Lead exposure in pregnancy: a review of the literature and argument for routine prenatal screening

Blood lead levels during different trimesters of pregnancy and the possible influencing factors in Chengdu, China

Lead is a toxic element. It can damage multiple human organs and systems. In present study, we detected the blood lead levels (BLLs) during the whole pregnancy period and 6-12th weeks after delivery and analyzed their influencing factors by healthy pregnant women. We recruited 128 healthy pregnant women absent of pregnancy or obstetric complications or abnormal pregnancy outcomes as the gravida group. The control group consisted of 120 healthy non-pregnant women. The lead concentrations of all the three pregnancy trimesters and postpartum were: 5.95 ± 2.27, 5.51 ± 1.93, 5.57 ± 1.85, and 6.88 ± 1.90 μg/dl; and the mean lead concentration of control group was 6.87 ± 2.29 μg/dl. We found that the BLLs of the gravida group were lower than that of control group during all three trimesters and occupations, supplement nutrition elements, and time of house painted could affect blood lead levels of pregnant women. Lead-related occupations, using cosmetics, and living in a house painted <1 year are risk factors of high BLLs among pregnant women, while calcium, iron, zinc, and milk supplements are protective factors. These may help people especially pregnant women to reduce lead exposure via supplement of calcium, iron, zinc, and milk or avoiding contacting above risk factors.

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?

OBJECTIVES

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Exposure sources and reasons for testing among women with low blood lead levels

Previous research has focused on highly elevated blood lead (PbB). This study examined reasons for testing and potential sources of exposure among women with PbBs less than 0.72 μmol/l (15 μg/dl). A questionnaire was mailed to 18- to 49-year-old women in upstate New York, USA, who were PbB tested in 2007. The most common testing reason was pregnancy among 125 women who returned the questionnaire. Among women tested for PbB during pregnancy, doctors ordered approximately 80% of tests regardless of lead level. Few women with PbBs less than 0.24 μmol/l (5 μg/dl) reported a potential source of lead exposure. However, among women with PbBs of 0.24-0.71 μmol/L (5-14.9 μg/dl), 29.2% had a job and 21.2% had a hobby with potential lead exposure. There are systematic differences in reasons for testing and exposure sources among women with PbBs less than 0.72 μmol/l and these differences have implications for screening.

Global gene expression analysis reveals dynamic and developmental stage-dependent enrichment of lead-induced neurological gene alterations

BACKGROUND

The underlying genetic mechanisms specific to subtle neurological alterations associated with environmental lead (Pb) exposures have not been clearly elucidated.

OBJECTIVES

The goal of this study was to identify novel gene targets and the underlying genetic mechanisms associated with developmental Pb neurotoxicity.

METHODS

We first exposed zebrafish embryos to a range of Pb concentrations throughout early development to establish relative toxicity. Using the data from that experiment, we exposed another group of zebrafish embryos to a sublethal dose of Pb (100 ppb) immediately after fertilization through 72 or 120 hr postfertilization (hpf). Global gene expression was then analyzed for molecular pathways and gene ontology enrichment, and Western blot analysis was performed to investigate the translation of gene expression changes to protein levels.

RESULTS

After 72 hpf, we identified 231 probes representing 90 nonredundant genes with well-established function or orthology to human genes as being altered by Pb exposure. This gene set was both confirmatory and novel in nature and was highly enriched for neurological development, function, and disease. Moreover, gene changes at this time point were correlated to altered protein levels. Alternatively, the gene set at 120 hpf did not share association with neurological development.

CONCLUSIONS

Global gene expression alterations associated with developmental Pb exposure were dynamic and dependent on developmental stage. Gene expression alterations at the 72-hpf time point were highly enriched with genes and molecular pathways associated with neurological development and disease. Moreover, we identified a number of novel targets for future exploration into their role in the genetic mechanisms underlying Pb-induced neurological alterations.

Hepatotoxicity studies in the progeny of pregnant dams treated with methimazole, monocrotophos and lead acetate

An experimental study was conducted to evaluate the hepatotoxic effects in the progeny of dams treated with methimazole, monocrotophos (MCP) and lead acetate. Female pregnant albino rats of Wistar kyoto strain were divided into five groups and treated as follows, from day 3 of pregnancy till weaning of pups on postnatal day (PND) 21. Group 1 served as sham control, group 2 received methimazole 0.02% in drinking water, group 3 received MCP (0.3 mg/kg orally), group 4 received lead acetate at 0.2% in drinking water and group 5 received MCP + lead acetate. Thyroid hormone profile was recorded on 14 ^thday of gestation in dams. Eight pups from each group were euthanized on PND 21 and 90, and liver tissues were collected for analysis. Thiobarbituric acid reactive substances (TBARS), protein carbonyls and reduced glutathione (GSH) of liver were studied on PND 21 and 90, while the activities of Na ⁺/K⁺ATPase and Mg ²⁺ATPase in the liver were studied on PND 90. T₃, T₄, GSH, Na⁺/K⁺ATPase and Mg²⁺ATPase were significantly (P<0.05) decreased, while TBARS and protein carbonyls were significantly (P < 0.05) increased in all the test groups as compared to group 1. From this study, it is concluded that both MCP and lead acetate have a possible influence on thyroid gland of dams as the thyroid profile was altered significantly and the hepatotoxic effects were comparable to those induced by methimazole.

Heavy metals (lead, cadmium and mercury) in maternal, cord blood and placenta of healthy women

Lead, cadmium and mercury were measured in placental tissue, umbilical cord and maternal blood samples of 1578 women who delivered at the Al-Kharj King Khalid Hospital between 2005 and 2006. The aim of this study was to evaluate the status of heavy metal exposure in mothers and their newborns and to identify predictors of maternal exposure. Lead was detected in all cord and maternal blood and in 96% of placental tissues. Only in 0.89% and 0.83% of cord and maternal blood samples were the levels of lead above the CDC threshold limit of 10 μg/dl. Maternal blood lead was also higher (2.3%) than the German Reference value in women of 7 μg/dl. Approximately 9.3% of women had a placental lead above the 95th percentile in the range of 0.83-78 μg/g dry wt., a level of possible developmental toxicity. Cadmium was detected in 94.8% and 97.9% of cord and maternal blood samples respectively, though only five newborns had a cadmium level above the OSHA threshold limit of 5 μg/l. Comparing our results to the newly revised German Reference value for nonsmokers, 48.6% of mothers had blood cadmium levels >1.0 μg/l. We found as well that 25% of women had placental cadmium in the >75th percentile, in the range of 0.048-4.36 μg/g dry wt., which is likely to affect fetal growth and development. Of the maternal and cord blood samples, 11.2% and 13%, respectively, had mercury levels >5.8 μg/l, which is the EPA reference dose. Nearly 49% of women had mercury levels >2.0 μg/l, the German Reference value for those who consume fish ≤3 times a month. Around 50% of the mothers had placental mercury in the range of 0.031-13.0 μg/g dry wt. Regression analyses indicated that the levels of metals in the blood and placenta were influenced by several factors. This study provides informative baseline biomonitoring data and reveals a substantial exposure to heavy metals in non-occupationally exposed Saudi mothers and their newborns that might jeopardize the health of both. Additional research is also urgently needed to explore factors such as environment, diet, lifestyle and/or cultural habits contributing to maternal and fetal exposures. Preventive measures to eliminate or minimize the unnecessary risk of fetus exposure to heavy metals or other pollutants during pregnancy should be initiated once these factors are identified.

Asymptomatic congenital lead poisoning - case report

CONTEXT

Congenital lead poisoning is uncommon and there is no consensus on the management of the newborn.

CASE DETAILS

A female infant was born to a lead-burdened woman identified by screening just prior to delivery. Maternal blood lead level (BLL) was 58 μg/dL. The infant's BLL on the second day of life was 72 μg/dL with a free erythrocyte protoporphyrin level of 175 μg/dL. The child was managed by an exchange transfusion followed by chelation. The BLL 6 h after exchange transfusion was 11.4 μg/dL. Follow-up 2 years later showed a BLL of 9 μg/dL and normal development.

DISCUSSION

We present the details of a case of congenital lead poisoning treated aggressively which appears to have resulted in a favorable outcome.

Increased tau phosphorylation and beta amyloid in the hipocampus of mouse pups by early life lead exposure

The aim of this study was to investigate the effects of maternal lead exposure on the learning and memory ability and expression of tau protein phosphorylation (P-tau) and beta amyloid protein (Abeta) in hippocampus of mice offspring. Pb exposure initiated from beginning of gestation to weaning. Pb acetate administered in drinking solutions was dissolved in distilled deionized water at the concentrations of 0.1%, 0.5% and 1% groups. On the 21 th of postnatal day, the learning and memory ability of the mouse pups was tested by Water Maze test and the Pb levels in blood and hippocampus of the offspring were also determined. The expression of P-tau and Abeta in hippocampus was measured by immunohistochemistry and Western blotting. The Pb levels in blood and hippocampus of all exposure groups were significantly higher than that of the control group ( P < 0.05). In Water Maze test, the performances of 0.5% and 1% groups were worse than that of the control group ( P < 0.05). The expression of P-tau and Abeta was increased in Pb exposed groups than that of the control group ( P < 0.05). Tau hyper-phosphorylation and Abeta increase in the hippocampus of pups may contribute to the impairment of learning and memory associated with maternal Pb exposure.

Early-life lead exposure affects the activity of TNF-alpha and expression of SNARE complex in hippocampus of mouse pups

This study aims to investigate the effects of maternal lead exposure on learning and memory ability and the protein expression of TNF-alpha and SNARE complex (SNAP-25, VAMP-2, and Syntaxin 1A) in hippocampus of mice offspring. Pb exposure was initiated from beginning of gestation to weaning. Pb acetate administered in drinking solutions was dissolved in distilled deionized water at 0.1%, 0.5%, and 1% groups, respectively. On the PND21, the learning and memory ability of mouse pups was tested by water maze test, and the Pb levels in their blood and hippocampus were also determined. The protein expression of TNF-alpha and SNARE complex in hippocampus was measured by immunohistochemistry and Western blotting. The Pb levels in blood and hippocampus of all exposure groups were significantly higher than control group (P < 0.05). In the water maze test, the performances of 0.5% and 1% groups were worse than that of control group (P < 0.05). The expression of TNF-alpha, Syntaxin 1A, and VAMP-2 was increased in Pb-exposed groups comparing control group (P < 0.05), but the expression of SNAP-25 was decreased (P < 0.05). Up-regulation of TNF-alpha and disturbance of SNARE expression in the hippocampus of pups may contribute to impairment of learning and memory ability associated with maternal Pb exposure.

The U.S. Food and Drug Administration risk assessment on lead in women's and children's vitamins is based on outdated assumptions

BACKGROUND

Following a recent report of lead in certain commercial vitamin products, the U.S. Food and Drug Administration (FDA) conducted a nationwide survey to determine the Pb content in 324 multivitamin/mineral products labeled for use by women and children. The FDA compared estimated Pb exposures from each product with safe/tolerable exposure levels, termed provisional total tolerable intake (PTTI) levels, previously developed for at-risk population groups in 1992.

OBJECTIVE

We investigated the FDA's conclusions that Pb concentrations in all vitamin products examined do not pose a hazard to health because they are below the PTTI levels for all groups considered.

DISCUSSION

For their initial estimations of PTTI levels, the FDA used a blood lead level (BLL) of 10 microg/dL as the threshold for adverse effects in children and in pregnant or lactating women. Studies have repeatedly linked chronic exposure to BLLs < 10 microg/dL with impairments in cognitive function and behavior in young children despite the absence of overt signs of toxicity. The FDA analysis also omitted any consideration of nonfood sources of Pb exposure, which is inconsistent with our current understanding of how most children develop elevated BLLs.

CONCLUSION

We feel that based on these oversights, the FDA's conclusions are unduly reassuring and that reconsideration of their current recommendations appears warranted.

Emerging aspects of assessing lead poisoning in childhood

This review covers the epidemiology of lead poisoning in children on a global scale. Newer sources of lead poisoning are identified. The methods that are used to assess a population of children exposed to lead are discussed, together with the ways of undertaking an exposure risk assessment; this includes assessing the time course and identifying sources of lead exposure. Human assessment measures for lead toxicity, such as blood lead concentrations, deciduous tooth lead, and use of zinc protoporphyrin estimations are evaluated. The role of isotopic fingerprinting techniques for identifying environmental sources of exposure is discussed. Among emerging data on the cognitive and behavioral effects of lead on children, the review considers the growing evidence of neurocognitive dysfunction with blood lead concentrations even below 10 µg/dl. The challenge of assessing and explaining the risk that applies to an individual as opposed to a population is discussed. Intervention strategies to mitigate risk from lead are examined together with the limited role for and limitations of chelation therapy for lead. Lessons learned from managing a population lead-dust exposure event in Esperance, Western Australia in 2007 are discussed throughout the review.

Neurotoxic effects and biomarkers of lead exposure: a review

Lead, a systemic toxicant affecting virtually every organ system, primarily affects the central nervous system, particularly the developing brain. Consequently, children are at a greater risk than adults of suffering from the neurotoxic effects of lead. To date, no safe lead-exposure threshold has been identified. The ability of lead to pass through the blood-brain barrier is due in large part to its ability to substitute for calcium ions. Within the brain, lead-induced damage in the prefrontal cerebral cortex, hippocampus, and cerebellum can lead to a variety of neurologic disorders. At the molecular level, lead interferes with the regulatory action of calcium on cell functions and disrupts many intracellular biological activities. Experimental studies have also shown that lead exposure may have genotoxic effects, especially in the brain, bone marrow, liver, and lung cells. Knowledge of the neurotoxicology of lead has advanced in recent decades due to new information on its toxic mechanisms and cellular specificity. This paper presents an overview, updated to January 2009, of the neurotoxic effects of lead with regard to children, adults, and experimental animals at both cellular and molecular levels, and discusses the biomarkers of lead exposure that are useful for risk assessment in the field of environmental health.

The clinical content of preconception care: environmental exposures

Environmental origins of disease risk and harm to health have been increasingly acknowledged for numerous outcomes, in both adult and pediatric populations. Adverse reproductive and developmental effects have also been linked to environmental exposures. In addition to the current queries about a patient's alcohol and smoking history, key determinants of a future pregnancy outcome should also be elicited during the preconception visit. These determinants include: (1) mercury intake via fish consumption; (2) nitrate exposure from well water sources; (3) exposure to chemical, physical, or biologic hazards on the job; and (4) lead and other toxic exposures--possibly from hobbies or the use of lead-glazed dinnerware in the home. Eliciting a detailed environmental history permits tailored recommendations to optimize the woman's health and that of her future pregnancy.

Lead hazards for pregnant women and children: part 1: immigrants and the poor shoulder most of the burden of lead exposure in this country. Part 1 of a two-part article details how exposure happens, whom it affects, and the harm it can do

Poor, urban, and immigrant populations are at far greater risk for lead exposure than are other groups in the United States. Children with even slightly elevated blood lead levels are at increased risk for significant neurobehavioral problems that can extend through adolescence. Research has shown that elevated blood lead levels in pregnant women, even those well below 10 micrograms per deciliter-the Centers for Disease Control and Prevention's "level of concern"-can cause miscarriage, premature birth, low birth weight, and subsequent developmental delays in their children. Despite these well-established dangers, routine prenatal lead screening and lead education is not a standard of care. Part 1 of this two-part article presents a short case example of a pregnant mother with lead poisoning and describes the epidemiology of lead exposure in the United States, the main sources of lead exposure, and the effects of lead on the pregnant mother and the developing fetus and child. Prevention is crucial. Treatment options such as chelation must be used selectively and will not reverse damage once it's occurred. Part 2 will describe recommendations for screening, education, nutrition, reducing environmental exposures, and treatment.

Maternal low-level lead exposure reduces the expression of PSA-NCAM and the activity of sialyltransferase in the hippocampi of neonatal rat pups

Highly polysialylated neural cell adhesion molecule (PSA-NCAM) is transiently expressed specifically in newly generated cells, and is important for cell migration and neurite outgrowth. Developmental lead (Pb) exposure has been considered to affect the expression of PSA-NCAM, which contributes to the neurotoxicity of Pb exposure. However, the effect of maternal low-level Pb exposure on the expression of PSA-NCAM in neonatal rat pups has not been reported. In the present study, female Wistar rats were exposed to vehicle or different dosages of lead chloride (0.5-4mM PbCl2) 2 weeks before and during pregnancy. This exposure protocol resulted in neonatal rat pups blood Pb levels up to 12.12+/-0.38 microg/dl, and hippocampal Pb levels up to 9.22+/-0.81 microg/g at postnatal day 1 (PND 1). Immunohistochemistry analysis and Western blot analysis revealed that the expressions of PSA-NCAM and NCAM in the hippocampi of neonatal rat pups at PND 1 were significantly reduced by the maternal low-level Pb exposures. Furthermore, the mRNA levels of NCAM and polysialyltransferases (STX and PST), measured by the fluorescent real-time quantitative RT-PCR, dosage-dependently and significantly decreased by 13.26-37.62%, 25.17-59.67%, and 10.78-47.81%, respectively. In addition, the sialyltransferase activity in neonatal rat pups was significantly reduced by 6.23-32.50% in the presence of the low-level Pb exposure, too. Taken together, these results suggest that maternal low-level Pb exposure reduces the expression of PSA-NCAM, NCAM, and the activity of sialyltransferase in the hippocampi of neonatal rat pups, which might contribute to the learning and memory impairments in the developmental pups following maternal low-level Pb exposure.

Elevated blood lead levels in pregnant women: identification of a high-risk population and interventions

There has been a significant decrease in the number of preschool children with elevated blood lead levels (BLL), from 88.2 to 4.4 per 10,000 children over the last three decades as shown by National Health and Nutritional Examination Survey (NHANES) data. However, there are still certain high-risk populations that have not been well studied. One such group is that of pregnant women. During pregnancy, BLL tends to increase due to greater bone turnover, which causes release of lead stored in bone. This increase may not affect the pregnant woman's health directly but could be extremely harmful to the rapidly developing central nervous system in the fetus as it crosses the placenta easily. This current study was undertaken to estimate the prevalence of elevated BLL in pregnant women in a community hospital, monitor the effect of routine preventive practices on maternal BLL, and to elucidate the relationship between maternal and neonatal BLL and their anthropometric indices. A retrospective chart review was conducted on all hospital deliveries occurring in the first six years after the initiation of universal blood lead screening of pregnant women (n=6880). The prevalence of elevated lead (> or =10 microg/dL) in our patient population was 1.7%. The factors associated with elevated lead levels were recent immigration to the US, poor socioeconomic status and low educational levels. Simple interventions such as hand washing as well as calcium and iron supplementation significantly reduced maternal BLL from 16.82+/-9.5 to 11.48+/-9.3 microg/dL (P<0.0001). A significant correlation (r=0.4, P<0.007) is present between the post-intervention but not the pre-intervention maternal BLL and the neonatal BLL. Given the vulnerability of the developing fetal brain and that CNS complications are associated with elevated lead levels, antenatal lead screening should be part of routine prenatal care. Simple preventive measures may play a role in decreasing maternal BLL and thereby decreasing transplacental transfer of lead to the fetus.

Globalization, binational communities, and imported food risks: results of an outbreak investigation of lead poisoning in Monterey County, California

OBJECTIVES

Although the burden of lead poisoning has decreased across developed countries, it remains the most prevalent environmental poison worldwide. Our objective was to investigate the sources of an outbreak of lead poisoning in Monterey County, California.

METHODS

An investigation in 3 county health department clinics in Monterey County, California, was conducted between 2001 and 2003 to identify risk factors for elevated blood lead levels (> or = 10 microg/dL) among children and pregnant women.

RESULTS

The prevalence of elevated blood lead levels was significantly higher in 1 of the 3 clinics (6% among screened children and 13% among prenatal patients). Risk factors included eating imported foods (relative risk [RR]=3.4; 95% confidence interval [CI]=1.2, 9.5) and having originated from the Zimatlan area of Oaxaca, Mexico, compared with other areas of Oaxaca (RR=4.0; 95% CI=1.7, 9.5). Home-prepared dried grasshoppers (chapulines) sent from Oaxaca were found to contain significant amounts of lead.

CONCLUSIONS

Consumption of foods imported from Oaxaca was identified as a risk factor for elevated blood lead levels in Monterey County, California. Lead-contaminated imported chapulines were identified as 1 source of lead poisoning, although other sources may also contribute to the observed findings. Food transport between binational communities presents a unique risk for the importation of environmental hazards [corrected]

Inadequate prenatal care and elevated blood lead levels among children born in Providence, Rhode Island: a population-based study

OBJECTIVE

This study was conducted to determine whether children born to mothers receiving inadequate prenatal care are at an increased risk for having an elevated blood lead level during early childhood.

METHODS

The authors conducted a population-based study of children born in Providence, Rhode Island, from 1997 to 2001 whose mothers had received adequate, intermediate, or inadequate prenatal care. The children's blood lead levels were compared between groups using bivariate and logistic regression. To understand the regulatory implications and public health impact of changing the definition of an elevated blood lead level, "elevated" was defined as 5 microg/dL, 10 microg/dL, and 15 microg/dL.

RESULTS

Children born to mothers who received inadequate prenatal care were at an elevated risk for having an elevated blood lead level later in life. This relationship remained statistically significant for each definition of elevated blood lead level and after controlling for other socio-economic status measures and birthweight (at 5 microg/dL, odds ratio [OR] = 1.36, 95% confidence interval [CI] 1.09, 1.68, p = 0.006; at 10 microg/dL, OR = 1.68, 95% CI 1.26, 2.24, p < 0.0004; at 15 microg/dL, OR = 1.83, 95% CI 1.10, 3.04, p = 0.019) represent an opportune moment to identify expectant mothers living in lead-contaminated environments.

CONCLUSIONS

Results suggest that conducting lead screening as a regular part of prenatal care provision could help identify women possibly experiencing ongoing lead exposure and help reduce or prevent exposures to their offspring.

Changes in blood lead levels associated with use of chloramines in water treatment systems

BACKGROUND

More municipal water treatment plants are using chloramines as a disinfectant in order to reduce carcinogenic by-products. In some instances, this has coincided with an increase in lead levels in drinking water in those systems. Lead in drinking water can be a significant health risk.

OBJECTIVES

We sought to test the potential effect of switching to chloramines for disinfection in water treatment systems on childhood blood lead levels using data from Wayne County, located in the central Coastal Plain of North Carolina.

METHODS

We constructed a unified geographic information system (GIS) that links blood lead screening data with age of housing, drinking water source, and census data for 7,270 records. The data were analyzed using both exploratory methods and more formal multivariate techniques.

RESULTS

The analysis indicates that the change to chloramine disinfection may lead to an increase in blood lead levels, the impact of which is progressively mitigated in newer housing.

CONCLUSIONS

Introducing chloramines to reduce carcinogenic by-products may increase exposure to lead in drinking water. Our research provides guidance on adjustments in the local childhood lead poisoning prevention program that should accompany changes in water treatment. As similar research is conducted in other areas, and the underlying environmental chemistry is clarified, water treatment strategies can be optimized across the multiple objectives that municipalities face in providing high quality drinking water to local residents.

"Veterinary" diagnosis of lead poisoning in pregnancy

A high index of suspicion in cases at risk of lead exposure is essential in pregnancy

Screening for elevated lead levels in childhood and pregnancy: an updated summary of evidence for the US Preventive Services Task Force

BACKGROUND

In 1996, the US Preventive Services Task Force provided recommendations for routine screening of asymptomatic children and pregnant women for elevated blood lead levels. This review updates the evidence for the benefits and harms of screening and intervention for elevated blood lead in asymptomatic children and pregnant women.

METHODS

We searched Medline, reference lists of review articles, and tables of contents of leading pediatric journals for studies published in 1995 or later that contained new information about the prevalence, diagnosis, natural course, or treatment of elevated lead levels in asymptomatic children aged 1 to 5 years and pregnant women.

RESULTS

The prevalence of elevated blood lead levels among children and women in the United States, like that in the general population, continues to decline sharply, primarily because of marked reductions in environmental exposure, but still varies substantially among different communities and populations. Similar to the findings in 1996, our searches did not identify direct evidence from controlled studies that screening children for elevated blood lead levels results in improved health outcomes, and there was no direct evidence identified from controlled studies that screening improves pregnancy or perinatal outcomes. No new relevant information regarding the accuracy of screening for lead toxicity was identified during the update, and we did not identify evidence that demonstrates that universal screening for blood lead results in better clinical outcomes than targeted screening. Substantial new relevant information regarding the adverse effects of screening and interventions was not identified.

CONCLUSIONS

There is no persuasive evidence that screening for elevated lead levels in asymptomatic children will improve clinical outcomes. For those children who are screened and found to have elevated levels, there is conflicting evidence demonstrating the clinical effectiveness of early detection and intervention.

[Lead exposure in pregnant women and newborns: a screening update]

Human lead exposure has many sources. Relative importance of these sources varies widely according to geographic regions and human lifestyle. The impact of lead exposure on health has been well studied and public health interventions have been conducted.

OBJECTIVE

The aim of this study was to evaluate current prevalence of lead burden in neonates, and seek for sources of maternal and fetal intoxication.

POPULATION AND METHODS

A prospective multicentre study was conducted by the "Réseau périnatal 92" on a population of pregnant women attending 3 maternal wards in the north of 'Hauts-de-Seine' department in France. Between December 2003 and May 2004, a total of 1021 pregnant women were included. All patients signed an informed consent before participating in the study. Cord blood samples were collected at delivery for lead measurements.

RESULTS

The mean cord blood lead concentration was 23.2 microg/l. Eighteen neonates over 1021 (1.8%) had lead levels above 100 microg/l. An environmental query was conducted by the social and public health office of the department (DDASS), and data were collected regarding the state of the housing and the lifestyle of the concerned family. Main sources of lead intoxication were 'tagine' food plates in 83.3% of cases, 'khôl' powder (used as eyeliner) in 88.9% of cases and substandard housings in 22.2% of cases. A specialized paediatric follow-up for the 18 neonates was performed.

CONCLUSION

With the exception of substandard housing (old lead painting), other sources of lead intoxication were discovered: 'tagine' plates and 'khôl' powder. Almost all of these products came from Morocco. A public health intervention would be able to inform the population about these yet unknown sources of lead intoxication.

Relation of in utero lead exposure with insulin-like growth factor-I levels and neonatal anthropometric parameters

Our aim was to establish whether independent relationships exist between either anthropometric parameters or insulin-like growth factor-I (IGF-I) and cord blood lead levels in newborns. Umbilical cord blood samples and anthropometric data were obtained at delivery. Cord blood lead levels were analyzed by atomic absorption spectrophotometer. IGF-I levels were measured using RIA. Blood lead levels >or=100 microg/l were considered elevated in accordance with CDC guidelines. Data on all variables of interest were obtained for 54 term neonates. The mean cord blood lead level was 144+/-89 microg/l with a range of 51-355 microg/l. Twenty-nine (53.7%) neonates had blood lead levels >or=100 microg/l. However, only 5 (9.2%) of the neonates had blood lead levels of >or=250 microg/l. No statistically significant difference was found in case of anthropometric parameters and IGF-I levels between neonates with high lead levels (>or=100 microg/l) and with low lead levels (<100mug/l) in cord blood (p>0.05). There was a significant correlation between lead and birth weight in neonates with high lead levels (r: -0.49, p=0.01) but not other anthropometric data and IGF-I levels. A multivariate regression analysis using the full range of lead values adjusted for the relevant confounders such as gestational age and socioeconomic status was performed. In the model birth weight (p: 0.01, beta: -0.81), birth length (p: 0.05, beta: 0.41) and midarm circumferences (p: 0.05, beta: 0.30) were the best predictors of lead levels, with the total variance explained being 36%. Significant relationship was found between birth weight and lead burden in newborns. Whether serum lead level predicts the development of failure to thrive in these children remains to be determined in follow-up studies.

Association of umbilical cord blood lead with neonatal behavior at varying levels of exposure

Background

In the light of the ongoing debate about lowering the cut-off for acceptable blood lead level to <5 μg/dL from the currently recommended level of <10 μg/dL, we considered whether prenatal exposure to varying levels of lead is associated with similar or disparate effects on neonatal behavior.

Methods

Using Brazelton's Neonatal Behavioral Assessment Scale (NBAS), an epidemiological approach and robust statistical techniques like multivariate linear regression, logistic regression, Poisson regression and structural equations modeling analyses we estimated the simultaneous indirect effects of umbilical cord blood lead (CBL) levels and other neonatal covariates on the NBAS clusters.

Results

We observed that when analyzed in all study subjects, the CBL levels independently and strongly influenced autonomic stability and abnormal reflexes clusters. However, when the analysis was restricted to neonates with CBL <10 μg/dL, CBL levels strongly influenced the range of state, motor and autonomic stability clusters. Abnormal walking reflex was consistently associated with an increased CBL level irrespective of the cut-off for CBL, however, only at the lower cut-offs were the predominantly behavioral effects of CBL discernible.

Conclusion

Our results further endorse the need to be cognizant of the detrimental effects of blood lead on neonates even at a low-dose prenatal exposure.

Lead exposure and birth outcomes in five communities in Shoshone County, Idaho

INTRODUCTION

This study examined birth outcomes in five towns in Shoshone County, Idaho, where residents were exposed to high levels of lead in air emissions during a 6-month period after a fire had damaged the main baghouse (pollution-control device) of a local lead smelter plant in September 1973.

METHODS

We studied birth certificate data of 169,878 live singleton infants born to mothers who resided in Idaho at the time of delivery. The outcomes evaluated were preterm infants, small-for-gestational-age (SGA) infants, low birthweight among term infants (TLBW), and mean birthweight among term infants (TMBW). The study compared births in the five towns in Shoshone County (exposed group) to births in the rest of Idaho during three exposure periods: "pre-fire," January 1, 1970-August 31, 1973; "high exposure," September 1, 1973-December 31, 1974; and "post-fire," January 1, 1975-December 31, 1981.

RESULTS

During the high-exposure period, the exposed group had an increased prevalence of TLBW (OR=2.4; 90% CI: 1.6-3.6) and SGA (OR=1.9; 90% CI: 1.3-2.8) compared with the rest of Idaho. During the pre- and post-fire periods, the ORs for TLBW were 0.8 and 1.3, respectively, and for SGA, 1.0, and 1.3, respectively. During the high-exposure period, TMBW for the exposed group was 71 g lower than in the comparison group. The TMBW in the exposed group was 8 g lower in the pre-fire period and 26 g lower in the post-fire period than in the comparison group. The study found no increased risk for preterm birth in the exposed group.

CONCLUSIONS

Maternal exposures to airborne lead emissions appeared to be associated with increased risks for SGA, TLBW, and reduced TMBW.

Effect of magnitude and timing of maternal pregnancy blood lead (Pb) levels on birth outcomes

OBJECTIVE

Associations between magnitude and timing of maternal pregnancy blood lead (Pb) levels (BLLs), birth weight, and total days of gestation were examined, as well as associations with related clinical diagnoses of low birth weight (LBW), preterm, and small-for-gestational-age (SGA) birth.

STUDY DESIGN

Among a sample of 262 mother-infant pairs studied retrospectively, one-way analysis of variance and regression statistics were used to measure the relationship between level of maternal pregnancy BLLs and birth outcomes while controlling for key maternal and newborn factors.

RESULTS

Women with maximum pregnancy BLLs (max-PBLLs) > or =10 microg/dl tended to give birth earlier and their babies were at substantially increased risk for preterm and SGA birth. By holding other explanatory factors constant, each unit increase in max-PBLL above 10 mug/dl was found to be associated with a decrease of -0.3 in total days of gestation. Compared to women with lower levels, women with max-PBLLs > or =10 microg/dl were at a threefold increased risk for preterm birth (adjusted OR=3.2, 95% CI 1.2-7.4) and more than a fourfold increased risk for having an SGA infant (adjusted OR=4.2, 1.3-13.9). Second trimester maximum BLLs > or =10 microg/dl were associated with a steep decrease in total days of gestation (a decrease of -1.0 days per each unit increase above 10 microg/dl).

CONCLUSIONS

These data provide evidence of the adverse effects of maternal pregnancy BLLs, particularly when levels are > or =10 microg/dl. Prenatal Pb exposure at these levels was associated with significant decreases in total days of gestation and an increased risk of preterm and SGA birth.

Succimer therapy for congenital lead poisoning from maternal petrol sniffing

An infant, born at 35 weeks' gestation to a woman who sniffed petrol, had a cord blood lead level eight times the accepted limit. Treatment with oral dimercaptosuccinic acid promptly reduced his blood lead levels. To our knowledge, this is the first reported case of congenital lead poisoning secondary to maternal petrol sniffing. We suggest that at-risk pregnancies should be identified, cord blood lead levels tested, and chelation therapy and developmental follow-up offered to affected infants.

Factors influencing the difference between maternal and cord blood lead

AIMS

To determine the factors that affect why some infants receive higher exposures relative to the mother's body burden than do others.

METHODS

A total of 159 mother-infant pairs from a cohort of women receiving prenatal care at Magee-Womens Hospital in Pittsburgh, PA from 1992 to 1995 provided blood samples at delivery for lead determination. The difference between cord and maternal blood lead concentration (PbB) and a dichotomous variable indicator of higher cord than maternal PbB, were examined as indicators of relative transfer. Women were interviewed twice during the pregnancy about lifestyle, medical history, calcium nutrition, and physical activity.

RESULTS

Higher blood pressure was associated with relatively greater cord compared with maternal PbB, as was maternal alcohol use. Sickle cell trait and higher haemoglobin were associated with a lower cord relative to maternal blood lead PbB. No association was seen with smoking, physical exertion, or calcium consumption.

CONCLUSION

While reduction in maternal exposure will reduce fetal exposure, it may also be possible to mitigate infant lead exposure by reducing transfer from the pregnant woman. Interventions aimed at reducing blood pressure and alcohol consumption during pregnancy may be useful in this regard.

Mechanisms of Pb(II) sorption on a biogenic manganese oxide

Macroscopic Pb(II) uptake experiments and Pb L3-edge extended X-ray absorption fine structure (EXAFS) spectroscopy were combined to examine the mechanisms of Pb(II) sequestration by a biogenic manganese oxide and its synthetic analogues, all of which are layer-type manganese oxides (phyllomanganates). Relatively fast Pb(II) sorption was observed, as well as extremely high sorption capacities, suggesting Pb incorporation into the structure of the oxides. EXAFS analysis revealed similar uptake mechanisms regardless of the specific nature of the phyllomanganate, electrolyte background, total Pb(II) loading, or equilibration time. One Pb-O and two Pb-Mn shells at distances of 2.30, 3.53, and 3.74 A, respectively, were found, as well as a linear relationship between Brunauer-Emmett-Teller (BET; i.e., external) specific surface area and maximum Pb(II) sorption that also encompassed data from previous work. Both observations support the existence of two bonding mechanisms in Pb(II) sorption: a triple-corner-sharing complex in the interlayers above/ below cationic sheet vacancies (N theoretical = 6), and a double-corner-sharing complex on particle edges at exposed singly coordinated -O(H) bonds (N theoretical = 2). General prevalence of external over internal sorption is predicted, but the two simultaneous sorption mechanisms can account for the widely noted high affinity of manganese oxides for Pb(ll) in natural environments.

Effects of lead exposure on proliferation and differentiation of neural stem cells derived from different regions of embryonic rat brain

Lead is a potent neurotoxin, causing brain damage and cognitive deficits in children even at low exposure levels. Although lead neurotoxicity can occur after prenatal or postnatal exposure, little is known of the effects of lead on embryonic neural stem cells (NSCs) or the extent to which NSCs originating in different brain regions may be differentially sensitive to the effects of lead exposure. The present study examined the effects of lead on proliferation and differentiation of neural stem cells (NSCs) originating from E15 rat cortex (CX), striatum (ST) or ventral mesencephalon (VM). Free-floating neurospheres were grown under standard conditions or in lead (0.01-100 microM)-containing conditioned media for 5 days and proliferation assessed by 3H-thymidine uptake. In other studies, control and lead-exposed neurospheres were collected, dissociated and re-plated in control or lead-containing differentiation media for 7 days. Cells were immunostained for visualization of mature neural and glial markers and counted. Lead exposure (0.01-10 microM) had no effect on neurosphere viability but caused a significant dose-dependent inhibition of proliferation in VM and ST but not CX neurospheres. The number of MAP2 positive neurons differentiated from lead-exposed neurospheres of VM and ST origin (but not CX) was significantly decreased from control as were the number of oligodendrocytes obtained, regardless of their region of origin. In contrast, lead exposure significantly increased the number of astrocytes obtained regardless of site of origin. These data suggest that even low levels of lead can differentially affect proliferation and differentiation of embryonic NSCs originating from different brain regions and supports the need for prevention of prenatal lead exposure.

Transition of cord blood lead level, 1985-2002, in the Taipei area and its determinants after the cease of leaded gasoline use

Lead has long been of concern for its toxicity, impairment of neurobehavioral and cognitive development, and electrophysiological deficits in children, even at levels less than 10 microg/dL. The present study was conducted to elucidate the extent of cord blood lead level decline in the Taipei area from 1985 to 2002 and to explore the factors affecting the cord blood lead level after the cease of leaded gasoline use. In the current study period of 2001-2002, 184 of 1310 newborns delivered in the Taipei Municipal Women and Children Hospital between September 2001 and August 2002 were eligible and randomly selected to participate in this study. Neither of their parents had an occupational lead exposure history. At each delivery, a sample of 5-10 mL umbilical cord blood was collected for lead determination by graphite furnace atomic absorption spectrometry. The cord blood lead level of the newborns in the current study period averaged 2.35 +/- 1.12 microg/dL. Together with the cord blood lead averages of 7.48 +/- 2.25 and 3.28 +/- 1.52 microg/dL obtained from two previous surveys conducted in 1985-1987 and 1990-1992, respectively, the cord blood lead level was significantly decreased (P < 0.005). It is estimated that such a reduction in cord blood lead from 7.48 to 2.35 microg/dL for each year's cohort of 260,000 newborns in Taiwan might benefit the economics, ranging from US$8.9 billion to US$12.1 billion by improving the worker productivity. For the time period from 1985 to 2002, there were consistent transition patterns among the yearly fluctuations of air lead level, leaded gasoline consumption, lead content in gasoline, estimated lead amount emitted from the consumed leaded gasoline, and average cord blood lead levels of the three respective study periods. Additionally, every 0.1-g/L reduction in lead content in gasoline might lead to a lowering of cord blood lead level by 1.78 microg/dL. Furthermore, at low level of around 2 microg/dL, a multiple regression analysis demonstrated that economic status was the most influential factor for cord blood lead variation (P = 0.0061) while the maternal working month during her pregnancy was retained in the model with borderline effect (P = 0.0625). After accounting for the effect of leaded gasoline on the cord blood lead level, future study to differentiate the primary contributors for the low-level cord blood lead variation around 1-2 microg/dL is warranted.

Combined Exchange Transfusion and Chelation Therapy for Neonatal Lead Poisoning

OBJECTIVE

To describe the results of combined exchange transfusion and chelation therapy in a neonate with an elevated blood lead level (BLL).

CASE SUMMARY

A 34-year-old Latina woman with a long history of pica (eating glazed pottery) gave birth to a healthy-appearing girl at 40 weeks of gestation. The mother's preconception BLL was 117 μg/dL and remained elevated throughout pregnancy. At parturition, the mother's BLL was 87 μg/dL and the infant's cord BLL was 100 μg/dL. The infant underwent single-volume exchange transfusion within 12 hours of birth. BLL was 28 μg/dL following the exchange, and a 5-day course of chelation with dimercaprol and CaNa2 ethylenediamine tetraacetic acid was initiated at 36 hours of life. The infant's BLL was 37 μg/dL at the end of inpatient chelation.

DISCUSSION

Long-term neurologic disability from in utero lead exposure is well described, but the optimal treatment of elevated neonatal BLLs in healthy-appearing infants at the time of birth is not established. This strategy of combined chelation and exchange transfusion therapy was well tolerated and resulted in decreased lead levels, but the long-term neurologic efficacy of our combination strategy remains to be seen.

CONCLUSIONS

Combined exchange transfusion and chelation therapy resulted in rapidly decreased lead levels in a neonate with chronic in utero lead exposure.

Lead exposure through gestation-only caused long-term learning/memory deficits in young adult offspring

Numerous observations in clinical and preclinical studies indicate that the developing brain is particular sensitive to lead (Pb)'s pernicious effects. However, the effect of gestation-only Pb exposure on cognitive functions at maturation has not been studied. We investigated the potential effects of three levels of Pb exposure (low, middle, and high Pb: 0.03%, 0.09%, and 0.27% of lead acetate-containing diets) at the gestational period on the spatial memory of young adult offspring by Morris water maze spatial learning and fixed location/visible platform tasks. Our results revealed that three levels of Pb exposure significantly impaired memory retrieval in male offspring, but only female offspring at low levels of Pb exposure showed impairment of memory retrieval. These impairments were not due to the gross disturbances in motor performance and in vision because these animals performed the fixed location/visible platform task as well as controls, indicating that the specific aspects of spatial learning/memory were impaired. These results suggest that exposure to Pb during the gestational period is sufficient to cause long-term learning/memory deficits in young adult offspring.

Effects of low-level lead exposure on cell survival and neurite length in primary mesencephalic cultures

The effects of low-level lead exposure on survival and neurite length of rat E15 primary ventral mesencephalic dopaminergic neurons were studied. Lead acetate (0.001-10 microM) added to primary cultures for 48 h (in serum-free defined media [DM]) caused a loss of tyrosine hydroxylase (TH)-positive neurons only at the highest concentrations (1 and 10 microM). In contrast, significant effects on neurite length were observed at concentrations as low as 0.001 microM. Lead-induced decrease in neurite length became more apparent at concentrations of 0.01 microM (mean 37.9% decrease) and 0.10 microM lead acetate (mean 43.9% decrease). These data show that very low concentrations of lead, well below the level necessary to adversely affect neuronal survival, can have dramatic effects on neurite growth. These results support recent clinical findings of detrimental effects of low-level lead exposure on brain development.

Severe lead poisoning in pregnancy

BACKGROUND

Lead freely crosses the placenta. Consequently, gestational lead poisoning is not only harmful to the woman but also to the developing fetus, invariably producing congenital lead poisoning. The scope and consequences of severe lead poisoning in pregnancy (blood lead level > or =45 microg/dL) have not been well characterized.

METHODS

We reviewed our experience in the management of women with severe gestational lead poisoning. Additionally, we reviewed the literature on this disorder in an effort to identify patterns in etiology and outcome.

RESULTS

Over a 3-year period treatment was provided to 7 severely lead-poisoned women. A 25-year review of the medical literature identified an additional 8 cases. Among these 15 women, 70% were Hispanic, all of whom developed lead poisoning from the ingestion of soil, clay, or pottery ("tierra"). Other sources of lead poisoning were paint chip ingestion (n = 2), household renovation, and use of a complementary-alternative medication (bone meal). Lead poisoning was discovered in the third trimester in 12 (86%) subjects after the women presented with subtle but characteristic findings of severe lead poisoning, including malaise, anemia, or basophilic stippling on blood smear; one woman was identified when she presented after a generalized seizure, having a blood lead level of 104 microg/dL. Five women received chelation therapy during pregnancy with CaNa(2) EDTA, dimercaprol, or succimer. At delivery mean maternal blood lead level was 55 microg/dL, whereas mean neonatal lead level was 74 microg/dL (P =.009). Thirteen neonates underwent chelation, all within the first 28 days of life. No infant in the current series had an identifiable birth defect.

CONCLUSIONS

On the basis of this experience we conclude that severe lead poisoning in pregnant women has the following characteristics: 1) it most often occurs because of intentional pica, 2) its presenting features are subtle, often consisting only of malaise and anemia, and 3) blood lead levels in the neonate are higher than simultaneous maternal lead levels.

Lead poisoning in pregnancy: a case study with implications for midwives

Lead poisoning remains a significant problem in the United States affecting the health of women and children. Although the damage is greatest at higher levels of accumulation, no level of lead has been found to be safe. Over the last 25 years, the blood level of lead thought to be associated with toxicity has dropped dramatically, from to 60 mcg/dL in 1960 to 10 mcg/dL today. Studies confirm that exposure to lead causes kidney damage, encephalopathy, and impaired cognitive function in children and in adults. Recent evidence indicates children with levels less than 10 mcg/dL may suffer from compromised development and intellectual performance later in life. This article discusses the case of a woman found to have lead poisoning during pregnancy. Environmental sources of lead, implications for the immediate and future health of the fetus and mother, and techniques clinicians can use in their practice to minimize the adverse effect of lead on their clients are reviewed.

Lead neurotoxicity in children: basic mechanisms and clinical correlates

Lead has been recognized as a poison for millennia and has been the focus of public health regulation in much of the developed world for the better part of the past century. The nature of regulation has evolved in response to increasing information provided by vigorous scientific investigation of lead's effects. In recognition of the particular sensitivity of the developing brain to lead's pernicious effects, much of this legislation has been addressed to the prevention of childhood lead poisoning. The present review discusses the current state of knowledge concerning the effects of lead on the cognitive development of children. Addressed are the reasons for the child's exquisite sensitivity, the behavioural effects of lead, how these effects are best measured, and the long-term outlook for the poisoned child. Of particular importance are the accumulating data suggesting that there are toxicological effects with behavioural concomitants at exceedingly low levels of exposure. In addition, there is also evidence that certain genetic and environmental factors can increase the detrimental effects of lead on neural development, thereby rendering certain children more vulnerable to lead neurotoxicity. The public health implications of these findings are discussed.

An analysis of maternal and fetal hair lead levels

Lead contamination of the environment is an important public health consideration. There is evidence of declining blood lead levels in Britain, however, there is still concern about chronic exposure of the fetus and young children to low levels of lead and the effect that this has on neurodevelopment. Hair lead levels have been found to correlate well with body lead contamination. This study is the first to document the level of hair lead in pregnant women and their babies from an urban British population. There was no evidence of toxic maternal lead levels and the fetus is protected by the placental barrier.