Impact of breastfeeding on the mobilization of lead from bone

To evaluate the hypothesis that lactation stimulates lead release from bone to blood, the authors analyzed breastfeeding patterns and bone lead concentrations as determinants of blood lead levels among 425 lactating women in Mexico City for 7 months after delivery (1994-1995). The authors measured in vivo patella and tibia lead concentrations at 1 month postpartum using K x-ray fluorescence. Maternal blood samples and questionnaire information were collected at delivery and at 1, 4, and 7 months postpartum. Blood lead was analyzed using graphite furnace atomic absorption spectroscopy. Mean blood lead level at delivery was 8.4 microg/dl (range: 1.8--23.4). Mean cortical and trabecular lead levels were 10.6 microg/g (range: nondetectable to 76.5) and 15.3 microg/g (range: nondetectable to 85.9), respectively, reflecting a population with elevated and diverse past and current lead exposure. The association of bone lead and breastfeeding with blood lead was estimated using generalized estimating equations. Breastfeeding practices and maternal bone lead were important predictors of blood lead level. After adjustment for bone lead and environmental exposure, women who exclusively breastfed their infants had blood lead levels that were increased by 1.4 microg/dl and women who practiced mixed feeding had levels increased by 1.0 microg/dl, in relation to those who had stopped lactation. These results support the hypothesis that lactation is directly related to the amount of lead released from bone.     

A new anthropometric phantom for calibrating in vivo measurements of stable lead in the human leg using x-ray fluorescence

A new anthropometric phantom has been developed for calibrating in vivo measurements of stable lead deposited in bone using x-ray fluorescence. The phantom reproduces the shape of the mid shaft of the adult human leg and is fabricated using polyurethanes and calcium carbonate to produce materials that exhibit the same density, energy transmission, and calcium content as cortical bone, bone marrow, and muscle. The phantom includes a removable tibia fabricated using simulants for cortical bone and bone marrow to which a precise amount of stable lead has been added to cortical bone. The formulations used in fabricating the new anthropometric phantom are much more uniform in density and composition than the conventional phantom made from Plexiglas cylinders filled with plaster-of-Paris. The energy spectrum from an x-ray fluorescence measurement of the phantom using a 109Cd source is indistinguishable from an in vivo x-ray fluorescence measurement of the human leg, demonstrating that the materials used in the phantom exhibit the same radiological properties as human tissue. Likewise, results from x-ray fluorescence measurements of the phantom exhibit the same positional dependency as the human leg and vary by approximately 36% when, for example, the phantom containing 54 ppm of stable lead in the tibia was rotated by only 15 degrees. The detection limit for a 30 min 109Cd K shell x-ray fluorescence in vivo measurement is approximately 20 ppm determined from a background measurement using the new phantom containing no added lead in the muscle, bone, or bone marrow. The new anthropometric phantom significantly improves in vivo x-ray fluorescence calibration measurements by (1) faithfully reproducing the anatomy of the human leg, (2) having components that exhibit radiological properties similar to that of human tissue, and (3) providing a realistic calibration standard that can be used for in vivo x-ray fluorescence intercomparison measurements.     

A pilot evaluation of tibia lead concentrations in Taiwan

BACKGROUND: The aims of this study were to examine some of the factors that influence tibia lead concentrations, tibia lead x-ray fluorescence measurement uncertainty and blood lead concentrations, and to compare tibia lead concentrations in Taiwanese lead workers to those observed in lead workers from other countries. METHODS: A pilot evaluation of 43 adult lead workers who underwent measurements of tibia lead and blood lead concentrations. RESULTS: Mean and maximum tibia lead concentrations were 54 microg of Pb per g of bone mineral(microg/g) and 193 microg/g, respectively. Mean and maximum blood lead concentrations were 44 microg/dl and 92 microg/dl, respectively. CONCLUSION: Past occupational control of lead exposure in Taiwan, ROC, did not prevent these workers from accumulating tibia lead concentrations greater than those in similar workers elsewhere in the world.     

X-ray fluorescence analysis of lead in teeth of urban children in situ: correlation between the tooth lead level and the concentration of blood lead and free erythroporphyrins.

The tooth lead level of 30 lead-exposed children was measured in situ using an X-ray fluorescence technique. The tooth lead concentration divided by the child's age correlated with the free erythroporphyrin (FEP) (r = 0.51) and the blood lead levels (r = 0.31). The mean tooth lead concentrations of 10 Class IV children (FEP greater than or equal to 190 micrograms/100 ml; blood lead 30-80 micrograms/ml) was 14.5 +/- 5.5 ppm/year. Reexamination of the histories of children who had been classified as Class II or III, but who had tooth lead concentrations within 1 SD of the Class IV level, indicated that many of these children could also be considered to be Class IV children. When the x-ray fluorescence technique was used to screen an urban population of 300 children, the tooth lead values indicated that 72% of the children had been exposed to low levels of environmental lead. Six percent of the children were found to have tooth lead concentrations in excess of 9 ppm/year and within 1 SD of the mean value exhibited by Class IV children. These children were considered to have a high body lead burden. The percentage of children having an elevated tooth lead level is similar to the number previously reported using exfoliated deciduous teeth.     

Lead in vertebral bone biopsies from active and retired lead workers

Samples of vertebral bone were obtained by skeletal biopsy and lead concentrations were determined by atomic absorption spectroscopy. The median level of lead in bone in 27 active lead workers was 29 micrograms/g wet weight (range 2-155), corresponding to 370 micrograms/g calcium (range 30-1,120). In 9 retired workers, the corresponding levels were 19 micrograms/g (5-76) and 250 micrograms/g calcium (60-700); in 14 reference subjects without occupational exposure, 1.3 micrograms/g (1-4) and 13 micrograms/g calcium (8-40). The bone lead content rose with time of exposure. Comparison of levels in vertebra with those in fingerbone, as measured by in vivo x-ray fluorescence in the same subjects, strongly suggested the presence of lead pools with different kinetics. The accumulation pattern, as well as the relation between levels in vertebra and fingerbone, suggests a much shorter half-time of lead in the mainly trabecular vertebral bone as compared to the mainly cortical fingerbone. Further, there was an association between vertebral and blood lead levels in the retired workers, which shows a considerable endogenous lead exposure from the skeletal pool.     

Dose reduction from loss of backscatter in superficial x-ray radiation therapy with the Pantak SXT 150 unit

Loss of backscatter has been measured for a Pantak Therapax SXT 150 superficial x-ray therapy unit. Ionisation chamber measurements at the surface were performed in solid water with and without underlying lead to confirm the applicability of previous published measurements. Measurements of loss of backscatter with and without lead allowed the effect of underlying lead to be separated from the effect of loss of backscatter. It was found that the difference between the effect of lead and that of air on surface dose is minimal for solid water phantom thickness exceeding 3 cm. Differences up to 3% in dose reduction at the surface were found between this work and previous published results with different x-ray units.     

铅作业工人血铅和氧化应激酶变化的研究

目的研究职业性铅接触者的氧化损伤,探讨血铅和氧化应激酶之间的变化关系,以探讨铅中毒的作用机制。方法采用火焰原子吸收分光光度法测定空气中的铅含量,用石墨炉原子吸收分光光度法测定血铅浓度,选择超氧化物歧化酶（SOD）和丙二醛脱氢酶（MDA）作为氧化应激损伤的效应指标,分析血铅与氧化效应指标的变化。结果共采集了车间内5个工作点的空气样品。接触组血铅浓度（244．274±124．59）μg／L,显著高于对照组（P〈0．01）;接触组SOD活性（61．27±6．97）KU／L,与对照组比较无统计学差异（P〉0．05）;接触组MDA含量（9．42±3．89）mmol／L,显著高于对照组（P〈0．01）;血清MDA含量与血铅之间存在正相关关系（r=0．3,P〈0．01）;吸烟、饮酒对SOD活性和MDA含量影响无统计学差异。结论职业性铅接触引起人体血铅升高,作业场所空气中铅浓度与血铅含量变化不一致,血铅是近期铅接触者的敏感内接触指标,且血铅浓度越高,SOD活性代偿性升高;MDA含量越高,氧化损伤越明显。     

Environmental Notes

Samples of vertebral bone were obtained by skeletal biopsy and lead concentrations were determined by atomic absorption spectroscopy. The median level of lead in bone in 27 active lead workers was 29 μg/g wet weight (range 2–155), corresponding to 370 μg/g calcium (range 30–1, 120). In 9 retired workers, the corresponding levels were 19 μg/g (5–76) and 250 μg/g calcium (60–700); in 14 reference subjects without occupational exposure, 1.3 μg/g (1–4) and 13 μg/g calcium (8–40). The bone lead content rose with time of exposure. Comparison of levels in vertebra with those in fingerbone, as measured by in vivo x-ray fluorescence in the same subjects, strongly suggested the presence of lead pools with different kinetics. The accumulation pattern, as well as the relation between levels in vertebra and fingerbone, suggests a much shorter half-time of lead in the mainly trabecular vertebral bone as compared to the mainly cortical fingerbone. Further, there was an association between vertebral and blood lead levels in the retired workers, which shows a considerable endogenous lead exposure from the skeletal pool.     

The determination of lead in paint films with a portable isotope fluorescence analyser

Summary The application of x-ray fluorescence to the determination of the lead content of paint films was evaluated using a portable isotope fluorescence analyser. Accurate determinations were achieved in the laboratory using prepared films in which the lead was dispersed through matrices of constant composition in a single layer. The presence of lead could be masked by overlying paint films of low lead content and was almost obscured by an overlying paint film of 77 mg/cm². The results for domestic paint films correlated with chemical analyses but the confidence limits were too widely separated to allow application of this technique to lead screening programs. The field results probably reflect non-homogeneity of domestic paint films.Wellcome Senior Research Fellow in Clinical Science.     

Relationship of lead in drinking water to bone lead levels twenty years later in Boston men: the Normative Aging Study.

Tap water in a city like Boston, which has old houses containing lead plumbing, is known to be a significant source of potential lead exposure. Bone lead levels integrate exposure over many years, and in vivo bone lead measurements have recently become possible with the advent of K x-ray fluorescence instruments. Thus we examined the relationship between first morning tap-water lead levels measured in homes in the 1970s and levels of lead in bone measured in the 1990s among middle-aged to elderly men who lived in those homes. We studied 129 participants in the Normative Aging Study who had lead measured in their homes' tap water in 1976 and 1977 by graphite furnace-atomic absorption spectrophotometry. From 1991 to 1995, the same subjects had blood lead levels measured by graphite furnace-atomic absorption spectroscopy and tibia and patella bone lead levels measured by K x-ray fluorescence. We ran multivariate linear regression models predicting bone lead levels that adjusted for factors which had previously been linked with this outcome in the Normative Aging Study (age, pack-years of smoking, and educational level). Among subjects who lived in houses with > or = 50 micrograms lead/liter of first morning tap water representing water that had been standing overnight in the plumbing in 1976 and 1977, those who reported medium or high levels of tap-water ingestion (> or = 1 glass/day) had progressively higher patella lead levels than did those with low levels of ingestion (< 1 glass/day). No such relationship was found among subjects who lived in houses with < 50 micrograms lead/liter of first morning tap water in 1976 and 1977. We conclude that ingestion of lead-contaminated tap water is an important predictor of elevated bone lead levels later in life.     

Sensitivity of in vivo X-ray fluorescence determination of skeletal lead stores

Eighteen patients with known past occupational lead exposure underwent parenteral diagnostic chelation with ethylenediaminetetraacetic acid and x-ray fluorescent determination of in vivo skeletal lead stores at the distal styloid process of the ulna and at the temporal base bone using a cobalt 57 source and measuring lead Ka x-rays. X-ray fluorescent lead measurements in both locations correlated with results of diagnostic chelation. Using a post-chelation urinary excretion of greater than 600 micrograms lead/24 h as the definition of "high-" lead stores, sensitivity of x-ray fluorescence at the wrist and temple was 56% and 39%, respectively.     

工作场所空气中铅及其化合物的氢化物发生-原子荧光光谱测定法

目的建立氢化物发生原子荧光光谱法测定空气中铅及其化合物的方法。方法用微孔滤膜采集空气样品,经高氯酸-硝酸（1＋9）加热消解后,以去离子水定容,通过氢化物原子荧光光谱法测定铅及其化合物的含量。结果该方法线性范围为0-160 ng/ml,检出限为0.1 ng/ml,RSD为0.56%-2.17%,相对误差为0.47%-1.30%。结论采用盐酸浓度1%（体积分数）,铁氰化钾浓度0.8%（质量浓度）,氢氧化钠浓度0.36%（质量浓度）,反应液pH值在8、9之间,荧光强度稳定。该法精密度和准确度高。测定标准物质结果在控制限范围内,该方法可以用于测定工作场所空气中铅及其化合物。     

Cumulative lead exposure and prospective change in cognition among elderly men: the VA Normative Aging Study

Lead exposure has been found to affect cognitive function in several different populations. Whether chronic low-level environmental exposure to lead results in cognitive decline among adults has not been examined. The authors assessed the relation between biomarkers of lead exposure and change in Mini-Mental State Examination (MMSE) scores in the Normative Aging Study, a cohort of elderly US men. Bone lead was measured with K-shell x-ray fluorescence. A total of 466 men aged 67.4 (standard deviation, 6.6) years took the MMSE on two occasions that were an average of 3.5 (standard deviation, 1.1) years apart during the period 1993-2001 and had bone lead concentrations measured during the period 1991-2002. A one-interquartile range (20 microg/g of bone mineral) higher patella bone lead concentration was associated with a change in MMSE score of -0.24 (95% confidence interval: -0.44, -0.05) after adjustment for age, education, smoking, alcohol intake, and time between MMSE tests. This effect is approximately equivalent to that of aging 5 years in relation to the baseline MMSE score in study data. The association with tibia lead was weaker and that with blood lead was absent. The data suggest that higher patella bone lead levels, a marker of mobilizable accumulated lead burden, are associated with a steeper decline over time in performance on the MMSE test among nonoccupationally exposed elderly men.     

冻干牛血中硒成分分析标准物质的研制

牛血样品通过低温冷冻、解冻及离心处理,除去细胞碎片后分成2份,1份为低水平,另1份加入Se~(+4)(高水平)。2份样品分别以2ml/瓶的量分装在棕色瓶中,冷冻干燥,辐射灭菌,最后于0℃以下保存。用荧光分光光度法测其均匀性与稳定性。结果本标准物质至少可以稳定1年。采用多个实验室多种方法确定的标准值为:低水平:(99.9±6.9)μg/L,高水平:(981±42)μg/L。     

Lead concentrations of enamel and dentine of deciduous teeth of children from two Finnish towns

The proton-induced x-ray emission method was used to analyze lead concentrations in enamel and dentine of deciduous teeth of 105 6- and 9-yr-old children living in two Finnish towns. Helsinki, the capital city, was assumed to represent high lead exposure and Kuopio, a country town in the middle of Finland, low or moderate lead exposure. In all but two teeth the enamel contained higher lead concentrations than dentine. The individual enamel-dentine lead concentration ratio was not stable but varied greatly. The median dentine lead concentration for 9-yr-old children in Helsinki and Kuopio was 2.0 ppm and 2.9 ppm, respectively, and for 6-yr-old children was 2.5 ppm and 2.7 ppm, respectively. The enamel lead concentrations found in 9-yr-olds in Helsinki and Kuopio were 4.2 and 4.5 ppm, and in 6-yr-olds were 9.1 and 4.4 ppm, respectively. The results reveal low or moderate lead concentrations. Nevertheless, a twofold and statistically significant (P less than .01) increase was found in the enamel of Helsinki children born in 1974 compared with those born in 1971.     

Lead exposure in a ship overhaul facility during paint removal

Lead exposures from paint sanding and chipping during ship overhaul were evaluated. Several hundred workers were included in the study. Lead concentrations in 275 bulk paint samples ranged from 0.03% to 17.0% with a 0.25% geometric mean. The geometric mean air lead concentration was 61.0 micrograms/m3 when these paints were sanded and 2.4 micrograms/m3 when they were chipped. Air lead concentrations exceeded the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) when paints containing as little as 0.2% lead were sanded but did not exceed the PEL or the action level when paints containing up to 6.0% lead were chipped. Poor correlation was found between paint lead contents and air lead concentrations for sanding (r = -0.27) and for chipping (r = 0.44). Similarly, poor correlation was found between air lead concentrations and blood lead levels for sanding (r = -0.14) and chipping (r = 0.24). Despite higher air lead concentrations, sanders' blood lead levels were not elevated compared with chippers and were only slightly elevated compared with non-lead workers. An extensive blood monitoring program was found to be particularly effective in assessing lead exposures and uptake while air lead monitoring was of limited value because of the high variability in air lead concentrations and in the nature of the sanding and chipping work during the overhaul. Lead-worker training was felt to be a particularly effective control measure. Blood samples collected toward the end of the overhaul revealed that blood lead and zinc protoporphyrin levels were not rising as the overhaul progressed and neared completion.     

Determination of toxic metals in blood by x-ray fluorescence spectrometry.

An application of X-ray fluorescence spectrometry for the analysis of various toxic metals (lead, cadmium, manganese, chromium, nickel, vanadium) in whole blood was studied, and two techniques for sample preparation (vacuum drying and nitric acid combustion) were compared. The acid combustion method appeared to be superior on the basis of the accuracy and precision of the determinations. The tungsten-target X-ray tube was suitable for determining manganese, nickel, and vanadium, the lowest limits of detection being 0.021 mug/ml, 0.035 mug/ml and 0.017 mug/ml, respectively, and the precisions being between 4.25 and 6.92%. The sensitivity and reproducibility for lead, cadmium, and chromium were unsatisfactory. A comparison between the recoveries of X-ray fluorescence and atomic absorption analyses demonstrated that the X-ray method is suitable for determining manganese, vandium, nickel, cadmium, and lead. The poor sensitivity of the X-ray method, however, restricts its practical use. For vandium the results obtained by X-ray fluorescence were superior to those measured by a colorimetric method. No significant differences were observed between the results of single component and multicomponent analyses at the metal concentrations usual in physiological and toxicological cases.     

Application of ultraviolet spectrophotometry to estimate occupational exposure to airborne polyaromatic compounds in asphalt pavers

An ultraviolet (UV) spectrophotometric procedure was devised for the determination of polycyclic aromatic compound-oriented organic soluble matter in vapors and particulate collected from emissions of hot asphalt mix. Ultrasonic extraction was carried out with acetonitrile, followed by UV measurements at 254 nm. Polycyclic aromatic compounds (PACs) in volatile and particulate fraction were quantified as phenanthrene or benzo[k]fluoranthene equivalents. A comparison between UV and high-pressure liquid chromatography with fluorescence detection showed that PACs were one to three orders of magnitude higher than the sum of 15 priority polycyclic aromatic hydrocarbons (PAHs); still, significant correlations were found between volatile or particulate PACs and, respectively, total volatile or particulate PAHs. Moreover, in the particulate phase, PACs correlated with total particulate matter quantified by gravimetry. The proposed procedure was employed in a field study for monitoring personal exposure to asphalt emissions of workers engaged in road construction. Observed levels of acetonitrile-soluble PACs in air samples were very low (2-20 microg/m3); however, asphalt pavers were exposed to significantly higher concentrations of volatile PACs than construction workers (geometric mean, 5.9 microg/m3 vs. 4.1 microg/m3). This method for estimating the global content of volatile or particulate PACs in air samples satisfies our requirements of simplicity and is suitable for conducting an initial screening to assess exposure to airborne polyaromatic organics in asphalt pavers.     

二氧化硫吸入对小鼠肺和心组织DNA-蛋白质交联作用的影响

[目的]研究二氧化硫（SO2）吸入致小鼠肺、心组织蛋白质氧化损伤和对DNA-蛋白质交联（DPC）率的影响.[方法]分别用浓度为14、28、56mg／m^3的SO2气体对小鼠动态染毒7d（每天6h）,对照组小鼠在同样饲养条件下吸入新鲜空气。用2,4．二硝基苯肼（DNPH）比色法测定蛋白质羰基（PCO）含量,用KCl-SDS法测定DPC率。[结果]SO2各染毒浓度组与对照组相比,均可致小鼠肺、心PCO含量和DPC率升高。雌性小鼠SO2染毒浓度与肺、心PCO含量的回归方程分别为：y=0．1744x＋4．192（R^2=0．9998）,y=0．0420x＋3．896（R^2=0．9763）;雄性小鼠分别为：y=0．0441x＋4．204（R^2=0．9945）,y=0．1553x＋4．488（R^2=0．9883）,均呈现明显的剂量．效应关系。雌性小鼠SO2染毒浓度与肺、心DPC率回归方程分别为：y=0．0395x＋1．404（R^2=0．9913）,y=0．0121x＋1．614（R^2=0．9902）;雄性小鼠分别为：y=0．0132x＋1．616（R^2=0．9821）,y=0．0329x＋1．45（R^2=0．9922）,同样呈现明显的剂量-效应关系。[结论]SO2吸入可致小鼠肺、心PCO含量和DPC率呈剂量依赖性升高。随着SO2浓度的增加,对肺、心蛋白质的氧化损伤加剧,DPC率升高。吸入同浓度SO2小鼠的肺、心PCO含量和DPC率结果表明,对肺的损伤远大于心。     

三氯硫磷车间卫生学调查

目的：为了研制车间空气中三氯硫磷的卫生标准。方法：对三氯硫磷生产车间进行了调查考核,在三氯硫磷车间采样共110个,对59名接触工人和60名对照组工人进行体验。结果：车间空气中三氯硫磷浓度范围0．086－2．147mg/m^3,两年平均浓度0．477mg/m^3。与对照组相比,作业工人鼻炎、咽喉炎发生率明显增高,结合我国国情,参照国外卫生标准,建议车间空气中三氯硫磷的最高容许浓度和时间加权平均浓度分别为0．5mg/m^3和0．3mg/m^3。