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PubMed1977

Relation between quantities of lead ingested and health effects of lead in humans.

Major metabolic effects of lead are briefly reviewed and available data on quantitative relationships between lead ingestion and development of toxicity in adults and children are discussed. Levels of lead ingestion producing clinical toxicity in adults are compared with normal levels of exposure. For children, comparison of levels of lead ingestion and quantities of lead producing toxic effects is not currently possible, as information on levels of lead producing clinical toxicity appears to be highly variable on the basis of the small amount of data available. However, recommendations on tolerable levels of lead exposure for childrne are proposed, based on estimates of lead exposure for children having normal and elevated body burdens of lead.

Child, Preschool↗
PubMed1996

Evidence of undue lead exposure in Cape Town before the advent of leaded petrol.

Lead concentrations were determined in the exhumed teeth of 28 people who lived in the Cape Town area before the combustion of leaded petrol (i.e. before 1922). The lead content of circumpulpal dentine was analysed by graphite-furnace atomic absorption spectrometry. The mean lead level in the dentine of primary teeth (N = 6) was 109 micrograms/g, while that in secondary teeth (N = 22) was 315 micrograms/g. The current lead levels in circumpulpal dentine of Cape Town residents are reported to be 74 micrograms/g and 16 micrograms/g for primary and secondary teeth respectively. It was found that lead pollution of the human body during the period 1812-1922 in the Cape Town area was substantially higher than at present. We conclude that the main reasons for this were the widespread use of lead piping and soldering of water tanks, which resulted in a higher incidence of lead poisoning than that attributable to leaded petrol.

Adolescent↗
PubMedDate not supplied

Succimer treatment during ongoing lead exposure reduces tissue lead in suckling rats.

There is a concern that oral treatment with succimer (meso-2, 3-dimercaptosuccinic acid, DMSA) can promote gastrointestinal lead absorption if not performed in a lead-safe environment. The scope of our investigation was to evaluate the efficacy of oral DMSA treatment during oral lead exposure on tissue lead in suckling rats. Six-day-old Wistar rats of both genders were divided into two groups-untreated (Pb) and treated (Pb + DMSA)-with 10 animals per group. Lead (as acetate) was given orally at a dose of 2 mg kg(-1) body weight day(-1) for eight consecutive days (total dose 16 mg kg(-1), i.e. 0.08 mmol kg(-1)). During this period the treated group received a daily dose of 0.5 mmol DMSA kg(-1) body weight p.o. six times on days 1-3 and 6-8 of the experiment (total dose 3 mmol kg(-1)). Tissue lead was determined by means of atomic absorption spectrometry. The DMSA efficiently reduced the lead concentration in the analysed tissues (carcass, liver, kidneys and brain) by approximately 50% compared with untreated controls. The pups' growth and organ weights were not affected. In conclusion, our results indicate that DMSA is an efficient oral lead chelator in sucklings even if challenged with ongoing lead exposure.

Animals↗
PubMed1999

Chelated lead in relation to lead in bone and ALAD genotype.

In order to assess whether lead in bone is available for chelation by 2,3 meso-dimercaptosuccinic acid (DMSA), 21 workers (10 active and 11 retired) from a secondary lead smeltery were studied. A morning urine sample was obtained from all participants, followed by ingestion of 10 mg per kg body weight of the chelating agent DMSA. All urine produced during the following 24 h was collected in consecutive 6- and 18-h portions. Concentrations of lead in blood (B-Pb) and urine were determined by flameless atomic absorption spectrometry (AAS), in plasma (P-Pb) by inductively coupled plasma mass spectrometry (ICP-MS), and in finger bone (Bone-Pb) by K X-ray fluorescence technique (XRF). DMSA-chelatable lead excreted in the 24-h portion correlated well with the excretion in the 6-h portion (U-Pb6h; rs=0.95; P<0.001). U-Pb6h showed a non-linear relationship to B-Pb (rs=0.84; P<0.001) and linear relationships to P-Pb (rs=0. 91; P<0.001) and lead in morning urine (rs=0.95; P<0.001). In active workers, but not in retired ones, P-Pb and U-Pb6h showed some relationship to Bone-Pb. In alternative multiple regression models B-Pb or P-Pb were both significant predictors of U-Pb6h, while Bone-Pb did not significantly improve the models. It can, thus, be concluded that DMSA-chelatable lead mainly reflects lead concentrations in blood, soft tissues, and possibly also trabecular bone. It is not a good index of total body burden and long-term exposure. For such estimations cortical Bone-Pb is more valid, as it contains the major fraction of long-term accumulated lead in the body. Further, the mobilization test did not give better information than measurements of lead levels in blood, plasma, or urine without chelation.

Age Factors↗
PubMed2001

Seasonal variation in bone lead contribution to blood lead during pregnancy.

Population blood lead level (PbB) often shows seasonal variation, frequently being higher in summer and lower in winter. As vitamin D metabolites also show seasonal variability, and the metabolites are associated with bone metabolism, some authors have posited a role for bone lead release in seasonal PbB changes. We made third trimester and postdelivery PbB measurements on 414 immigrant women (98% Latina) in Los Angeles. We measured in vivo tibia and calcaneus (heel) lead concentration postdelivery via K-shell X-ray fluorescence. We saw evidence of seasonal variation in prenatal PbB, but not postnatal PbB. PbB was highest in spring and lowest in autumn. Tibia lead concentration was associated with prenatal PbB, as reported before. The contribution of tibia lead to prenatal PbB varied seasonally, with the greatest contribution occurring in the winter quarter and the least in the summer quarter. The temporal pattern of bone lead contribution to PbB follows the seasonal alteration of insolation. There was no seasonal component in prenatal PbB associated with calcaneus lead, nor were there seasonal variations in either calcaneus or tibia lead contributions to postnatal PbB. Bone turnover in the third trimester of pregnancy may be higher in winter months than in summer months, resulting in greater fetal lead exposure in spring than at other times of the year.

Bone and Bones↗
PubMed1989

Distribution of lead in the cerebellum of suckling rats following low and high dose lead exposure. A micro-PIXE analysis.

The distribution of lead in the cerebellum of suckling Sprague-Dawley rats was examined using a nuclear microprobe for elemental mapping of tissue sections (particle-induced X-ray emission, 3-microns beam of 2.5 MeV protons; micro-PIXE). The rats were injected intraperitoneally with a lead-containing vehicle or vehicle only from ages 1 to 14 days. The calculated doses were 7.8 (low-dose) and 15.6 (high-dose) micrograms lead/g body weight. The rats were killed at 20 days of age. The vascular system was rinsed quickly with 0.15 M ammonium acetate to obtain determinations of intra-parenchymal lead with minimal influence of lead bound to erythrocytes and plasma proteins. Brains were frozen in propane/propylene in liquid nitrogen. Cryostat sections, 15 microns thick, were air dried on formvar coats that covered a hole, 15 mm in diameter, in a plastic disc, and were used for lead analysis by micro-PIXE. Very low concentrations of lead were found in the brain of controls. Lead levels in homogenates from cerebrum and cerebellum measured by atomic absorption spectrometry (AAS) were: low-dose 1.2-2.2 micrograms/g wet weight and high-dose 1.4-2.4 micrograms/g wet weight. The lead levels measured with the micro-PIXE method were in good agreement with the levels found with AAS. Lead was present in the cerebellar white matter in two to three times higher amounts than in the cortical grey (low-dose white matter 11-18 micrograms/g dry weight, grey matter 2.0-5.5 micrograms/g dry weight). This was true for both low and high dose exposed rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

A composite index of lead effects. Comparative study of four occupational groups with different levels of lead absorption.

Biological indicators of lead effects on the central nervous system (CNS), hematogenous bone marrow, and kidney function as measured by performance tests, hemoglobin (Hgb) and BUN levels respectively were combined in an integrative index (INDEX). Such an index was calculated by removing age effects in measures of performance and kidney function and then transforming all the variables to Z (standard) units. The relationships between INDEX and biological indicators of lead exposure and absorption (Pb-B and ZPP) were studied in four groups: 191 non-lead exposed males (control group), 169 copper smelter workers, 133 autobody shop workers and 87 secondary lead smelter workers. We found that: 1) the magnitude of the correlation coefficient between INDEX and ZPP was much higher than were the correlations between the various single indicators of lead effects (performance test scores, Hgb, and BUN); and 2) the magnitude of the correlation coefficients was related to the degree of lead exposure and absorption (as reflected in distribution patterns of Pb-B and ZPP) in each group. The concept of an integrative index of biological effects of lead is important for the evaluation of early manifestations of lead toxicity and also for the correct assessment of adverse health effects of lesser intensity than those characteristic for the classic picture of overt lead poisoning.

Adult↗
PubMed1983

Lead toxicity in the pregnant rat. I. The effect of high-level lead on delta-aminolevulinic acid dehydratase activity in maternal and fetal blood or tissues.

A study was made of the effects of administration of 500 ppm of lead in the drinking water of pregnant rats and their fetuses. The delta-aminolevulinic acid dehydratase (ALAD) activity of erythrocytes in lead-treated dams showed 82.7 and 74.8% inhibition on Days 18 and 21 of pregnancy, respectively. ALAD activity of erythrocytes in the lead-treated fetuses showed 59.7 and 73.0% inhibition on Days 18 and 21 of pregnancy, respectively. ALAD activities in the liver and placenta were not significantly different between the lead-treated and control animals. The lead concentrations of blood and liver in the lead-treated dams and fetuses were higher than in the control animals, but the lead level of amniotic fluid was not significantly different from that of the control animals. Significant correlations were observed between maternal and fetal blood lead, liver lead, and erythrocyte ALAD, but there was no significant correlation between maternal and fetal liver ALAD.

Animals↗
PubMed1993

Effect of the reduction of petrol lead on the blood lead levels of South Africans.

Lead has no metabolic role in the human body and its presence is associated with various toxic effects. Several countries have responded to this health hazard reducing petrol lead additives or entirely eliminating them. Studies have shown that there has been a resultant fall in blood lead levels of the particular populations. This study reports on the progressive decline in blood lead levels of South Africans during the period 1984-1990 which coincided with a stepwise reduction in petrol lead additives from 0.8 g/l to 0.4 g/l. During this period the blood lead levels of Cape Town city dwellers decreased significantly (P < 0.01) from 9.7 micrograms/dl to 7.2 micrograms/dl. This blood lead level compares favourably with that of other more industrialized countries with less lead in their petrol. Therefore, the authors question the need for further reduction of petrol lead content bearing in mind the considerable financial burden that such a step will entail and the dubious health advantage that may be gained.

Adult↗
PubMed2003

Isotopic evidence of the persistent dominance of blood lead concentrations by previous gasoline lead emissions in Yerevan, Armenia.

Recent (1999) blood lead (PbB) isotopic compositions (n=17) of males and females in Yerevan, Armenia, indicate that previous emissions of leaded gasoline still dominate the populace's PbB concentrations 2 years after the country's apparent de facto elimination of leaded gasoline in Armenia. The range of PbB isotopic compositions overlaps those of air and near-road surface soils in Yerevan, and the averages of those isotopic compositions in blood (208Pb/207Pb=2.442; 206Pb/207Pb=1.158) and near-road soils (208Pb/207Pb=2.442; 206Pb/207Pb=1.157) are indistinguishable. Using a proxy for historic leaded-gasoline emissions in Armenia, these analyses suggest that leaded gasoline was, is, and will continue to be via the resuspension of lead-bound soils contaminated by previous depositions from leaded-gasoline emissions, a relatively important source of industrial lead in both Yerevan's atmosphere and its populace. However, the level of lead contamination in the Armenian populace, based on the PbB geometric mean of 4.0microg/dL (n=49) measured in this initial survey, appears to be much lower than recently proposed by the Armenian Ministry of Nature Protection.

Adolescent↗
PubMed2003

A study of pediatric blood lead levels in a lead mining area in South Africa.

This study aimed to determine the blood lead distributions among young children in the lead mining town of Aggeneys in South Africa's Northern Cape Province, and in the comparison community of Pella, about 40 Km away. A further objective of the study was to explore factors associated with elevated blood lead levels. Children aged between 6 and 10 years (average age, 8 years) were studied, 86 from Aggeneys and 68 from Pella. The results showed that blood lead levels among the children of Aggeneys averaged around 16 microg/dL, while in Pella the mean blood lead level equaled 13 microg/dL. Overall, children with raised blood lead levels performed less well at school relative to other children. Within Aggeneys, fathers of "high" lead children tended to shower at work rather than at home, which may have been insufficient to prevent lead from being transported into the home. In conclusion, more stringent environmental control measures are needed, as well as stricter personal hygiene measures, to prevent childhood lead exposure in the mining community.

Child↗
PubMed1992

Lead sources to California sea otters: industrial inputs circumvent natural lead biodepletion mechanisms.

Lead levels (as Pb/Ca atom ratios) and stable isotopic compositions were measured in teeth of preindustrial and contemporary California sea otters (Enhydra lutris) to determine if postindustrial changes had occurred in the magnitude and source of accumulated lead. Lead/calcium atom ratios (means +/- SD) in teeth of some contemporary animals (110 +/- 37 x 10(-8), n = 3) were significantly elevated compared to levels in other contemporary (13 +/- 6.0 x 10(-8), n = 4) and preindustrial (7.3 +/- 3.9 x 10(-8), n = 6) otters. The isotopic ratios (means +/- 2 sigma means) revealed a change in the sources of accumulated leads, from natural continental-derived leads in the preindustrial animals (207Pb/206Pb = 0.820 +/- 0.002) to industrial sources dominated by aerosol leads in the contemporary otters (207Pb/206Pb = 0.836 +/- 0.003). The one exception was a contemporary Monterey Bay animal (207Pb/206Pb = 0.853), who contained lead derived from an industrial waste lead deposit in Monterery Harbor. These data establish distinguishable sources of lead assimilated by sea otters, and indicate that elevated exposures to some animals circumvented the natural biodepletion of lead through marine trophic pathways.

Age Factors↗
PubMed2000

Proteoglycans synthesized by cultured bovine aortic smooth muscle cells after exposure to lead: lead selectively inhibits the synthesis of versican, a large chondroitin sulfate proteoglycan.

To investigate the effects of lead on the formation of extracellular matrix in the vascular wall, we characterized proteoglycans synthesized by cultured vascular smooth muscle cells after exposure to the metal by biochemical techniques. Confluent cultures of bovine aortic smooth muscle cells were metabolically labeled with [(35)S]sulfate or [(35)S]methionine/cysteine in the presence of lead nitrate. The amount of glycosaminoglycans (GAGs) was evaluated by the incorporation of [(35)S]sulfate into GAGs by the cetylpyridinium chloride precipitation method. The labeled proteoglycans were characterized by DEAE-Sephacel ion exchange chromatography and Sepharose CL-2B molecular sieve chromatography. The GAG M(r) and composition were analyzed by Sepharose CL-6B chromatography, and the core protein M(r) was analyzed by SDS-polyacrylamide gel electrophoresis, before and after digestion with papain or chondroitin ABC lyase. Lead significantly decreased the [(35)S]sulfate incorporation into GAGs accumulated in the cell layer and the conditioned medium. [(35)S]Sulfate-labeled proteoglycans obtained from the cell layer and the conditioned medium were separated into three peaks on DEAE-Sephacel chromatography and only the peak with the highest charge density was decreased by lead. The highly charged peak was eluted near the void volume on Sepharose CL-2B molecular sieve chromatography and sensitive to chondroitin ABC lyase on Sepharose CL-6B chromatography, indicating that lead selectively inhibits the synthesis of large and highly charged chondroitin/dermatan sulfate proteoglycans (CS/DSPGs). However, the size of chondroitin/dermatan sulfate chains of the CS/DSPGs was M(r) approximately 47000 in both the control and lead-treated cultures. On the other hand, lead decreased the accumulation of a large CS/DSPG with a core protein of approximately 450 kDa in the cell layer and the conditioned medium; the core protein was identified as versican core by Western blot analysis. It is therefore suggested that lead inhibits the synthesis of the versican core protein in vascular smooth muscle cells without a change in length of chondroitin/dermatan sulfate side chains. As a result, versican-poor extracellular matrix would be induced by lead in vascular smooth muscle cells.

Animals↗
PubMed2004

Modeling lead input and output in soils using lead isotopic geochemistry.

The aim of this study is to model downward migration of lead from the plow layer of an experimental site located in Versailles (about 15 km southwest of Paris, France). Since 1928, samples have been collected annually from the topsoil of three control plots maintained in bare fallow. Thirty samples from 10 different years were analyzed for their lead and scandium contents and lead isotopic compositions. The fluxes are simple because of the well-controlled experimental conditions in Versailles: only one output flux, described as a first-order differential function of the anthropogenic lead pool, was taken into account; the inputs were exclusively ascribed to atmospheric deposition. The combination of concentration and isotopic data allows the rate of migration from the plowed topsoil to the underlying horizon and, to a lesser extent, the atmospheric fluxes to be assessed. Both results are in good agreement with the sparse data available. Indeed, the post-depositional migration of lead appears negligible at the human time scale: less than 0.1% of the potentially mobile lead pool migrates downward, out of the first 25 cm of the soil, each year. Assuming future lead inputs equal to 0, at least 700 yr would be required to halve the amount of accumulated lead pollution. Such a low migration rate is compatible with the persistence of a major anthropogenic lead pool deposited before 1928. Knowledge of pollution history seems therefore to be of primary importance.

Agriculture↗
PubMed2005

Estimation of fugitive lead emission rates from secondary lead facilities using hierarchical Bayesian models.

Fugitive emissions from secondary lead recovery facilities are difficult to estimate and can vary significantly from site to site. A methodology is presented for estimating fugitive emissions using back inference from observed ambient concentrations at nearby monitors, in conjunction with an atmospheric transport and dispersion model. Observed concentrations are regressed against unit source-monitor transfer terms computed by the model, and the fitted parameters of the regression equation include the background ambient lead concentration, the fugitive lead emission rate, and (when stack emissions are assumed to be unknown) the stack lead emission rate. The methodology is implemented at three sites, one each in Florida, Texas, and New York. A hierarchical Bayesian method is used to estimate the parameters of the model, allowing inferences to be made for both site-specific values and multisite (national) distributions of fugitive emissions and background concentrations. Informed prior distributions must be specified for the background lead concentrations and for fugitive and stack emission rates in order to obtain stable estimates. Sensitivity analyses with alternative priors indicate that posterior estimates of background concentrations and fugitive emission rates are relatively insensitive to the assumed priors, although estimated stack emission rates can vary with alternative priors, especially for the New York facility, where the stack emission rate is highly uncertain and poorly resolved by the model. The fugitive lead emission rates estimated for the sites are comparable to, or in some cases (especially Texas and New York) likely larger than the stack emissions that are determined for these facilities. An aggregate predictive distribution is derived for the average fugitive lead emission rate from secondary lead smelting facilities, with a median value of 9.2 x 10(-7) g Pb/m2/sec, and a 90% credible interval from 2.1 x 10(-7)-5.3 x 10(-6) g Pb/m2/sec. This wide range reflects both the variation in fugitive lead emissions from site to site and the high degree of uncertainty resulting from an estimate based on only a very small sample of sites. As such, the primary contribution of this study is methodological, demonstrating how information from multiple sites can be combined and considered simultaneously for the estimation of fugitive emission rates, but recognizing that additional sites must be included to obtain a more precise characterization.

Air Pollutants↗
PubMed2006

Chronicling a century of lead pollution in Mexico: stable lead isotopic composition analyses of dated sediment cores.

Analyses of lead isotopic compositions (204Pb, 206Pb, 207Pb, and 208Pb) of dated sediment cores from two coastal estuaries and two inland lakes chronicle the predominance of industrial lead emissions in Mexico over the past century. These isotopic ratios exhibit a shift in composition from the turn of the previous century (1900) that corresponds with measurable increases (from 2- to 10-fold) in lead concentrations in the cores above their baseline values (3-22 microg/g)--both changes are consistent with the development of Mexican lead production for export and the manufacture of tetraethyl lead additives for Mexican gasolines. While subsequent changes in lead concentrations in the cores correspond with calculated emissions from the combustion of leaded gasoline in Mexico, isotopic compositions of the cores remain relatively constant throughout most of the 1900s (e.g., 206Pb/207Pb = 1.200 +/- 0.003; 208Pb/207Pb = 2.463 +/- 0.004). That isotopic constancy is attributed to the widespread pollution from lead production in Mexico and the dispersion of some of that lead used as an additive in Mexican gasolines.

Environmental Monitoring↗
PubMed1975

Epidemic lead absorption near an ore smelter. The role of particulate lead.

Blood lead levels were determined on a random sample of persons in all age groups living near a lead-emitting smelter in El Paso, Texas. A blood lead level of greater than or equal to 40 mug per 100 ml, which was considered indicative of undue lead absorption, was found in 53 per cent of the children one to nine years old living within 1.6 km of the smelter and in 18 per cent of those from 1.6 to 6.6 km; beyond that distance in older persons levels were lower. Children in the first 1.6 km with blood levels of greater than or equal to mug per 100 ml were exposed to 3.1 times as much lead in dust as children there with lower blood values (6447 vs 2067 ppm). There was also airborne lead exposure (8 to 10 mug per cubic meter, annual mean). Paint, water, food, and pottery were less important as sources. The data suggest that particulate lead in dust and air accounted for most of the lead absorption in El Paso children. The smelter was the principal source of this lead, especially within 1.6km of itself.

Adult↗
PubMedDate not supplied

Lead reduction of petrol and blood lead concentrations of athletes.

In 1984, it was determined that the blood of long-distance runners in South Africa contained unacceptably high concentrations of lead. Subsequently, the petrol lead level in South Africa was reduced from 0.8 g/l to 0.4 g/l. In view of this reduction, a followup investigation of its effect on the blood lead concentration of South African runners was undertaken. Blood lead samples were analyzed by graphite furnace atomic absorption spectrophotometry. The mean values of blood lead concentrations dropped from 52 to 13 micrograms/dl and from 20 to 8.5 micrograms/dl for the urban and rural trainers, respectively. A highly significant decrease in blood lead levels was found and was mainly attributable to the reduction in the petrol lead levels. The blood lead results for rural trainers indicated that there still exists a certain degree of lead pollution in athletes from nonremote areas.

Adult↗