Recommendations for medical management of adult lead exposure

Individual susceptibility and genotoxicity in workers exposed to hazardous materials like lead

The present study was undertaken to investigate lead-induced toxicity in occupationally exposed humans and to evaluate whether genetic damage can be correlated with the known clinical indicators of lead poisoning. For this purpose, genotoxicity biomarkers along with some clinical indices of lead poisoning were determined in blood samples of battery plant workers and compared with healthy control subjects. Workers had significantly increased chromosomal aberrations, micronuclei and DNA damage compared to the controls. Increased blood lead levels (BLLs), decreased hemoglobin, PCV and symptoms of lead poisoning were used as clinical indices of lead toxicity. In addition gene polymorphisms in ALAD and MGP gene were investigated and correlated with BLL and hemoglobin content. Our results showed no significant effects of the ALAD G177C polymorphism on BLL concentrations and BLL concentrations varied to levels much above the normal reference ranges independent of the genotype. Although, significance could not be achieved, ALAD 1-2/2-2 type subjects had numerically higher BLLs (76.2-89.1 microg/dl), compared to ALAD 1-1 volunteers (21.8-79.1 microg/dl). Similarly, this study also aimed to identify the relation of some SNPs with emphasis on lead toxicity and since MGP gene is an important biomarker associated with calcium metabolism; it was hypothesized that it may be associated with lead toxicity. However, we did not find any significant association of MGP T-138C and lead poisoning. Further studies on the role of gene polymorphisms over a larger population along with genotoxicity parameters and biochemical analyses may serve to understand lead toxicity.

Pyrithione and 8-hydroxyquinolines transport lead across erythrocyte membranes

Acute and chronic lead poisoning remains a significant health problem. Although chelating agents can bind to plasma lead, they cannot cross cell membranes where the total body lead burden resides, and are thus inefficient at reducing the total body lead burden. Recently, calcium and sodium ionophores have been shown to transport lead across cell membranes providing a novel method for reducing total body lead stores. We recently found that clioquinol, an 8-hydroxyquinoline derivative, can act as a zinc ionophore. We postulated that zinc ionophores might also be able to transport lead across biological membranes. To study this, we loaded lead in vitro into human erythrocytes and then studied the ability of zinc ionophores to transport lead into the extracellular space, where it was trapped with a lead chelator. Using inductively coupled plasma mass spectrometry (ICP-MS), we found that several 8-hydroxyquinoline derivatives, as well as the zinc and sodium salts of pyrithione (N-hydroxypyridine-2-thione), reduced erythrocyte lead content. The water-soluble compound, sodium pyrithione, was able to reduce lead in citrated whole blood, without partitioning into the erythrocytes. These results indicate that two classes of zinc ionophores can transport lead across a biological membrane, and they confirm that these ionophores are not cation-specific. Lead ionophores may prove useful in mobilizing lead into the extracellular space, thereby improving the efficacy of chelation therapy, in vivo or ex vivo.

The Erlenmeyer flask bone deformity in the skeletal dysplasias

Erlenmeyer flask bone deformity (EFD) is a long-standing term used to describe a specific abnormality of the distal femora. The deformity consists of lack of modeling of the di-metaphysis with abnormal cortical thinning and lack of the concave di-metaphyseal curve resulting in an Erlenmeyer flask-like appearance. Utilizing a literature review and cohort study of 12 disorders we found 20 distinct disorders were associated with EFD. We interrogated the International Skeletal Dysplasia Registry (ISDR) radiographic database (1988-2007) to determine which skeletal dysplasias or syndromes were highly associated with EFD, whether it was a uniform finding in these disorders, and if forms of EFD could be differentiated. EFD was classified into three groups. The first catogory was the typical EFD shaped bone (EFD-T) resultant from absent normal di-metaphyseal modeling with relatively normal appearing radiographic trabecular bone. EFD-T was identified in: frontometaphyseal dysplasia, craniometaphyseal dysplasia, craniodiaphyseal dysplasia, diaphyseal dysplasia-Engelmann type, metaphyseal dysplasia-Pyle type, Melnick-Needles osteodysplasty, and otopalatodigital syndrome type I. The second group was the atypical type (EFD-A) due to absence of normal di-metaphyseal modeling with abnormal radiographic appearance of trabecular bone and was seen in dysosteosclerosis and osteopetrosis. The third group was EFD-marrow expansion type (EFD-ME) in which bone marrow hyperplasia or infiltration leads to abnormal modeling (e.g., Gaucher disease). Further, radiographic review determined that it was not always a consistent finding and that there was variability in both appearance and location within the skeleton. This analysis and classification aided in differentiating disorders with the finding of EFD.

Elevated blood lead levels in a riverside population in the Brazilian Amazon

Lead (Pb) is recognized as one of the most toxic metals. Sources of Pb exposure have been widely documented in North America, and the removal of Pb additives from gasoline was reflected in a dramatic lowering of blood Pb concentration. In Latin America, the removal of Pb from gasoline resulted in decreased exposure, but Pb levels in many areas remain high due to occupational and environmental sources of exposure. While many of the Pb sources have been identified (mining, industries, battery recycling, lead-based paint, ceramics), new ones occasionally crop up. Here we report on blood Pb (B-Pb) levels in remote riverside communities of the Brazilian Amazon. Blood Pb (B-Pb) levels were determined in 448 persons from 12 villages of the Lower Tapajós River Basin, Pará, Brazil. Socio-demographic and dietary information, as well as occupational, residential and medical history was collected using an interview-administered questionnaire. B-Pb, measured by ICP-MS, showed elevated concentrations. Mean B-Pb was 13.1 microg/dL +/- 8.5, median B-Pb was 11.2 microg/dL and ranged from 0.59 to 48.3 microg/dL. Men had higher B-Pb compared to women (median: 15.3 microg/dL vs 7.9 microg/dL respectively). B-Pb increased with age for women, while it decreased for men. For both genders, B-Pb decreased with education. There were significant differences between villages. Exploratory analyses, using linear partition models, showed that for men B-Pb was lower among those who were involved in cattle-raising, and higher among those who hunted, farmed and fished. The distribution profile of B-Pb directed us towards artisanal transformation of manioc to flour (farinha), which requires heating in a large metal pan, with stirring primarily done by young men. In the village with the highest B-Pb, analysis of Pb concentrations (dry weight) of manioc (prior to transformation) and farinha (following transformation) from 6 houses showed a tenfold increase in Pb concentration (mean: 0.017 +/- 0.016 to 0.19 +/- 0.10 microg/g). This was confirmed in one of these villages where we sampled manioc paste (just before roasting) and the roasted farinha (0.05 microg/g vs 0.20 microg/g). While there may be other sources (ammunition, sinkers for fishing nets), the high concentrations in farinha, a dietary staple, assuredly makes an important contribution. Further action needs to reduce Pb sources in this region.

The lead industry and public health

In 2003, the Association of Occupational and Environmental Clinics (AOEC) formed a panel to develop consensus guidelines for the treatment of lead-exposed adults. However, a consensus was never reached due to interference from lead industry representatives. Lead industry interference in the AOEC panel is one instance of a long history of industry opposition to occupational and public health measures to prevent lead poisoning because of potential costs to the industry. At the time the AOEC panel was formed, no published guidelines existed for the medical management of lead exposure in adults comparable to the Center for Disease Control and Prevention (CDC) guidelines for managing lead exposure in children. Representatives of the lead industry frustrated the AOEC panel by insisting that "feasibility" (economic issues) be part of the medical decision-making process.

Lead poisoning due to adulterated marijuana in leipzig

BACKGROUND

Between August and December 2007, a mass poisoning due to adulterated marijuana was uncovered in the area of Leipzig, Germany.

METHODS

Retrospective reports of patients with lead poisoning who were treated at Leipzig University Hospital. Analysis of data from the local health office, where marijuana consumers could have their blood lead concentration determined.

RESULTS

At Leipzig University Hospital, 35 patients (7 female; age 24.2 +/- 4.4 years) had to be treated for lead poisoning (blood lead levels 1063.3 +/- 864.0 microg/L). Five hundred ninety-seven marijuana consumers (439 men, 158 women; age 26.9 +/- 4.8 years) had their blood lead levels measured at the local health office. Among them, 27.3% had lead levels above the HBM-II threshold, 12.2% had concentrations that required monitoring, and 60.5% had levels below the HBM-I threshold.

CONCLUSION

Drug consumption should be considered in otherwise unexplained anemia and abdominal colic. Several hundred people suffered lead poisoning presumably resulting from the desire of drug dealers to maximize profits.

Characteristics of US workers whose blood lead levels trigger the medical removal protection provision, and conformity with biological monitoring requirements, 2003-2005

BACKGROUND

Workers with blood lead levels (BLL) > or =60 microg/dl (50 microg/dl for construction workers) or with three or more consecutive BLLs over at least 6 months that average 50 microg/dl or greater are required to be removed from work involving lead exposure that exceeds the OSHA action level. This study estimates the proportion of workers with BLLs that trigger the medical removal provision by industry sector, and examines whether workers received appropriate follow-up blood lead testing.

METHODS

Three years (2003-2005) of data from the Adult Blood Lead Epidemiology and Surveillance program were analyzed to identify those industries with a high percentage of workers with BLLs that trigger the medical removal provision. Adjusted rate ratios (RR) of adults with such BLLs were estimated by industry sector compared to the battery manufacturing industry using Poisson regression models.

RESULTS

Out of 13,724 adults with BLLs > or =25 microg/dl, a total of 533 adults had BLLs that triggered the medical removal provision. RRs of adults with BLLs triggering medical removal were highest for "painting and wall covering contractors" (RR = 22.1) followed by "highway, street and bridge construction" (RR = 14.7), "amusement, gambling, and recreation" (RR = 11.4), and "glass product manufacturing" (RR = 10.1). Overall, 29% of adults with BLLs triggering medical removal received appropriate follow-up blood lead tests and met the eligibility to return to lead work.

CONCLUSIONS

These findings suggest that additional efforts are needed to prevent occupational overexposure to lead in adults, and to ensure proper medical management of those workers who meet medical removal criteria.

Exposure to heavy metals (lead, cadmium and mercury) and its effect on the outcome of in-vitro fertilization treatment

We investigated the effect of lead, cadmium and mercury exposure on pregnancy and fertilization rate outcome among 619 Saudi women (age 19-50 years) who sought in-vitro fertilization (IVF) treatment between 2002 and 2003. The concentrations of lead, cadmium and mercury were measured in both blood and follicular fluids. At levels well below the current US occupational exposure limit guidelines (40microg/dL) and even less than the current Centers for Disease Control and Prevention level of concern for preventing lead poisoning in children (10microg/dL), blood lead level was negatively associated with fertilization outcome in both adjusted and unadjusted logistic regression models. We found that among various demographic, socioeconomic and environmental factors, fish consumption was positively associated with blood lead levels. These results support the hypothesis that a raised blood lead level affects infertility and intervention to reduce the lead exposure might be needed for women of reproductive age. The present results also revealed unexpected finding - the positive relationship between follicular cadmium levels and fertilization outcome, which points to the necessity for further investigation. Though adverse effect of mercury on pregnancy outcome or fertilization rate was not evident in this study, mercury5.8microg/L (EPA safety limit) was found in the blood and follicular fluid of 18.7% and 8.3% of the women, respectively. Concerns about its possible adverse effects on the physiology of reproduction or fetal development cannot be ruled out. It should be noted that skin-lightening creams and dental amalgam were important contributors to mercury exposure. Such finding is alarming and priority for further studies are, urgently, needed.

Evaluation of a second-generation portable blood lead analyzer in an occupational setting

BACKGROUND

A new blood lead testing instrument has qualities that make the instrument attractive for on-site testing of occupational lead exposures. This study evaluated the accuracy of the instrument when used in a manufacturing setting, and examined the impact of blood storage and shipment on results.

METHODS

Venous blood specimens (n=121) were obtained and immediately analyzed on-site using the new instrument. They were then shipped to a reference laboratory and analyzed using electro-thermal atomization atomic absorption spectrometry (ETAAS), and retested using the new instrument.

RESULTS

The cohort blood lead concentration averaged 40.1 microg/dl. Results obtained on the new analyzer with freshly collected blood averaged 38.7 microg/dl. The mean difference of 1.2 microg/dl on paired samples was not statistically significant. Following blood shipment and storage, results on the analyzer increased to an average of 42.4 microg/dl. The mean increase of 3.0 microg/dl on stored blood samples also failed to reach statistical significance. Under OSHA proficiency test acceptability requirements, 94% of the results had satisfactory agreement.

CONCLUSIONS

The new analyzer might be a useful tool for on-site monitoring of occupational lead exposures. The manufacturer's instructions should be adhered to with respect to specimen age and storage requirements.

Lead and cognitive function in adults: a questions and answers approach to a review of the evidence for cause, treatment, and prevention

Lead has been extensively used worldwide in gasoline, consumer products, commercial applications, and industrial settings. Its use in gasoline and paint has been particularly hazardous to public health leading to widespread population exposure and substantial lifetime cumulative doses in most Americans over age 40 years. Cumulative lead dose can be estimated by measuring the current concentration of lead in tibia bone by X-ray fluorescence. A growing literature has documented that tibia lead levels are associated with decrements in cognitive function and declines in cognitive function over time. Furthermore, there are several interesting lines of biochemical and epidemiological investigation that have demonstrated potential links of lead to neurodegenerative diseases. These studies support the inference that a proportion of what has been termed 'normal' age-related cognitive decline may, in fact, be due to exposure to neurotoxicants such as lead. Well-designed studies of cumulative lead dose and Alzheimer's disease risk should be conducted to follow-up on these leads. The strong and compelling body of literature on lead and cognitive dysfunction and decline also supports a need for intervention studies to prevent lead-related cognitive decline.

Update on the clinical management of childhood lead poisoning

Childhood lead poisoning is still an enormous public health issue in the United States, affecting thousands of children and their families. New evidence suggests that even very low blood lead levels, less than 10 microg/dL, can be associated with neurologic injury. This article discusses characteristics of children at high risk for lead poisoning, unusual sources of lead contamination, and new aspects of lead's pathophysiology. It includes current thinking on the clinical management and prevention of childhood lead poisoning.

Cumulative lead dose and cognitive function in adults: a review of studies that measured both blood lead and bone lead

OBJECTIVE

We review empirical evidence for the relations of recent and cumulative lead dose with cognitive function in adults.

DATA SOURCES

A systematic search of electronic databases resulted in 21 environmental and occupational studies from 1996 to 2006 that examined and compared associations of recent (in blood) and cumulative (in bone) lead doses with neurobehavioral outcomes.

DATA EXTRACTION

Data were abstracted after consideration of exclusion criteria and quality assessment, and then compiled into summary tables.

CONCLUSIONS

At exposure levels encountered after environmental exposure, associations with bio-markers of cumulative dose (mainly lead in tibia) were stronger and more consistent than associations with blood lead levels. Similarly, in studies of former workers with past occupational lead exposure, associations were also stronger and more consistent with cumulative dose than with recent dose (in blood). In contrast, studies of currently exposed workers generally found associations that were more apparent with blood lead levels; we speculate that the acute effects of high, recent dose may mask the chronic effects of cumulative dose. There is moderate evidence for an association between psychiatric symptoms and lead dose but only at high levels of current occupational lead exposure or with cumulative dose in environmentally exposed adults.

Adult lead exposure: time for change

We have assembled this mini-monograph on adult lead exposure to provide guidance to clinicians and public health professionals, to summarize recent thinking on lead biomarkers and their relevance to epidemiologic research, and to review two key lead-related outcomes, namely, cardiovascular and cognitive. The lead standards of the U.S. Occupational Safety and Health Administration are woefully out of date given the growing evidence of the health effects of lead at levels of exposure previously thought to be safe, particularly newly recognized persistent or progressive effects of cumulative dose. The growing body of scientific evidence suggests that occupational standards should limit recent dose to prevent the acute effects of lead and separately limit cumulative dose to prevent the chronic effects of lead. We hope this mini-monograph will motivate renewed discussion of ways to protect lead-exposed adults in the United States and around the world.