Cord Blood Lead Levels Research Articles

Prenatal exposure to environmental contaminants and behavioural problems at age 7–8 years

Animal studies showed that the developing brain is particularly sensitive to chemical exposure. Human studies carried out in areas with high exposures have proven neurodevelopmental disorders in relation to e.g. lead and PCBs. Whether these chemicals are associated with behavioural problems in childhood at current environmental levels is not well known. Therefore, we assessed the association between prenatal exposure to lead, cadmium, PCBs, dioxin-like compounds, HCB and p,p′-DDE and behavioural problems in 7–8year old children. Prenatal exposure data were obtained from the Flemish mother–new-born cohort. Lead, cadmium, PCBs, dioxin-like compounds, HCB and p,p′-DDE were analysed in cord blood. When the child reached 7–8years, 270 mothers completed the Strengths and Difficulties Questionnaire assessing their children's behavioural health. We found that doubling the prenatal lead exposure (cord blood lead levels) was associated with a 3.43 times higher risk for hyperactivity in both boys and girls. In addition, total difficulties were 5.08 times more likely in the highest tertile for prenatal lead exposure compared to the lowest tertile. In girls, total difficulties were 4.92 more likely when doubling cord blood p,p′-DDE, whereas no significant association was found in boys. Further, we noted in boys a 1.53 times higher risk for emotional problems when doubling cord blood cadmium, whereas no significant association was found in girls. These results indicate that the presence of environmental contaminants influences the mental health of the next generation.

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.

Developmental Effects of Exposures to Environmental Factors: The Polish Mother and Child Cohort Study

This paper estimates the effects of exposure to environmental factors, including lead, mercury, environmental tobacco smoke (ETS), and polycyclic aromatic hydrocarbons (PAH), on child psychomotor development. The study population consists of mother-child pairs in the Polish Mother and Child Cohort Study. Prenatal and postnatal exposure to environmental factors was determined from biomarker measurements as follows: for lead exposure—cord blood lead level, for mercury—maternal hair mercury level, for ETS—cotinine level in saliva and urine, and for PAH—1-hydroxypyrene (1-HP) in urine. At the age of 12 (406 subjects) and 24 months (198 subjects) children were assessed using Bayley Scales of Infant and Toddler Development. There were no statistically significant effects of prenatal exposure to mercury or 1-HP on child psychomotor development. After adjusting for potential confounders, adverse effects of prenatal exposure to ETS on motor development (β = −2.6; P = 0.02) and postnatal exposure to ETS on cognitive (β = −0.2; P = 0.05) and motor functions (β = −0.5; P = 0.01) were found. The adverse effect of prenatal lead exposure on cognitive score was of borderline significance (β = −6.2; P = 0.06). The study underscores the importance of policies and public health interventions that aim to reduce prenatal and postnatal exposure to lead and ETS.

Association between Prenatal Exposure to Cadmium and Atopic Dermatitis in Infancy

Our objective was to evaluate the relationship between intrauterine exposure to cadmium and the presence of atopic dermatitis in infants 6 months of age, adjusted for covariates including exposure to other heavy metals. The present research is a component of the Mothers' and Children's Environmental Health (MOCEH) study, a multi-center birth cohort project conducted in Korea. Study subjects were restricted to pregnant women in whom cadmium and lead levels were measured at delivery and whose infants were assessed for the presence of atopic disease at 6 months of age. The odds ratio (OR) for the presence of atopic dermatitis in 6-month-old infants whose cord blood had elevated cadmium levels, after adjustment for other covariates, was 2.350 (95% CI, 1.126-4.906). The OR for the presence of atopic dermatitis in infants whose cord blood had elevated lead levels was not significant. In the present study, the cord blood cadmium level was significantly associated with the presence of atopic dermatitis in 6-month-old infants; this was not true of the cord blood lead level. To the best of our knowledge, this is the first prospective study to show a relationship between prenatal exposure to cadmium and atopic dermatitis in infancy.

Association of cord blood levels of lead, arsenic, and zinc with neurodevelopmental indicators in newborns: A birth cohort study in Chitwan Valley, Nepal

In this study, we aimed to investigate the association between in utero toxic (lead [Pb] and arsenic [As]) and essential element (zinc [Zn]) levels and neurodevelopmental indicators after birth in Chitwan Valley, Nepal. We conducted a hospital-based birth cohort study with 100 pregnant women in Chitwan, Nepal. We measured Pb, As, and Zn concentrations in cord blood. We assessed 100 infants at 1 day after birth, using the Brazelton neonatal behavioral assessment scale, third edition (NBAS III). Multivariate regression was performed to adjust for mother's age, parity, educational level, and body mass index (BMI); family income; and newborn's birth weight, gestational age, and age in hours at the time of NBAS III assessment. Among the 7 clusters of NBAS III, the motor cluster score was inversely associated with the cord blood levels of Pb (coefficient=−2.15, at 95% confidence interval [CI]=−4.27 to −0.03). The cord blood levels of As were inversely associated with the state regulation cluster score (coefficient=−6.71, at 95% CI=−12.17 to −1.24). The cord blood levels of Zn were not associated with NBAS III scores. The cord blood levels of Pb and As, but not Zn, showed significant inverse association with the neurodevelopment of newborns. These results suggest that high levels of Pb or As exposure during the prenatal period may induce retardation during in utero neurodevelopment.

98 Lead, Mercury and Cadmium Levels in Cord Blood, Breast Milk and Newborn Hair

Background and aimLead, mercury and cadmium are widely exposed environmental pollutants throughout the world. In this study, we aimed to investigate the level of exposure to lead(Pb), mercury(Hg) and cadmium(Cd)...

Association of Maternal Blood Lead Level During Pregnancy with Child Blood Lead Level and Pregnancy Outcome in Kuwait

High blood lead levels (BLL) in pregnancy are associated with poor pregnancy outcome and neuro-behavioral deficits in infants. We investigated the prevalence of high BLL in pregnant women and its impact on pregnancy outcome in Kuwait. Blood from 194 mother–infant pairs were analyzed for lead by Atomic Absorption Spectrophotometry. Data were collected on birth weight, crown–heel length, head circumference, APGAR score, gestational age, and placental weight. Results revealed that 28% of pregnant women and 58% of infants had BLL >10 g/dL. Cord BLL was significantly higher than maternal BLL (10.92 vs. 5.77 g/dL, p < .001). Maternal BLL was not significantly associated with any of the outcome variables tested, whereas, cord BLL was a significant negative predictor of APGAR score only in boys. A significant proportion of pregnant women and their children in Kuwait have lead levels well above the safety limit, which is a matter of public health concern.

Birth outcomes related to informal e-waste recycling in Guiyu, China

To assess the impact of exposure to informal e-waste recycling on birth outcomes. We compared record-based birth outcomes (n=24,493) and levels of cord blood lead (CBPb) (n=531) in Guiyu and a control area in Xiamen. Guiyu births showed significantly higher rates of adverse birth outcomes including stillbirth (4.72% vs. 1.03%), low birth weight (6.12% vs. 4.12%), term low birth weight (3.40% vs. 1.57%), and lower Apgar scores (9.6 vs. 9.9) and mean birth weight (3168g vs. 3258g) than did births from the control site, all P<0.01. Regression analysis showed Guiyu had about four times higher risk of stillbirth compared with Xiamen. The median level of CBPb was much higher in neonates of Guiyu than those in the control group (10.78μg/dL vs. 2.25μg/dL). Prenatal exposure to informal e-waste recycling related to high rate of adverse birth outcomes, lower Apgar scores and unsafe lead level in cord blood.

The effects of metallothionein 2A polymorphism on lead metabolism: are pregnant women with a heterozygote genotype for metallothionein 2A polymorphism and their newborns at risk of having higher blood lead levels?

Numerous studies indicate that certain genetic polymorphisms modify lead toxicokinetics. Metallothioneins are protective against the toxicity of many metals, including lead. The aim of this study was to determine whether the maternal metallothionein 2A (MT2A) -5 A/G single-nucleotide polymorphism is related to the lead levels in maternal blood, placental tissue and cord blood in 91 pregnant women and their newborns. Venous blood from the mother was collected to investigate lead levels and MT2A polymorphism. Cord blood and placenta were collected for lead levels. Analyses were made using an Atomic Absorption Graphite Furnace Spectrophotometer. Standard PCR-RFLP technique was used to determine MT2A polymorphism. Blood lead levels of heterozygote genotype (AG) mothers were statistically higher than those of homozygote genotype (AA) (P < 0.05). Maternal lead levels were significantly associated with cord blood lead levels for pregnant women with AA genotype (P < 0.001). This association was not statistically significant for pregnant women with AG. In contrast, the mean value of cord blood lead level for newborns with mothers of AG genotype was slightly higher than others, though the difference was not significant. No significant difference existed in placenta lead levels between the groups. This study suggests that pregnant women with AG genotype for MT2A polymorphism might have high blood lead levels and their newborns may be at risk of low-level cord blood lead variation.

Lead levels in umbilical cord blood in Belgium: A cross-sectional study in five maternity units

The average blood lead concentration has significantly decreased over the last two decades among the general population. However, in Belgium, there are still high-risk populations such as groups of pregnant women who have shown elevated lead levels. The objective of this study was to evaluate the current situation of lead cord blood levels and identify sources of lead exposure by a questionnaire survey. The study was conducted in 5 maternity units in Belgium; for each, umbilical cord blood samples were collected from 50 consecutive births. At the same time a questionnaire on possible sources of lead exposure was administered to the mother. The dependent variable was a dichotomous lead level variable (<20 μg/L vs. ≥ 20 μg/L). The factors associated with elevated lead levels (≥ 20 μg/L) were mother's country of origin from south Mediterranean and from Sub-Saharan Africa, mother's educational level, using 'tagine' plates for cooking and using khol for make-up, but, after adjusting for potential confounding factors, only the mother's country origin from south Mediterranean (adjusted odds ratio, 5.51; 95% confidence interval [CI], 1.68-18.08; p=0.005) and from Sub-Saharan Africa (adjusted odds ratio, 8.14; 95% CI, 2.26-29.40; p=0.001) were significantly associated with elevated cord blood lead concentrations (≥ 20 μg/L). The results of this study are similar to those found by a previous study in Belgium in 2004. Sources of exposure are difficult to distinguish with this questionnaire, which might be due to other important sources of exposure that were not included in the questionnaire. Confirmation of these risk factors in future studies could lead to new prevention strategies for populations who are at risk for subsequent lead exposure.

Umbilical cord blood lead levels

Umbilical cord blood lead levels

Prenatal exposure to lead in Spain: Cord blood levels and associated factors

Introduction and Objective Lead is a known neurotoxic. Fetuses and infants are very vulnerable to lead exposure, since their blood-brain barrier is not completely formed. Hence, there is an importance for monitoring of blood lead levels prenatally and during early infancy. The aim of this study is to evaluate the prenatal exposure to lead and its association with maternal factors in four population based mother–child cohorts in Spain. The present research was carried out within the framework of the INMA project INfancia y Medio Ambiente (Environment and Childhood). Methods A total of 1462 pregnant women were recruited between 2004 and 2008. Lead was analyzed in a sample of cord blood by thermal decomposition, amalgation, and Atomic Absorption Spectrometry. Maternal sociodemographic, lifestyle and dietary factors were obtained by questionnaires during pregnancy. A multivariate logistic regression model was constructed. The dependent variable was a dichotomous lead level variable (detected vs no detected, i.e. ≥ vs < 2 μg/dL). Results A low percentage of cord blood samples with lead levels ≥ 2 μg/dL were found (5.9%). Geometric mean and maximum were 1.06 μg/dL and 19 μg/dL, respectively. Smoking at the beginning of pregnancy, age, social class, weight gain during pregnancy, gravidity, and place of residence were the maternal factors associated with detectable cord blood lead levels. Mother's diet does not appear to be a determining factor of lead exposure. Nevertheless, daily intake of iron and zinc may act as a protective factor against having cord blood lead levels ≥ 2 μg/dL. Conclusion In the different regions of Spain taking part in this study, lead levels to which newborns are exposed are low. Mobilization of lead from bones may be the main contributor to the cord blood levels.

Associations between petrol-station density and manganese and lead in the cord blood of newborns living in Taiwan

Although the anti-knocking agents used in Taiwan do not contain manganese, there are relatively high concentrations of the element in diesel fuel. As such, there have been many concerns about the impact of exposure to diesel fuels on health. This study was conducted in Taiwan to investigate the relationship between the concentration of manganese in cord blood of Taiwanese newborns and the geographic density of petrol stations as a surrogate for determining manganese emissions from vehicular traffic. A total of 1526 full-term newborns without major congenital malformations were consecutively recruited from various medical facilities from May 2004 to July 2005. Questionnaires were completed by the newborns' mothers after delivery to collect information on demographic characteristics, medical history, living environment, and other factors. Cord blood samples were collected at birth and analyzed for manganese and lead using inductively coupled plasma mass spectrometry. The geographic density of petrol stations within a 10 km zone around each newborn's residence was calculated for 1343 newborns using the Arc9 Geographic Information System. The geometric means of cord blood manganese and lead concentrations were 47.0 μg/L (GSD=1.42) and 12.6 μg/L (GSD=1.76), respectively. After adjusting for potential confounding factors, including maternal age, and maternal education, the results of a multiple linear regression model indicated that the concentration of cord blood manganese increased monotonically with an increasing density of petrol stations. However, no such association was found for levels of lead in cord blood. Further smoothing spline model analysis indicated that a ten unit increment in petrol station density made cord blood manganese and lead levels change by factors of 1.0092 (95% CI: 1.0058, 1.0127) and 0.9994 (95% CI: 0.9890, 0.9998), respectively. This finding suggests that exposure to manganese-containing fuel from motor vehicles may result in elevated manganese levels in the fetus. Further research is warranted to explore the relationship between traffic-related manganese exposure and potential adverse effects on fetal development.

Prenatal low-level lead exposure on neonatal neurological, physical, hearing the impact of development

Objective To investigate the prenatal low-level lead exposure neonatal nerve, physical,hearing and development impact. Methods 235 pregnant women in the delivery of umbilical cord blood of 1mL, using graphite furnace atomic absorption spectrometry determination of lead content in umbilical cord blood; on neonatal birth weight, length, head circumference measurements, using 20 neonatal behavioral neurological assessment Detection of neural behavior; teoae methods used to conduct hearing screening for newborns. According to umbilical cord blood lead levels, will study the subjects were divided into low-lead group, in the lead group, the high lead group 3 group, a comparative analysis between the different groups of nerves, physical, hearing and development level. Conclusion prenatal low-level lead exposure on neonatal neurobehavioral development have an adverse effect, but did not result in significant differences; on neonatal physical development and hearing development did not cause significant impact. Key words: Newborn; Umbilical cord blood lead; Neural behavior; Physical development; Hearing development

Prenatal and adolescent blood lead levels in South Africa: Child, maternal and household risk factors in the Birth to Twenty cohort

The risk factors for lead exposure in developing countries have not been fully described. This study looks at child, maternal and household factors associated with increased risk of lead exposure at birth and at 13 years of age in the Birth to Twenty cohort. Mothers were recruited from antenatal clinics in the Johannesburg-Soweto metropolitan area in 1990 (n=3273). Lead levels were analysed in cord blood collected at birth (n=618) and at 13 years (n=1546). Data on selected child, maternal and household factors were collected using a structured questionnaire in the third trimester and at 13 years of age. Statistical analyses were conducted to determine the associated risk factors. The mean blood lead level at birth was 5.85 microg/dl, and at 13 years of age it was 5.66 microg/dl. The majority of children had blood lead levels above 5 microg/dl (52% at birth and 56% at 13 years). At birth, being a teenage mother and having low educational status were strong predictors for elevated cord blood lead levels. Being a male child, having an elevated cord blood level, and lack of household ownership of a phone were significant risk factors for high blood lead levels at 13 years. Significant associations found in the study point to the low socio-economic status of lead-affected mothers and children. These poor circumstances frequently persist into later childhood, resulting in continued high lead levels. Thus broader measures of poverty alleviation and provision of better education may help decrease the risk of exposure.

Levels of Cord Blood Lead in Pregnant Women from the Inma-Gipuzkoa Cohort (Basque Country; Spain)

ISEE-0272 Background and Objective: The INMA project (Childhood and Environment) studies the possible effects of environmental contaminants on infant growth and development. Exposure to lead (Pb) during the prenatal period has been associated with adverse effects on fetal development. This study aims to investigate exposure to Pb in 524 children born in Zumarraga hospital (INMA-Gipuzkoa cohort), which serves 25 municipalities in Gipuzkoa (Basque country, Spain). Methods: During 2003–2007, Pb and PM10 levels in the air were measured in urban centres with metallurgical activity and in one municipality without such activity. Cord blood Pb was analysed in 524 children, as an indicator of exposure. The level of Pb in drinking water was analyzed throughout all 25 municipalities. Pb, PM2.5 and PM10 levels were determined using gravimetric analysis and inductively coupled plasma atomic emission spectroscopy. Cord blood Pb was determined using electrothermal atomic absorption. Pb in drinking water was analysed quarterly using graphite furnace atomic absorption spectrophotometry. Results: Only in Zumarraga were atmospheric Pb levels detected that were higher than the limit established by law (0.5 μg/m3) (Mean: 0.5 μg/m3), exceeding the limit on 23.9% of days. Eighty-six percent of drinking water samples presented levels lower than the detection threshold (1 μg/l), with the mean level for all samples at 4.5 μg/l. Ninety-two percent of cord blood samples displayed values lower than the detection threshold (1 μg/l), with a mean level for all samples of 2.6 μg/l. Conclusions: Exposure to lead via air and water, at levels that are below the values required by law, is reflected in low cord blood lead levels in the study area.

CHILDREN’S HEALTH: Sex-Specific Cognitive Effects of Lead

Vol. 117, No. 9 NewsOpen AccessCHILDREN’S HEALTH: Sex-Specific Cognitive Effects of Lead Julia R. Barrett Julia R. Barrett Search for more papers by this author Published:1 September 2009https://doi.org/10.1289/ehp.117-a393Cited by:1AboutSectionsPDF ToolsDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InReddit As a neurotoxicant, lead is especially harmful to the developing brain, and early exposures can irreversibly impair children’s cognitive and behavioral development. Although a blood lead level of 10 μg/dL is used as a benchmark for intervention, a growing body of research demonstrates that neurologic effects occur well below this level. Based on research published in Early Human Development in August 2009, boys may be even more susceptible than girls to damage related to very low-level lead exposure.Sex-based susceptibility to low-level lead exposure was previously suspected, but this study is the first to document a statistically significant difference. “Entering into this research, we did not expect to find such a strong gender-based difference in response to very low lead levels, but this hypothesis was confirmed by a long series of analyses,” says lead author Wieslaw Jedrychowski, chair of epidemiology and preventive medicine in the College of Medicine at Jagiellonian University in Krakow.The study population included 457 infants born in Krakow between January 2001 and February 2004. For inclusion in the study, mothers had to be nonsmokers aged 18 to 35 years with no history of chronic diseases such as diabetes or hypertension.Upon enrolling in the study, expectant mothers completed a detailed questionnaire that covered demographic characteristics, pregnancy dates, and medical and reproductive history. Interviews during pregnancy and after birth provided information about secondhand tobacco smoke exposure during pregnancy and duration of breastfeeding.At birth a cord blood sample was collected to measure lead concentration, and the Mental Development Index (MDI) of the Bayley Scales of Infant Development—a widely used tool for assessing mental development in young children—was administered to the women’s children at ages 12, 24, and 36 months to assess factors such as problem solving, memory, vocalization, and language. Normal MDI scores are 85 and above, whereas scores below 85 indicate delayed development.Cord blood lead levels ranged from 0.44 to 4.60 μg/dL, with a median level of 1.21 μg/dL. Mean blood lead levels were not significantly different between boys and girls, nor were maternal education (an indicator of socioeconomic status), number of siblings, or prenatal and postnatal secondhand smoke exposure. Among boys, but not girls, cord blood lead levels were significantly associated with a lower MDI score at 36 months after controlling for confounding factors. With the median blood lead level (1.21 μg/dL) delineating low and high exposures, high exposure was associated with a 4.5-point deficit in boys’ MDI scores.The research was very well done according to Herbert Needleman, a professor of psychiatry and pediatrics at the University of Pittsburgh School of Medicine. “Further,” he says, “I think it’s important because it concerns what other people have shown: that very small amounts of lead are neurotoxic.”A probable explanation for the observed sex-based difference relates to males generally having fewer receptors for estrogen throughout the central nervous system than females, says Jedrychowski, who with his colleagues wrote, “The consequences of neurotoxicant exposure and the gender differences in the response to toxic exposure can partially depend on the protective effects of estrogen.”Adds Needleman, “Boys are more sensitive to almost all [brain] insults—head injuries and things like that. The basic brain is female; masculinity is ‘tacked onto it,’ and it’s a more fragile apparatus.”FiguresReferencesRelatedDetailsCited by Sen A, Heredia N, Senut M, Hess M, Land S, Qu W, Hollacher K, Dereski M and Ruden D (2015) Early life lead exposure causes gender-specific changes in the DNA methylation profile of DNA extracted from dried blood spots, Epigenomics, 10.2217/epi.15.2, 7:3, (379-393), Online publication date: 1-Jun-2015. Vol. 117, No. 9 September 2009Metrics About Article Metrics Publication History Originally published1 September 2009Published in print1 September 2009 Financial disclosuresPDF download License information EHP is an open-access journal published with support from the National Institute of Environmental Health Sciences, National Institutes of Health. All content is public domain unless otherwise noted. Note to readers with disabilities EHP strives to ensure that all journal content is accessible to all readers. However, some figures and Supplemental Material published in EHP articles may not conform to 508 standards due to the complexity of the information being presented. If you need assistance accessing journal content, please contact [email protected]. Our staff will work with you to assess and meet your accessibility needs within 3 working days.

Determinants of low birth weight in urban Pakistan

To identify determinants of low birth weight (LBW) in Karachi, Pakistan, including environmental exposures and nutritional status of the mother during pregnancy. Cross-sectional study.ParticipantsFive hundred and forty mother-infant pairs. We interviewed mothers about obstetric history, diet and exposure to Pb. We measured birth weight and blood lead level (BLL). We performed multiple log binomial regression analysis to identify factors related to LBW. Of 540 infants, 100 (18.5 %) weighed <or=2.5 kg. Umbilical cord BLL was not significantly associated with LBW. Maternal poor self-rated health (adjusted prevalence ratio (adjPR) = 1.83; 95 % CI 1.09, 3.07) and none or one prenatal visit (adjPR = 2.18; 95 % CI 1.39, 3.43) were associated with LBW. A statistically significant interaction between mothers' mid upper-arm circumference (MUAC) and dietary vitamin C intake was noted. Compared with mothers with MUAC above the median and dietary vitamin C intake above the 3rd quartile (>208.7 mg/d), infants of mothers with MUAC less than or equal to the median and dietary vitamin C intake >208.7 mg/d (adjPR = 10.80; 95 % CI 1.46, 79.76), mothers with MUAC above the median and vitamin C intake <or=208.7 mg/d (adjPR = 10.67; 95 % CI 1.50, 76.02) and mothers with MUAC less than or equal to the median and vitamin C intake <or=208.7 mg/d (adjPR = 13.19; 95 % CI 1.85, 93.79) more likely to give birth to an LBW infant. In Pakistan, poor nutritional status and inadequate prenatal care were major determinants of LBW in this setting. Environmental factors including umbilical cord BLL were not significantly associated with LBW.

Gender specific differences in neurodevelopmental effects of prenatal exposure to very low-lead levels: The prospective cohort study in three-year olds

The primary purpose of this study was to assess the relationship between very low-level of prenatal lead exposure measured in the cord blood (< 5 µg/dL) and possible gender-specific cognitive deficits in the course of the first three years of life. The accumulated lead dose in infants over the pregnancy period was measured by the cord blood lead level (BLL) and cognitive deficits were assessed by the Bayley Mental Development Index (MDI). The study sample consisted of 457 children born to non-smoking women living in the inner city and the outlying residential areas of Krakow. The relationship between prenatal lead exposure and MDI scores measured at 12, 24 and 36 months of age and adjusted to a set of important covariates (gender of child, maternal education, parity, breastfeeding, prenatal and postnatal environmental tobacco smoke) was evaluated with linear multivariate regression, and the Generalized Estimating Equations (GEE) longitudinal panel model. The median of lead level in cord blood was 1.21 µg/dL with the range of values from 0.44 to 4.60 µg/dL. Neither prenatal BLL (dichotomized by median) nor other covariates affected MDI score at 12 months of age. Subsequent testing of children at 24 months of age showed a borderline significant inverse association of lead exposure and mental function (beta coefficient = − 2.42, 95%CI: − 4.90 to 0.03), but the interaction term (BLL × male gender) was not significant. At 36 months, prenatal lead exposure was inversely and significantly associated with cognitive function in boys (Spearman correlation coefficient = − 0.239, p = 0.0007) but not girls ( r = − 0.058, p = 0.432) and the interaction between BLL and male gender was significant (beta coefficient = − 4.46; 95%CI: − 8.28 to − 0.63). Adjusted estimates of MDI deficit in boys at 36 months confirmed very strong negative impact of prenatal lead exposure (BLL > 1.67 µg/dL) compared with the lowest quartile of exposure (beta coefficient = − 6.2, p = 0.002), but the effect in girls was insignificant (beta coefficient = − 0.74, p = 0.720). The average deficit of cognitive function in the total sample over the first three years of life (GEE model) associated with higher prenatal lead exposure was also significant (beta coefficient = − 3.00; 95%CI: − 5.22 to − 0.70). Beside prenatal lead exposure, presence of older siblings at home and prenatal environmental tobacco smoke had a negative impact on MDI score. Better maternal education showed a strong beneficial effect on the cognitive development of children. Conclusion: the study suggests that there might be no threshold for lead toxicity in children and provides evidence that 3-year old boys are more susceptible than girls to prenatal very low lead exposure. The results of the study should persuade policy makers to consider gender-related susceptibility to lead and possibly to other toxic hazards in setting environmental protection guidelines. To determine whether the cognitive deficit documented in this study persists to older ages, the follow-up of the children over the next several years is to be carried out.

Very Low Prenatal Exposure to Lead and Mental Development of Children in Infancy and Early Childhood

Background: The primary purpose of the study was to establish a possible association between very low levels of prenatal exposure to lead and mental development of children at 12, 24 and 36 months of age. Methods: The study sample consisted of 444 children born to mothers who attended ambulatory prenatal clinics in Krakow inner city in the first and second trimesters of pregnancy. We assessed exposure to lead by the cord blood lead measurements, and mental development in infancy and early childhood using the Bayley Mental Development Index (MDI). The relationship between prenatal lead exposure and MDI scores at each follow-up period was evaluated with linear multivariate regression. To test the overall effect of maternal exposure to lead during pregnancy on the Bayley test scores at 12, 24 and 36 months of age, we used the generalized estimating equations (GEE) longitudinal panel model as well. Results: The median lead level in cord blood was 1.23 μg/dl, in the range of 0.44–6.90 μg/dl. An adverse effect of prenatal lead exposure (log-transformed lead concentrations) on MDI scores at 12 months of age was of border significance (β = –5.42, 95% CI: –11.19 to 0.35). Subsequent testing of children at 24 months of age showed a significant inverse association of mental function and lead exposure (β = –7.65, 95% CI: –14.68 to –0.62). A significant deficit in cognitive function due to prenatal lead exposure was also confirmed at 36 months of age (β = –6.72, 95% CI: –12.5 to –0.89). The GEE panel model showed that the average deficit in the cognitive development attributable to lead exposure over 3 years was also significant (β = –6.62, 95% CI: –1.52 to –1.72). Mental function scores of girls were better than boys, and the effect of maternal education remained strongly significant in relation to mental function of 3-year-olds. Conclusion: The results of the study demonstrate that the neurotoxic impact of very low levels of prenatal lead exposure (below 5 μg/dl) may occur in infants and very young children, and suggest a revision of established health guidelines for prenatal lead exposure criteria.