Long-term effect of increased lead absorption on intelligence of children

Green Tea (Camellia sinensis): A Review of Its Phytochemistry, Pharmacology, and Toxicology

Objectives Green tea (Camellia sinensis) is a kind of unfermented tea that retains the natural substance in fresh leaves to a great extent. It is regarded as the second most popular drink in the world besides water. In this paper, the phytochemistry, pharmacology, and toxicology of green tea are reviewed systematically and comprehensively. Key findings Green tea has been demonstrated to be good for human health. Nowadays, multiple pharmacologically active components have been isolated and identified from green tea, including tea polyphenols, alkaloids, amino acids, polysaccharides, and volatile components. Recent studies have demonstrated that green tea shows versatile pharmacological activities, such as antioxidant, anticancer, hypoglycemic, antibacterial, antiviral, and neuroprotective. Studies on the toxic effects of green tea extract and its main ingredients have also raised concerns including hepatotoxicity and DNA damage. Summary Green tea can be used to assist the treatment of diabetes, Alzheimer’s disease, oral cancer, and dermatitis. Consequently, green tea has shown promising practical prospects in health care and disease prevention.

A blood lead benchmark for assessing risks from childhood lead exposure

Lead exposure is an insidious problem, causing subtle effects in children at low exposure levels where clinical signs are not apparent. Although a target blood lead concentration (Pb(B)) of ten micrograms per deciliter (10 microg/dL) has been used as the basis for environmental decision-making in California for nearly two decades, recent epidemiologic evidence suggests a relationship between cognitive deficits and Pb(B) at concentrations < 10 microg/dL. Based on a published meta-analysis of children's IQ scores and their blood lead concentrations, we developed a new blood lead benchmark: an incremental increase in blood lead concentration (DeltaPb(B)) of 1 microg/dL, an increase that we estimate could decrease the IQ score in an average school child in California by up to one point. Although there is no evidence to date for a threshold for the neurobehavioral effects of lead, a one-point IQ decrement was chosen to represent a de minimus change. To safeguard the intellectual potential of all children, additional efforts to reduce or eliminate multiple-source exposures to lead are warranted.

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.

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.

The effect of lead-based paint hazard remediation on blood lead levels of lead poisoned children in New York City

Despite the widespread use of lead paint hazard control for children with lead poisoning, few controlled studies that estimate the effect of such control on children's blood lead levels have been published. This retrospective follow-up study examined the effects of lead hazard remediation and its timing on the blood lead levels of lead-poisoned children. From the New York City child blood lead registry, 221 children were selected who had an initial blood lead level of 20-44 micro g/dL between 1 July 1994 and 31 December 1996; were 6 months to 6 years of age; had a report of a follow-up blood lead test between 10 and 14 months after the initial test; had a lead-based paint hazard identified in the primary dwelling unit prior to the 10- to 14-month follow-up blood lead test; had resided or spent time at only one address with an identified lead-based paint hazard; and were not chelated. The decline in geometric mean blood lead levels from baseline to 10-14 months later was compared for children whose homes were remediated and whose homes were not remediated during the follow-up period. Regardless of remediation, geometric mean blood lead levels declined significantly from 24.3 micro g/dL at the initial diagnosis to 12.3 micro g/dL at the 10- to 14-month follow-up blood lead test (P<0.01). Among the 146 children whose homes were remediated the geometric mean blood lead levels declined 53% compared to 41% among the 75 children whose homes were not remediated by the follow-up blood lead test, a remediation effect of approximately 20% (P<0.01). After adjusting for potential confounders, the remediation effect was 11%, although it was no longer significant. Race was the only factor that appeared to confound the relationship: Black children had higher follow-up blood lead levels even after controlling for other factors, including the natural logarithm of the initial blood lead level. The effect of remediation appeared to be stronger for younger (10 to <36 months old) than for older (36 to 72 months old) children (P=0.06). While children in homes with earlier remediation (within less than 3 months) appeared to have greater declines in blood lead levels at the follow-up test than children in homes with later remediation (after 3 or more months), this trend was not significant when controlling for confounding factors. The findings of this study suggest that early identification of lead-poisoned children and timely investigation and abatement of hazards contribute to reducing blood lead levels. However, the apparent effect is modest and further research is needed to systematically test and improve the effectiveness of lead hazard controls.

Increased high-affinity nicotinic receptor-binding in rats exposed to lead during development

Receptor autoradiography and membrane radioligand-binding assays were used to determine the expression of nicotinic cholinergic receptors in the brains of weanling rats exposed to low-levels of lead (Pb) during development. Nicotinic receptors were identified with the frog toxin epibatidine (EB) that binds with high affinity to a variety of receptors containing alpha and beta subunits. Rat pups were exposed to Pb from their mothers given 750-ppm Pb in the diet beginning on gestational day 0 through postnatal day (PN) 21. Blood Pb levels ranged from 36.5 to 46.5 microg/dl in the PN21 pups, and this exposure did not alter their body weight when compared to control rats. Several brain regions identified by autoradiographic studies as having significant binding of EB were dissected from control and Pb-treated pups and used in saturation-binding experiments with membrane preparations to determine the affinity constant (K(d)) and maximal-binding capacity (B(max)) of [3H]EB. Results indicate that the B(max) of [3H]EB was increased in several brain regions in Pb-treated rat pups, without a significant effect on K(d) estimates. [3H]EB-binding to membranes from untreated rats was not affected by in vitro exposure to 20-microM Pb, indicating that the effect of Pb on [3H]EB-binding in vivo was not likely due to direct influence of free Pb remaining in the tissue at the time of assay. The data therefore suggest that expression of nicotinic receptors that bind [3H]EB were increased by developmental exposure to Pb. Several possible mechanisms for these effects and the potential toxicological significance are discussed.

Brainstem neural conduction biomarkers in lead-exposed children of Andean lead-glaze workers

Pediatric lead (Pb) intoxication remains a major medical challenge in some developing countries where Pb is used in glazing industries. Pb exposure is reported to induce neurophysiological and neurocognitive impairment in children. However, the threshold and level of Pb intoxication necessary to induce neuropathology have not been established. Brainstem auditory evoked responses (BAERs) have been used widely as a sensitive biomarker for Pb-induced neurotoxicity. In this field study, BAER neural conduction time was used as a biomarker for central nervous system impairment in Andean children living in areas of high Pb contamination from Pb-glazing cottage industries. The mean Pb level in blood (PbB) for 112 Pb-exposed children was 49.25 microg/dL (SD, 270 microg/dL range, 4.4-119.1 microg/dL). Although BAERs in some children showed prolongations in neural conduction times, regression analyses revealed no significant correlation between PbB levels and BAER interpeak conduction times for 112 replicate recordings (I-III, r = 0.008, P = 0.93; II-V, r = 0.13, P = 0.16; I-V, r = 0.09, P = 0.35; and I-VI, r = 0.14, P = 0.27). A subgroup of 69 children in the study area with PbB levels in the United States Centers for Disease Control and Prevention (CDC) medical intervention-emergency classifications (CDC IV and V; mean, 67.0 microg/dL, SD, 15.8 microg/dL; range, 45.1-119.1 microg/dL) showed no significant correlation between PbB and BAER interpeak interval and no significant differences in BAER than a normal subgroup (t test, P > 0.05). The results demonstrate some evidence of abnormal possibly Pb-induced neural conduction delays in some individual children but a remarkable overall neurobiological functioning in severe, chronic pediatric Pb intoxication without measurable impairment of brainstem auditory nuclei and tracts, as evidenced by neurophysiological conduction times. The findings also demonstrate the variability in the threshold level and duration of Pb exposure necessary to induce brainstem neuropathology.

Neurotoxic effect of lead at low concentrations

The effects of lead exposure at low concentrations were evaluated by studying the post-rotatory nystagmus (PRN) in two groups of rats exposed for 3 months to 50 parts per million (ppm) of sodium acetate and 50 ppm of lead acetate, respectively, in the drinking water. Only animals treated with lead acetate showed changes of the PRN parameters which were significantly related to the concentration of lead in the blood and in brain structures. The patterns of PRN responses were characterized and classified into four types: progressively inhibitory (40%), prematurely inhibitory (25%), late inhibitory (25%), and excitatory-inhibitory (10%). No alterations of the PRN parameters were observed in the animals treated with sodium acetate. The results show that exposure to lead, even at low concentrations, impairs both sensory and motor functions. The findings also point out that the vestibular system and brain stem structures which generate and control the PRN represent targets of the action of this heavy metal. Finally, the results indicate that the evaluation of the vestibulo-ocular-reflex can provide a test suited for the screening of the neurotoxic effects of lead even in the absence of clinical signs typical of lead intoxication.