Influence of blood lead on the ability and attainment of children in Edinburgh

Lead Exposure and Developmental Disabilities in Preschool-Aged Children

CONTEXT

Lead is a preventable environmental toxin that has been previously associated with deficits in cognition, academic performance, attention, and behavior in children. Very few studies, however, have examined the relationship between exposure to lead and documented developmental disabilities.

OBJECTIVE

This study examined the relative risk of lead exposure on developmental disabilities in preschool-aged children.

DESIGN

A statewide lead surveillance data set containing blood lead level (BLL) was integrated with another statewide data set containing developmental disability classifications for special education placement for preschool-aged children.

PARTICIPANTS

The participants were the 85 178 children (average age 2.6 years) whose records in both data sets were able to be linked. Forty-six percent of the participants had an identified developmental disability.

MAIN OUTCOME MEASURE

Developmental disability classification served as the main outcome measure.

RESULTS

A high BLL, defined as 5 μg/dL or more, was associated with significantly increased risk for developmental disabilities (risk ratio [RR] = 1.04; 95% CI = 1.01-1.08), particularly intellectual disability (RR = 1.58, 95% CI = 1.10-2.25) and developmental delay (DD; RR = 1.11, 95% CI = 1.06-1.17).

CONCLUSIONS

The results of this study are consistent with previous research identifying an association between lead exposure and numerous intellectual and educational outcomes and demonstrate that high BLL is associated with meeting eligibility criteria for developmental disabilities in young children. Continued research, surveillance, and prevention efforts are needed to further reduce the negative impacts of lead on individuals and society. Reducing or eliminating lead exposure would improve outcomes for individual children (eg, better academic performance) and reduce the burden to society (eg, lower enrollments in special education systems).

In Vitro Effects of Lead on Gene Expression in Neural Stem Cells and Associations between Up-regulated Genes and Cognitive Scores in Children

BACKGROUND

Lead (Pb) adversely affects neurodevelopment in children. Neural stem cells (NSCs) play an essential role in shaping the developing brain, yet little is known about how Pb perturbs NSC functions and whether such perturbation contributes to impaired neurodevelopment.

OBJECTIVES

We aimed to identify Pb-induced transcriptomic changes in NSCs and to link these changes to neurodevelopmental outcomes in children who were exposed to Pb.

METHODS

We performed RNA-seq-based transcriptomic profiling in human NSCs treated with 1 μM Pb. We used qRT-PCR, Western blotting, ELISA, and ChIP (chromatin immunoprecipitation) to characterize Pb-induced gene up-regulation. Through interrogation of a genome-wide association study, we examined the association of gene variants with neurodevelopment outcomes in the ELEMENT birth cohort.

RESULTS

We identified 19 genes with significantly altered expression, including many known targets of NRF2-the master transcriptional factor for the oxidative stress response. Pb induced the expression of SPP1 (secreted phosphoprotein 1), which has known neuroprotective effects. We demonstrated that SPP1 is a novel direct NRF2 target gene. Single nucleotide polymorphisms (SNPs) (rs12641001) in the regulatory region of SPP1 exhibited a statistically significant association (p = 0.005) with the Cognitive Development Index (CDI).

CONCLUSION

Our findings revealed that Pb induces an NRF2-dependent transcriptional response in neural stem cells and identified SPP1 up-regulation as a potential novel mechanism linking Pb exposure with neural stem cell function and neurodevelopment in children.

Neurotoxicants, Micronutrients, and Social Environments

SUMMARY—Systematic research evaluating the separate and interacting impacts of neurotoxicants, micronutrients, and social environments on children's cognition and behavior has only recently been initiated. Years of extensive human epidemiologic and animal experimental research document the deleterious impact of lead and other metals on the nervous system. However, discrepancies among human studies and between animal and human studies underscore the importance of variations in child nutrition as well as social and behavioral aspects of children's environments that mitigate or exacerbate the effects of neurotoxicants.

In this monograph, we review existing research on the impact of neurotoxic metals, nutrients, and social environments and interactions across the three domains. We examine the literature on lead, mercury, manganese, and cadmium in terms of dispersal, epidemiology, experimental animal studies, effects of social environments, and effects of nutrition.

Research documenting the negative impact of lead on cognition and behavior influenced reductions by the Center for Disease Control in child lead-screening guidelines from 30 micrograms per deciliter (μg/dL) in 1975 to 25 μg/dL in 1985 and to 10 μg/dL in 1991. A further reduction is currently being considered. Experimental animal research documents lead's alteration of glutamate-neurotransmitter (particularly N-methyl-D-aspartate) activity vital to learning and memory. In addition, lead induces changes in cholinergic and dopaminergic activity. Elevated lead concentrations in the blood are more common among children living in poverty and there is some evidence that socioeconomic status influences associations between lead and child outcomes. Micronutrients that influence the effects of lead include iron and zinc.

Research documenting the negative impact of mercury on children (as well as adults) has resulted in a reference dose (RfD) of 0.1 microgram per kilogram of body weight per day (μg/kg/day). In animal studies, mercury interferes with glutamatergic, cholinergic, and dopaminergic activity. Although evidence for interactions of mercury with children's social contexts is minimal, researchers are examining interactions of mercury with several nutrients.

Research on the effects of cadmium and manganese on child cognition and behavior is just beginning. Experimental animal research links cadmium to learning deficits, manganese to behaviors characteristic of Parkinson's disease, and both to altered dopaminergic functioning.

We close our review with a discussion of policy implications, and we recommend interdisciplinary research that will enable us to bridge gaps within and across domains.

Levels and source apportionment of children's lead exposure: could urinary lead be used to identify the levels and sources of children's lead pollution?

As a highly toxic heavy metal, the pollution and exposure risks of lead are of widespread concern for human health. However, the collection of blood samples for use as an indicator of lead pollution is not always feasible in most cohort or longitudinal studies, especially those involving children health. To evaluate the potential use of urinary lead as an indicator of exposure levels and source apportionment, accompanying with environmental media samples, lead concentrations and isotopic measurements (expressed as (207)Pb/(206)Pb, (208)Pb/(206)Pb and (204)Pb/(206)Pb) were investigated and compared between blood and urine from children living in the vicinities of a typical coking plant and lead-acid battery factory. The results showed urinary lead might not be a preferable proxy for estimating blood lead levels. Fortunately, urinary lead isotopic measurements could be used as an alternative for identifying the sources of children's lead exposure, which coincided well with the blood lead isotope ratio analysis.

Isotopic ratio based source apportionment of children's blood lead around coking plant area

Lead exposure in the environment is a major hazard affecting human health, particularly for children. The blood lead levels in the local children living around the largest coking area in China were measured, and the source of blood lead and the main pathways of lead exposure were investigated based on lead isotopic ratios ((207)Pb/(206)Pb and (208)Pb/(206)Pb) in blood and in a variety of media, including food, airborne particulate matter, soil, dust and drinking water. The children's blood lead level was 5.25 (1.59 to 34.36 as range) μg dL(-1), lower than the threshold in the current criteria of China defined by the US Centers for Disease Control (10 μg dL(-1)). The isotopic ratios in the blood were 2.111±0.018 for (208)Pb/(206)Pb and 0.864±0.005 for (207)Pb/(206)Pb, similar to those of vegetables, wheat, drinking water, airborne particulate matter, but different from those of vehicle emission and soil/dust, suggesting that the formers were the main pathway of lead exposure among the children. The exposure pathway analysis based on the isotopic ratios and the human health risk assessment showed that dietary intake of food and drinking water contributed 93.67% of total exposed lead. The study further indicated that the coal used in the coking plant is the dominant pollution source of lead in children's blood.

Blood lead levels in children attending a tertiary teaching hospital in Enugu, south-eastern Nigeria

BACKGROUND

Reports have demonstrated widespread lead contamination of the Enugu environment and the possibility of childhood lead poisoning.

OBJECTIVE

To determine the blood lead levels of children attending University of Nigeria Teaching Hospital, Ituku Ozalla, Enugu, Enugu State.

METHOD

Blood samples from 100 children were analysed for blood lead concentration using an atomic absorption spectrometer.

RESULTS

The mean (SD) age was 6·2 (2·13) years (range 1-15) and the mean (SD) blood lead level was 8·7 (5·4) μg/dl (range 0·3-17·7). Thirty-three per cent of the children had blood lead levels >10 μg/dl, which is the United States Center for Disease Prevention and Control action limit, and 36% of the children had blood lead levels of 5-10 μg/dl. Mean (SD) blood lead level in the 6-10-years age group was 11·3 (5·7) μg/dl and 9·4 (4·6) μg/dl in the >10-years age group, which is significantly higher than in the 1-5-years age group [7·5 (5·1) μg/dl, P = 0·03]. Males had significantly higher mean (SD) blood lead levels than females [9·6 (5·8) vs 6·8 (3·8), P = 0·03].

CONCLUSION

One-third of children had blood lead levels >10 μg/dl, particularly older and male children. Blood lead screening should be considered for sick children, and further screening of blood lead levels in children should be undertaken in Enugu and other parts of Nigeria, and efforts made to identify the sources of exposure.

Pb neurotoxicity: neuropsychological effects of lead toxicity

Neurotoxicity is a term used to describe neurophysiological changes caused by exposure to toxic agents. Such exposure can result in neurocognitive symptoms and/or psychiatric disturbances. Common toxic agents include heavy metals, drugs, organophosphates, bacterial, and animal neurotoxins. Among heavy metal exposures, lead exposure is one of the most common exposures that can lead to significant neuropsychological and functional decline in humans. In this review, neurotoxic lead exposure's pathophysiology, etiology, and epidemiology are explored. In addition, commonly associated neuropsychological difficulties in intelligence, memory, executive functioning, attention, processing speed, language, visuospatial skills, motor skills, and affect/mood are explored.

Protective effects of mangiferin in subchronic developmental lead-exposed rats

Lead is a ubiquitous environmental and industrial pollutant. Exposure to excessive amounts of lead is especially harmful to the central nervous systems of infants and young children, and oxidative stress has been reported as a major mechanism of lead-induced toxicity. To evaluate the ameliorative potential of antioxidant mangiferin (MGN) on lead-induced toxicity, Morris water maze test, determination of blood and bone lead concentration, determination of antioxidant status in plasma, as well as observation of ultrastructural changes in the hippocampus were carried out. In the present study, under a transmission electron microscope, ameliorated morphological damages in the hippocampus were observed in MGN-treated groups. Blood and bone lead concentration in MGN-treated groups lowered to some extent (p < 0.05, p < 0.01). The activities of antioxidant enzymes, glutathione (GSH) content, and the GSH/oxidized glutathione ratio in MGN-treated groups were increased, respectively. Further studies are needed to establish whether the observed differences were a direct cause of mangiferin on lead-induced toxicity or not. This study might provide clues for the treatment of lead-induced toxicity.

Teeth as a biomarker of past chemical exposure

PURPOSE OF REVIEW

Accurate prenatal exposure assessment is one of the major challenges in environmental epidemiologic studies. Variations in placental transport make maternal biospecimens unreliable for many chemicals and fetal specimens collected at birth do not provide information on exposure timing over the prenatal period.

RECENT FINDINGS

The skeletal compartment is an important chemical repository, making calcified tissues important for measuring exposure. For decades teeth have been used to estimate long-term cumulative exposure to metals and some organic chemicals. Recently developed methodologies that combine sophisticated histological and chemical analysis to precisely sample tooth layers that correspond to specific life stages have the potential to reconstruct exposure in the second and third trimesters of prenatal development and during early childhood.

SUMMARY

Such a retrospective biomarker that precisely measures exposure intensity and timing during prenatal development would substantially aid epidemiologic investigations, particularly case-control studies of rare health outcomes.

Mapping of drinking water research: a bibliometric analysis of research output during 1992-2011

A bibliometric analysis based on the Science Citation Index Expanded from the Web of Science was carried out to provide insights into research activities and tendencies of the global drinking water from 1992 to 2011. Study emphases included performance of publication covering annual outputs, mainstream journals, Web of Science categories, leading countries, institutions, research tendencies and hotspots. The results indicated that annual output of the related scientific articles increased steadily. Water Research, Environmental Science & Technology, and Journal American Water Works Association were the three most common journals in drinking water research. The USA took a leading position out of 168 countries/territories, followed by Japan and Germany. A summary of the most frequently used keywords obtained from words in paper title analysis, author keyword analysis and KeyWords Plus analysis provided the clues to discover the current research emphases. The mainstream research related to drinking water was water treatment methods and the related contaminants. Disinfection process and consequent disinfection by-products attracted much attention. Ozonation and chlorination in disinfection, and adsorption were common techniques and are getting popular. Commonly researched drinking water contaminants concerned arsenic, nitrate, fluoride, lead, and cadmium, and pharmaceuticals emerged as the frequently studied contaminants in recent years. Disease caused by contaminants strongly promoted the development of related research.

Lead exposure and the 2010 achievement test scores of children in New York counties

BACKGROUND

Lead is toxic to cognitive and behavioral functioning in children even at levels well below those producing physical symptoms. Continuing efforts in the U.S. since about the 1970s to reduce lead exposure in children have dramatically reduced the incidence of elevated blood lead levels (with elevated levels defined by the current U.S. Centers for Disease Control threshold of 10 μg/dl). The current study examines how much lead toxicity continues to impair the academic achievement of children of New York State, using 2010 test data.

METHODS

This study relies on three sets of data published for the 57 New York counties outside New York City: school achievement data from the New York State Department of Education, data on incidence of elevated blood lead levels from the New York State Department of Health, and data on income from the U.S. Census Bureau. We studied third grade and eighth grade test scores in English Language Arts and mathematics. Using the county as the unit of analysis, we computed bivariate correlations and regression coefficients, with percent of children achieving at the lowest reported level as the dependent variable and the percent of preschoolers in the county with elevated blood lead levels as the independent variable. Then we repeated those analyses using partial correlations to control for possible confounding effects of family income, and using multiple regressions with income included.

RESULTS

The bivariate correlations between incidence of elevated lead and number of children in the lowest achievement group ranged between 0.38 and 0.47. The partial correlations ranged from 0.29 to 0.40. The regression coefficients, both bivariate and partial (both estimating the increase in percent of children in the lowest achievement group for every percent increase in the children with elevated blood lead levels), ranged from 0.52 to 1.31. All regression coefficients, when rounded to the nearest integer, were approximately 1. Thus, when the percent of children showing elevated lead increases by one percent, the percent of children in the lowest achievement group, according to the regression equations generated, also increases by about one percent. All associations were significant at the 0.05 level.

CONCLUSION

Despite public health advances, and despite the imprecision of measures, an association between the incidence of elevated blood lead and achievement in New York counties is still apparent, not attributable to confounding by income. Efforts to reduce lead exposure should persist with vigor.

The relationships between low levels of urine fluoride on children's intelligence, dental fluorosis in endemic fluorosis areas in Hulunbuir, Inner Mongolia, China

There has been public concern about children's intellectual performance at high levels of fluoride exposure, but few studies provide data directly to the question of whether low fluoride exposure levels less than 3.0 mg/L in drinking water adversely associated with children's intelligence. In this survey, we investigated the effects of low fluoride exposure on children's intelligence and dental fluorosis. 331 children aged from 7 to 14 were randomly recruited from four sites in Hulunbuir City, China. Intelligence was assessed using Combined Raven Test-The Rural in China while dental fluorosis was diagnosed with Dean's index. Mean value of fluoride in drinking water was 1.31±1.05 mg/L (range 0.24-2.84). Urine fluoride was inversely associated with IQ in the multiple linear regression model when children's age as a covariate variable was taken into account (P<0.0001). Each increase in 1 mg/L of urine fluoride associated with 0.59-point decrease in IQ (P=0.0226). Meanwhile, there was a dose-response relationship between urine fluoride and dental fluorosis (P<0.0001). In conclusion, our study suggested that low levels of fluoride exposure in drinking water had negative effects on children's intelligence and dental health and confirmed the dose-response relationships between urine fluoride and IQ scores as well as dental fluorosis.

Lead in children's blood is mainly caused by coal-fired ash after phasing out of leaded gasoline in Shanghai

Lead (Pb) is a highly toxic element to the human body. After phasing out of leaded gasoline we find that the blood lead level of children strongly correlates with the lead concentration in atmospheric particles, and the latter correlates with the coal consumption instead of leaded gasoline. Combined with the (207)Pb/(206)Pb ratio measurements, we find that the coal consumption fly ash is a dominate source of Pb exposure to children in Shanghai, rather than vehicle exhaust, metallurgic dust, paint dust, and drinking water. Those particles are absorbed to children's blood via breathing and digesting their deposition on ground by hand-to-mouth activities. Probably the same situation occurs in other large cities of developing countries where the structure of energy supply is mainly based on coal-combustion.

Influence of vitamin D receptor haplotypes on blood lead concentrations in environmentally exposed children of Uygur and Han populations

OBJECTIVE

To explore the association between polymorphism of vitamin D receptor (VDR) and lead poisoning in Uygur and Han children in China.

METHODS

The BsmI, ApaI and TaqI restriction sites of VDR genotyping were determined by polymerase chain reaction-restriction fragment length polymorphism in 443 Uygur and 469 Han children from Xinjiang province. The correlation between the polymorphism of VDR haplotypes and blood lead levels was explored.

RESULTS

The genotype frequencies of VDR had significant differences in Han and Uygur children (p <0.01). According to VDR-BsmI, ApaI and TaqI haplotype analysis in Han children, haplotypes Atb and AtB were considerably decreased in the lead poisoning group (p <0.05) while haplotype aTb and ATb were significantly increased in the lead poisoning group (p <0.01). However, such results were not found in Uygur children (p < 0.05).

CONCLUSION

A significant difference was seen in the frequency distribution of the VDR genotype among the different races. Haplotypes Atb and AtB might be protective factors while haplotypes ATb and aTb might be risk factors in Han children.

Comparing lead poisoning risk assessment methods: census block group characteristics vs. zip codes as predictors

OBJECTIVE

We determined which children should be tested for elevated blood lead levels (BLLs) in the face of financial and practical barriers to universal screening efforts and within 2009 Centers for Disease Control and Prevention recommendations allowing health departments to develop BLL screening strategies.

METHODS

We used the Michigan database of BLL tests from 1998 through 2005, which contains address, Medicaid eligibility, and race data. Linking addresses to U.S. Census 2000 data by block group provided neighborhood sociodemographic and housing characteristics. To derive an equation predicting BLL, we treated BLL as a continuous variable and used Hierarchical Linear Modeling to estimate the prediction equation.

RESULTS

Census block groups explained more variance in BLL than tracts and much more than dichotomized zip code risk (which is current pediatric practice). Housing built before 1940, socioeconomic status and racial/ethnic characteristics of the block group, child characteristics, and empirical Bayesian residuals explained more than 41% of the variance in BLL during 1998-2001. By contrast, zip code risk and Medicaid status only explained 15% of the BLL variance. An equation using 1998-2001 BLL data predicted well for BLL tests performed in 2002-2005. While those who received BLL tests had above-average risk, this method produced minimal bias in using the prediction equation for all children.

CONCLUSIONS

Our equation offers better specificity and sensitivity than using dichotomized zip codes and Medicaid status, thereby identifying more high-risk children while also offering substantial cost savings. Our prediction equation can be used with a simple Internet-based program that allows health-care providers to enter minimal information and determine whether a BLL test is recommended.

A method for source apportionment of lead in fine particulate matter based on individual particle analysis using a synchrotron X-ray fluorescence microprobe

A source apportionment method based on individual particle analysis carried out using a synchrotron X-ray fluorescence microprobe was developed for source apportionment of lead in fine particulate matter. Mass contributions of every emission source were obtained by intensity ratios of the characteristic X-ray spectrum of lead in individual airborne particles. The validity of the method was evaluated. The uncertainty of the source apportionment was estimated, which was within 10% in this work. The method was applied to the apportionment of lead in fine airborne particles of Shanghai, indicating that the method has a finer performance for source apportionment.

Atmospheric lead pollution in fine particulate matter in Shanghai, China

The Pb-monitoring program was extended for 6 years from 2002 to 2007 at 17 representative urban sites (6 traffic, 5 industrial, and 6 residential sites), and 3 suburban sites to assess the lead pollution in fine particulate matter (PM2.5) after phasing out leaded gasoline in Shanghai. Compared with Pb levels reported in other places, the Pb pollution in Shanghai is still serious after phasing out leaded gasoline, which remains at high concentration range (213-176 ng/m3) in PM2.5 in winter. Significant spatial variation of Pb concentrations and strong seasonal variation of higher Pb concentration in winter than that in summer were detected. The size distribution of Pb in particulate matter has a unimodal mode that peaks at approximately 0.154-1.59 microm particle diameter, indicating that Pb is mainly concentrated in fine fraction. Lead in the fine fraction is enriched by a factor of 10(3)-10(4) relative to Pb abundance in crust. Eight categories of Pb pollution sources were identified in the PM2.5 in the winter of 2007 in Shanghai. The important emission sources among them are vehicle exhaust derived from combustion of unleaded gasoline, metallurgic industry emission, and coal combustion emission.

Estimated burden of blood lead levels 5 microg/dl in 1999-2002 and declines from 1988 to 1994

In light of recent data suggesting adverse health effects at blood lead levels (PbB) <10 microg/dl, lowering the current definition of elevated blood lead (>or=10 microg/dl) has been recommended. To ascertain the population level impact of such a change, we calculated the prevalence of PbB >or=5 microg/dl in 1-21-year-old population in the United States. Furthermore, we characterized changes in PbB between 1988-1994 and 1999-2002. We analyzed data from the National Health and Nutrition Examination Survey (NHANES) III (n=10,755) and NHANES 1999-2002 (n=8013). In 1999-2002, about 91.7% of study children had detectable levels of lead in the blood. Among them, 7.3%, 2.8%, and 1.0% children and adolescents aged 1-5, 6-11, and 12-21 years, respectively, had PbB between 5 and 9.9 microg/dl. This number translates to approximately 2.4 million individuals. Between 1988-1994 and 1999-2002, the geometric mean PbB declined from 2.88 to 1.94 microg/dl in children 1-5 years, 1.80 to 1.36 microg/dl in children 6-11 years, and 1.24-1.02 microg/dl in children and adolescents 12-21 years of age. Also, the prevalence of PbB >or=5 microg/dl declined from 25.7% to 8.8%, 12.8% to 3.0%, and 7.5% to 1.2% in these age groups, respectively.A substantial proportion of children may be at risk for adverse health effects from lead exposure below 10 microg/dl and a large number of children will be classified as having elevated PbB if 5 microg/dl is considered the threshold. Significant public health resources will have to be mobilized for intervention, screening, and case management of these children.

The relationship between early childhood blood lead levels and performance on end-of-grade tests

BACKGROUND

Childhood lead poisoning remains a critical environmental health concern. Low-level lead exposure has been linked to decreased performance on standardized IQ tests for school-aged children.

OBJECTIVE

In this study we sought to determine whether blood lead levels in early childhood are related to educational achievement in early elementary school as measured by performance on end-of-grade (EOG) testing.

METHODS

Educational testing data for 4th-grade students from the 2000-2004 North Carolina Education Research Data Center were linked to blood lead surveillance data for seven counties in North Carolina and then analyzed using exploratory and multivariate statistical methods.

RESULTS

The discernible impact of blood lead levels on EOG testing is demonstrated for early childhood blood lead levels as low as 2 microg/dL. A blood lead level of 5 microg/dL is associated with a decline in EOG reading (and mathematics) scores that is roughly equal to 15% (14%) of the interquartile range, and this impact is very significant in comparison with the effects of covariates typically considered profoundly influential on educational outcomes. Early childhood lead exposures appear to have more impact on performance on the reading than on the mathematics portions of the tests.

CONCLUSIONS

Our emphasis on population-level analyses of children who are roughly the same age linked to previous (rather than contemporaneous) blood lead levels using achievement (rather than aptitude) outcome complements the important work in this area by previous researchers. Our results suggest that the relationship between blood lead levels and cognitive outcomes are robust across outcome measures and at low levels of lead exposure.

Blood lead levels and specific attention effects in young children

The detrimental effects of early exposure to lead are credible and persistent, but there is presently no agreement on a safe threshold for circulating lead levels. Although several research groups have found significantly poorer cognitive performance in children who have whole blood levels as low as 5 microg/dL, most government agencies, including the EPA and the CDC, continue to use 10 microg/dL as the criterion for concern in public health advisories. Prior research has consistently indicated a negative relation between lead levels and attention. Similarly, the results of the present study show a relation between blood lead level and neurobehavioral outcome in 7-year-old children (N=506). Higher lead levels were associated significantly with decreased scores on measures of intelligence (i.e., overall, performance and verbal IQ), lengthened reaction time, hyperactivity, and social and delinquent behavior problems. Importantly, the present study documents a significant negative impact of blood lead levels on attention, but not impulsivity, in early elementary age children, further delineating the specific aspects of attention related to blood lead concentrations. Analyses were also conducted to identify a "safe" blood lead level threshold. Visual inspection of non-parametric regression plots suggested a gradual linear dose-response relationship for each endpoint. None of the neurobehavioral outcomes assessed showed evidence of a threshold under which lead levels appear to "safe". In light of the consistency of these findings with those of several other groups, it is advisable to consider whether the threshold for an acceptable blood lead level should be reduced.

Comprehensive study of lead pollution in Shanghai by multiple techniques

Aerosol samples of PM10 particulates were examined with particle-induced X-ray emission (PIXE and micro-PIXE ), inductively coupled plasma-mass spectrometry, and X-ray absorption fine structures (XAFS) to investigate atmospheric Pb concentrations and its chemical species and to decide the source assignment. From the elemental analyses, lead concentrations were averaged at 369 and 237 ng.m-3 in aerosol samples of PM10 collected from 19 monitor sites in Shanghai in the winter of 2002 and 2003, respectively. The XAFS results show that major chemical forms of the lead particulates are probably PbCl2, PbSO4, and PbO. A calculation of isotope ratio and chemical mass balance of the PM10 samples revealed that the atmospheric lead particulates in Shanghai in the two periods were mainly from coal combustors, iron and steel plants, and automobile exhausts, with coal combustion dominating the lead pollution after the phasing out of leaded gasoline in 1997 in Shanghai.

Maternal depression and violence exposure: double jeopardy for child school functioning

OBJECTIVE

The goal was to determine how violence exposure affects the relationship between maternal depression, cognitive ability, and child behavior.

METHODS

A multivariate regression analysis of data for a nationally representative sample of kindergarten students was performed. Maternal depression and violence exposure were measured with standardized parent interviews. Standardized T scores were derived from direct testing of children in reading, mathematics, and general knowledge; child behavior was reported by teachers.

RESULTS

A total of 9360 children had neither maternal depression nor violence exposure, 779 violence only, 1564 depression only, and 380 both. Maternal depression alone was associated with poorer mean T scores for reading, mathematics, and general knowledge. However, this effect was attenuated by nearly 25% for reading and general knowledge with adjustment for violence. Children with concurrent exposure to depression and violence had lower mean T scores for reading, mathematics, and general knowledge, as well as more-concerning behaviors, than did those exposed to either factor alone. Across all outcome measures, boys seemed more affected than girls.

CONCLUSIONS

Violence compounds the effect of maternal depression on school functioning and behavior. Research and intervention planning for children affected by maternal depression should consider violence exposure.

A rationale for lowering the blood lead action level from 10 to 2 microg/dL

Fifteen years ago, in 1991, the U.S. Centers for Disease Control and Prevention (CDC) established 10 microg/dL as the lowest level of concern for children's blood lead levels. This value is extremely important because, historically, policy makers and public health officials generally have acted to remove sources of lead exposure only after the CDC's level of concern had been exceeded. A growing body of evidence, however, reveals that blood lead levels below 10 microg/dL may impair neurobehavioral development. There is now sufficient and compelling scientific evidence for the CDC to lower the blood lead action level in children. This review argues that a level of 2 microg/dL is a useful and feasible replacement. Although it can be argued, in turn, that no threshold for the health effects of lead is demonstrable, analytically a blood level of 2 microg/dL is readily and accurately measured and provides a benchmark for successful prevention. Lowering the level of concern would encourage and accelerate the investments needed to ensure that children are protected from lead exposure in their homes, schools, and play settings. Such a program would also offer economic advantages because of the coupling between lead, educational attainment, earnings and anti-social conduct. By lowering the blood action level, CDC will promote policies and initiatives designed to further reduce children's exposure to this potent developmental neurotoxicant.

Childhood lead poisoning: the torturous path from science to policy

The long history of lead poisoning provides many lessons about the process by which scientific knowledge is translated into public health policy. In the United States, lead was added to paint and to gasoline in enormous quantities long after medical evidence clearly showed that excessive lead exposure caused considerable morbidity in the population. This article discusses some of the factors that contributed to the slow pace of efforts to address this problem, including the ubiquity and magnitude of lead exposure during much of the twentieth century, which produced a distorted notion about the blood lead level that can be considered "normal"; the prevailing model of disease during this period, notably the novelty of the concept of subclinical disease; the fact that childhood lead poisoning affected mostly families that were politically and economically disenfranchised, fostering a "blame the victim" attitude; and that controlling lead exposure would have impeded efforts to achieve other desirable goals, illustrating the role that value trade-offs often play in policy decisions.

Intoxicação por chumbo e saúde infantil: ações intersetoriais para o enfrentamento da questão

Inquérito epidemiológico realizado pela Secretaria de Estado da Saúde de São Paulo e Secretaria Municipal de Saúde de Bauru visou à realização de exames de plumbemia em 853 crianças de 0 a 12 anos, em Bauru, São Paulo, Brasil (2002), a partir de indícios de chumbo oriundo de resíduos industriais nas proximidades de uma fábrica de baterias. Os níveis sangüíneos de chumbo no grupo controle foram inferiores aos apresentados pelo grupo exposto (p < 0,05). Mediante a existência de 314 crianças com taxas de plumbemia superiores àquelas aceitáveis pelo Centers for Disease Control and Prevention (10µgPb/dl sangue), foi desencadeado um conjunto de ações com participação dos serviços públicos, universidades e voluntariado, para promover o diagnóstico e a assistência à saúde da população atingida. Ações emergenciais, visando a reduzir riscos de recontaminação, incluíram a raspagem de camada superficial das vias públicas, resultando em 1.392m³ de terra contendo material tóxico, que permanece depositada nas dependências da fábrica. Foi promovida a aspiração de poeira do interior das residências e a lavagem e vedamento das caixas d'água. O Grupo de Estudo e Pesquisa da Intoxicação por Chumbo em Crianças de Bauru, por meio deste trabalho, faz o compartilhamento de uma experiência intersetorial, multidisciplinar e interinstitucional.

Critical dose of lead affecting postural balance in workers

BACKGROUND

The threshold blood lead (BPb) level for nervous system dysfunction in adults has been estimated to be 30-40 microg/dl. This study was carried out to estimate the critical dose of lead affecting the neuromotor function in workers by introducing the benchmark dose (BMD) approach, as well as to identify the specific postural sway to lead exposure.

METHODS

Postural sway parameters with spectral analysis were compared between 121 lead workers with BPb levels of 6-89 (mean 40) microg/dl and 60 unexposed controls.

RESULTS

All sway parameters, except for sagittal sways with eyes open, were significantly larger in the lead workers than in the controls; also, the Romberg quotient for sagittal sway was significantly higher in the lead workers. The BPb level in the lead workers was significantly related to sagittal sways at 1-2 Hz and 2-4 Hz with eyes open, and sagittal and transversal sways at 1-2 Hz and 2-4 Hz with eyes closed. The BMD levels of BPb (i.e., lower 95% confidence limits of BMD) were estimated to be 12.1-17.3 (mean 14.4) microg/dl for postural sway.

CONCLUSIONS

Neuromotor dysfunction in lead workers may be initiated at BPbs below the level previously accepted as effectless, and be characterized mainly by an increased sway of high frequency (1-4 Hz) in the sagittal direction with eyes closed (high Romberg quotient).

Low-level environmental lead exposure and children's intellectual function: an international pooled analysis

Lead is a confirmed neurotoxin, but questions remain about lead-associated intellectual deficits at blood lead levels < 10 microg/dL and whether lower exposures are, for a given change in exposure, associated with greater deficits. The objective of this study was to examine the association of intelligence test scores and blood lead concentration, especially for children who had maximal measured blood lead levels < 10 microg/dL. We examined data collected from 1,333 children who participated in seven international population-based longitudinal cohort studies, followed from birth or infancy until 5-10 years of age. The full-scale IQ score was the primary outcome measure. The geometric mean blood lead concentration of the children peaked at 17.8 microg/dL and declined to 9.4 microg/dL by 5-7 years of age; 244 (18%) children had a maximal blood lead concentration < 10 microg/dL, and 103 (8%) had a maximal blood lead concentration < 7.5 microg/dL. After adjustment for covariates, we found an inverse relationship between blood lead concentration and IQ score. Using a log-linear model, we found a 6.9 IQ point decrement [95% confidence interval (CI), 4.2-9.4] associated with an increase in concurrent blood lead levels from 2.4 to 30 microg/dL. The estimated IQ point decrements associated with an increase in blood lead from 2.4 to 10 microg/dL, 10 to 20 microg/dL, and 20 to 30 microg/dL were 3.9 (95% CI, 2.4-5.3), 1.9 (95% CI, 1.2-2.6), and 1.1 (95% CI, 0.7-1.5), respectively. For a given increase in blood lead, the lead-associated intellectual decrement for children with a maximal blood lead level < 7.5 microg/dL was significantly greater than that observed for those with a maximal blood lead level > or = 7.5 microg/dL (p = 0.015). We conclude that environmental lead exposure in children who have maximal blood lead levels < 7.5 microg/dL is associated with intellectual deficits.

Cutaneous Resorption of Lead After External Use of Lead-Containing Ointments in Volunteers with Healthy Skin

Lead-containing ointments are frequently used in anthroposophic medicine. In a prospective, open-label phase 1 study, 33 volunteers at the Ambulatory Clinic for Complementary and Alternative Medicine at the Free University of Berlin, aged 18-65 years, were exposed to 100 g Plumbum metallicum 0.4% ointment (Weleda, Germany) over a 4-week period. The lead-containing ointment was regularly applied to the cubital side of the forearm. Regular measurements of lead concentrations in whole blood, urine, and scalp hair were determined. None of the 33 volunteers showed an increase in lead concentrations in the 3 investigated compartments after 4 and 8 weeks. Blood lead levels (average value) decreased significantly from baseline to the first week (P < 0.05). Average values in the following investigations (weeks 3, 4, and 8) were significantly lower than at baseline (P < 0.05). There was no increase in lead levels in the scalp hair after 8 weeks (P < 0.05). The results show that the commonly prescribed lead-containing ointment Plumbum metallicum 0.4% in humans with an intact skin does not present a toxic risk.

Lead‐Contaminated Drinking Waters in the Public Schools of Philadelphia

Lead exposure is a preventable environmental health concern. Young children between the ages of 1 to 6 are most susceptible to its clinical effects. This article reports the results of lead level determinations in the drinking water of Philadelphia's public school buildings and remediation efforts aimed at dealing with this public health concern.

METHODS

Water samples were collected from drinking sources in 292 school buildings in Philadelphia from May 2000 through January 2001. These samples were collected and sent to reference laboratories for determination of lead levels.

RESULTS

A total of 42.5% (124) of schools had water lead levels not exceeding the action level of 20 ppb, of which 3.1% had nondetectable levels or levels less than 5 ppb. A total of 28.7% of buildings had water lead levels ranging from 20 to 50 ppb, 11.6% had levels between 50-100 ppb, and 17.1% had water lead levels of 100 ppb or more.

CONCLUSION

A total of 57.4% of Philadelphia's public school buildings had water lead levels exceeding the Environmental Protection Agencies (EPA) action level of 20 ppb, and 28.7% of school buildings had water with mean lead levels in excess of 50 ppb. Depending on the volume of water consumed, drinking water from school buildings may be a significant source of lead exposure for children in their formative years of development. Although Philadelphia's public school buildings were evaluated, lead-contaminated drinking water in schools is not only an urban concern. School buildings in suburban and rural areas may have similar water lead levels, and testing programs are desirable.

The US EPA reference dose for methylmercury: sources of uncertainty

The US Environmental Protection Agency (EPA) derived a reference dose for methylmercury in 2001, based on an extensive analysis by the National Research Council (NRC) of the National Academy of Sciences. The NRC performed benchmark dose analysis on a number of endpoints from three longitudinal prospective studies: the Seychelles Islands, the Faroe Islands, and the New Zealand studies. Adverse effects were reported in the latter two studies, but not in the Seychelles study. The NRC also performed an integrative analysis of all three studies. Dose conversion from cord blood or maternal hair mercury concentration was performed by EPA using a one-compartment pharmacokinetic model. A total uncertainty factor of 10 was applied for intrahuman pharmacokinetic and pharmacodynamic variability. There are numerous decisions made by the NRC/EPA that could greatly affect the value of the reference dose (RfD). Some of these include the choice of a linear model for the relationship between mercury body burden and neuropsychological performance, the choice of values of P0 and the benchmark response, the use of the "critical study/critical endpoint" approach in the interpretation of the maternal body burden that corresponds to the RfD, the use of central tendencies in a one-compartment pharmacokinetic model rather than the inclusion of the distributions of variables for the population of reproductive-age women, the assumption of unity for the ratio of fetal cord blood to maternal blood methylmercury concentrations, the choice of a total of 10 as an uncertainty factor, and the lack of dose-response analysis for other health effects such as cardiovascular disease. In addition, it may be argued that derivation of a RfD for methylmercury is inappropriate, given that there does not appear to be a threshold for adverse neuropsychological effects based on available data.

The relationship between lead and crime

This study investigates the association between air-lead levels and crime rates across 2,772 U.S. counties. Data for the analysis come from the Environmental Protection Agency, the Bureau of Census, and the Federal Bureau of Investigation. Results suggest that air-lead levels have a direct effect on property and violent crime rates even after adjusting for general levels of air pollution and several structural covariates of crime. We also find that resource deprivation interacts with air-lead levels. The association between air-lead levels and crime rates-property and violent-is strongest in counties that have high levels of resource deprivation and weakest in counties that have low levels of deprivation. This interaction is consistent with arguments and evidence in the health care literature that populations most at risk of lead poisoning are least likely to get the resources required to prevent, screen, and treat the illness.

Reducing the risks of children living near the site of a former lead smeltery

The sources of lead exposure, soil, household dust, diet and ambient air near a former lead smeltery were studied. The blood lead level of small children was also determined. The aim of the study was to define, based primarily on blood lead measurements, whether children living in the contaminated area may be at risk. Within 500 m from the site of the smeltery, there were several areas where the Finnish limit value for soil Pb, i.e. 300 mg/kg, was exceeded. In the recently built areas, the surface soil has been replaced and soil remediation has taken place in schoolyards and the playgrounds of children's day-care centres. Lead content in household dust was clearly elevated in the contaminated areas. In approximately 20 years, after the smeltery was closed in 1984, the lead concentrations of the fruits and berries in local gardens have decreased to one-tenth. In some samples, the limit values are still exceeded. The lead concentration in ambient air is now 50 times lower than in the 1970s. The blood lead level of the children living in the area is slightly but statistically significantly higher than that of the children in the control areas. The critical blood lead level, i.e. 10 microg/100 ml, was not exceeded in any of the children examined. The average and maximum lead concentrations of 63 analysed blood samples were 2.2 and 5 microg/100 ml, respectively. In contrast, the average and maximum blood lead levels of school children in 1981 were 6.7 and 13.0 microg/100 ml, respectively. The risk reduction measures undertaken during the past 20 years are described.

Lead Poisoning

Understanding of lead toxicity has advanced substantially over the past three decades, and focus has shifted from high-dose effects in clinically symptomatic individuals to the consequences of exposure at lower doses that cause no symptoms, particularly in children and fetuses. The availability of more sensitive analytic methods has made it possible to measure lead at much lower concentrations. This advance, along with more refined epidemiological techniques and better outcome measures, has lowered the least observable effect level until it approaches zero. As a consequence, the segment of the population who are diagnosed with exposure to toxic levels has expanded. At the same time, environmental efforts, most importantly the removal of lead from gasoline, have dramatically reduced the amount of lead in the biosphere. The remaining major source of lead is older housing stock. Although the cost of lead paint abatement is measured in billions of dollars, the monetized benefits of such a Herculean task have been shown to far outweigh the costs.

[Association between blood lead and sociodemographic parameters among children]

OBJECTIVE

To determine the relationship between blood lead concentration (Pb-S), and sociodemographic parameters among children.

METHODS

Blood lead concentration (Pb-S) was determined in 243 children (aged 5.94 +/- 2.78 years) in the district of Valencia. The required analysis was performed at the Center for Toxicological Investigations of University of Carabobo (CITUC), Venezuela, between January 1st, 1998 to December 31st, 2000. Geographical Information Systems (GIS) technology was used for data mapping.

RESULTS

Average Pb-S (11.62 ug/dl) was significantly higher than the allowed levels. One hundred and fifty (61.7%) children had Pb-S levels above the allowed concentration (VSLP) and this amount was significantly high in relation to the total number of subjects studied. The logistic regression analysis showed a significant association of sectors 12 (status A) and 16 and 28 (status C) with VSLP (R=0.1189; p<0,01; R=0.1202, p<0,01 and R=0.1189; p<0.01, respectively). Odds ratio showed that children from status C are 7,286 times more likely to have Pb-S VSLP than those from A or B.

CONCLUSIONS

This study confirms that SGI and epidemiological-statistical methods widen the possibilities of preventing contaminants' adverse health effects. It also shows that correlating geographical and health data has allowed to identifying "high risk" areas, leading to a pro-active public health action

Intellectual impairment in children with blood lead concentrations below 10 microg per deciliter

BACKGROUND

Despite dramatic declines in children's blood lead concentrations and a lowering of the Centers for Disease Control and Prevention's level of concern to 10 microg per deciliter (0.483 micromol per liter), little is known about children's neurobehavioral functioning at lead concentrations below this level.

METHODS

We measured blood lead concentrations in 172 children at 6, 12, 18, 24, 36, 48, and 60 months of age and administered the Stanford-Binet Intelligence Scale at the ages of 3 and 5 years. The relation between IQ and blood lead concentration was estimated with the use of linear and nonlinear mixed models, with adjustment for maternal IQ, quality of the home environment, and other potential confounders.

RESULTS

The blood lead concentration was inversely and significantly associated with IQ. In the linear model, each increase of 10 microg per deciliter in the lifetime average blood lead concentration was associated with a 4.6-point decrease in IQ (P=0.004), whereas for the subsample of 101 children whose maximal lead concentrations remained below 10 microg per deciliter, the change in IQ associated with a given change in lead concentration was greater. When estimated in a nonlinear model with the full sample, IQ declined by 7.4 points as lifetime average blood lead concentrations increased from 1 to 10 microg per deciliter.

CONCLUSIONS

Blood lead concentrations, even those below 10 microg per deciliter, are inversely associated with children's IQ scores at three and five years of age, and associated declines in IQ are greater at these concentrations than at higher concentrations. These findings suggest that more U.S. children may be adversely affected by environmental lead than previously estimated.

Intellectual impairment in children with blood lead concentrations below 10 microg per deciliter

BACKGROUND

Despite dramatic declines in children's blood lead concentrations and a lowering of the Centers for Disease Control and Prevention's level of concern to 10 microg per deciliter (0.483 micromol per liter), little is known about children's neurobehavioral functioning at lead concentrations below this level.

METHODS

We measured blood lead concentrations in 172 children at 6, 12, 18, 24, 36, 48, and 60 months of age and administered the Stanford-Binet Intelligence Scale at the ages of 3 and 5 years. The relation between IQ and blood lead concentration was estimated with the use of linear and nonlinear mixed models, with adjustment for maternal IQ, quality of the home environment, and other potential confounders.

RESULTS

The blood lead concentration was inversely and significantly associated with IQ. In the linear model, each increase of 10 microg per deciliter in the lifetime average blood lead concentration was associated with a 4.6-point decrease in IQ (P=0.004), whereas for the subsample of 101 children whose maximal lead concentrations remained below 10 microg per deciliter, the change in IQ associated with a given change in lead concentration was greater. When estimated in a nonlinear model with the full sample, IQ declined by 7.4 points as lifetime average blood lead concentrations increased from 1 to 10 microg per deciliter.

CONCLUSIONS

Blood lead concentrations, even those below 10 microg per deciliter, are inversely associated with children's IQ scores at three and five years of age, and associated declines in IQ are greater at these concentrations than at higher concentrations. These findings suggest that more U.S. children may be adversely affected by environmental lead than previously estimated.

Prevention of lead toxicity in US children

During the past 2 decades, the proportion of US children who have blood lead concentrations of 10 microg/dL or higher declined by over 80% after the elimination of leaded gasoline and lead solder from canned foods, and a ban on leaded paint used in housing and other consumer products. Fatalities and symptomatic lead poisoning are now rare. Residential lead hazards, which are exceedingly difficult to control, are currently the major source of lead intake for children. Undue lead exposure has retreated into 2 major risk groups; impoverished children who live in older, poorly maintained rental housing and more affluent children who live in older housing undergoing renovation. Despite the dramatic decline in children's blood lead levels, lead toxicity remains epidemic among impoverished children who live in older rental housing, especially those who live in the northeastern and midwestern regions of the United States. There are increasing data linking lead exposure with other systemic effects including delinquency, dental caries, and learning problems. Moreover, there is evidence indicating that there is no discernible threshold for lead-associated cognitive deficits. Thus, it is increasingly important to shift our efforts toward the primary prevention of childhood lead exposure from residential hazards. This article reviews the epidemiology and control of childhood lead exposure, focusing especially on steps necessary to shift toward primary prevention.

Lead-associated deficits in stature, mental ability and behaviour in children in Karachi

This study was conducted to evaluate the cumulative and steady-state lead burden in children from Karachi, an area of high lead exposure, and to assess the degree of damage to physical growth and mental ability related to lead exposure. A cross-sectional survey was conducted in seven primary schools from around Karachi. Shed primary teeth and blood samples were collected from students of grades I to III (age range 6-10 years) and were analysed for lead by atomic absorption spectrophotometry. Haemoglobin concentration, height, weight and head circumference were measured. IQ was estimated using Raven's Standard Progressive Matrices. Classroom behaviour was rated by teachers and school performance was estimated from the percentage mark in a school examination taken just before the date of the IQ test. Complete data were available for 138 children. Over 80% of children had lead levels above the safety limit set by the United States Centers for Disease Control and Prevention. The blood lead levels in boys did not differ significantly from that in girls. Significant differences were observed between the schools. Univariate analysis showed negative association of blood lead with haemoglobin, IQ and height. Tooth lead was negatively associated with height, classroom behaviour and performance. When adjusted for other confounding variables, blood lead was negatively associated with haemoglobin and IQ, whereas tooth lead was negatively associated only with classroom behaviour. Height was negatively associated with blood or tooth lead. These results were further supported when the upper and lower quintiles for blood or tooth lead were compared. Tooth lead level was not a better marker of lead poisoning than blood lead level in our study population. These data demonstrate the association of increased lead with impaired learning and adverse behaviour in Karachi children and call for strict government regulations to limit environmental lead burden.

Childhood lead poisoning from paint chips: a continuing problem

Although lead poisoning (plumbism) has been recognized for centuries, lead exposures still occur frequently today because of its varied uses and persistence in the environment. Despite the awareness of the adverse effects of lead on adults, childhood plumbism was first reported only about a century ago. Young children are one of the most vulnerable groups to the adverse effects of lead because of their rapidly developing central nervous systems. Federal regulations in the 1970s have been successfully implemented to decrease the amount of environmental lead by decreasing the content of lead in gasoline and indoor paint. However, almost 30 years after these laws were passed, inner-city housing with leaded paint still exists. We describe three children living in New York City who developed plumbism from the ingestion of leaded paint chips.

Environmental factors associated with a spectrum of neurodevelopmental deficits

A number of environmental agents have been shown to demonstrate neurotoxic effects either in human or laboratory animal studies. Critical windows of vulnerability to the effects of these agents occur both pre- and postnatally. The nervous system is relatively unique in that different parts are responsible for different functional domains, and these develop at different times (e.g., motor control, sensory, intelligence and attention). In addition, the many cell types in the brain have different windows of vulnerability with varying sensitivities to environmental agents. This review focuses on two environmental agents, lead and methylmercury, to illustrate the neurobehavioral and cognitive effects that can result from early life exposures. Special attention is paid to distinguishing between the effects detected following episodes of poisoning and those detected following lower dose exposures. Perinatal and childhood exposure to high doses of lead results in encephalopathy and convulsions. Lower-dose lead exposures have been associated with impairment in intellectual function and attention. At high levels of prenatal exposure, methylmercury produces mental retardation, cerebral palsy and visual and auditory deficits in children of exposed mothers. At lower levels of methylmercury exposure, the effects in children have been more subtle. Other environmental neurotoxicants that have been shown to produce developmental neurotoxicity include polychlorinated biphenyls (PCBs), dioxins, pesticides, ionizing radiation, environmental tobacco smoke, and maternal use of alcohol, tobacco, marijuana and cocaine. Exposure to environmental agents with neurotoxic effects can result in a spectrum of adverse outcomes from severe mental retardation and disability to more subtle changes in function depending on the timing and dose of the chemical agent.

Lead poisoning: case studies

Early clinical features of lead toxicity are non-specific and an occupational history is particularly valuable. Lead in the body comprises 2% in the blood (t1/2 35 days) and 95% in bone and dentine (t1/2 20-30 years). Blood lead may remain elevated for years after cessation from long exposure, due to redistribution from bone. Blood lead concentration is the most widely used marker for inorganic lead exposure. Zinc protoporphyrin (ZPP) concentration in blood usefully reflects lead exposure over the prior 3 months. Symptomatic patients with blood lead concentration >2.4 micromol l-1 (50 microg dl-1) or in any event >3.8 micromol l-1 (80 microg dl-1) should receive sodium calciumedetate i.v., followed by succimer by mouth for 19 days. Asymptomatic patients with blood lead concentration >2.4 micromol l-1 (50 microg dl-1) may be treated with succimer alone. Sodium calciumedetate should be given with dimercaprol to treat lead encephalopathy.

On being a whistleblower: the Needleman case

We believe that members of the scientific community have a primary obligation to promote integrity in research and that this obligation includes a duty to report observations that suggest misconduct to agencies that are empowered to examine and evaluate such evidence. Consonant with this responsibility, we became whistleblowers in the case of Herbert Needleman. His 1979 study (Needleman et al., 1979), on the effects of low-level lead exposure on children, is widely cited and highly influential in the formulation of public policy on lead. The opportunity we had to examine subject selection and data analyses from this study was prematurely halted by efforts to prevent disclosure of our observations. Nevertheless, what we saw left us with serious concerns. We hope that the events here summarized will contribute to revisions of process by which allegations of scientific misconduct are handled and that such revisions will result in less damage to scientists who speak out.

Relationships between blood lead concentrations, intelligence, and academic achievement of Saudi Arabian schoolgirls

This cross-sectional study examined the association between blood lead levels and neuropsychological and behavioural problems of 533 schoolgirls (6-12 years of age) who attended public schools in Riyadh, Capital of Saudi Arabia. Regression models were used to determine the best predictors of Beery VMI Saudi-based standard scores, TONI Saudi-based scores and rank percentile. The mean blood lead level was 8.11 +/- 3.50 micrograms/dl in the range of 2.3 to 27.36 micrograms/dl. Significant negative associations were noted between blood lead levels and Beery VMI Saudi-based standard scores as well as rank percentile. Lead had no effect on TONI Saudi-based standard scores. Beery VMI Saudi-based standard scores, TONI Saudi-based standard scores and rank percentiles were inversely related to pupils with blood lead levels > 9 micrograms/dl. These findings attest an association between neuropsychological and behavioural impairment and lead exposure at blood lead levels in the range of 9.02 to 27.36 micrograms/dl. The results of this study should be seriously considered by public health authorities to give more attention to this pediatric health problem.