A comparison of different lead biomarkers in their associations with lead-related symptoms

A State-of-the-Science Review on Metal Biomarkers

PURPOSE OF REVIEW

Biomarkers are commonly used in epidemiological studies to assess metals and metalloid exposure and estimate internal dose, as they integrate multiple sources and routes of exposure. Researchers are increasingly using multi-metal panels and innovative statistical methods to understand how exposure to real-world metal mixtures affects human health. Metals have both common and unique sources and routes of exposure, as well as biotransformation and elimination pathways. The development of multi-element analytical technology allows researchers to examine a broad spectrum of metals in their studies; however, their interpretation is complex as they can reflect different windows of exposure and several biomarkers have critical limitations. This review elaborates on more than 500 scientific publications to discuss major sources of exposure, biotransformation and elimination, and biomarkers of exposure and internal dose for 12 metals/metalloids, including 8 non-essential elements (arsenic, barium, cadmium, lead, mercury, nickel, tin, uranium) and 4 essential elements (manganese, molybdenum, selenium, and zinc) commonly used in multi-element analyses.

RECENT FINDINGS

We conclude that not all metal biomarkers are adequate measures of exposure and that understanding the metabolic biotransformation and elimination of metals is key to metal biomarker interpretation. For example, whole blood is a good biomarker of exposure to arsenic, cadmium, lead, mercury, and tin, but it is not a good indicator for barium, nickel, and uranium. For some essential metals, the interpretation of whole blood biomarkers is unclear. Urine is the most commonly used biomarker of exposure across metals but it should not be used to assess lead exposure. Essential metals such as zinc and manganese are tightly regulated by homeostatic processes; thus, elevated levels in urine may reflect body loss and metabolic processes rather than excess exposure. Total urinary arsenic may reflect exposure to both organic and inorganic arsenic, thus, arsenic speciation and adjustment for arsebonetaine are needed in populations with dietary seafood consumption. Hair and nails primarily reflect exposure to organic mercury, except in populations exposed to high levels of inorganic mercury such as in occupational and environmental settings. When selecting biomarkers, it is also critical to consider the exposure window of interest. Most populations are chronically exposed to metals in the low-to-moderate range, yet many biomarkers reflect recent exposures. Toenails are emerging biomarkers in this regard. They are reliable biomarkers of long-term exposure for arsenic, mercury, manganese, and selenium. However, more research is needed to understand the role of nails as a biomarker of exposure to other metals. Similarly, teeth are increasingly used to assess lifelong exposures to several essential and non-essential metals such as lead, including during the prenatal window. As metals epidemiology moves towards embracing a multi-metal/mixtures approach and expanding metal panels to include less commonly studied metals, it is important for researchers to have a strong knowledge base about the metal biomarkers included in their research. This review aims to aid metals researchers in their analysis planning, facilitate sound analytical decision-making, as well as appropriate understanding and interpretation of results.

Cardiovascular dysfunction and oxidative stress following human contamination by fluoride along with environmental xenobiotics (Cd & Pb) in the phosphate treatment area of Togo, West Africa

In Togo, the phosphate ore mill discharges waste containing xenobiotics like cadmium, lead and fluoride. If the role of heavy metals in the appearance of pathologies is known, the role of fluoride remains to be studied alongside xenobiotics. This study tested the hypothesis that the toxicity of fluoride contributes, along with heavy metals, to physiological dysfunction. In this process, we have studied the variation in the parameters of cardiovascular functioning, depending on the level of human contamination by fluoride and xenobiotics. The concentration of Cd and Pb in blood samples were determined by AAS and fluoride by titanium-chloride method. Lipid peroxidation, the total antioxidant potential of collected blood samples and the parameters of cardiovascular dysfunction were also measured. Cd, Pb and F contents and lipid peroxidation were found to be significantly elevated in polluted areas than control zone as well as total cholesterol, LDL and triglyceride. HDL and antioxidant potential of blood decreased in the polluted areas. Correlation tests showed that fluoride levels are related to variations in the bio-indicators of high blood pressure and oxidative stress (R varied from 0.354 to 0.907). Togo phosphate treatment leads to human contamination with fluoride, along with Cd and Pb, increasing the risk of cardiovascular dysfunction and oxidative stress.

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.

Advanced pharmacotherapy evidenced by pathogenesis of autism spectrum disorder

In clinical practice, pharmacological treatment is mostly focused on behavioral symptoms in everyday life. Nevertheless, persistent effort continues to develop medication for causal treatment. Recent changes in diagnostic criteria from Diagnostic and Statistical Manual of Mental Disorders, 4th edition, text revision (DSM-IV-TR) to DSM-5 would affect not only diagnosing approaches, but also therapeutic approaches. Because previous pervasive developmental disorders have been integrated into a single entity, the autism spectrum disorder (ASD), we have to prepare for what medications are valuable for the ASD. In this article, we reviewed the following etiological treatment: acetylcholine and glutamate related medicine; amino acid medicine such as secretin, endogenous opioid, and oxytocin; complementary and alternative medicine such as chelating agents, vitamins, and omega-3; promising drugs related to the scope of pharmacogenetics currently under study.

Magnesium, calcium, and trace elements excretion in 24-h urine

Urine is a clinical specimen often used in medical diagnostics for monitoring of elements concentrations and kidneys function. We determined the contents of magnesium (Mg), calcium (Ca), zinc (Zn), copper (Cu), iron (Fe), lead (Pb), and cadmium (Cd) in 74 samples of 24-h urine (from 46 women and 28 men). The measurements were realized by the atomic absorption spectrometry (AAS) with atomization in the flame (FAAS) and in the graphite furnace (GFAAS). The received results were the subject of statistical analysis including the sex and age of volunteers. Moreover, correlations between the elements and the relationships between age and amounts of excreted elements with urine were tested. We found the statistically significant higher content of Zn in men's urine than in women(')s one. Moreover, both adult women and men (>18 years) excreted much more Ca in urine in comparison to young subjects. Only in case of Pb the significant positive correlation between its amount in 24-h urine of all donors and age was stated. The correlation analysis has shown the significant positive relationships between Ca-Mg, Ca-Fe, Mg-Fe, Cu-Fe, Cu-Cd, Fe-Cd, and Pb-Cd in total samples of urine. Basing on our results, we concluded that the gender and age of donors may impact on the elemental status of 24-h urine.

Clinical evaluation of a lead mobilization test using the chelating agent dimercaptosuccinic acid

BACKGROUND

The lead mobilization test reflects the mobilizable and likely toxicologically active fraction of the lead body burden. We propose a safe and convenient protocol for this test, to assess concomitant copper and zinc excretion and to determine the size of the chelatable lead pool in nonoccupationally exposed adults.

METHODS

The study population included 80 white adults: 40 controls [median blood lead concentration (PbB), 25 microg/L] and 40 lead-exposed individuals (315 microg/L). After collection of 4- and 24-h baseline urine specimens and a blood sample, dimercaptosuccinic acid (DMSA) was administered orally (1 g), and additional 4- and 24-h urine specimens were obtained. Determinants of the chelatable urinary lead (DMSA-PbU) were traced by linear regression analysis.

RESULTS

Urinary DMSA and lead excretion peaked within 2-3 h after DMSA administration. The amounts of DMSA, lead, copper, and zinc recovered in the 4-h urinary collections were highly correlated with those in 24-h collections (r = 0.857, 0.859, 0.958, and 0.757, respectively). At PbB concentrations >300 microg/L, the relationship between DMSA-PbU and PbB showed a steep increase and a widespread dispersion of DMSA-PbU around the regression line. After DMSA, copper and zinc excretion rates were increased up to 91- and 33-fold, respectively. No side effects were reported after DMSA.

CONCLUSIONS

Determination of DMSA-PbU in a 4-h collection after DMSA is convenient, apparently safe, and inexpensive. An upper reference limit value of 22 microg/4 h is proposed for Belgian reference individuals. The diagnostic value of DMSA-PbU is likely to be contributive for PbB >300 microg/L.

Comparison of colorimetric and HPLC methods for determination of delta-aminolevulinic acid in urine with reference to dose-response relationship in occupational exposure to lead

Both traditional colorimetry and recently developed HPLC-fluorometry have been in use for determination of delta-aminolevulinic acid in urine (ALA-U), an effect marker of occupational exposure to lead (Pb). The present study was initiated to compare the values by the two methods on an epidemiology basis among workers occupationally exposed to lead (Pb), to estimate quantitatively the colorimetry-associated increment over the values by the HPLC method, to evaluate ALA-U determination in occupational health service for Pb-exposed workers, and to identify a critical Pb-B to induce an elevation in ALA-U. For this purpose, blood and urine samples were collected from three groups of Pb-exposed workers (both men and women in combination, including smokers) and analyzed for Pb in blood (Pb-B; measured in all subjects) and ALA-U (by colorimetry or HPLC), i.e., Group 1 (164 subjects with urinalysis by the two methods), Group 2 (2,923 subjects by colorimetry), and Group 3 (2,540 subjects by HPLC). ALA-U when measured by colorimetry was higher than the values by HPLC, and that the mean difference on a group basis was 1.4 mg/l (in a range of 1.1 to 1.8 mg/l), irrespective of Pb-B levels. It was also found that the increase in ALA-U was small when Pb-B was relatively low (e.g., < or = 40 microg/100 ml), and that the increase on a group basis in response to an increase in Pb-B from 5 to 40 microg/100 ml was as small as < or = 0.6 mg/l. Thus, ALA-U appeared to be not a sensitive marker of Pb effects at low Pb-B levels. ALA-U however increased substantially with a point of inflection at the Pb-B level of about 17-34 microg/100 ml. Thus it was concluded that ALA-U as measured by colorimetry is greater than ALA-U by HPLC by 1.4 mg/l on average irrespective of intensity of Pb-exposure, which may induce bias in evaluation of health effect, and that ALA-U levels will increase when Pb-B is in excess of 17-34 microg/100 ml.

Biomarkers of lead exposure in petrol station attendants and auto-mechanics in Abeokuta, Nigeria: effect of 2-week ascorbic acid supplementation

In order to study the ameliorative effects of ascorbic acid in chronic lead poisoning, petrol station attendants and auto-mechanics in Abeokuta, Nigeria, who have been shown to be occupationally exposed to lead and university students (serving as control), were supplemented daily with 500mg ascorbic acid for 2 weeks. Blood and urine samples were collected from the subjects before and after ascorbic acid regimen and analysed for lead and biochemical effects associated with lead toxicity. The 2-week ascorbic acid supplementation resulted in a significant (P < 0.05) reduction in blood lead in the occupationally exposed subjects. The reduction in blood lead amounted to 57% in male petrol station attendants, 50% in female petrol station attendants and 44% in the auto-mechanics. Urinary excretion of lead increased remarkably in the occupationally exposed subjects (P < 0.05). The biochemical effects associated with the toxic effects of lead also responded positively to the ascorbic acid regimen. Plasma and urine aminolevulinic acid (ALA) were reduced significantly (P < 0.05) by as much as 55% and 57% respectively. Plasma calcium also increased significantly (P < 0.05) in the subjects. Decreased levels of reduced glutathione (GSH) and hemoglobin observed in the occupationally exposed subjects were reversed by ascorbic acid. Glutathione-S-transferase (GST) and catalase (CAT) activities were not affected. Our findings indicate that ascorbic acid may be useful as an economical and convenient prophylactic agent for lead poisoning.