Body Burden Of Lead Research Articles

Lead burden in prehistorical, historical and modern human bones

From archaeological findings it is well known that, in the past, lead has been intensively used by man. The toxicological aspects of increased lead exposure are perceived onward from the 2nd century B.C.; between 90 and 95% of the absorbed lead is stored in bone. Therefore measurement of lead levels in ancient bones seemed to be a suitable approach to determine the real body burdens at different periods of time and to compare the results with the present situation. Approximately 650 bones from a total of 332 individuals of the following epochs were analysed: prehistorical Peruvians, prehistorical Teutons, late Romans, Middle Age (further differentiated), present time Germans. The determination of lead was made by graphite furnace atomic absorption spectroscopy. The possibilities of postmortem alterations of lead concentrations were thoroughly investigated. For this purpose the dependence of the lead concentrations found were compared with the age, sex, type of bone, conditions of preservation and storage. It is concluded that only the series “prehistorical Teutons” may be exposed to levels which are relevant to postmortem changes. The lead concentration of the group “prehistorical Peruvians” can be taken as the “physiological zero point”; from this culture no use of lead is known. The present body burden for lead in Germany is about 20 times greater than this “physiological zero point”. In the late Roman epoch, but also in the Middle Age the lead concentrations and body burden was 41–47% of that today. Only at the time after the Barbarian Invasions did this value drop to 13% as a result of a lower living standard. The different sources of lead exposure during Roman times, the Middle Age and today are discussed.

Assessment of the body burden of chelatable lead: a model and its application to lead workers.

A hypothetical model was introduced to estimate the body burden of chelatable lead from the mobilisation yield of lead by calcium disodium ethylenediamine tetra-acetate (CaEDTA). It was estimated that, on average, 14 and 19% of the body burden was mobilised into the urine during the 24 hours after an injection of 53.4 mumol (20 mg) and 107 mumol (40 mg) CaEDTA per kg bodyweight, respectively. The body burden of chelatable lead ranged from 4 mumol (0.8 mg) to 120 mumol (24.9 mg) (mean 37 mumol (7.7 mg) in lead workers with blood lead concentrations of 0.3-2.9 mumol/kg (6-60 microgram/100 g) (mean 1.4 mumol/kg (29 microgram/100 g)). There were linear relationships between blood lead concentrations and body burden of chelatable lead on a log scale.

Increased Lead Burdens and Trace-Mineral Status in Mentally Retarded Children

Recent research has suggested that children with a moderate increase in body burden of lead, although clinically asymptomatic, may be subject to impaired mental development. This study investigated the relationship between low-level lead absorption and mild and borderline mental retardation, and evaluated the relationships among nutrient minerals, heavy metals, and increased lead burdens. Hair trace-mineral concentrations were compared in a group of retarded children with a non-retarded control group. The retarded group had significantly raised hair-lead concentrations. There were also differences in the mean levels of six nutrient minerals. Further, there were indications that lead and other toxic metals occur together in the retarded. It is concluded that continuing research is needed to study the relationship between retardation and lead burdens.

In vivo metabolism and excretion of propoxur and malathion in the rat: Effect of lead treatment

Lead was administered to Long-Evans rats by daily oral gavage for 30 days at doses of 200, 400, or 600 mg lead/kg/day. The rats were then administered one of the radiolabeled insecticides and the metabolic products examined. The lead-treated rats had blood lead concentrations of ca. 200 μg/dl in the 200 mg/kg/day group and ca. 475 in the 400 mg/kg/day group. Concentrations of lead in the femur were 500 μg/g or higher. Despite this high body burden of lead (accompanied by a 30% weight deficit at 600 mg/kg/day), no difference in the rate of elimination of radiolabeled material was observed. Furthermore, the lead treatments did not change the relative proportions of the detected metabolites. Thus, despite the known effects of lead on heme synthesis, these treatments had no detectable effect in vivo on the metabolism of propoxur or malathion.

Chelatable lead body burden (by calcium-disodium EDTA) and blood lead concentration in man.

The cheletable part of lead body burden was measured in 32 workers and seven office workers after an infusion test with CaNa2EDTA. The workers had been exposed to lead at a lead and zinc processing unit for one to three years (mean one year). There was good correlation (r = 0.87) between blood lead and chelatable urinary lead excretion described by the equation y = 0.07 . 10(0.46.x). From this equation it can be predicted that the generally accepted limit value for chelatable urinary lead excretion, 0.42 mumol/mmol CaNa2EDTA administered per 24 hours (3.1 mumol/24 hours or 650 micrograms/24 hours), corresponds to a blood lead concentration (PbB) of 1.7 mumol/l (or 35 micrograms/100 ml), which is lower than the commonly accepted limit value of 2.9 mumol/l (or 60 micrograms/100 ml) for occupationally lead-exposed persons. There was a better correlation between the cheletable lead excretion and the urinary ALA-excretion (r = 0.45; p less than 0.001) than between PbB and the urinary ALA-excretion (r = 0.26; p greater than 0.05).

Bone lead mobilization in lactating mice and lead transfer to suckling offspring

Drinking water containing 200 μg/ml lead (labeled with 210Pb) was provided to adult female mice for 105 days prior to the date of mating or for 105 days prior to mating and during the periods of gestation and lactation (160 days total exposure). During lactation there was an increased rate of lead elimination from adult mice exposed prior to mating compared to nonlactating female mice. The magnitude of the additional lead elimination during lactation was similar to the magnitude of the decrease in femur ash weights during lactation. These data support the hypothesis that lead mobilization during lactation is the result of bone mineral mobilization. Approximately 3% of the lead body burden of mothers exposed to lead prior to mating was retained in litters of suckling pups as a result of lead transferred in milk. The magnitude of lead mobilized from maternal bone during lactation was not increased by a diet which was moderately calcium deficient. Continuous ingestion of lead by mothers during lactation significantly increased the net transfer of lead to suckled pups. Lead transferred from mother to offspring during lactation greatly exceeded transfer during gestation for all treatment groups. These data indicate that both prior and current maternal lead exposure should be considered in assessing potential lead exposure of suckling infants.

The distribution of lead in a roadside environment and its consequences for health

The distribution of deposited and absorbed lead originating from vehicle exhaust emissions along a section of the A52 trunk road is examined. Significant quantities of the metal are found. Roadside dust contains up to 210 ppm with both dilution and concentration occurring at different locations after rainfall. The level of contamination in soil is shown to relate to the distance from the roadway and the depth of sampling. Grasses growing on the verges retain airborne lead-containing particles which then concentrate into the upper levels of the soil. Blackberry plants absorb 1·6 ppm of lead in their shoots whilst the fruit is contaminated with up to 6·36 ppm, mainly as a surface deposit, at sites adjacent to lay-bys where gathering is most facile. The pattern of distribution observed suggests that fruit and vegetables grown in gardens in close proximity to a major roadway may present a potential health hazard. Where possible new houses should not be built with gardens extending to within 15 m of such a road. Wild blackberry fruit collected from the hedgerows in areas of high traffic density could significantly add to the lead body burden; particularly when used to make preserves where up to 4 ppm could be present. Steps should be taken to warn the public of the inherent dangers in such wild fruit and Local Councils should remove readily accessible plants.

Variables affecting body burdens of lead, zinc and cadmium in a roadside population of the snailCepaea hortensis Müller.

Application of multiple regression analysis to the lead, zinc and cadmium contents of 985Cepaea hortensis collected from a suburban roadside site over two years showed that body weight, age and daylength were the major factors affecting soft tissue body burdens. Other highly significant influences were physiological changes at the juvenile-adult transition, vapour pressure deficit for the two days before sampling, and mean rainfall for the ten days before. Together these factors accounted for 69%, 79% and 87% of the total variance in lead, zinc and cadmium body burdens respectively. Unexplained variance was provisionally ascribed to individual differences in recent diet and digestive activity. The digestive gland contined the majority of the total body burden of each metal and played an important role in lead and zinc elimination. Whereas levels of lead inC. hortensis fluctuated rapidly, zinc was exchanged more slowly, perhaps by active regulation, and cadmium was effectively immobile, accumulating progressively with age. The implications of these results to the predators of land snails, and to terrestrial monitoring programmes, are discussed.

The effects of body burdens of lead on the growing rat kidney

The long-term sequelae of increased body burdens of lead on renal growth and development were studied in rats poisoned during the weanling stage. Thirty-two weeks after poisoning there was a significant elevation in the lead concentrations of whole blood and of kidney tissue as compared to those of controls ( P < 0.05). However, the body weight, kidney weight, and renal tissue DNA and RNA concentrations were not significantly different from those of the controls. Hypertrophied renal tubular cells and intranuclear inclusions were found in the experimental group at 8 weeks after poisoning but were markedly reduced in number by 32 weeks. There was no evidence of generalized, progressive nephropathy. These results indicate that an increased body burden of lead in the growing rat does not cause alterations in renal growth or development or initiate the development of progressive interstitial nephropathy despite persistent elevations of renal tissue lead concentrations into adulthood.

Body burden of chromium, copper, cadmium and lead in the neustonic copepod Anomalocera patersoni (pontellidae) collected from the Mediterranean sea

The amounts of Cr, Cu, Cd and Pb in the copepod Anomalocera patersoni were determined for 47 individuals by flameless atomic absorption spectrophotometry. The following mean body burdens of these elements were obtained: Cr 0.6, Cu 13, Cd 0.5, Pb 1.5 ng individual-1, or Cr 2.1, Cu 42, Cd 1.5 and Pb 4.8 ng mg-1 (dry weight). Cr, Cu and Cd contents did not differ significantly between males and females, however Pb did, with males having more. The data indicate that while the Cr, Cu and Pb body Hurden in these copepods follows the logarithmic normal distribution, Cd follows a normal distribution. Thus, the arithmetic means and the modes of Cd body burden are almost the same, while for the other elements the arithmetic means differ from the geometric means. This indicates that measurements of a few individuals suffice for estimating the mean body burden of Cd. On the other hand, many measurements are necessary for the body burden estimation of other elements, especially Cu.

The body burden of lead: Comparison of mathematical models for accumulation

Compartmental models for kinetic studies of lead metabolism can be generalized to include power function distributions of residence time of lead molecules in bone, as well as exponential distributions. The predicted long-term accumulation of lead is shown to differ by a factor of 1.3 among several proposed models. Satisfactory models will require at least two bone compartments with mixed power function and exponential distributions of residence time.

In Vivo X-Ray Fluorescence Analysis for Medical Diagnosis

Occupational exposure to lead is common in many industrial applications and hence it is of considerable medical interest to control the body-burden of lead in living man. More than 90 % of the lead in the body is concentrated in bone and hence in vivo measurements of the lead in the skeleton should give the most satisfactory way for estimating the body-burden. The routine method used today for checking on lead contamination is that of measurements on blood samples. However, since the concentration of lead in the blood is a sensitive function of the actual exposure conditions, this method provides only a poor indication of the total body-burden and the integrated lead exposure.

Metal survey of the marine clam Pitar morrhuana collected near a Rhode Island (USA) electroplating plant

Benthic fauna were collected from 17 stations in mid-Narragansett Bay, Rhode Island, during September 1973 from the vicinity of the recently-closed Quonset Point electroplating facility. Despite repeated sampling, most of the 14 species of molluscs taken, including the widgeon clam Pitar morrhuana, were absent from stations in the immediate vicinity of plant outfalls. In general, P. morrhuana captured near outfall sites exhibited high moisture content and elevated body burdens of silver, cadmium, cobalt, chromium, copper, iron, manganese, nickel, lead, and zinc compared to clams of similar size from more distant stations. Observed changes in metal concentrations and moisture content of P. morrhuana were probably attributable to plant operations during the preceding 30 years.

Acromegalic gigantism and tuberous sclerosis

respectively; apparent retention was therefore O. Because metabolic balance studies are known to overestimate retention.v it is likely that the infant was actually in negative lead balance. Negative lead balance is not unusual in the case of normal infants without prenatal exposure to lead, especially when intake of lead is less than 5 pg/kg/day.'o Although a single balance study carried out with the infant at 10I days of age may not reflect well the relation between intake and excretion from birth to that age, the decreasing concentration of lead in the irifant's blood suggests that her body burden of lead was not increasing. In the absence of important postnatal exposure to lead, it appears that an infant exposed prenatally can su bstan­ tially reduce the body burden of lead, at least relative to body mass, during the early months of life.

Health assessment of employees with different body burdens of lead.

Proposed rulemaking by the Department of Labor, OSHA, with regard to occupational exposure to lead was set forth in the Federal Register of October 3, 1975. Among the recommendations were that those persons working with lead whose blood lead concentrations exceed 60 ..mu..g/dl on two occasions undergo biological monitoring and medical examination every two months until the blood lead concentration falls below that level. Since the recommended frequency of examination appeared to be unnecessarily demanding, we undertook a review of our experience to determine whether a program of health approval which was based on less critical assessment would be protective of the employees' health. Results of the study have been used to evaluate the OSHA proposal.

377 THE MEASUREMENT OF FREE ERYTHROCYTE PORPHYRIN (FEP) AS AN INDEX OF THE BODY LEAD BURDEN

The measurement of FEP is now widely used as a means of screening for lead poisoning. Very little data is available to demonstrate its utility as an index of the body lead burden. To assess this relationship 156 patients were studied with FEP, blood lead, hemoglobin, serum iron, and an 8-hour EDTA mobilization test. There was a significant correlation between FEP, blood lead and the urinary excretion of lead following EDTA administration. Only 2% of patients with blood lead values of less than 40 μg/dl excreted more than 0.54 μg of lead/mg of EDTA administered; 32% of those with blood leads of more than 40 μg/dl had abnormal lead excretions. With the use of the FEP it was found that 7% of patients with FEP of less than 60 μg/dl of whole blood had abnormal lead mobilization tests while 23% of those with FEP greater than 60 μg/dl had excessive amounts of lead in their urine following the administration of EDTA. The FEP was less reliable as an index of body lead burden in children more than 5 years of age. Results indicate that patients with an FEP of less than 30 μg/dl were at almost no risk of an increased body lead burden. Patients with an FEP value that is greater than 30 μg/dl may have an excessive body lead burden and should have blood lead levels measured to determine if an EDTA mobilization test is required in the diagnostic evaluation.

Factors affecting the absorption and excretion of lead in the rat

A reliable method for studying lead absorption and excretion in rats is described. Lead absorption occurs primarily in the duodenum where lead enters the epithelial mucosal cells. There is a relative mucosal block for lead with increasing intraluminal doses. Certain substances which bind lead and increase its solubility enhance its absorption. Iron, zinc, and calcium decrease the absorption of lead without affecting its solubility, probably by competing for shared absorptive receptors in the intestinal mucosa. The total body burden of lead does not affect lead absorption. Thus, lead does not have a feedback mechanism which limits absorption. Lead absorption is increased during rapid periods of growth and in iron-deficient animals. It is diminished with starvation and in iron-overloaded animals. The excretion and kinetics of tracer doses of radiolead were quantified. Erythrocytes seem to serve an important role in transport. Excretion occurs in urine and stool. Bile is an important route of excretion in the gut. Although most of a tracer dose is rapidly excreted, the excretory process is limited permitting lead accumulation primarily in bone.

378 THE INFLUENCE OF IRON ON LEAD MOBILIZATION BY EDTA

Urinary excretion of lead following administration of calcium ethylenediaminetetraacetic acid (EDTA) is widely employed as an index of the body lead burden. In our experience, as well as that of others, the relationship of blood lead to that removed in the EDTA mobilization test has been imprecise. In an attempt to identify the variables multiple factors were examined in 117 lead mobilization tests conducted in 110 patients. Variables included: age, hemoglobin, free erythrocyte porphyrin (FEP), serum iron, blood lead, and urinary lead excretion expressed as μg urine lead per mg of EDTA administered (Pb/EDTA). Analysis indicates that mobilization results can be best predicted from the blood lead and serum iron values (r = .79; F = 96.5, p & z.Lt;.001). The multiple correlation equation is:The multiple correlation equation indicates that urinary lead excretion is greater with either greater blood lead or serum iron, or both. Correlations with lead alone (r = 0.67), iron (0.65), or FEP (0.19) were not as great as the combination of lead and iron. The enhancement of lead excretion in the presence of normal, or increased serum iron concentrations suggests that iron and lead share similar binding sites and that iron displaces lead from these sites making it more available for chelation.

The summer disease: An integrative model of the seasonality aspects of childhood lead poisoning

Crises of childhood lead poisoning reach a peak each summer among industrial societies in the mid-latitudes of the world. Sources of environmental lead intoxication include household dust and paint, soil around houses, gutter dirt, lead in canned foods, and lead in the air. Lead concentrations are geographically concentrated in older residential areas and along traffic arteries. At the macrolevel, they generally correspond with the nexus of industrial conurbations. Weather factors may seasonally influence aerosol lead levels, but the paramount seasonal influence in human lead poisoning is solar radiation. This affects the mobilization of the body burden of lead, often precipitating a child into a summer crisis of lead-induced encephalopathy. An integrative model of seasonality factors is presented; different risk groups, notably black children, are recognized; and, importantly, implications for public health planning are emphasized.

Quantities of lead producing health effects in humans: sources and bioavailability.

Levels of lead ingestion and inhalation producing increased body burden of lead and clinical toxicity in adults and children are compared with usual levels of exposure. The magnitude of lead exposure from air, water, and food is estimated. Sources of high level exposure to lead are described; urban street dirt, house dust, and paint are particularly common sources of high concentrations of lead. The bioavailability of different lead compounds is reviewed as well as factors affecting susceptibility to lead.