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PubMedDate not supplied

QT interval measurement in the dog: chest leads versus limb leads.

INTRODUCTION: An accurate measurement of the QT interval is dependent on the accurate identification of the end of the T wave. Although chest leads have been recommended in dog toxicology studies, their use has not been widely put into practice, as shown by a recent survey on methodology for ECG collection in the pharmaceutical industry. Therefore, there is little published data on dog QT measurement from chest leads. METHODS: Electrocardiograms (ECGs) were taken from 100 beagle dogs (50 males, 50 females), with the dogs restrained in a sling. On the day of recording, measurements were performed at time zero and 1 h later. Recordings were repeated 7 to 10 days later. QT interval measurements were taken simultaneously from Lead II and the chest Lead CV5RL. Heart rate was taken from Lead II. Statistical analyses included the calculation of a QT correction formula, comparison of the mean values and variability of QT and QTc measurements from Leads II and CV5RL, the comparison of T-wave polarity from both leads, and a power analysis for QT and QTc. RESULTS: The T wave was positive in almost all dogs (99/100) in the Lead CV5RL at all measurement periods, while it was either positive or negative in Lead II (64-75/100), and the incidence of positive T wave varied between measurement periods. The QT interval was significantly shorter (194+/-11 to 197+/-12 vs. 197+/-13 to 200+/-12 ms) when measured from the CV5RL lead at all recording periods and in both sexes. In addition, the standard deviation for QT measurement within each individual ECG record demonstrates less intra-animal variation when QT is measured from Lead CV5RL compared with Lead II (3.8 vs. 13.2 ms). The linear regression between QT and heart rate was improved when QT measurements were taken from CV5RL, as shown by the percentage of variability R2. DISCUSSION: Estimates of the sample sizes showed that fewer animals would be required to detect a change at both the high and the mid-doses when using the chest Lead CV5RL. Using Lead II, we are able to detect within-animal changes of 10% in either QT or QTc; with Lead CV5RL, we are able to detect 10% change in QT and 5% change in QTc.

Animals↗

PubMed1993

Long-term follow up of ventricular endocardial pacing leads. Complications, electrical performance, and longevity of 561 right ventricular leads.

Five hundred and sixty-one endocardial pacing leads implanted in the right ventricle of 502 patients between 1971 and 1990 were followed for up to 17 years regarding their complications, stimulation threshold behavior, and overall longevity. Lead tip dislodgment occurred in 16 leads (2.9%), in 14 of which dislodgement occurred within 2 months after implantation. The incidence of dislodgement was significantly smaller in tined leads than in nontined leads. Lead conductor fracture occurred in 19 leads (3.4%), in 15 of which fracture occurred within 5 years after implantation. Two particular sites of lead fracture were identified; i.e., one within the pacemaker pocket and the other at a particular point in the subclavian vein between the clavicle and the first rib. Fixation ligature in the former site and the venopuncture point for lead insertion in the latter site are thought to be related to lead fracture. Other complications included insulator break in 3 leads (0.5%), exit block in 7 leads (1.2%), and poor sensing in 2 leads (0.4%). The cumulative survival of leads was 94.1 +/- 2.7% (mean +/- 95% confidence interval) at 5 years, 86.3 +/- 6.3% at 10 years, and 74.2 +/- 14.0% at 15 years after implantation. The minimal stimulation threshold, lead impedance and R wave amplitude were all found to be stable for up to 10 years, and there were no tendencies toward higher stimulation threshold during the observation period of this study.

Electrodes, Implanted↗

PubMed1978

Widening perspectives of lead toxicity. A review of health effects of lead exposure in adults.

Lead has a wide range of applications, and its production and use result in contamination of the environment, including food and drinking water. Geochemical studies indicate that the majority of lead in ecosystems originated from industrial operations, and that human lead intake has increased 100-fold above the "natural" level. Prehistoric human skeletons contain about two orders of magnitude less lead than present-day samples. Biochemical interference with heme biosynthesis can be detected as a result of current lead exposures, inhibition of aminolevulinate dehydratase and accumulation of zinc protoporphyrin in erythrocytes being the earliest effects. Anemia is uncommon except for cases of lead poisoning, but even slightly increased lead absorption results in a decrease in hemoglobin concentrations. Modern neurobehavioral test methods have disclosed increased prevalence of psychological dysfunction associated with augmented lead absorption. Biochemical and behavioral changes occur below the recommended limit for blood lead concentration of 60 micrograms/100 ml. Several diagnostic tests for lead toxicity are available. The protoporphyrin concentration in the blood seems to be the best risk indicator. The highest occupational lead exposures occur in lead smelters and storage battery plants, but several other industrial operations may result in high lead levels. As much as 1% of the working population may have a significantly increased lead absorption with possible adverse effects.

Cross-Sectional Studies↗

PubMed1992

Lead poisoning in cattle--transfer of lead to milk.

The transfer of lead to milk in cattle in relation to blood lead levels and the uptake of lead in edible tissues was studied for an accidental exposure over 1 or 2 days to lead in excessive amounts from the licking of burnt storage batteries. The degree of exposure was monitored by determination of blood lead levels. Milk and blood samples were taken from eight cows, without acute symptoms of lead poisoning, during a period of 18 weeks. Two weeks after the accidental exposure, lead levels (mean +/- SD) in milk were 0.08 +/- 0.04 mg kg-1 and in blood 0.36 +/- 0.04 mg kg-1 in six of the cows. The relationship between lead concentration in blood and those in milk was found to be exponential and could be expressed by the equation: log y = 3.19x - 2.36 (r = 0.85, p less than 0.001), where y and x are the lead concentrations in milk and blood, respectively. The lead level in milk was relatively constant up to a blood lead level of 0.2-0.3 mg kg-1, and increased sharply at higher blood levels. The biological half-life of lead in blood was shown to be approximately 9 weeks. In eight acutely sick cows, which were emergency slaughtered, the range of lead levels in edible muscle tissue was 0.23-0.50 mg kg-1 wet weight. Very high concentrations were found in the kidneys, with a range of 70-330 mg kg-1, and in the livers, with a range of 10-55 mg kg-1. Four of the cows were pregnant, in the first or second month of gestation, during the episode of exposure. The lead exposure was not found to disturb the gestation or development of the fetuses.

Animals↗

PubMed2006

Effect modification by delta-aminolevulinic acid dehydratase, vitamin D receptor, and nitric oxide synthase gene polymorphisms on associations between patella lead and renal function in lead workers.

Genetic polymorphisms that affect lead toxicokinetics or toxicodynamics may be important modifiers of risk for adverse outcomes in lead-exposed populations. We recently reported associations between higher patella lead, which is hypothesized to represent a lead pool that is both bioavailable and cumulative, and adverse renal outcomes in current and former Korean lead workers. In the present study, we assessed effect modification by polymorphisms in the genes encoding for delta-aminolevulinic acid dehydratase (ALAD), the vitamin D receptor (VDR), and endothelial nitric oxide synthase on those associations. Similar analyses were conducted with three other lead biomarkers. Renal function was assessed via blood urea nitrogen, serum creatinine, measured and calculated creatinine clearances, urinary N-acetyl-beta-D-glucosaminidase, and retinol-binding protein. Mean (SD) blood, patella, tibia, and dimercaptosuccinic acid-chelatable lead values were 30.9 (16.7) microg/dl, 75.1 (101.1)and 33.6 (43.4) microg Pb/g bone mineral, and 0.63 (0.75) microg Pb/mg creatinine, respectively, in 647 lead workers. Little evidence of effect modification by genotype on associations between patella lead and renal outcomes was observed. The VDR polymorphism did modify associations between the other lead biomarkers and the serum creatinine and calculated creatinine clearance. Higher lead dose was associated with worse renal function in participants with the variant B allele. Models in two groups, dichotomized by median age, showed that this effect was present in the younger half of the population. Limited evidence of effect modification by ALAD genotype was observed; higher blood lead levels were associated with higher calculated creatinine clearance among participants with the ALAD(1-2) genotype. In conclusion, VDR and/or ALAD genotypes modified associations between all the lead biomarkers, except patella lead, and the renal outcomes.

Acetylglucosaminidase↗

PubMedDate not supplied

Cross-sectional study of blood lead effects on iron status in Korean lead workers.

OBJECTIVE: This study assessed the iron status of Korean male lead workers by measuring the dietary iron intake and biochemical indices, and tested the hypothesis that a high blood lead level is associated with impaired iron function, which results in higher prevalence of iron deficiency when the route of exposure is not the gastrointestinal tract. METHODS: One hundred eighteen lead workers and 42 non-lead workers were recruited from mandatory annual health surveillance sites for industrial workers. Blood lead, hemoglobin, and hematocrit levels were evaluated as hematologic parameters, and serum iron concentrations, total iron-binding capacity, and percentage of transferrin saturation were evaluated as iron-status parameters. Dietary iron intake was assessed by a 24-h recall method. RESULTS: Lead workers had significantly lower hemoglobin, hematocrit, serum iron levels, percentage of transferrin saturation, and dietary iron intake than did non-lead workers, and they had significantly higher (P < 0.01) total iron-binding capacity. The occurrence of iron-deficiency cases, as assessed by hematocrit values, was significantly higher (P < 0.001) in lead workers than in non-lead workers, and the prevalence of iron deficiency was associated with high blood lead levels (P = 0.033). The dietary iron intake was inversely associated with zinc protoporphyrin (P = 0.032). CONCLUSIONS: This study confirmed the adverse effects of high blood lead levels on hematologic pathways and the effectiveness of dietary iron intake as a secondary preventive intervention against lead toxicity. To promote health and to prevent toxic effects of lead exposure in Korean lead workers, an adequate intake of dietary iron is strongly recommended.

Adult↗

PubMedDate not supplied

Longitudinal relationship between dentin lead levels in childhood and bone lead levels in young adulthood.

A retrospective cohort study was conducted to examine the relationship between tooth lead in children and bone lead levels in young adults. Members of a cohort of young adults were reassessed 13 y after initial examination at an ambulatory clinical research center. Dentin lead levels were measured by anodic stripping voltammetry during the years 1975-1978, and bone lead levels of the tibia and patella were measured by K-x-ray fluorescence technique during 1989 and 1990. A total of 63 subjects who had no history of chelation or had no missing information on potential confounders were studied. The median follow-up interval was 13.2 y. Dentin lead levels averaged 13.4 micrograms/g (standard deviation [SD] = 10.7 micrograms/g, range = 2.9-51.8 micrograms/g), and bone lead levels averaged 1.3 micrograms/g (SD = 4.4 micrograms/g, range = -9-13 micrograms/g) for tibia and 5.4 micrograms/g (SD = 8.4 micrograms/g, range = -10-25 micrograms/g) for patella. The authors controlled for age, sex, race, and mother's socioeconomic status, and dentin lead levels were predictive of higher tibia, patella, and mean bone lead levels in 32 subjects (follow-up interval of 11.8-13.2 y). A correction for measurement errors in dentin lead measurements was made, and it was determined that a 10-micrograms/g increase in dentin lead levels in childhood was predictive of a 1-microgram/g increase in tibia lead levels, a 5-micrograms/g increase in patella lead levels, and a 3-micrograms/g increase in mean bone lead levels among the young adults. It was concluded, therefore, that lead exposure in early life may be used to predict elevated body burden up to 13 y later.

Adolescent↗

PubMed1986

delta-Aminolaevulinic acid dehydratase as an index of the presence and severity of lead poisoning in acute and chronic lead exposure.

The activity of delta-aminolaevulinic acid dehydratase (ALA-D; porphobilinogen synthase) was measured in whole blood from a group of workers with acute exposure to lead and with low blood lead levels, a group of workers with chronic lead exposure and high blood lead levels, and a group of people without undue environmental lead exposure. The activity of ALA-D was reduced significantly at low blood lead levels only if undue exposure to lead had occurred, and was thus a reflection of low level lead poisoning. In chronic lead exposure the enzyme was not invariably reactivated fully with dithiothreitol, indicating more severe enzyme poisoning. The one lead worker with symptomatic lead poisoning had the most marked enzyme suppression. Measurement of both ALA-D activity and blood lead levels was more useful than the measurement of blood lead levels alone in the diagnosis and assessment of the severity of lead poisoning.

Acute Disease↗

PubMed2005

Associations among lead dose biomarkers, uric acid, and renal function in Korean lead workers.

Recent research suggests that both uric acid and lead may be nephrotoxic at lower levels than previously recognized. We analyzed data from 803 current and former lead workers to determine whether lead biomarkers were associated with uric acid and whether previously reported associations between lead dose and renal outcomes were altered after adjustment for uric acid. Outcomes included uric acid, blood urea nitrogen, serum creatinine, measured and calculated creatinine clearances, and urinary N-acetyl-ss-d-glucosaminidase (NAG) and retinol-binding protein. Mean (+/- SD) uric acid, tibia lead, and blood lead levels were 4.8 +/- 1.2 mg/dL, 37.2 +/- 40.4 microg/g bone mineral, and 32.0 +/- 15.0 microg/dL, respectively. None of the lead measures (tibia, blood, and dimercaptosuccinic-acid-chelatable lead) was associated with uric acid, after adjustment for age, sex, body mass index, and alcohol use. However, when we examined effect modification by age on these relations, both blood and tibia lead were significantly associated (ss = 0.0111, p < 0.01 and ss = 0.0036, p = 0.04, respectively) in participants in the oldest age tertile. These associations decreased after adjustment for blood pressure and renal function, although blood lead remained significantly associated with uric acid (ss = 0.0156, p = 0.01) when the population was restricted to the oldest tertile of workers with serum creatinine greater than the median (0.86 mg/dL). Next, in models of renal function in all workers, uric acid was significantly (p < 0.05) associated with all renal outcomes except NAG. Finally, in the oldest tertile of workers, associations between lead dose and NAG were unchanged, but fewer associations between the lead biomarkers and the clinical renal outcomes remained significant (p less than or equal to 0.05) after adjustment for uric acid. In conclusion, our data suggest that older workers comprise a susceptible population for increased uric acid due to lead. Uric acid may be one, but not the only, mechanism for lead-related nephrotoxicity.

Adolescent↗

PubMed1990

Acute lead poisoning in nursing home and psychiatric patients from the ingestion of lead-based ceramic glazes.

To our knowledge, acute inorganic lead poisoning from single ingestions of lead compounds has been only rarely reported. During a 14-month period, we were contacted regarding eight instances of acute ingestions of liquid lead-based ceramic glazes by mentally impaired residents of nursing homes or psychiatric facilities participating in ceramic arts programs. While some ingestions did not cause toxic effects, some patients developed acute lead poisoning characterized by abdominal pain, anemia, and basophilic stippling of red blood cells. In the blood of several patients, lead concentrations were far above normal (4 to 9.5 mumol/L). Urinary lead excretions were tremendously elevated during chelation therapy, with one patient excreting 535.9 mumol/L of lead during a 6-day period, the largest lead excretion ever reported in a patient suffering from acute lead poisoning, to our knowledge. All patients recovered following supportive care and appropriate use of chelating agents. Lead-based glazes are commonly found in nursing homes and psychiatric facilities. We suspect that acute or chronic lead poisoning from the ingestion(s) of lead-based ceramic glazes may be an unrecognized but not uncommon problem among such residents. We urge physicians to take ingestions of lead-based glazes seriously and to consider the diagnosis of lead poisoning in nursing home and psychiatric patients who have participated in ceramic crafts programs.

Acute Disease↗

PubMed1978

Exploratory skin penetration findings relating to the use of lead acetate hair dyes. Hair as a test tissue for monitoring uptake of systemic lead.

Two experiments were conducted. In the first, 9 adult male subjects applied a marketed hair dye containing 2% lead acetate according to prescribed directions daily for a period of 90 days. Scalp, axillary and pubic hair were monitored for lead content before and at the end of the test period. Scalp hair analyses were used to confirm application of the hair dye; axillary and pubic hair were analyzed as biologic indicators of systemic lead absorption, i.e., metabolic incorporation of lead in hair growing at sites different from the dyed site. The axillary and pubic hair lead levels ranged from less than 6 to 41 ppm at the start and rose to 27 to 466 ppm at the conclusion of the experiment. Using 80 ppm hair lead as a measure of significant systemic absorption, 7 of 9 subjects showed this effect according to uptake by axillary hair and 4 of 9 according to pubic hair uptake. In the second experiment, blood and hair lead levels and blood erythroporphyrin were measured in 11 children from a pica clinic. Blood lead and hair lead levels were significantly correlated, i.e., r = +0.84. A regression formula was constructed relating these two parameters and blood lead values were predicted for the data of experiment 1, using observed hair lead values. The technique has important limitations; nevertheless, within these limitations, 1 of 9 subjects might be expected to have sustained an elevated blood lead level, i.e., in excess of 50 microgram/100 ml. It therefore appears that in the use of lead acetate hair dyes, some lead is absorbed systemically from the scalp.

Adult↗

PubMed1993

Mechanisms of the toxic effect of lead. I. Free lead in erythrocyte.

In this work, a selection of children was examined based on their free erythrocyte protoporphyrin (FEP) and total blood lead (PbB) contents. Two groups with clear differences in lead sensibility were selected. One group with high FEP levels (deep lead alteration), named "normal," and one group with low FEP levels (discrete lead alteration), named "lead tolerant," and both with similar PbB concentration, were formed. The selection, based on FEP level, showed a correlation with other indicators (neuromotor alterations). A lower activity of the enzymes Glyceraldehyde 3-phosphate dehydrogenase (GA3PD), Glucose 6-phosphate dehydrogenase (G6PD), 6-phosphogluconate dehydrogenase (6PGD), and Lactate dehydrogenase (LDH) was found in the normal group when compared to the tolerant group. Therefore, the influence of the lead acetate upon the same erythrocyte enzyme activities was investigated. Lead inhibition of the enzymes GA3PD and G6PD was found, and this inhibition could be related to the free lead content found in the erythrocytes. Inhibition of the enzymes 6PGD and LDH was also found, but these enzymes were not inhibited by exposure to lead acetate. Erythrocyte free lead content was high in the normal group when compared to the lead tolerant group and could be a determinant factor in the biochemical alterations found. Low erythrocyte free lead contents could be an indicator of lead tolerance. TCA-precipitation was found to be a useful method to evaluate free lead content; it gave similar results to gel filtration molecular chromathography.

Case-Control Studies↗

PubMed1997

The effect of the OSHA lead exposure in construction standard on blood lead levels among iron workers employed in bridge rehabilitation.

Over 50,000 workers are at risk of occupational exposure to lead in the course of renovating the nation's deteriorating infrastructure. In mid-1993, to control exposure to lead in the construction setting OSHA promulgated a Lead in Construction Standard. In this study, we assessed the effect of the mandated changes in exposure conditions which followed the introduction of this new standard. We analyzed changes in baseline and maximum blood lead concentrations and in maximum increments in blood lead levels before and after introduction of the standard among iron workers employed in the renovation of a large, lead-painted, steel bridge in New York City. Results indicated that baseline and maximum blood lead levels fell significantly after the implementation of the provisions of the standard, as did maximum increments in blood lead concentrations. Seventy-six percent of the workers maintained blood lead concentrations below 20 micrograms/dl after the OSHA standard, as compared with 66% prior to its implementation. Increments of 20 micrograms/dl or more occurred considerably more frequently before introduction of the standard (13% before vs. 4% after; p = 0.01). Evidence of decreased exposure to lead was observed among iron workers who were present both before and after the introduction of the OSHA standard, as well as among iron workers newly hired after the OSHA provisions were put in place. These findings document the effectiveness of the OSHA construction lead standard in controlling exposure to lead in this complex and variable environment. The data indicate the utility of blood lead determinations in assessing the outcome of industrial hygiene interventions to reduce exposures to lead in the construction setting.

Adult↗

PubMed1998

Contrasting associations of blood and semen lead concentrations with semen quality among lead smelter workers.

While blood lead concentration has been inversely associated with indicators of reproductive health in occupationally exposed male workers, the utility of lead concentration in semen as an indicator of lead exposure to the male reproductive system has not been fully explored. Blood and semen lead concentrations from 81 lead smelter workers were examined in relation to semen quality and endocrine function parameters. Mean blood and semen lead concentrations were 22.8 micrograms/dl (range 5-58) and 1.9 micrograms/dl (range 0.1-17.6), respectively. Total sperm count and concentration decreased with increasing blood lead concentration; p for trend was 0.003 and 0.009, respectively. Semen lead concentration was inversely related to total sperm count (p = 0.05), ejaculate volume (p = 0.001), and serum testosterone (p = 0.004), but not to sperm concentration. The association between semen lead concentration and total sperm count was eliminated when volume was included in the model. Blood lead concentration was more consistently associated with indicators of sperm production than was semen lead. In contrast, semen lead concentration was negatively associated with circulating testosterone concentrations. Our findings indicate that measurement of semen lead may not be a valuable adjunct to conventional blood lead monitoring for investigations of male reproductive system toxicity.

Adult↗

PubMed2006

Plasma-lead concentration: investigations into its usefulness for biological monitoring of occupational lead exposure.

BACKGROUND: The lead concentration in plasma is correlated to that in whole blood with a two to fourfold variation. It has never been investigated if this variation is inter-individual. METHODS: Lead and hemoglobin were determined in blood and plasma from 13 lead workers with a history of relatively high blood-lead concentrations, sampled three times during 1 day. The variation in the distribution of lead between cells and plasma was studied, but not the variation in the lead concentrations as such. RESULTS: Blood hemoglobin decreased with rising plasma lead (0.9-3.0 microg/L). Regarding the distribution of lead, no effect of current exposure during the day or of recent meals appeared. As much as 84% of the overall variance of the distribution of lead between cells and plasma could be attributed to individual factors. After adjustment for erythrocyte volume fraction this decreased to 67%. Plasma samples with elevated hemoglobin concentrations (due to in vitro hemolysis) had somewhat elevated lead concentrations. CONCLUSIONS: Plasma lead is not significantly altered by variation in a single day's exposure and, therefore, the choice of time of the day is not critical for sampling. However, plasma lead is negatively correlated to blood hemoglobin and mild hemolysis (not visible by the eye) in a sample may increase plasma lead with up to 30%. Finally, plasma provides lead exposure information that differs from whole blood, but it is not clear which one of these is the biomarker with the closest relation to exposure and/or effects.

Adult↗

PubMed1999

A multivariate linear regression model for predicting children's blood lead levels based on soil lead levels: A study at four superfund sites.

For the purpose of examining the association between blood lead levels and household-specific soil lead levels, we used a multivariate linear regression model to find a slope factor relating soil lead levels to blood lead levels. We used previously collected data from the Agency for Toxic Substances and Disease Registry's (ATSDR's) multisite lead and cadmium study. The data included the blood lead measurements (0.5 to 40.2 microg/dL) of 1015 children aged 6-71 months, and corresponding household-specific environmental samples. The environmental samples included lead in soil (18.1-9980 mg/kg), house dust (5.2-71,000 mg/kg), interior paint (0-16.5 mg/cm2), and tap water (0.3-103 microg/L). After adjusting for income, education of the parents, presence of a smoker in the household, sex, and dust lead, and using a double log transformation, we found a slope factor of 0.1388 with a 95% confidence interval of 0.09-0.19 for the dose-response relationship between the natural log of the soil lead level and the natural log of the blood lead level. The predicted blood lead level corresponding to a soil lead level of 500 mg/kg was 5.99 microg/kg with a 95% prediction interval of 2. 08-17.29. Predicted values and their corresponding prediction intervals varied by covariate level. The model shows that increased soil lead level is associated with elevated blood leads in children, but that predictions based on this regression model are subject to high levels of uncertainty and variability.

Child↗

PubMed1999

Internalization of carcinogenic lead chromate particles by cultured normal human lung epithelial cells: formation of intracellular lead-inclusion bodies and induction of apoptosis.

Occupational exposure to certain particulate hexavalent chromium [Cr(VI)] compounds, such as lead chromate, has been associated with lung cancer and respiratory tract toxicity. We have previously shown that apoptosis is a major mode of death in cultured rodent cells treated with soluble sodium chromate and particulate lead chromate. Here we report the cellular and molecular effects of lead chromate and sodium chromate in normal human lung small airway epithelial (HSAE) cells, which may be one of the targets for Cr(VI)-induced lung cancer and respiratory tract toxicity. Phagocytosed lead chromate particles and intracellular lead-inclusion bodies (LIB) were observed by transmission electron microscopy and confirmed by X-ray analysis. HSAE cells exposed to lead chromate and sodium chromate underwent dose-dependent apoptosis. The cellular uptake and genomic interactions of both Cr and lead (Pb) were examined by inductively coupled plasma mass spectrometry (ICPMS) coupled with a novel, direct-injection high-efficiency nebulizer (DIHEN). Using this approach, we have quantitated a dose-dependent formation of Cr-DNA adducts and DNA-associated Pb in lead chromate-treated HSAE cells. The formation of LIB in normal human lung cells exposed to lead chromate indicates that ionic Pb is released from the particles and thus might contribute to the cell toxicity caused by lead chromate. Internalization and dissolution of lead chromate particles and the interaction of ionic Cr and Pb with DNA, may be components of the mechanism of lead chromate carcinogenesis. Lead chromate-induced apoptosis may be a mechanism to eliminate cells with chromium- and/or lead-damaged DNA.

Apoptosis↗

PubMed1982

Models for the relationship between blood lead and air lead.

A "lead exposure" model is proposed for the relationship between blood lead and air lead. Unlike the commonly-used log-log model, this model describes blood lead as a function of both air lead exposure and lead intake from sources other than the air (i.e., food, water, etc.). The blood lead-air lead relationship at low air lead levels is also studied. It is shown that the mathematical characteristics of the log-log model can result in an overestimate of the effect of air lead on blood lead at air lead levels less than 1 to 2 micrograms/m3. The lead exposure model is shown to give a good description of data collected in studies in which subjects' air lead levels were measured by personal monitor.

Air Pollutants↗