Lead absorption and psychological function in Zagreb (Croatia) school children

Childhood lead exposure and sex-based neurobehavioral functioning in adolescence

It is well documented that childhood lead exposure is associated with long-term decreases in intelligence quotients (IQ). Lesser known is the relationship with neurobehavioral domains, especially in adolescence. This study sought to identify cross-sectional and longitudinal associations between lead exposure and adolescent executive and visual-motor functioning and examine sex-based differences. Participants were 681 children from Jintan, China who had their blood lead levels (BLLs) assessed at age 3-5 years and 12 years old and neurobehavioral functioning assessed through the University of Pennsylvania Computerized Neurocognitive Battery (PennCNB) platform http://www.med.upenn.edu/bbl at 12 years old. Mean BLLs were 6.41 mcg/dl at age 3-5 years and 3.10 mcg/dl at 12. BLLs at 3-5 years and 12 years were used as predictors for the individual neurobehavioral domains in general linear models while controlling for father and mother occupation and education, residence location, age, and adolescent IQ. Models were run separately for males and females. In adjusted models, males BLLs at 3-5 years were associated with increased time to correctly complete tasks in multiple domains including abstraction/flexibility (β = 19.90, 95% CI( 4.26, 35.54) and spatial processing (β = 96.00, 95% CI 6.18, 185.82) at 12 years. For females in adjusted models, BLLs at 3-5 years were associated with increasing time to correctly complete tasks on the episodic memory domain task (β = 34.59, 95% CI 5.33, 63.84) at 12 years. Two adolescent cross-sectional relationships remained in the adjusted models for males only, suggesting a positive association between BLLs and increasing time for correct responses on the attentional domain task (β = 15.08, 95% CI 0.65, 29.51) and decreasing time for correct responses on the episodic memory task (β = -73.49, 95% CI -138.91, -8.06) in males at 12 years. These associations remained with and without controlling for IQ. These results suggest that lead exposure is associated with overall deficits in male and female neurobehavioral functioning, though in different domains and different timing of exposure.

Correlation between lead exposure and cognitive function in 12-year-old children: a systematic review and meta-analysis

Lead exposure as a toxic material especially in children can be recognized as a harmful factor for cognitive function system. This meta-analysis was conducted to estimate the lead exposure effect on cognitive function among 6979 children less than 12 years. The 16 studies were divided into two clusters according to "duration of exposure" and "dose" using k-means partitioning clustering algorithm. Then, subgroup analysis has been performed based on the clustered studies. According to the results of the k-means clustering, dose and duration of exposure were significant factors between all considered variables. A stronger negative significant pooled correlation was observed in higher dose and duration cluster in comparison with another cluster including lower dose and duration (r = - 0.29, P-value < 0.001 vs. r = - 0.08, P-value < 0.001). Overall, a negative significant correlation was observed between lead exposure and cognitive function test score (r = - 0.22, P-value < 0.001). This study confirms the negative effect of lead on cognitive function in children, but needed further investigations to achieve the safe dose and duration of the lead exposure.

Blood lead levels ≤10 micrograms/deciliter and executive functioning across childhood development: A systematic review

At low levels, the effects of lead on specific neurocognitive processes, such as executive functioning, is not well understood. The aim of this systematic review is to synthesize the empirical literature examining the relationship between prenatal and postnatal low blood lead levels and executive function across childhood development. This review considers the unity and diversity model of executive functioning by assessing the domains of working memory, cognitive flexibility, inhibition, attention, and unitary executive function separately. Nineteen studies met the inclusion criteria and were synthesized in the review. The results suggest an inverse association between postnatal lead exposure and executive function processes across childhood. The inverse relationship between postnatal lead exposure and working memory and cognitive flexibility in middle childhood is most strongly represented. Additionally, a marginal inverse relationship between postnatal lead exposure and unitary executive functioning and attention in middle childhood is suggested. The evidence does not support a relationship between postnatal lead and inhibition in middle childhood. Although there is support for the inverse relationship between low level lead exposure and executive function, lack of repeated exposure and outcome measures limit firm conclusions. Furthermore, the long-term impact of lead exposure on executive function outcomes is relatively unknown given lack of studies on adolescent populations.

Environmental toxic agents: The impact of heavy metals and organochlorides on brain development

Exposure to environmental toxicants can have deleterious effects on the development of physical, cognitive, and mental health. Extensive laboratory and clinical studies have demonstrated how the developing brain is uniquely sensitive to toxic agents. This chapter focuses on the main neurologic impairments linked to prenatal and postnatal exposure to lead, methylmercury, and polychlorinated biphenyls, three legacy environmental contaminants whose neurotoxic effects have been extensively studied with respect to cognitive and behavioral development. The main cognitive, emotion regulation, sensory, and motor impairments in association with these contaminants are briefly reviewed, including the underlying neural mechanisms such as neuropathologic damages, brain neurotransmission, and endocrine system alterations. The use of neuroimaging as a novel tool to better understand how the brain is affected by exposure to environmental contaminants is also discussed.

[Characterization of language disorders in children with lead poisoning]

BACKGROUND

lead poisoning can have a negative impact on the neuropsychological functions, including language, due to the damage it causes to the development of the Central Nervous System.

AIM

to verify the occurrence of language disorders in children who suffered from led poisoning and to verify the correlation between the lead concentration level in the blood and the language disorders presented by the children.

METHOD

language evaluation of 20 preschoolers, with lead concentration level in the blood above 10 microg/dl.

RESULTS

13 children presented language impairment involving only phonology or more than one language subsystem. The statistical analysis indicated that no correlation exists between the severity of the language impairment and the concentration levels of lead.

CONCLUSION

the number of children with language impairment indicates lead poisoning as a risk factor for the present alterations, even though other risk factors for language disorders were found and the absence of correlation between the investigated variables.

Protective effect of curcumin against lead neurotoxicity in rat

Curcumin (diferuloylmethane), an active ingredient of turmeric, is known to have multiple activities, including an antioxidant property, and has been suggested to be of use in treatment of several diseases. The present study has been undertaken to investigate the protective effect of curcumin against lead-induced neurotoxicity in rats. Exposure of rats to lead (50 mg/kg po) for 45 days caused an increase in lipid peroxidation (LPO) and a decrease in reduced glutathione (GSH) levels in cerebellum, corpus striatum, hippocampus and frontal cortex as compared with controls. Lead levels were significantly increased in these rats. Activity of antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) decreased in all the brain regions following lead exposure. Interestingly, cotreatment with curcumin (100 mg/kg po) and lead (50 mg/kg po) for 45 days caused a significant decrease in LPO with concomitant decrease in lead levels in all the brain regions as compared with those treated with lead alone. A significant increase in reduced glutathione (GSH) levels, SOD and CAT activities was also observed in all the four brain regions in rats simultaneously treated with curcumin and lead. The results suggest that curcumin may prevent lead-induced neurotoxicity.

Recent developments in low-level lead exposure and intellectual impairment in children

In the last decade children's blood lead levels have fallen significantly in a number of countries, and current mean levels in developed countries are in the region of 3 Mu g/dL. Despite this reduction, childhood lead poisoning continues to be a major public health problem for certain at-risk groups of children, and concerns remain over the effects of lead on intellectual development in infants and children. The evidence for lowered cognitive ability in children exposed to lead has come largely from prospective epidemiologic studies. The current World Health Organization/Centers for Disease Control and Prevention blood level of concern reflects this and stands at 10 Mu g/dL. However, a recent study on a cohort of children whose lifetime peak blood levels were consistently less than 10 Mu g/dL has extended the association of blood lead and intellectual impairment to lower levels of lead exposure and suggests there is no safety margin at existing exposures. Because of the importance of this finding, we reviewed this study in detail along with other recent developments in the field of low-level lead exposure and children's cognitive development. We conclude that these findings are important scientifically, and efforts should continue to reduce childhood exposure. However, from a public health perspective, exposure to lead should be seen within the many other risk factors impacting on normal childhood development, in particular the influence of the learning environment itself. Current lead exposure accounts for a very small amount of variance in cognitive ability (1-4%), whereas social and parenting factors account for 40% or more.