their third trimester. A secondary objective was to determine whether the PBDEs or their metabolites were associated with maternal thyroid hormones.

METHODS

One hundred forty pregnant women > 34 weeks into their pregnancy were recruited into this study between 2008 and 2010. Blood samples were collected during a routine prenatal clinic visit. Serum was analyzed for a suite of PBDEs, three phenolic metabolites (i.e., containing an -OH moiety), and five thyroid hormones.

RESULTS

PBDEs were detected in all samples and ranged from 3.6 to 694 ng/g lipid. Two hydroxylated BDE congeners (4´-OH-BDE 49 and 6-OH-BDE 47) were detected in > 67% of the samples. BDEs 47, 99, and 100 were significantly and positively associated with free and total thyroxine (T4) levels and with total triiodothyronine levels above the normal range. Associations between T4 and PBDEs remained after controlling for smoking status, maternal age, race, gestational age, and parity.

CONCLUSIONS

PBDEs and OH-BDEs are prevalent in this cohort, and levels are similar to those in the general population. Given their long half-lives, PBDEs may be affecting thyroid regulation throughout pregnancy. Further research is warranted to determine mechanisms through which PBDEs affect thyroid hormone levels in developing fetuses and newborn babies.