Environmental lead exposure and activity of delta-aminolevulinic acid dehydratase (ALA-D) in maternal and cord blood

Use of Generalized Additive Model to Detect the Threshold of δ-Aminolevulinic Acid Dehydratase Activity Reduced by Lead Exposure

Background: Lead inhibits the enzymes in heme biosynthesis, mainly reducing δ-aminolevulinic acid dehydratase (ALAD) activity, which could be an available biomarker. The aim of this study was to detect the threshold of δ-aminolevulinic acid dehydratase activity reduced by lead exposure. Methods: We collected data on 121 lead workers and 117 non-exposed workers when annual health examinations were performed. ALAD activity was determined by the standardized method of the European Community. ALAD G177C (rs1800435) genotyping was conducted using the polymerase chain reaction and restricted fragment length polymorphism (PCR-RFLP) method. In order to find a threshold effect, we used generalized additive models (GAMs) and scatter plots with smoothing curves, in addition to multiple regression methods. Results: There were 229 ALAD1-1 homozygotes and 9 ALAD1-2 heterozygotes identified, and no ALAD2-2 homozygotes. Lead workers had significantly lower ALAD activity than non-exposed workers (41.6 ± 22.1 vs. 63.3 ± 14.0 U/L, p < 0.001). The results of multiple regressions showed that the blood lead level (BLL) was an important factor inversely associated with ALAD activity. The possible threshold of BLL affecting ALAD activity was around 5 μg/dL. Conclusions: ALAD activity was inhibited by blood lead at a possible threshold of 5 μg/dL, which suggests that ALAD activity could be used as an indicator for lead exposure regulation.

Environmental lead exposure and its relationship to traffic density among Senegalese children: a cross-sectional study

Leaded-gasoline is probably the primary source of lead (Pb) exposure in Dakar (Senegal). The present cross sectional study was undertaken to investigate the levels of Pb in Senegalese children and to present helpful data on the relationship between Pb levels and changes in biological markers of heme biosynthesis and oxidative stress. A total of 330 children, living since birth either in rural or urban areas (ie, Khombole (n=162) and Dakar (n=168), respectively) were included. During this cross sectional study, the mean blood (B)-Pb level in all children was 7.32±5.33 ųg/dL, and was influenced by the area of residence and gender. In rural children, 27 subjects (16.7%), 18 boys (19.6%) and nine girls (12.9%), had a B-Pb level >10 ųg Pb/dL, whereas 99 urban children (58.9%), respectively, 66 boys (71.8%) and 33 girls (43.4%), had alarmingly high B-Pb levels. Accordingly, urine delta-aminolevulinic acid levels were higher in children living in the urban area than in the rural areas (P B±0.001), and closely correlated with the B-Pb levels (P B±0.01). Moreover, glutathione peroxidase (GPx) activity, selenium (Se) level, glutathione reductase (GR) activity, and glutathione status were significantly influenced by area of residence and/or by gender. GPx activity and Se level were not only negatively correlated with B-Pb levels, but also positively correlated together (P B±0.01). Taken together, the present results allow us to conclude that urban children have higher B-Pb levels than rural children, and that of these children, boys have higher B-Pb levels than girls, leading thereby to alterations of heme biosynthesis and pro-oxidant/antioxidant balance. We also suggest that exposure to Pb and the Pb-induced adverse effects merits attention and that the development of preventive actions are of increasing importance in Senegal.

Association between delta-aminolevulinic acid dehydratase polymorphism and placental lead levels

Lead inhibits the delta-aminolevulinic acid dehydratase (ALAD) activity and results in neurotoxic aminolevulinic acid accumulation in the blood. During pregnancy, lead in the maternal blood can easily cross the placenta. The aim of this study was to determine whether the maternal ALAD G177C polymorphism (rs1800435) was related to the placental lead levels. The study population comprised 97 blood samples taken from mothers to investigate ALAD G177C polymorphism and their placentas to measure lead levels. ALAD G177C polymorphism was detected by standard polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP) technique and atomic absorption spectrometry (AAS) equipped with a graphite furnace and Zeeman background correction system was used for lead determination. The median placental lead levels for ALAD1-1, ALAD1-2 and ALAD2-2 genotypes were 7.54 μg/kg, 11.78 μg/kg and 18.53 μg/kg, respectively. Statistically significant association was found between the maternal ALAD G177C polymorphism and placental lead levels (p<0.05). This study suggested that maternal ALAD G177C polymorphism was associated with placental lead levels.

Effects of environmental cadmium and lead exposure on adults neighboring a discharge: Evidences of adverse health effects

The purpose of the study was to determine Pb and Cd concentrations in humans and to assess the effect of co-exposure to these metals on biomarkers of oxidative stress and nephrotoxicity. Blood and urine levels of Pb and Cd, oxidative stress and urinary renal biomarkers were measured in 77 subjects neighboring a discharge and 52 in the control site. Exposed subjects showed significantly higher levels of lead and cadmium in blood and urine than the controls. Excessive production of reactive oxygen species induced by these metals in exposed subjects conducted to a decrease in antioxidant defense system (GPx, Selenium, GSH) and an increase in lipid peroxidation (MDA). Moreover, changes in markers of nephrotoxicity (high urinary concentrations of total protein, RBP and CC16, as well as GSTα and LDH increased activities) suggested the occurrence of discrete and early signs of impaired renal function for the discharge neighboring population.

Comparative In Vivo Study of Biocompatibility of Apatites Incorporated with 1% Zinc or Lead Ions versus Stoichiometric Hydroxyapatite

Hydroxyapatite is the main ceramic material that has being used in bone repair, although its physico-chemical and in vivo behavior should be better understood. A method to improve the biocompatibility of HA is the substitution of calcium with divalent cations which enhance mechanic resistance and can modulate inflammatory response against implanted material. In this study we analyzed the biocompatibility of HA doped with one per cent of Zn2+ or Pb2+. The first one has being described as an inflammation modulator and the second would be a model for chronic toxicity assay. Biocompatibility of the both materials was studied in vivo following the ISO 10993-6 standard. HA cylinders (ZnHA, PbHA and stoichiometric HA as positive control) were implanted into subcutaneous tissue of 45 Balb-c mice and after 1, 3 and 9 weeks the animals were euthanized (5 for each experimental condition). Necropsies of the skin containing reactional tissue were removed, fixed in 10% formaldehyde and followed the histological processing for paraffin embedding and staining with Hematoxylin-Eosine and Picrosirius red. Microscopic analysis showed for all groups moderate inflammatory response, decreasing throughout the experimental periods, with ZnHA group showing more intense response. Similar presence of macrophages, fibrosis and angiogenesis were observed among the groups. Thereby, we can conclude that ZnHA and PbHA are biocompatible and not bioresorbable, being the ZnHA potentially indicated as bone graft. Detailed studies are required to better understand the role of PbHA as chronic model for lead toxicity.

Acute exposure to low lead levels and its implications on the activity and expression of cytosolic thioredoxin reductase in the kidney

Renal thioredoxin reductase-1 (TrxR-1) activity is stimulated at lead doses lower than that necessary to inhibit δ-aminolevulinate dehydratase activity (δ-ALA-D), which is a classical early biomarker of lead effects. Thus, we hypothesized that the activity of TrxR-1 could be a more sensitive early indicator of lead effects than is δ-ALA-D. To evaluate this hypothesis, we assessed the blood and renal TrxR-1 activity and its gene expression along with biomarkers of oxidative damage, antioxidant enzyme activities and biomarkers of lead exposure in rats acutely exposed to lead. A histopathological analysis was performed to verify renal damage. The increase in renal TrxR-1 activity paralleled the increase in the blood and renal lead levels at 6, 24 and 48 hr after the exposure to 25 mg/kg lead acetate (p < 0.05), whereas its expression was increased 24 and 48 hr after exposure. These effects were not accompanied by oxidative or tissue damage in the kidneys. Blood TrxR-1 activity was not affected by lead exposure (up to 25 mg/kg). Erythrocyte δ-ALA-D activity was inhibited 6 hr after the exposure to 25 mg/kg lead acetate (p < 0.05) but recovered thereafter. Renal δ-ALA-D activity decreased 24 and 48 hr after the exposure to 25 mg/kg lead acetate. There were no changes in any parameters at lead acetate doses <25 mg/kg. Our results indicate that blood TrxR-1 activity is not a suitable indicator of lead effects. In contrast, the increase in renal TrxR-1 expression and activity is implicated in the early events of lead exposure, most likely as a protective cellular mechanism against lead toxicity.

High prevalence of elevated lead levels in pediatric dialysis patients

BACKGROUND

After parents raised concerns about potential lead (Pb) contamination of calcium carbonate for treatment of hyperphosphatemia in chronic kidney disease (CKD), we measured blood Pb using high-resolution sector field inductively coupled mass spectrometry in a quality-assurance investigation of ten pediatric dialysis patients (nine on hemodialysis) and six patients before dialysis.

METHODS

We assessed the kidney function as cystatin C estimated glomerular filtration rate (eGFR), blood Pb levels, calcium carbonate dose, and standard laboratory parameters, as well as Pb levels in the dialysis feed water.

RESULTS

Mean blood Pb concentration in the 16 pediatric CKD patients was 21.1 ± 15.8 µg/l with a maximum of 58 µg/l, which was significantly higher than that of 467 apparently healthy controls (median 6.35 µg/l, interquartile range 4.47, 8.71) and comparable to that of ten adult peritoneal dialysis (PD) patients. Lead levels correlated with red blood cell distribution width, eGFR, and calcium carbonate dose. Pb in dialysate feed water was always <0.00018 mg/l, which is below the accepted limit for water for dialysis of 0.005 mg/l.

CONCLUSIONS

We found a high prevalence of elevated Pb levels in pediatric CKD patients that correlated with the calcium carbonate dose and GFR. Lead levels should be monitored in these patients.

Low-level environmental exposure to lead and renal adverse effects: a cross-sectional study in the population of children bordering the Mbeubeuss landfill near Dakar, Senegal

This study deals with the health effects within a child population, neighbouring a landfill. After detecting metals in soil and air samples collected in the surroundings of the landfill and in a control site, we have studied: (i) levels of lead (Pb) and exposure biomarkers in blood and urine, (ii) oxidative stress biomarkers and (iii) renal injury by applying a set of early effect biomarkers. Levels of Pb were higher in the exposed site (i.e. 1129 mg/kg and 640 ng/m(3) in soil and air samples, respectively) versus those in the control site (i.e. 14.3 mg/kg and 9.3 ng/m(3) in soil and air samples, respectively). Pb impregnation and levels of delta-aminolevulinic acid in urine were influenced by the living site that shows the prevailingly alarming situation in the Mbeubeuss landfill. Malondialdehyde changes indicated Pb-induced excessive production of reactive oxygen species. Lactate dehydrogenase activities and proteinuria were found to be higher in the children living in the exposed site. These evidences may reveal the usefulness of these two effect biomarkers to monitor the kidney injury entailed by relatively low-environmental exposure to Pb. Overall, these results show that the Mbeubeuss landfill constitutes a real source of environmental and health risk, be it living or working on site, of the surrounding population, predominantly for children.

Benchmark dose approach for low-level lead induced haematogenesis inhibition and associations of childhood intelligences with ALAD activity and ALA levels

Lead (Pb) levels, delta-aminolevulinic acid dehydratase (ALAD) activities, zinc protoporphyrin (ZPP) levels in blood, and urinary delta-aminolevulinic acid (ALA) and coproporphyrin (CP) concentrations were measured for 318 environmental Pb exposed children recruited from an area of southeast China. The mean of blood lead (PbB) levels was 75.0μg/L among all subjects. Benchmark dose (BMD) method was conducted to present a lower PbB BMD (lower bound of BMD) of 32.4μg/L (22.7) based on ALAD activity than those based on the other three haematological indices, corresponding to a benchmark response of 1%. Childhood intelligence degrees were not associated significantly with ALAD activities or ALA levels. It was concluded that blood ALAD activity is a sensitive indicator of early haematological damage due to low-level Pb exposures for children.

Maternal blood lead levels and the risk of pregnancy-induced hypertension: the EDEN cohort study

BACKGROUND

Prior studies revealed associations of environmental lead exposure with risks of hypertension and elevated blood pressure.

OBJECTIVE

We examined the effect of blood lead levels on blood pressure and the incidence of pregnancy-induced hypertension (PIH) in the second and third trimesters of pregnancy.

METHODS

One thousand seventeen pregnant women were enrolled in two French municipalities between 2003 and 2005 for the EDEN (Etude des Déterminants pré et post natals du développement et de la santé de l' Enfant) cohort study. Blood lead concentrations were measured by atomic absorption spectrometry in mothers between 24 and 28 weeks of gestation.

RESULTS

PIH was diagnosed in 106 subjects (10.9%). Age, parity, weight gain, alcohol, smoking habits, and calcium supplementation were comparable between hypertensive and nonhypertensive women. Lead levels were significantly higher in PIH cases (mean +/- SD, 2.2 +/- 1.4 microg/dL) than in normotensive patients (1.9 +/- 1.2 microg/dL; p = 0.02). Adjustment for potential confounder effects slightly attenuated but did not eliminate the significant association between blood lead levels and the risk of PIH (adjusted odds ratio of PIH = 3.3; 95% confidence interval, 1.1-9.7). We also observed geographic differences in lead exposure and in the incidence of PIH and found significant correlations between blood lead levels and unadjusted as well as adjusted systolic and diastolic blood pressures after 24 weeks of gestation.

CONCLUSIONS

These findings confirm the relationship between blood lead levels at mid-pregnancy and blood pressure and suggest that environmental lead exposure may play an etiologic role in PIH.

delta-Aminolevulinic acid dehydratase activity, urinary delta-aminolevulinic acid concentration and zinc protoporphyrin level among people with low level of lead exposure

To evaluate the relationship of delta-aminolevulinic acid dehydratase (ALAD) activity, urinary delta-aminolevulinic acid (ALAU) level and blood zinc protoporphyrin (ZPP) concentration to low blood lead (PbB) levels, these biomarkers were determined for all subjects enrolled from a rural area of southeast China where people had low levels of exposure to lead. The mean values of PbB, ALAD, ALAU and ZPP were 67.11 microg/L (SD: 1.654, range: 10.90-514.04), 339.66 nmol ml(-1)h(-1) (1.419, 78.33-793.13), 20.64 microg/L (1.603, 2.00-326.00), and 0.14 micromol/L (3.437, 0.01-2.26), respectively. ALAD was inversely associated with low levels of PbB. ZPP was inversely related to low levels of PbB but positively related to relatively higher levels of PbB. Alcohol drinking contributed to low ALAD in men. Women had higher ZPP than men. ALAU had no significant association with PbB. In conclusion, ALAD possibly has a non-linear relation with low to moderate levels of PbB. At moderate levels of PbB, ZPP increases with increasing levels of PbB. ALAU is not suitable as an indicator for low levels of lead exposure.

Applications of Tripodal [S(3)] and [Se(3)] L(2)X Donor Ligands to Zinc, Cadmium and Mercury Chemistry: Organometallic and Bioinorganic Perspectives

The tripodal tris(2-mercapto-1-R-imidazolyl)hydroborato ligand system, [Tm(R)], and its selenium counterpart, [Tse(R)], provide useful platforms for investigating organometallic and bioinorganic aspects of the chemistry of zinc, cadmium and mercury in sulfur-rich and selenium-rich coordination environments. For example, the tridentate [Tm(R)] ligand provides an [S(3)] donor array that is of use for mimicking aspects of zinc enzymes and proteins that have sulfur-rich active sites, such as the Ada DNA repair protein. With respect to mercury, an interesting application of the [Tm(Bu(t) )] ligand is the synthesis of the mercury alkyl compounds [Tm(Bu(t) )]HgR (R = Me, Et) that react with PhSH to yield [Tm(Bu(t) )]HgSPh and RH, a reaction that emulates mercury detoxification by the organomercurial lyase, MerB. In addition to the tridentate [Tm(R)] and [Tse(R)] ligands, applications of the bidentate counterparts, [Bm(R)] and [Bse(R)] are also described.

[Lead exposure in pregnant women and newborns: a screening update]

Human lead exposure has many sources. Relative importance of these sources varies widely according to geographic regions and human lifestyle. The impact of lead exposure on health has been well studied and public health interventions have been conducted.

OBJECTIVE

The aim of this study was to evaluate current prevalence of lead burden in neonates, and seek for sources of maternal and fetal intoxication.

POPULATION AND METHODS

A prospective multicentre study was conducted by the "Réseau périnatal 92" on a population of pregnant women attending 3 maternal wards in the north of 'Hauts-de-Seine' department in France. Between December 2003 and May 2004, a total of 1021 pregnant women were included. All patients signed an informed consent before participating in the study. Cord blood samples were collected at delivery for lead measurements.

RESULTS

The mean cord blood lead concentration was 23.2 microg/l. Eighteen neonates over 1021 (1.8%) had lead levels above 100 microg/l. An environmental query was conducted by the social and public health office of the department (DDASS), and data were collected regarding the state of the housing and the lifestyle of the concerned family. Main sources of lead intoxication were 'tagine' food plates in 83.3% of cases, 'khôl' powder (used as eyeliner) in 88.9% of cases and substandard housings in 22.2% of cases. A specialized paediatric follow-up for the 18 neonates was performed.

CONCLUSION

With the exception of substandard housing (old lead painting), other sources of lead intoxication were discovered: 'tagine' plates and 'khôl' powder. Almost all of these products came from Morocco. A public health intervention would be able to inform the population about these yet unknown sources of lead intoxication.

Peptidic models for the binding of Pb(II), Bi(III) and Cd(II) to mononuclear thiolate binding sites

Herein, we evaluate the binding of Pb(II) and Bi(III) to cysteine-substituted versions of the TRI peptides [AcG-(LKALEEK)4G-NH2] which have previously been shown to bind Hg(II) and Cd(II) in unusual geometries as compared with small-molecule thiol ligands in aqueous solutions. Studies of Pb(II) and Bi(III) with the peptides give rise to complexes consistent with the metal ions bound to three sulfur atoms with M-S distances of 2.63 and 2.54 A, respectively. Competition experiments between the metal ions Pb(II), Cd(II), Hg(II) and Bi(III) for the peptides show that Hg(II) has the highest affinity, owing to the initial formation of the extremely strong HgS2 bond. Cd(II) and Pb(II) have comparable binding affinities at pH > 8, while Bi(III) displays the weakest affinity, following the model, M(II) + (TRI LXC)3(3-) --> M(II)(TRI LXC)3(-). While the relevant equilibria for Hg(II) binding to the TRI peptides corresponds to a strong first step forming Hg(TRI LXC)2(HTRI LXC), followed by a single deprotonation to give Hg(TRI LXC)3(-), the binding of Cd(II) and Pb(II) is consistent with initial formation of M(II)(TRI LXC)(HTRI LXC)2 (+) at pH < 5 followed by a two-proton dissociation step (pK(a2)) yielding M(II)(TRI LXC)3(-). Pb(II)(TRI LXC)(HTRI LXC)2(+) converts to Pb(II)(TRI LXC)3(-) at slightly lower pH values than the corresponding Cd(II)-peptide complexes. In addition, Pb(II) displays a lower pK (a) of binding to the "d"-substituted peptide, (TRI L12C, pK(a2) = 12.0) compared with the "a"-substituted peptide, (TRI L16C, pK (a2) = 12.6), the reverse of the order seen for Hg(II) and Cd(II). Pb(II) also showed a stronger binding affinity for TRI L12C (K(bind) = 3.2 x 10(7) M(-1)) compared with that with TRI L16C (K(bind) = 1.2 x 10(7) M(-1)) at pH > 8.

Lead content of dietary calcium supplements available in Brazil

The lead and calcium content of calcium supplements available in Brazil were determined by graphite furnace and flame atomic absorption spectrometry, respectively. Samples were microwave-digested in concentrated HNO(3). Citric acid was used as a chemical modifier in the lead analysis. Supplements were classified into six categories: oyster industrialized (OI, n=4), oyster prepared in pharmacy (OP, n=3), refined industrialized (RI, n=6), refined prepared in pharmacy (RP, n=3), bone meal (B, n=3), and dolomite (D, n=4). Lead levels (microg g(-1) of measured calcium) were higher in D products (2.33), followed by OI, RP, OP, and RI products (1.46, 1.32, 1.29, 0.75), while B products had levels lower than the limit of quantification (0.02 microg g(-1) unit weight). Daily lead intake of eight supplements exceeded the limit of California, USA (1.5 microg g(-1) calcium), but none exceeded the federal limit of USA (7.5 microg g(-1) calcium) or the provisional tolerable lead intake by FAO/WHO (25 microg kg(-1) per week).

Reversal of aminolevulinic acid dehydratase (ALAD) inhibition and reduction of erythrocyte protoporphyrin levels by Vitamin C in occupational lead exposure in Abeokuta, Nigeria

In order to investigate the toxic effects of lead during occupational exposure to this metal, the activity of aminolevulinic acid dehydratase (ALAD) and the concentrations of erythrocyte protoporphyrin (EPP) were determined in blood of various artisans in Abeokuta, Nigeria and these were related to blood lead levels. ALAD activity in the artisans was inhibited to varying extents. ALAD activity was inhibited to the tune of 77% in petrol station attendants while the lowest inhibition of 36% was obtained in the welders. EPP was also significantly increased in the artisans (p<0.001). The highest EPP level of 241.57±89.27μg/100ml of red blood cell was observed in upholsterers. A significant (p<0.001) negative correlation was observed between ALAD activity and blood lead levels on one hand (r=-0.631) and between ALAD activity and EPP on the other hand (r=-0.461). Administration of a daily dose of 500mg ascorbic acid for 2 weeks reversed the lead-induced inhibition of ALAD. Increased EPP levels observed in the artisans also responded positively to the ascorbic acid supplementation. A significant reduction (p<0.001) in blood lead was also observed in the artisans at the end of the 2-week ascorbic acid therapy. Our findings indicate that ascorbic acid may offer more advantages over the conventional agents for the treatment of lead poisoning, especially in cases where the subjects cannot be removed from the source of lead exposure.

Blood lead levels in iron-deficient and noniron-deficient adults

Iron deficiency (ID) has been reported to increase lead absorption. This relationship has been investigated in detail in children but not in adults. This study was designed to investigate whether blood lead levels are significantly higher in iron-deficient adults. ID-parameters (haemoglobin, mean corpuscular volume, mean corpuscular haemoglobin, serum iron, total iron-binding capacity, iron-binding saturation, soluble transferrin receptors, washed zinc protoporphyrin and ferritin) together with whole blood lead were measured in three different adult groups - blood donors (n = 73), pregnant women (n =74) and haemodialysis patients (n = 72). Of a total of 219 subjects tested, 7.7% was found to have a lead level above 10 microg/dl (maximum 16 microg/dl). No association was found between blood lead level and ID [iron-deficient subjects (n: 139), mean: 5.6 microg/dl (SD: 3 microg/dl) and noniron-deficient subjects (n: 80), mean: 5.4 microg/dl (SD: 3 microg/dl)]. The results suggest that the inverse association between blood lead and serum iron in studies carried out on children does not occur in adults.

Factors influencing the difference between maternal and cord blood lead

AIMS

To determine the factors that affect why some infants receive higher exposures relative to the mother's body burden than do others.

METHODS

A total of 159 mother-infant pairs from a cohort of women receiving prenatal care at Magee-Womens Hospital in Pittsburgh, PA from 1992 to 1995 provided blood samples at delivery for lead determination. The difference between cord and maternal blood lead concentration (PbB) and a dichotomous variable indicator of higher cord than maternal PbB, were examined as indicators of relative transfer. Women were interviewed twice during the pregnancy about lifestyle, medical history, calcium nutrition, and physical activity.

RESULTS

Higher blood pressure was associated with relatively greater cord compared with maternal PbB, as was maternal alcohol use. Sickle cell trait and higher haemoglobin were associated with a lower cord relative to maternal blood lead PbB. No association was seen with smoking, physical exertion, or calcium consumption.

CONCLUSION

While reduction in maternal exposure will reduce fetal exposure, it may also be possible to mitigate infant lead exposure by reducing transfer from the pregnant woman. Interventions aimed at reducing blood pressure and alcohol consumption during pregnancy may be useful in this regard.

Ebselen and diphenyl diselenide do not change the inhibitory effect of lead acetate on delta-aminolevulinate dehidratase

It is known that lead is toxic to several species of animals, and growing data support the participation of oxidative in lead toxicity. Selenium compounds, like diphenyl diselenide and Ebselen have a thiol-peroxidase like and other antioxidant properties. In this work, we determine whether these non-thiol-containing compounds with antioxidant properties could reverse the toxicity produced by Pb(2+). Lead acetate injection followed by injection with Ebselen or diphenyl diselenide did not change the levels of non-protein thiol groups (NPSH), whereas simultaneous treatment with lead plus Ebselen reduced NPSH levels in liver. Lead and Ebselen caused a marked reduction in TBARS level in kidney, whereas lead or selenium compounds did not change TBARS levels in brain or liver. Lead acetate inhibited, δ-aminolevulinate dehydratase (ALA-D) activity in blood, liver, kidney and brain. Selenium compounds did not change enzyme activity nor the inhibitory effect of lead acetate in kidney and liver. Ebselen reversed brain ALA-D inhibition caused by Pb(2+). Reactivation index for ALA-D by DTT was higher in lead-treated groups than control groups in all tissues. Lead acetate or selenium compounds did not demonstrate alteration on [(3)H]-glutamate uptake by synaptosomes, whereas lead acetate plus Ebselen showed an increase on [(3)H]-glutamate uptake. The results of the present study indicate that ALA-D inhibition antecedes the overproduction of reactive oxygen species, which is becoming well documented in the literature.

Blood and hair lead levels in boys and girls living in two Sardinian towns at different risks of lead pollution

This study reports blood and hair lead levels measured in 1998 in 222 children from two Sardinian towns: Portoscuso and Sestu. Portoscuso is in a polluted area of Sardinia due to its vicinity to the industrial zone of Portovesme. As a consequence of its economy and location, Sestu is not exposed to lead pollution. Blood lead (PbB) concentration was determined in heparinized venous blood samples by graphite furnace atomic absorption spectrophotometry (AAS). Hair lead (PbH) concentration was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). With respect to blood lead levels, the boys of Portoscuso have the highest arithmetic mean value (11.30 microg/dL), followed by the Portoscuso girls (7.39 microg/dL); they are followed, but with much lower values, by the boys (4.09 microg/dL) and girls (3.34 microg/dL) of Setsu. For hair lead levels, the Portoscuso boys have the highest arithmetic mean value (15.51 microg/g), followed by the Portoscuso girls (8.82 microg/g) and the Sestu boys (4.03 microg/g) and girls (2.83 microg/g). Therefore the mean values of PbB and PbH follow similar patterns in the boys and girls of the two Sardinian towns. Two-way ANOVA reveals a significant effect of sex and town on log PbB and log PbH. Moreover, values of the Bravais-Pearson coefficients of correlation between log PbB and log PbH are statistically significant for the total sample (r=0.5086; P<0.001), for males (r=0.4275; P<0.01), and for females (r=0.4859, P<0.001). The sensitivity of the hair lead analysis in identifying lead concentrations above 10 microg/g is 49%. The results support the hypothesis that hair lead levels can be considered an indicator of different relative exposure of populations to lead pollution.

Elevated blood lead resulting from maxillofacial gunshot injuries with lead ingestion

PURPOSE

The purpose of this study was to identify the contribution of ingested lead particles to elevated blood lead concentrations in victims of gunshot injury to the maxillofacial region.

PATIENTS AND METHODS

As part of a larger study of the effects of retained lead bullets on blood lead, a retrospective review of study findings was completed on 5 of 8 patients who sustained injuries to the maxillofacial region. These 5 patients were recruited into the larger study within 11 days of injury and showed a penetration path for the projectile that engaged the upper aerodigestive tract. All subjects were recruited from patients presenting for care of their gunshot injuries to a large inner-city trauma center with a retained bullet resulting from a gunshot injury. An initial blood lead level was measured for all recruited patients and repeated 1 to 17 weeks later. Medical history was taken along with a screening and risk factor questionnaire to determine other potential or actual sources (occupational/recreational) of lead exposure. (109)Cd K-shell x-ray fluorescence determinations of bone lead were completed to determine past lead exposure not revealed by medical history and risk factor questionnaire. Radiographs taken of the abdomen and chest, required as a part of the patient's hospital care, were retrospectively reviewed for signs of metallic fragments along the aerodigestive tract.

RESULTS

All 5 patients retained multiple lead pellets or fragments at the site of injury, sustained fractures of the facial bones, and showed increases in blood lead. Three of the 5 study subjects who sustained maxillofacial gunshot injuries involving the mouth, nose, or throat region showed metallic densities along the gastrointestinal tract indicative of ingested bullet fragments. Each patient with ingested bullet fragments showed rapid elevation of blood lead exceeding 25 microg/dL and sustained increases well beyond the time when all ingested fragments were eliminated. A 3-year follow-up on these 3 patients showed significantly sustained elevation of blood lead but less than that observed during the initial 6 months after injury. None of the 5 study subjects showed any evidence of metallic foreign bodies within the tracheobronchial regions indicative of aspiration.

CONCLUSION

Ingestion of lead fragments can result from gunshot injuries to the maxillofacial region and may substantially contribute to a rapid increase in blood lead level. Prompt diagnosis and elimination of ingested lead fragments are essential steps necessary to prevent lead being absorbed from the gastrointestinal tract. Increased blood lead in victims after gunshot injuries must be fully evaluated for all potential sources, including recent environmental exposure, absorption of lead from any remaining bullets in body tissues, and the possibility of mobilization of lead from long-term body stores such as bone.

Exposure to lead during critical windows of embryonic development: differential immunotoxic outcome based on stage of exposure and gender

Previous rat studies with lead (Pb) have shown that exposure throughout the full gestational period results in persistent immunotoxicity detectable in both juvenile and adult offspring. Gender differences are also evident. However, little is known about the persistent immunotoxic effects of Pb when administered during specific stages of embryonic development. Adult Sprague-Dawley female rats were administered Pb acetate (or control acetate) in their drinking water early in gestation (days 3-9) or late in gestation (days 15-21). Significantly depressed delayed type hypersensitivity (DTH) responses as well as elevated IL-10 production, relative monocyte numbers, and increased relative thymic weights were observed in late-gestation Pb-exposed female offspring assessed as adults. In contrast, late-gestation Pb-treated male offspring had significantly increased IL-12 production and decreased IL-10 production, while the DTH response, relative monocyte numbers and thymic weights were unchanged. With early exposure, the primary alteration was decreased nitric oxide production in Pb-treated males, whereas in Pb-treated females nitrite production was unaltered. These results suggest that at the Pb dosage employed, the embryo may be more sensitive to the full range of Pb-induced immunotoxic effects with late gestational Pb exposure, and the effects of Pb on DTH function are more pronounced in females. The data also indicate that adherent splenocytes (probably macrophages) and T lymphocytes are the primary immune cells affected during fetal Pb exposure, and that gender may influence the impact of Pb exposure on these cells. Therefore, additional developmental immunotoxicity studies are needed to examine critical windows of immune development for immunotoxicity and differential susceptibility based on gender.

Color vision and occupational toluene exposure

We examined the relationship between acquired color vision loss and exposure to toluene and total hydrocarbons among 125 male workers. Seventy-two toluene-exposed printers were compared with 34 workers from the same photogravure plant with ambient background exposure, and with 19 workers from a bookbinding plant located in the same town (nonexposed). Environmental mean toluene exposure level at workstation was estimated from individual 8-h sampling. Historic exposure data from the last 30 years were used to construct two cumulative exposure indices, one for toluene and one for total hydrocarbons. Airborne toluene levels were overall lower than the current Threshold Limit Value (TLV) of 50 ppm. Color vision was assessed by the Lanthony D-15 desaturated panel. Color vision loss was quantitatively established by the Color Confusion Index (CCI) and classified by type of acquired dyschromatopsia according to Verriest's classification. CCI was positively related to current airborne toluene levels, and cumulative exposure indices for toluene and total hydrocarbons (.18< or =r< or =.35). Odds ratios of acquired dyschromatopsia were significant for current airborne toluene, toluene, and total hydrocarbon past exposure (1.27 [1.02-1.58], 1.21 [1.04-1.39], 1.15 [1.02-1.31], respectively). In conclusion, this study suggests that the Lanthony D-15 desaturated panel detects early neurotoxic effects among workers exposed to toluene.

Spectrophotometric Microassay for δ-Aminolevulinate Dehydratase in Dried-Blood Spots as Confirmation for Hereditary Tyrosinemia Type I

Background: Hereditary tyrosinemia type I (HT) fulfills the criteria for inclusion in neonatal screening programs, but measurement of tyrosine lacks clinical specificity and quantitative assay of succinylacetone is laborious. We developed a semiquantitative assay based on inhibition of δ-aminolevulinate dehydratase (ALA-D) by succinylacetone.

Methods: Preincubation of 3-mm discs from dried-blood spots and reaction of the enzyme with δ-aminolevulinic acid as substrate were performed in microtiter plates. After separation of the supernatant and 10 min of color reaction with modified Ehrlich reagent, the formation of porphobilinogen was measured at 550 nm in a plate reader.

Results: The detection limit for succinylacetone was 0.3 μmol/L; imprecision (CV) was &lt;5.5% within-run and 10–16% between-run. Storage of blood spots at ambient temperature for several days led to a significant decrease of ALA-D activity. Enzyme activity was lost in filter cards at 45 °C, but remained stable at 2–37 °C. Enzyme activity was decreased in EDTA blood. The absorbance at 550 nm was 0.221 (± 0.073) in healthy neonates and 0.043–0.100 in 11 patients with HT. All neonates with increased tyrosine (above the 99.5th centile) in neonatal screening (97 of 47 000) had normal results by the new assay.

Conclusions: The spectrophotometric microassay for ALA-D is a simple and sensitive test for HT. This represents a basis for further examination of its general reliability as a confirmatory test if tyrosine is found to be increased.

The Effects of Retained Lead Bullets on Body Lead Burden

BACKGROUND

Numerous case reports have demonstrated that lead poisoning with potentially fatal consequences can result from retained lead projectiles after firearm injuries. To assess the impact of retained projectiles on subsequent lead exposure in the population, one cannot rely on self-selected cases presenting with symptoms of lead intoxication. This preliminary study seeks to identify increased lead burden and identify risk factors of elevated blood lead levels for individuals with retained lead bullets.

METHODS

Forty-eight patients were originally recruited from gunshot victims presenting for care at the King/Drew Medical Center in Los Angeles, California. An initial blood level was measured for all recruited patients and repeated for the 28 participants available for follow-up, 1 week to 8 months later. Medical history, including a history of prior firearm injuries and other retained projectiles, was taken, along with a screening and risk factor questionnaire to determine other sources of lead (occupational/recreational) to which the patient might have been, or is at present, exposed. The participants also had K-shell x-ray fluorescence determinations of bone lead in the tibia and calcaneus in order to determine past lead exposures not revealed by medical history and risk factor questionnaire. Multivariate models of blood level were made using risk factor and bone lead concentration data.

RESULTS

We demonstrated that blood lead tends to increase with time after injury in patients with projectile retention, and that the increase in significant part depended on the presence of a bone fracture caused by the gunshot.

CONCLUSION

We encountered evidence suggesting that the amount of blood lead increase in time after injury is also dependent on the tibia lead concentration. There were too few cases in the study to fully test the effects of bullet location, or the interaction of bullet location with bone fracture or bullet fragmentation.