[Effect of chronic lead exposure on expression of autophagy-associated proteins in rat hippocampus]

OBJECTIVE

To investigate the effects of chronic lead exposure on expression of autophagy-associated proteins in rat hippocampus.

METHODS

SD rats were randomly divided into three groups: control group was given distilled water, lead-exposed groups were given 0.5 g/L (low-dose) or 2.0 g/L(high-dose) lead acetate solution in drinking water. The rat pups started to drink the lead content water until 60 d maturity. The lead contents in blood and brain samples were analyzed by graphite furnace atomic absorption spectrophotometry. The expressions of Beclin 1, LC3, LAMP2 and cathepsin B proteins were detected by Western blot and immunohistochemistry.

RESULTS

Compared with control group, the contents of lead were significantly higher in blood and hippocampus samples in chronic lead-exposed rats (P<0.01). Western blot showed that the expression of Beclin 1 and LC3-II/LC3-I increased significantly in high dose lead-exposed group compared with control group (P<0.05 or P<0.001). The confocal laser immunostaining results demonstrated that increased immunofluorescence staining of cathepsin B in hippocampal neurons compared with control animals.

CONCLUSION

The disturbance of autophagy-lysosome signaling molecules might be partially contribute to neurotoxicity of chronic lead exposure.

A latent variable approach to study gene-environment interactions in the presence of multiple correlated exposures

Many existing cohort studies initially designed to investigate disease risk as a function of environmental exposures have collected genomic data in recent years with the objective of testing for gene-environment interaction (G × E) effects. In environmental epidemiology, interest in G × E arises primarily after a significant effect of the environmental exposure has been documented. Cohort studies often collect rich exposure data; as a result, assessing G × E effects in the presence of multiple exposure markers further increases the burden of multiple testing, an issue already present in both genetic and environment health studies. Latent variable (LV) models have been used in environmental epidemiology to reduce dimensionality of the exposure data, gain power by reducing multiplicity issues via condensing exposure data, and avoid collinearity problems due to presence of multiple correlated exposures. We extend the LV framework to characterize gene-environment interaction in presence of multiple correlated exposures and genotype categories. Further, similar to what has been done in case-control G × E studies, we use the assumption of gene-environment (G-E) independence to boost the power of tests for interaction. The consequences of making this assumption, or the issue of how to explicitly model G-E association has not been previously investigated in LV models. We postulate a hierarchy of assumptions about the LV model regarding the different forms of G-E dependence and show that making such assumptions may influence inferential results on the G, E, and G × E parameters. We implement a class of shrinkage estimators to data adaptively trade-off between the most restrictive to most flexible form of G-E dependence assumption and note that such class of compromise estimators can serve as a benchmark of model adequacy in LV models. We demonstrate the methods with an example from the Early Life Exposures in Mexico City to Neuro-Toxicants Study of lead exposure, iron metabolism genes, and birth weight.

Effect of lead acetate toxicity on experimental male albino rat

OBJECTIVE

To evaluate the effect of different doses of lead acetate (1/20, 1/40 and 1/60 of LD50) on body weight gain, blood picture, plasma protein profile and the function of liver, kidney and thyroid gland.

METHODS

Male albino rats were divided into four groups, the first group represented the health control animals, while the second, third and fourth groups were ingested orally with sub lethal doses of lead acetate (1/20, 1/40 and 1/60) of the oral LD50, respectively. One dose was ingested every two days during the experimental period (14 weeks) including the adaptation time. Blood was collected and used for all analysis.

RESULTS

The results showed that, the ingestion of Pb(2+) induced significant stimulation in glutamic-pyruvic transaminase (ALT) and glutamic-oxalacetic transaminease (AST) activity. Also, total soluble protein and albumin contents of plasma were significantly decreased, while the content of globulin was changed by the Pb(2+) treatments. The cholinesterase activity was inhibited, but the activities of alkaline and acid phosphates and lactate dehydrogenase were stimulated, while plasma glucose level was elevated as a result of lead acetate intoxication. In case of blood picture, Pb(2+) ingestion reduced the contents of hemoglobin and RBCs count of intoxicated rat's blood and the plasma levels of T3, T4 and blood WBCs count were decreased.

CONCLUSIONS

It can be concluded that lead acetate has harmful effect on experimental male albino rats. Therefore, the present work advises people to prevent exposure to the lead compound to avoid injurious hazard risk.

Health concerns of heavy metals and metalloids

There is a long history and an overwhelming amount of data on the toxicity of heavy metal compounds. Here a brief look is taken of some aspects of the toxicity of lead, cadmium, mercury and arsenic, chosen for their historical importance and environmental significance, highlighting especially the contrast between the acute and chronic toxicity of purely inorganic species and their organic derivatives. For further details of other toxic metal compounds, the reader might like to consult "Elements of murder: a history of poison" by John Emsley (2005, Oxford University Press).

The effect of lead acetate toxicity on experimental male albino rat

The toxic effect of Pb ion (lead acetate) was investigated using male albino rats, which was ingested at 1/20, 1/40, and 1/60 sublethal doses. Relative to normal control, the ingestion of Pb(2+) induced significant stimulation in ALT and AST activity. In addition, total soluble protein and albumin contents of plasma were decreased, while the content of globulin was changed by the Pb(2+) treatments. The cholinesterase activity was inhibited, but the activities of alkaline and acid phosphates as well as lactate dehydrogenase were stimulated as a result of lead acetate intoxication. These observations were gradually paralleled across the experiment dose of the three doses of intoxicated Pb(2+). In the case of blood picture, Pb(2+) ingestion significantly reduced the contents of hemoglobin and RBC count of intoxicated rat's blood, while the plasma levels of T3 and T4 and blood WBC count were insignificantly decreased or unchanged. All results of the present study showed that the Pb(2+) ingestion was more effective in the case of the high dose (1/20 LD(50)) than that of the low dose (1/60 LD(50)) ingestion relative to the normal healthy control. The results of the present work advice the need to avoid exposure of humans to the lead compound to avoid injurious hazard risk.

Ultrastructural changes in lung tissue after acute lead intoxication in the rat

Pulmonary toxicity of lead was studied in rats after an intraperitoneal administration of lead acetate at a dose of 25 mg/kg. Three consecutive days of treatment increased lead content in the whole blood to 2.1 µg/dl and in lung homogenate it attained 9.62 µg/g w.w. versus control values of 0.17 µg/dl and 0.78 µg/g w.w., respectively. At the ultrastructural level, the effects of lead toxicity were observed in lung capillaries, interstitium, epithelial cells and alveolar lining layer. Accumulation of aggregated platelets, leucocytic elements and monocytes was found within capillaries. Interstitium comprised a substantial number of collagen, elastin filaments and lipofibroblasts. Lamellar bodies of type II pneumocytes contained phospolipid lamellae, which stratified into an irregular arrangement. Pulmonary alveoli were filled with macrophages. The extracellular lining layer of lung alveoli was partially destroyed. This study provided evidence that acute lead intoxication affects the whole lung parenchyma and by impairing production of the surfactant might disturb the regular respiratory function.

Placenta and umbilical cord blood deserve attention

OBJECTIVES

This work follows up with our already published results concerning consequences of lead on prenatal and postnatal development of child in connection with the rise of hyperkinetic syndrome (ADHD). This disease has in children increasing tendency all over the world.

METHODS

In our work we used a set of histological and histochemical methods, method of scanning electron microscopy, infrared spectroscopy and statistical evaluation.

RESULTS

Our new method for proof of lead in placenta enabled us to show how lead is cumulated in syncytiotrophoblast. We have found release of lead from mother's erythrocytes in the intervillous space and receipt of lead by erythrocytes of fetus in the vessels of the villi of placenta. This finding enriches knowledge about relation between mother's erythrocytes, lead, calcium that is lead carrier, syncytiotrophoblast, and erythrocytes of fetus in the vessels of placental villi. We have proved that syncytiotrophoblast is the most frequent place for cumulation of lead deposits. We verified our ecomorphologic results by means of infrared spectroscopy in cooperation with physicists and statistically evaluated occurrence of ADHD in particular age categories what helps to fill gaps in knowledge of ADHD etiology.

CONCLUSIONS

Our finding of lead in umbilical cord blood immediately after the child birth is forewarning against the possible rise of the ADHD. This finding facilitates early diagnostics and means preventing step against the rise, development and consequences of this disease. The obtained results give evidence about the serious influence of mother's dwelling in environment polluted with neurotoxic metal - lead on the prenatal and postnatal development of child.

[Effect of potassium iodide on prevention of experimental lead nephropathy and expression of nuclear factor-kappaB and fibronectin]

OBJECTIVE

To investigate the effect of potassium iodide on the expression of nuclear factor-kappaB and fibronectin.

METHODS

The experiment was performed with 72 SD rats weighing about 180-220 g. The animals were randomly assigned into nine groups. Group A, B, C (n=8) served as control and were fed with distilled water for 1 month, 2 month, 3 month respectively. Group D, E, F (n=8) served as lead exposed and were fed with water with 0.5% lead acetate for 1 month, 2 month, 3 month respectively. Group G, H, I (n=8) served as potassium iodide and lead exposed and were treated with 0.5% lead acetate simultaneously taking potassium iodide 3 mg/100 g weight by intragastric administration for 1 month, 2 month, 3 month respectively. Animals of different groups were sacrificed at the end of the treatment. Ultrastructure of kidney was observed by electron microscopy; Expression of NF-kappaB and FN protein and mRNA in kidney were measured respectively by immunohistochemistry and RT-PCR.

RESULTS

Electron microscopic examination revealed potassium iodide could restrain the denaturalization in epithelial cells and mitochondrial cristae. The expressions of NF-kappaB protein (0.2315 +/- 0.0624, 0.3213 +/- 0.0740, 0.4729 +/- 0.0839) and mRNA (0.4370 +/- 0.0841, 0.5465 +/- 0.0503, 0.6443 +/- 0.0538) in all the lead exposed groups continuously increased compared with correspondent control groups; Group I was decreased obviously compared with group F. The expressions of FN protein (0.4243 +/- 0.0595, 0.4917 +/- 0.0891) and mRNA (0.8650 +/- 0.0880, 0.8714 +/- 0.0980) in group E and F increased compared with group B and C, but the expressions of FN protein in group I significantly decreased compared with group F; The expressions of FN mRNA in Group H and I significantly decreased compared with group E and F.

CONCLUSION

The potassium iodide can ameliorate renal ultrastructure and degrade expression of nuclear factor-kappaB and fibronectin induced by lead.

Hepatic morphopathologic findings of lead poisoning in a drug addict: a case report

We describe the case of a 40-year old Iranian man who was admitted to our hospital with severe abdominal pain, abnormal liver function tests and normocytic anemia. Suffering from multiple sclerosis, he was a regular user of opium for pain relief. Basophilic stippling of erythrocytes pointed towards the diagnosis of lead intoxication, the most likely source being contaminated Iranian opium. Serum lead and zinc protoporphyrin levels were strongly elevated. To assess the hepatotoxic effects of lead poisoning a liver biopsy was performed. Pathomorphologic findings of hepatotoxicity, rarely reported in humans, included active hepatitis together with extensive microvesicular and macrovesicular steatosis, hemosiderosis and cholestasis, and a lymphocytic cholangitis. Whilst treated with chelating therapy, liver enzymes returned to normal, suggesting reversibility of the histological findings.

Renal dysfunction and hyperuricemia with low blood lead levels and ethnicity in community-based study

The objective of this study was to assess the correlation between blood lead levels (BLL) with both renal dysfunction and hyperuricemia among aboriginals and non-aboriginals in Taiwan. 1318 aboriginals and 1247 non-aboriginals over 40 years of age volunteered for this study. During routine health examinations at a clinic, blood samples were taken and a questionnaire was administered. Male uric acid (BUA) concentration (7.2 mg/dL) in serum was higher than for females (5.9 mg/dL). BUA concentration among aboriginals was higher (6.9 mg/dL) than among non-aboriginals (5.9 mg/dL). A test for trend of odds ratio (OR) for renal dysfunction and hyperuricemia indicated a significant correlation with BLL for both ethnic groups. Multiple logistic regression showed people who had BLLs exceeding 7.5 microg/dL were at a higher risk for renal dysfunction (OR=1.92, 95% CI: 1.18-3.10) and hyperuricemia (OR=2.72, 95% CI: 1.64-4.52). We concluded that BLL was significantly correlated with renal dysfunction and hyperuricemia in both ethnic groups. Further research is needed to investigate the exact mechanism causing a higher incidence of related disease among aboriginal Taiwanese.

The effect of adrenomedullin on rats exposed to lead

Adrenomedullin (AdM) was originally discovered as a vasorelaxant peptide. The antioxidative properties of AdM have been reported recently. Through its antioxidative effect, adrenomedullin can protect organs from damage induced by stressors. Lead, commonly detected in air, soil, water and food, is a major source of oxidative stress. The effect of AdM in the liver of rats exposed to lead was investigated. Twenty-four female Wistar rats were divided into four groups: a control group (C), adrenomedullin group (AdM), lead (Pb) group and lead + adrenomedullin (Pb + AdM) group. In the Pb-treated groups, the animals were exposed to lead in drinking water containing 250 ppm PbCl2 for 4 weeks. In the AdM-treated group, the animals received an i.p. injection of AdM (3000 ng kg(-1) body weight) in the third week of lead treatment for 1 week. The activities of catalase (CAT), glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) and the level of malondialdehyde (MDA) were determined in the liver of rats. Histological changes in the liver were examined by light and electron microscopy as well. The MDA levels were increased significantly in the Pb-treated groups, but in the Pb + AdM group the MDA levels were decreased significantly when compared with the Pb group. AdM reduced hepatic damage in the Pb + AdM group, but the difference in the total histopathological scores between the Pb and Pb + AdM groups was not significant. When the results are taken together, it can be concluded that AdM may have protective or compensating effects in lead toxicity.

Renal gangliosides are involved in lead intoxication

The biological effects of lead are well defined; however, neither the risk exposure level nor the subcellular mechanism of its action is completely clear. The present work was undertaken to investigate the effects of low level and long term lead exposure on the composition and expression of rat renal gangliosides. In order to identify ganglioside expression, frozen sections of kidneys were stained with monoclonal antibodies GMB16 (GM1 specific), GM28 (GM2 specific), AMR-10 (GM4 specific) and CDW 60 (9-O-Ac-GD3 specific). Strong reactivity was observed for GMB28, AMR-10 and CDW 60, while GMB16 developed only weak labelling in treated kidney compared with the control. The alterations in the expression of renal gangliosides observed by immunohistochemistry were accompanied by quantitative and qualitative changes in the thin layer chromatography of total gangliosides isolated from kidney tissues. Lead treatment produced a significant increase in 9-O-Ac GD3, a ganglioside involved in apoptotic processes. In agreement with this result, a significant decrease in the number of apoptotic glomerular cells was observed with the TUNEL assay. These findings lead us to suggest that alterations in renal gangliosides produced by low level lead exposure are associated with the apoptotic processes that take place in the kidney. These findings provide evidence that low level and long term lead exposure produces renal ganglioside alterations with urinary microalbumin excretion. The results suggest that lead levels within the limits of biological tolerance already cause molecular renal damage without clinical signs of toxicity.

Lead hepatotoxicity & potential health effects

Occupational and environmental exposures to lead (Pb), one of the toxic metal pollutants, is of global concern. Health risks are increasingly associated with environmental exposures to Pb emissions from, for example, the widespread use of leaded gasoline in developing countries. Exposure occurs mainly through the respiratory and gastrointestinal systems, and the ingested and absorbed Pb is stored primarily in soft tissues and bone. Autopsy studies of Pb-exposed patients have shown a large amount (approximately 33%) of the absorbed Pb in soft tissue stored in liver. In addition to neuronal encephalopathy observed in persons after exposure to very high concentrations of Pb, gastrointestinal colic (abdominal pain, constipation, intestinal paralysis) is a consistent early symptom of Pb poisoning in humans. Such severe gastrointestinal effects are consistently observed in patients with a blood Pb range of 30 to 80 microg/dl. Ingestion of Pb is one of the primary causes of its hepatotoxic effects. Hepatocarcinogenic effects of Pb reported in animal toxicology studies have led to new research into the biochemical and molecular aspects of Pb toxicology. Gains in the molecular understanding of Pb effects on hepatic drug metabolizing enzymes, cholesterol metabolism, oxidative stress, and hepatic hyperplasia suggest a potential role for Pb in damaging extrahepatic systems, including the cardiovascular system. This review also discusses the therapeutic potential of chelation therapy in treating Pb-induced hepatotoxicity in animals.

Clioquinol and vitamin B12 (cobalamin) synergistically rescue the lead-induced impairments of synaptic plasticity in hippocampal dentate gyrus area of the anesthetized rats in vivo

Lead (Pb(2+)) exposure in development induces impairments of synaptic plasticity in the hippocampal dentate gyrus (DG) area of the anesthetized rats in vivo. The common chelating agents have many adverse effects and are incapable of alleviating lead-induced neurotoxicity. Recently, CQ, clioquinol (5-chloro-7-iodo-8-hydroxy-quinoline), which is a transition metal ion chelator and/or ionophore with low affinity for metal ions, has yielded some promising results in animal models and clinical trials related to dysfunctions of metal ions. In addition, CQ-associated side effects are believed to be overcome with vitamin B12 (VB12) supplementation. To determine whether CQ treatment could rescue impairments of synaptic plasticity induced by chronic Pb(2+) exposure, we investigated the input/output functions (I/Os), paired-pulse reactions (PPRs) and long-term potentiation (LTP) of different treatment groups in hippocampal DG area of the anesthetized rat in vivo by recording field potentials and measured hippocampal Pb(2+) concentrations of different treatment groups by PlasmaQuad 3 inductive coupled plasma mass spectroscopy. The results show: CQ alone does not rescue the lead-induced impairments of synaptic plasticity in hippocampal DG area of the anesthetized rats in vivo; VB12 alone partly rescues the lead-induced impairments of LTP; however the co-administration of CQ and VB12 totally rescues these impairments of synaptic plasticity and moreover, the effects of CQ and VB12 co-administration are specific to the lead-exposed animals.

Toxic effects seen in a herd of beef cattle following exposure to ash residues contaminated by lead and mercury

Lead poisoning was diagnosed in three cattle along with increased mercury levels in the liver and kidney tissues of two of these animals. The clinical signs were different in each case and included salivation, anorexia, delayed menace response, delayed withdrawal reflex, head pressing, localized muscle fasciculation, reduced tongue tone, ataxia, rumen atony and seizures. Blood lead concentration was increased in all three cases to 0.76, 0.37 and 0.454ppm. Post mortem changes characteristic of lead poisoning were only recognized in one case and included cerebro-cortical oedema, cortical neuronal necrosis and endothelial proliferation, especially at the tips of the cerebral gyri. The animals were poisoned by ingestion of lead-contaminated ash residues from a bonfire. The abnormal levels of mercury in the liver and kidney tissues of two animals may also be at least partly attributable to the intake of the metal in the ash residues. The levels of mercury in the three samples from the ash residue were relatively low (1.31, 0.7 and 2.1ppm).

Therapeutic potentials of combined use of DMSA with calcium and ascorbic acid in the treatment of mild to moderately lead intoxicated mice

The aim of this study was to explore the therapeutic efficacies of combined use of meso-2,3-dimercaptosuccinic acid (DMSA) with calcium and ascorbic acid in the treatment of mild to moderately lead-intoxicated mice. Female albino mice were exposed to lead by drinking water contaminated with 0.1% (moderate lead exposure) or 0.05% (mild lead exposure) lead acetate. After the cessation of lead exposure, mice were supplemented by gavage with saline solution, 50 mg/kg body weight (b.w) DMSA, 100 mg/kg b.w DMSA, calcium and ascorbic acid, or 50 mg/kg b.w DMSA and calcium as well as ascorbic acid, respectively. Atomic absorption spectrophotometric method was used to analyze lead levels in blood, bone, liver, kidney and brain. Activities of blood delta-aminolevulinic acid dehydratase (ALAD) were determined by colorimetric method. DMSA supplemented alone could reduce lead levels in both soft tissues and bone and reverse lead-inhibited activities of blood ALAD in mild to moderately lead-intoxicated mice. On the other hand, combined use of DMSA with calcium and ascorbic acid achieved better therapeutic efficacies in mobilizing lead in blood, liver and kidney, and reversing lead-inhibited activities of blood ALAD in moderately lead intoxicated mice than DMSA supplemented alone. Moreover, the better therapeutic efficacies were also found in mildly lead intoxicated mice in mobilizing lead in blood and bone achieved by combined use of DMSA with calcium and ascorbic acid. Combined use of DMSA with calcium and ascorbic acid seems to be the better choice in the treatment of mild to moderate lead-intoxication.

Magnetic Resonance Spectroscopy and Environmental Toxicant Exposure

The study of neurological impacts of toxicants has emphasized neuropsychological tests as important outcome variables. Direct assessment of neural substrates of environmental impacts could offer many advantages. I discuss our use of magnetic resonance spectroscopy (MRS) in the neurological assessment of adult lead poisoning of monozygotic twins as an example. Cognitive testing showed frontal lobe dysfunction in both twins, and more dramatic hippocampal dysfunction in the twin with higher lead exposure (JG). MRS showed lower N-acetylaspartate/creatine ratios in JG. The findings illustrate the potential utility of MRS in assessing impacts of not only lead, but other toxicants as well.

Oxidative damage in liver after perinatal intoxication with lead and/or cadmium

Lead acetate (300 mg Pb/L) and/or cadmium acetate (10mg Cd/L) in blood and liver were administrated as drinking water to pregnant Wistar rats from day 1 of pregnancy to parturition (day 0) or until weaning (day 21), to investigate the toxic effects in blood and in the liver. Both metals produced mycrocitic anaemia in the pups as well as oxidative damage in the liver, as suggested by the significant increase in TBARS production and the high catalase activity. Moreover, intense alkaline and acid phosphatase activity, used as biomarkers of liver adaptation to damaging factors, was observed. In addition, the toxikinetics are different for Pb and Cd: while Cd is a hepatotoxic from day 0, Pb is not until day 21. Finally, simultaneous perinatal administration of both metals seems to protect, at least, in the liver TBARS production against the toxicity produced by Cd or Pb separately.

Environmental agents affect skeletal growth and development

In this treatise we will examine complexities in the development and function of cells of the musculoskeletal system. Specifically, the role of chondrocytes and their ontogeny and osteoblasts and their ontogeny will be discussed as they regulate cartilage and bone formation. This background information will provide the foundation for evaluating the effects of environmental toxicants on skeletal development. A number of agents such as heavy metals (i.e. lead) and polycyclic aromatic hydrocarbons (i.e. pesticides and cigarette smoke) interact with cells of the skeletal system and adversely affect development. These agents have not been of major research interest, nevertheless, given changes in the environmental profile of the United States and other developed countries, it is important that we understand their effects in bone and cartilage. Research in this area will identify strategies that may be used to help prevent musculoskeletal diseases due to toxicant exposure.

Retinal lead toxicity

A 35-year-old female who had suffered from acute lead poisoning when she was 22 years old, presented 13 years later with loss of vision in the right eye and normal vision in the left eye. She had a pale disc, narrowed arterioles and mid-peripheral heavy pigmentation, right eye being more affected than the left eye. Electrodiagnostic tests identified marked asymmetry of visual function. We would postulate lead retinal toxicity as the cause of the asymmetric findings.

Lead nephropathy: early leads from descriptive studies

Chronic lead exposure is recognized as a potential cause of hyperuricaemia, kidney damage and hypertension. The fascinating story of lead poisoning and nephrotoxicity illustrates the utility of descriptive studies in the early elucidation of a new disease entity. The pursuit towards understanding lead nephropathy is presented as a successful illustration of human occupational and public health.

Acute Lead Toxicosis in a Harbor Seal (Phoca vitulina richardsi) Consequent to Ingestion of a Lead Fishing Sinker

An adult female harbor seal (Phoca vitulina richardsi) stranded in northern California on 25 June 2004, exhibited progressive weakness, disorientation, and seizures, and despite therapy, died within 4 days. On pathologic examination, a lead fishing sinker was in the stomach, and changes in the brain, heart, kidney, liver, lymph nodes, and spleen were supportive of acute lead toxicosis. The diagnosis was made on the basis of concentrations of lead in the sinker (90-98% lead), antemortem whole blood (0.66 ppm), and postmortem tissues (84 ppm, wet weight liver). This first documented case of lead toxicosis in a wild marine mammal demonstrates an additional way in which human fishing activities can harm marine mammals.

Past adult lead exposure is linked to neurodegeneration measured by brain MRI

OBJECTIVE

To determine whether cumulative lead dose in former organolead workers was associated with MRI measures of white matter lesions (WML) and global and structure-specific brain volumes.

METHODS

MRIs, tibia lead, and other measures were obtained from 532 former organolead workers with a mean age of 56 years and a mean of 18 years since last occupational exposure to lead. Cumulative lead dose was measured by tibia lead, obtained by X-ray fluorescence, and expressed as microg lead per gram of bone mineral (microg Pb/g). WML were evaluated using the Cardiovascular Health Study grading scale. A total of 21 global and specific brain regions were evaluated.

RESULTS

A total of 36% of individuals had WML grade of 1 to 7 (0 to 9 scale). Increasing peak tibia lead was associated with increasing WML grade (p = 0.004). The adjusted OR for a 1 microg Pb/g increase in tibia lead was 1.042 (95% CI = 1.021, 1.063) for a CHS grade of 5+ (> or = 5 vs < 5). In linear regression, the coefficient for tibia lead was negative for associations with all structures. Higher tibia lead was significantly related to smaller total brain volume, frontal and total gray matter volume, and parietal white matter volume. Of nine smaller specific regions of interest, higher tibia lead was associated with smaller volumes for the cingulate gyrus and insula.

CONCLUSIONS

These data suggest that cumulative lead dose is associated with persistent brain lesions, and may explain previous findings of a progressive decline in cognitive function.