Lead concentrations in cortical and trabecular bones in deceased smelter workers

Cadmium and Lead Exposure, Nephrotoxicity, and Mortality

The present review aims to provide an update on health risks associated with the low-to-moderate levels of environmental cadmium (Cd) and lead (Pb) to which most populations are exposed. Epidemiological studies examining the adverse effects of coexposure to Cd and Pb have shown that Pb may enhance the nephrotoxicity of Cd and vice versa. Herein, the existing tolerable intake levels of Cd and Pb are discussed together with the conventional urinary Cd threshold limit of 5.24 μg/g creatinine. Dietary sources of Cd and Pb and the intake levels reported for average consumers in the U.S., Spain, Korea, Germany and China are summarized. The utility of urine, whole blood, plasma/serum, and erythrocytes to quantify exposure levels of Cd and Pb are discussed. Epidemiological studies that linked one of these measurements to risks of chronic kidney disease (CKD) and mortality from common ailments are reviewed. A Cd intake level of 23.2 μg/day, which is less than half the safe intake stated by the guidelines, may increase the risk of CKD by 73%, and urinary Cd levels one-tenth of the threshold limit, defined by excessive ß₂-microglobulin excretion, were associated with increased risk of CKD, mortality from heart disease, cancer of any site and Alzheimer's disease. These findings indicate that the current tolerable intake of Cd and the conventional urinary Cd threshold limit do not provide adequate health protection. Any excessive Cd excretion is probably indicative of tubular injury. In light of the evolving realization of the interaction between Cd and Pb, actions to minimize environmental exposure to these toxic metals are imperative.

Characterization and imaging of lead distribution in bones of lead-exposed birds by ICP-MS and LA-ICP-MS

Lead (Pb) poisoning in raptors and water birds is a serious problem in many countries. However, only a small fraction of Pb poisoning has been detected in birds. Bone specimens may be useful indices of Pb exposure because bones contain ∼90% of the total Pb body burden. The original purpose of this study was to comprehensively analyze Pb accumulation in various bone types using inductively coupled plasma-mass spectrometry (ICP-MS). Since our results showed that Pb accumulation differed greatly depending on bone type, a secondary objective was defined, aiming to investigate the fine Pb distribution and its relation to bone structure and bone marrow by using laser ablation (LA)-ICP-MS. Our findings suggested that bone samples (1) consisting of trabecular tissue and (2) those that contain bone marrow could accumulate high levels of Pb following acute exposure. The shorter turnover time of trabecular bone can cause a rapid accumulation of Pb, and bone marrow may have an important role for internal exposure of Pb to bone tissue. Pb is accumulated in bones via blood flow, and bone marrow receives blood from outside the bones. In conclusion, bone samples provide valuable information on Pb exposure and could be useful to investigate and understand mortalities related to suspected Pb poisoning.

Lead exposure is a risk for worsening bone mineral density in middle-aged male workers

OBJECTIVE

Lead exposure linked to osteoporosis in women. However, there is no direct evidence whether lead exposure has effects on bone metabolism in middle-aged male subjects. Therefore, the present study investigated the relationship between bone mineral densitometry measurements, bone markers, endocrine hormones and blood lead levels.

MATERIAL AND METHODS

The present study included lead exposure patients (n: 30) and control subjects (n: 32). We recorded information on patient demographics and risk factors of osteoporosis. Blood lead levels were evaluated using Varian AA 240Z atomic absorption spectrophotometry. Bone mineral density measurements were measured using dual-energy X-ray absorptiometry.

RESULTS

Each lumbar T and Z scores in the lead exposure group were lower than the control group. There were no significant differences in femur neck and femur total T and Z scores between two groups. Blood lead levels were also negatively correlated with lumbar 2-4 T score, total lumbar T score, lumbar 2-4 Z score and total lumbar Z score. Urinary hydroxyproline and urinary deoxypyridinoline levels in the lead exposure group were significantly higher compared to controls. Blood lead levels were strong, positively correlated with urinary deoxypyridinoline. Endocrine hormone levels and 1,25-dihydroxy-vitamin D3 levels were comparable between lead exposure and control group.

CONCLUSION

Lead exposure in male workers is an important factor for deterioration in bone mineral density. We should be screening blood lead levels and history of lead exposure in male osteoporosis.

Chemical elements of human bone tissue investigated by nuclear analytical and related methods

The mass fractions (in milligrams per kilogram given on a dry mass basis) of 69 chemical elements in the intact rib bone of 84 apparently healthy 15- to 58-year-old citizens (38 females and 46 males) of a nonindustrial region were investigated using five instrumental analytical methods: neutron activation analysis with high-resolution spectrometry of short- and of long-lived radionuclides, particle-induced gamma-ray emission spectrometry, inductively coupled plasma atomic emission, and mass spectrometry. The mass fractions of chemical elements were measured for rib bone of both males and females, taken separately and together. The present results indicate that rib bone can be used as exposure monitors in occupational medicine and environmental health studies to assess, or indicate, the body burden of Al, B, Ba, Be, Ca, Cr, F, Li, Mg, Na, Ni, P, Pb, rare-earth elements (REEs), Sr, and Zn. Our data show an exponential increase with the age of the content of REEs in the rib of people living in an ecologically safe region.

Trace metals and micronutrients in bone tissues of the red fox Vulpes vulpes (L., 1758)

In this study we determined the levels of trace elements (zinc, copper, lead, cadmium and mercury) in three layers of bones of the hip joint (cartilage, compact bone and spongy bone) of 30 red foxes (Vulpes vulpes) from north-western Poland. Concentrations of Cu, Zn, Pb and Cd were determined by atomic absorption spectrophotometry (ICP-AES) in inductively coupled argon plasma using a Perkin-Elmer Optima 2000 DV. Determination of Hg concentration was performed by atomic absorption spectroscopy. In cartilage, compact bone and spongy bone samples from the red fox, median concentrations of the metals studied could be arranged in the following descending series: Zn > Cu > Pb > Cd > Hg, the values ranging from 142 to 0.002 mg/kg dw. There was a significant difference in Cu concentrations, among all the materials analyzed, with much more Cu found in spongy bone than in compact bone. Significant differences were also noted in the case of Hg concentrations in cartilage with compact bone and the spongy bone, and between concentrations of this metal in compact bone and spongy bone. In males, the concentration of Hg in spongy bone was greater than in females. Younger foxes had a higher concentration of this metal in cartilage than adults. The strongest synergistic relationships were observed in spongy bone between the Zn and Cu, Zn and Cd, as well as between Cu and Cd. Statistically significant antagonistic relationships were detected between zinc and lead in compact bone. In addition to monitoring studies conducted on the abiotic environment, an urgent need exists for long-term monitoring of concentrations of heavy metals with long-term effects on living organisms. An important addition is provided by biomonitoring studies on domesticated and free-living mammals, including Canidae.

Lead and calcium content in the human hip joint

Concentration of lead in bone, unlike in soft tissues, increases during the lifetime and reflects severity of exposure to this element. The main aim of the study was to determine concentrations of lead and calcium and to find possible relationship between calcium and lead in the tissues of the hip joints obtained from inhabitants of the Upper Silesian Industrial Area. We also attempted to identify factors that might affect this relationship. The samples were harvested intraoperatively during total hip replacement procedures; in most cases, the indication for the surgery was hip osteoarthritis. Concentrations of lead and calcium were measured with a Pye Unicam SP-9 acetylene-oxygen flame atomic absorption spectrometer. The highest mean concentration of lead was found in the cancellous bone from the femoral head, followed by articular cartilage, cortical bone and the intertrochanteric cancellous bone (0.75 μg/g). The smallest concentration was found in the joint capsule (0.19 μg/g). The highest mean concentration of calcium was found in cancellous bone from the femoral head, followed by cancellous bone from the intertrochanteric area, cortical bone, articular cartilage and joint capsule. The concentration of lead showed no correlation with sex. The bone concentration of calcium decreased with age. In the analysed hips, this finding was true in the cortical bone, as well as in the cancellous bone of the intertrochanteric area. Statistically significant correlation between calcium and lead was found only in the hip articular cartilage.

Effect of lead on apoptosis in cultured rat primary osteoblasts

To investigate the effect of lead exposure on apoptosis of cultured rat primary osteoblasts (ROBs), which were derived from newborn calvariae of Sprague Dawley rat. They were identified by the staining of alkaline phosphatase and mineralized matrix. The ROBs were received at 0, 20, 40 and 80 μM Pb2+ of lead acetate solution for 24 h, respectively, before being doubly marked by Annexin V-fluorescein isothiocyanate/propidium iodide. The intracellular concentration of calcium ([Ca2+]i) was detected under the laser scan confocal microscope. The activities of phosphatidylcholine-specific phospholipase C (PC-PLC) were measured and the effect of lead exposure on the expression of PC-PLC was observed by immunoblotting assay. The results showed that when compared with that of the control group, lead exposure induced an increase of [Ca2+]i of lead-treated ROBs, resulting in a significant development in apoptosis. In the meantime, a significant decline in protein level and enzymatic activities of PC-PLC were observed in a dose-dependent manner. It was concluded that lead can induce apoptosis in ROBs, and one of the mechanisms of lead-induced apoptosis may be that activating intracellular calcium stores by decreasing protein levels and enzymatic activities of PC-PLC can increase the [Ca2+]i, and consequently, the apoptotic signal pathway can be induced.

Cellular accumulation and distribution of uranium and lead in osteoblastic cells as a function of their speciation

Uranium (U) and lead (Pb) are accumulated and fixed for long periods in bone, impairing remodeling processes. Their toxicity to osteoblasts, the cells responsible for bone formation, is poorly documented. It has been previously shown that cytotoxicity and phenotypic effects of both metals on osteoblasts are highly influenced by metal speciation. Differences in sensitivity between cell types have been underlined as well. In this paper, cellular accumulation of U and Pb in cultured and primary osteoblastic cells was assessed by trace element analysis. Distribution of different species at the cell scale was investigated by electron microscopy. Internalization of both metals was shown to be correlated to cytotoxicity and population growth recovery after exposure. For each metal, the amount of metal uptake leading to 50% cell death was shown to be speciation-dependent. Scanning and transmission electron microscopy showed the formation of precipitates with phosphate in lysosomes for both metals, whose role in toxicity or cell defence remains to be clarified. Although a clear link was established between cytotoxicity and accumulation, differences in sensitivity observed in terms of speciation could not be fully explained and other studies seem necessary.