Statistically significant hematopoietic effects of low blood lead levels

Genetic susceptibility of δ-ALAD associated with lead (Pb) intoxication: sources of exposure, preventive measures, and treatment interventions

Delta-aminolevulinic acid dehydratase (δ-ALAD) is involved in the synthesis of haem and exhibits a polymorphic nature. δ-ALAD polymorphism produces two alleles, namely δ-ALAD-1 and δ-ALAD-2, which in turn produce three different phenotypes, namely δ-ALAD1-1, δ-ALAD1-2, and δ-ALAD2-2. δ-ALAD gene is more susceptible to lead (Pb) toxicity than any other genes. Its genotype and phenotype frequencies change with respect to different geographical areas and extent of Pb exposure. The δ-ALAD-2 allele dominancy is linked with high concentration of lead in the body. It has also been thought that the δ-ALAD-2 allele can provoke Pb toxicity by producing a protein that binds more tightly with Pb than δ-ALAD-1 protein. However, few evidences suggest that δ-ALAD-2 may reduce harmful effects by increasing excretion of Pb from the body, thus producing its unavailability towards pathophysiologic alterations. However, the recent evidences have supported that the individuals who are heterozygote for the δ-ALAD-1 allele may be associated with a higher risk of long-term Pb toxicity. In this regard, the individuals who are exposed at occupational levels are among the most frequent study population. The main objective of our study was to explore the gene susceptibility associated with Pb poisoning. Moreover, this study also summarizes various sources of Pb exposure and thereafter outlined multiple strategies to minimize the Pb toxicity in order to save the exposed residential communities.

Ameliorative effects of nutritional minerals on lead-induced hematological alterations in male Wistar albino rats

The deficiency of essential minerals increases lead absorption and thus aggravates the lead-induced toxic effects. This study was aimed at understanding the ameliorative effect of essential minerals on lead-induced alterations in hematological parameters in rats. To achieve this objective, the study was conducted in 320 male Wistar albino rats, grouped into two, with equal numbers. One of the groups of rats was fed on a mineral-supplemented food referred to as a 'well-nourished group' and another group 'undernourished group' on food without mineral supplements. Each group of rats was further subdivided into 'Subjects' and 'Controls.' Subjects of both the groups of rats were exposed to 500 ppm lead acetate up to a period of 300 days (10 months) in drinking water and the role of minerals on lead-induced alterations in hematological parameters was evaluated. A significant decrease (p < 0.001) in hemoglobin (Hb) and δ-aminolevulinic acid dehydratase (δ-ALAD) levels and a significant increase (p < 0.001) in urinary δ-aminolevulinic acid (δ-ALAU) levels were seen in subjects without mineral supplementation compared to those fed on a mineral-enriched diet. A positive correlation was observed between blood lead levels (PbB) and δ-ALAU (r = 0.792) and a negative correlation with Hb (r = -0.926) and δ-ALAD (r = -0.836) in the subjects. These changes were very prominent in the undernourished subjects when compared to the well-nourished subjects. Observations of the present study indicate that mineral supplementation with ongoing lead exposure may help in minimizing the absorption of lead and reduce lead-induced toxic effects.

Should all patients with unexplained anaemia be screened for chronic lead poisoning?

The global prevalence of lead poisoning is declining. However, the prevalence of lead poisoning in patients with either microcytic or normocytic anaemia is unknown. Blood samples from anaemic patients residing in south-east London without an obvious cause for anaemia had their blood lead concentration (BLC) analysed.A batch of 988 samples was analysed for BLC using atomic absorption spectroscopy. Median haemoglobin was 10.3 g/dL (range: 4.2–10.9) in females, 10.6 g/dL (range: 5.2–11.4) in males and 10.7 g/dL (range: 6.7–10.9) in children. Median BLC was 2.63 μg/dL (0.21–24.0 μg/dL; 95th centile 7.54 μg/dL). Fifteen samples (1.5%) had a BLC>10.0 μg/dL, five samples (1%)>15.0 μg/dL and one sample (0.1%)>20.0 μg/L. In the 106 children, median BLC was 2.34 μg/dL (0.5–14.5 μg/dL; 95th centile 6.12 μg/ dL). Only one child (14.5 μg/L) had a BLC>10.0 μg/dL. There was a poor correlation between haemoglobin and BLC (r2=0.08).Routine screening for lead poisoning cannot be justified in all patients with unexplained anaemia, unless there is a history or clinical features to suggest lead toxicity. Additionally, we have shown that in this former high-risk area for lead exposure, there is a low point prevalence of significant lead poisoning, even in an anaemic population.

Assessment of heavy metal exposure via the intake of oriental medicines in Korea

Oriental medical herbs are mainly natural products that are generated by simple processes, and therefore there is the possibility of contamination with various pollutants, including heavy metals. Heavy metals produce adverse effects in humans, and the toxicities of lead (Pb) and cadmium (Cd) are well established. This study evaluated the effects of exposure to Pb and Cd via the intake of the frequent prescriptions of oriental medicines, and assessed the risk to the Korean population based on domestic data. The average daily exposures to Pb and Cd were estimated. This is the first study to evaluate exposure and risk of heavy metal intoxication through intake of oriental medicines in Korea. Despite the uncertainties and limits of the data, these results simulate realistic exposure levels.

Benchmark dose of lead inducing anemia at the workplace

To estimate the critical dose of lead inducing anemia in humans, the effects of lead on hemoglobin (Hb) and hematocrit (Hct) levels and red blood cell (RBC) count were examined in 388 male lead-exposed workers with blood lead (BPb) levels of 0.05-5.5 (mean 1.3) micromol/L by using the benchmark dose (BMD) approach. The BPb level was significantly related to Hb (regression coefficient beta=-0.276), RBC (beta=-11.35), and Hct (beta=-0.563) among the workers (p < 0.001) when controlling for age and working status. The average BPb levels were significantly higher in the workers with anemia (1.85 micromol/L), based on the WHO criteria, than in those without anemia (1.26 micromol/L). The benchmark dose levels of BPb (i.e., lower 95% confidence limits of BMD), calculated from the K-power model set at an abnormal probability of 5% in unexposed workers and an excess risk of 5% in exposed workers were estimated to be 0.94 micromol/L (19.5 microg/dl) for Hb, 0.94 micromol/L (19.4 microg/dl) for RBC, and 1.43 micromol/L (29.6 microg/dl) for Hct. These findings suggest that reduction in hematopoietic indicators may be initiated at BPbs below the level currently considered without effect.

The effect of low-level blood lead on hematologic parameters in children

A health survey of school children living in polluted regions of eastern Germany provided us with data necessary to examine the effects of lead on the blood system at levels below current standards for blood lead content. Data collected for 797 children, aged 5-14 years, with low blood lead levels (GM, 33.3 microg Pb/L; range, 7.5-239 microg Pb/L) allowed us to examine the relationship between blood lead content and hematological parameters. Using linear regression analyses and controlling for a number of potential confounding factors, we found that increasing blood lead levels by 10 microg/L were associated with a small increase in the number of red blood cells and in girls with reduced MCV and MCH. The reasons for our observation, especially the gender difference, are still uncertain. In conclusion the morphology and function of erythrocytes might be sensitive parameters of low dose lead toxicity.

Adverse effects of reduced-dose d-penicillamine in children with mild-to-moderate lead poisoning

BACKGROUND

Oral chelation therapy with d-penicillamine (d-PCN) has been proven to be effective in the treatment of mild-to-moderate lead poisoning. However, d-PCN is associated with a relatively high incidence of adverse effects when given in the standard dose of 25-30 mg/kg/d. Lower doses of d-PCN may reduce the rate of adverse effects without a significant reduction in the drug's efficacy.

OBJECTIVE

To examine the incidence of rash, white blood cell and platelet count depression, and abnormal urinalysis with d-PCN when given in a dose of 15 mg/kg/d to children with blood lead concentrations <40 microg/dL.

METHODS

Retrospective analysis of a clinical treatment course of children who received d-PCN during 1996 in the Lead and Toxicology Clinic of Children's Hospital, Boston. All children were treated under a reduced-dose d-PCN chelation protocol.

RESULTS

During the study period, 55 children (mean age 37.4 mo) received 66 courses of d-PCN. Mean blood lead concentration before chelation was 24 microg/dL (range 15-37), with a corresponding erythrocyte protoporphyrin concentration of 42 microg/dL. After 77 days of treatment with d-PCN, blood lead concentration was reduced to mean 16 microg/dL (mean fall 35%; p = 0.005) and erythrocyte protoporphyrin was reduced to 28 microg/dL (p = 0.009). During chelation therapy, the white blood cell count fell below 5,000/mm3 in seven cases (9.7%); there were no episodes of platelet counts falling below 150,000/mm3. No cases of abnormal urinalysis were reported; three episodes of rash (4.5%) were recorded. The only patients prematurely terminated from therapy were those who developed rash; in all three cases, drug eruption was an isolated occurrence, which resolved within 48 hours of diphenhydramine therapy. All adverse effects were transient and resolved during or immediately after chelation therapy.

CONCLUSIONS

Reduced-dose d-PCN appears to maintain efficacy at reducing blood lead concentrations. Reduced-dose d-PCN also appears to be associated with a rate of adverse effects lower than previously reported; observed adverse effects appear to be benign and transient.

Temporal changes in blood lead levels of hazardous waste workers in New Jersey, 1984-1987

The blood lead levels of 568 New Jersey hazardous waste workers were determined at least once in the period 1984-1987. Workers almost always wore protective clothing in the field, which should have prevented exposure to lead. Therefore, despite their occupation, these workers are probably representative of the New Jersey suburban population in the mid-1980s. Blood lead levels ranged from 2.0-20.7 µg/dL, with an arithmetic mean value of 5.8 µg/dL, representing a decline from levels measured a decade earlier, but there was no clear change over the four years of the study. Blood lead levels increased with age of the worker up to age 60. Women showed lower levels than men in every age group.