Genotoxic effects of lead: an updated review

A novel approach in water quality assessment based on fuzzy logic

The present work aimed at developing a novel water quality index based on fuzzy logic, that is, a comprehensive artificial intelligence (AI) approach to the development of environmental indices for routine assessment of surface water quality, particularly for human drinking purposes. Twenty parameters were included based on their critical importance for the overall water quality and their potential impact on human health. To assess the performance of the proposed index under actual conditions, a case study was conducted at Mamloo dam, Iran, employing water quality data of four sampling stations in the water basin of the dam from 2006 to 2009. Results of this study indicated that the general quality of water in all the sampling stations over all the years of the study period is fairly low (yearly averages are usually in the range of 45-55). According to the results of ANOVA test, water quality did not significantly change over time in any of the sampling stations (P > 0.05). In addition, comparison of the outputs of the fuzzy-based proposed index proposed with those of the NSF water quality index (the WQI) and Canadian Water Quality Index (CWQI) showed similar results and were sensitive to changes in the level of water quality parameters. However, the index proposed by the present study produced a more stringent outputs compared to the WQI and CWQI. Results of the sensitivity analysis suggested that the index is robust against the changes in the rules. In conclusion, the proposed index seems to produce accurate and reliable results and can therefore be used as a comprehensive tool for water quality assessment, especially for the analysis of human drinking water.

Genotoxic effects of occupational exposure to lead and influence of polymorphisms in genes involved in lead toxicokinetics and in DNA repair

Lead is still widely used in many industrial processes and is very persistent in the environment. Although toxic effects caused by occupational exposure to lead have been extensively studied, there are still conflicting results regarding its genotoxicity. In a previous pilot study we observed some genotoxic effects in a population of lead exposed workers. Thus, we extended our study analysing a larger population, increasing the number of genotoxicity endpoints, and including a set of 20 genetic polymorphisms related to lead toxicokinetics and DNA repair as susceptibility biomarkers. Our population comprised 148 workers from two Portuguese factories and 107 controls. The parameters analysed were: blood lead levels (BLL) and δ-aminolevulinic acid dehydratase (ALAD) activity as exposure biomarkers, and T-cell receptor (TCR) mutation assay, micronucleus (MN) test, comet assay and OGG1-modified comet assay as genotoxicity biomarkers. Lead exposed workers showed markedly higher BLL and lower ALAD activity than the controls, and significant increases of TCR mutation frequency (TCR-Mf), MN rate and DNA damage. Oxidative damage did not experience any significant alteration in the exposed population. Besides, significant influence was observed for VDR rs1544410 polymorphism on BLL; APE1 rs1130409 and LIG4 rs1805388 polymorphisms on TCR-Mf; MUTYH rs3219489, XRCC4 rs28360135 and LIG4 rs1805388 polymorphisms on comet assay parameter; and OGG1 rs1052133 and XRCC4 rs28360135 polymorphisms on oxidative damage. Our results showed genotoxic effects related to occupational lead exposure to levels under the Portuguese regulation limit of 70 μg/dl. Moreover, a significant influence of polymorphisms in genes involved in DNA repair on genotoxicity biomarkers was observed.

Genotoxicity of sediment extracts of the Berre lagoon (France)

To evaluate the genotoxic risk that contaminated sediment could constitute for benthic organisms, three contaminated (VA, VC and VN) and one uncontaminated (RN) sediment samples were collected in the Berre lagoon (France). Potentially bioavailable contaminants in sediments were obtained using sediment extraction with synthetic seawater adjusted to pH 4 or pH 6, simulating the range of pH prevailing in the digestive tract of benthic organisms. The genotoxic activities of these extracts were evaluated by three short-term bioassays: the Salmonella mutagenicity test using the Salmonella typhimurium strain TA102, the alkaline comet assay and the micronucleus assay on the Chinese Hamster Ovary cells CHO-K1. Results of the Salmonella mutagenicity assay detected a mutagenic response for RN extract at pH 6, and for VA extract at pH 4. Results of the comet and micronucleus assays detected low genotoxic/clastogenic activities for VA and VC extracts at pH 6 and higher activities for RN, VA and VC extracts at pH 4. To identify if metals (Al, Fe, Mn, As, Cd, Co, Cr, Cu, Hg, Ni, Pb and Zn) were involved in these genotoxic activities, their concentrations were determined in the extracts, and their speciation was assessed by thermodynamic calculations. Results showed that extracts from sites VA, VC and VN generally presented the highest trace metal contents for both extractants, while the site RN presented lower trace metal contents but the highest Fe and Mn contents. Thermodynamic calculations indicated that Fe, Mn, As and in a lower extend Co, Ni and Zn were mainly present under free forms in extracts, and were consequently, more likely able to induce a genotoxic effect. Results globally showed no correspondence between free metal contents and genotoxic activities. They suggested that these positive results could be due to uncharacterized compounds, acting as direct genotoxic agents or enhancing the genotoxic properties of analyzed metals.

Childhood blood lead levels and intellectual development after ban of leaded gasoline in Taiwan: a 9-year prospective study

BACKGROUND

Lead (Pb) exposure is associated with children's neurodevelopment, even at low doses. Leaded gasoline was banned in Taiwan in 2000 to reduce environmental exposure to Pb.

OBJECTIVES

To evaluate the neurodevelopmental effect of low-level Pb exposure in young children.

METHODS

In 2001-2002, we have recruited 430 pregnant women in the third-trimester in Taichung, Taiwan who answered detailed questionnaires in the obstetric clinic. A total of 119, 76, and 66 children were followed up at 2-3, 5-6 and 8-9 years, respectively. We collected blood samples from pregnant women, Umbilical cord and children, and evaluated children's neurodevelopment and cognition function at all three time points using Bayley and Wechsler tests. Blood samples were analyzed for whole blood lead (BPb) levels.

RESULTS

Geometric mean of BPb in pregnant women, cord blood and children at 2-3, 5-6 and 8-9 years old were 2.21, 1.30, 2.48, 2.49 and 1.97 μg/dl, respectively. Low-level postnatal Ln BPb was significantly associated with not only decreasing intelligence quotient (IQ), but also delayed cognitive function in children at 5-8 years (β: -5.97, SE: 2.59, p=0.025), after adjustment for maternal education, maternal BPb exposure, Home Observation for Measurement of the Environment Inventory (HOME), and gender of child, using linear mixed models. No significant relation was observed between prenatal and cord blood Pb levels and children's cognitive function in children 2-8 years.

CONCLUSIONS

Low-level postnatal BPb levels in children at 2-5 years may have lagged effects on neurodevelopment in those at 5 to 8 years. Action is warranted to reduce even very low environmental Pb levels to reduce the developmental burden of Pb on children.

Lead poisoning: historical aspects of a paradigmatic "occupational and environmental disease"

Lead poisoning is one of the earliest identified and most known occupational disease. Its acute effects have been recognized from antiquity when this condition principally afflicted manual workers and slaves, actually scarcely considered by the medicine of that time. The Industrial Revolution caused an epidemic of metal intoxication, urging scientists and physician of that period to study and identify specific symptoms and organ alterations related to chronic lead poisoning. During the 20th century, the acknowledgment of occupational and environmental toxicity of lead fostered public awareness and legislation to protect health. More recently, the identification of sub-clinical effects have greatly modified the concept of lead poisoning and the approaches of medicine towards this condition. Nowadays, lead poisoning is rarely seen in developed countries, but it still represents a major environmental problem in certain areas. Consequently, it may appear as a paradigm of "occupational and environmental disease," and the history of this condition seems to parallel the historical development of modern "Occupational and Environmental Health" as a more complete medical discipline.

Spectrofluorimetric determination of picogram level Pb(II) using a dimercaptothiadiazole fluorophore

This paper describes the spectrofluorimetric determination of picogram level Pb(II) using 2,5-dimercapto-1,3,4-thiadiazole (DMT) as a fluorophore. Excitation of DMT at 330 nm shows an emission maximum at 435 nm. The colorless solution of DMT changes into highly emittive yellow color immediately after the addition of 0.5 μM Pb(II) and nearly 245-fold increase in emission intensity at 435 nm was observed. These changes were attributed to the complex formation between Pb(II). The emission intensity linearly increases in the concentration range of 10-100 nM Pb(II) and DMT. Based on the fluorescence enhancement, the concentration of Pb(II) was determined. Interestingly, the emission intensity was increased even in the presence of 0.1 pM Pb(II). The fluorophore showed an extreme selectivity towards 100 nM Pb(II) even in the presence of 50,000-fold higher concentrations of common metal ions interferences such as Na(+), K(+), Ca(2+), Mg(2+), Fe(2+), Cd(2+), Cr(3+), Mn(2+), Zn(2+), Co(2+), Ni(2+) and 5000-, 100- and 40-fold of Cu(2+), Hg(2+) and Ag(+) ions, respectively. The lowest detection of 20 pg L(-1) Pb(II) was achieved for the first time using DMT. The proposed method was successfully utilized for the determination of Pb(II) in tap water, polluted river water and industrial waste water samples. The results obtained in the present study were validated with both AAS and ICP-AES methods.

Prevalence of at-risk genotypes for genotoxic effects decreases with age in a randomly selected population in Flanders: a cross sectional study

BACKGROUND

We hypothesized that in Flanders (Belgium), the prevalence of at-risk genotypes for genotoxic effects decreases with age due to morbidity and mortality resulting from chronic diseases. Rather than polymorphisms in single genes, the interaction of multiple genetic polymorphisms in low penetrance genes involved in genotoxic effects might be of relevance.

METHODS

Genotyping was performed on 399 randomly selected adults (aged 50-65) and on 442 randomly selected adolescents. Based on their involvement in processes relevant to genotoxicity, 28 low penetrance polymorphisms affecting the phenotype in 19 genes were selected (xenobiotic metabolism, oxidative stress defense and DNA repair, respectively 13, 6 and 9 polymorphisms). Polymorphisms which, based on available literature, could not clearly be categorized a priori as leading to an 'increased risk' or a 'protective effect' were excluded.

RESULTS

The mean number of risk alleles for all investigated polymorphisms was found to be lower in the 'elderly' (17.0 ± 2.9) than the 'adolescent' (17.6 ± 3.1) subpopulation (P = 0.002). These results were not affected by gender nor smoking. The prevalence of a high (> 17 = median) number of risk alleles was less frequent in the 'elderly' (40.6%) than the 'adolescent' (51.4%) subpopulation (P = 0.002). In particular for phase II enzymes, the mean number of risk alleles was lower in the 'elderly' (4.3 ± 1.6 ) than the 'adolescent' age group (4.8 ± 1.9) P < 0.001 and the prevalence of a high (> 4 = median) number of risk alleles was less frequent in the 'elderly' (41.3%) than the adolescent subpopulation (56.3%, P < 0.001). The prevalence of a high (> 8 = median) number of risk alleles for DNA repair enzyme-coding genes was lower in the 'elderly' (37,3%) than the 'adolescent' subpopulation (45.6%, P = 0.017).

CONCLUSIONS

These observations are consistent with the hypothesis that, in Flanders, the prevalence of at-risk alleles in genes involved in genotoxic effects decreases with age, suggesting that persons carrying a higher number of at risk alleles (especially in phase II xenobiotic-metabolizing or DNA repair genes) are at a higher risk of morbidity and mortality from chronic diseases. Our findings also suggest that, regarding risk of disease associated with low penetrance polymorphisms, multiple polymorphisms should be taken into account, rather than single ones.

Evaluating chromosomal damage in workers exposed to hexavalent chromium and the modulating role of polymorphisms of DNA repair genes

PURPOSE

Welders have been chronically exposed to hexavalent chromium with potential consequences on chromosomal integrity. Our study is focused on the extent of any such chromosomal aberrations with respect to chromium levels in the blood of welders as well as on the tentative modulating role of polymorphisms in DNA repair genes XPD Lys751Gln, XPG Asn114His, XPC Lys939Gln, hOGG1 Ser326Cys and XRCC1 Arg399Gln on chromosomal damage.

METHODS

The study was conducted on 144 individuals consisting of 73 welders exposed to chromium for 10.2 ± 1.67 years and 71 control individuals without known exposures. Chromosomal aberrations, their chromatid-type and chromosome-type aberrations were detected by conventional cytogenetic analysis. XPD, XPG, XPC, hOGG1 and XRCC1 gene polymorphisms were assayed for by Taqman SNP genotyping assay ("Assay-by-Demand") using Real-Time allelic discrimination on AB 7500 equipment. Chromium concentration in the blood was determined by atomic absorption spectrophotometry.

RESULTS

The level of chromium in the blood of welders ranged between 0.032 and 0.182 μmol l(-1) and was significantly higher than that in controls (0.07 ± 0.04 μmol l(-1) vs. 0.03 ± 0.007 μmol l(-1)). Parameters of chromosomal damage were similar in both the exposed and the control individuals (1.89% vs. 1.70% for total chromosomal aberrations, 0.97% vs. 0.88% for chromosome-type and 0.92% vs. 0.80% for chromatid-type, respectively). Chromatid-type of aberrations positively correlated with the level of chromium in the blood (r = 0.28; P = 0.02). Significantly higher total chromosomal aberrations were detected in individuals with homozygous variant polymorphism in XRCC1 Arg399Gln gene as compared to those with heterozygous and homozygous wild-type genotypes (2.20, 1.89 and 1.48%, respectively; P = 0.01). A similar tendency was found for chromatid-type aberrations (1.30% for homozygous variant genotype bearers, 0.94% for those with heterozygous genotype and 0.75% for carriers of homozygous wild-type genotype, respectively; P = 0.04).

CONCLUSIONS

Although no apparent increase in chromosomal damage was recorded in chromium-exposed welders in comparison with controls, genetic make-up in DNA repair genes may increase susceptibility toward adverse effect of chromium.

Peripheral blood signatures of lead exposure

BACKGROUND

Current evidence indicates that even low-level lead (Pb) exposure can have detrimental effects, especially in children. We tested the hypothesis that Pb exposure alters gene expression patterns in peripheral blood cells and that these changes reflect dose-specific alterations in the activity of particular pathways.

METHODOLOGY/PRINCIPAL FINDING

Using Affymetrix Mouse Genome 430 2.0 arrays, we examined gene expression changes in the peripheral blood of female Balb/c mice following exposure to per os lead acetate trihydrate or plain drinking water for two weeks and after a two-week recovery period. Data sets were RMA-normalized and dose-specific signatures were generated using established methods of supervised classification and binary regression. Pathway activity was analyzed using the ScoreSignatures module from GenePattern.

CONCLUSIONS/SIGNIFICANCE

The low-level Pb signature was 93% sensitive and 100% specific in classifying samples a leave-one-out crossvalidation. The high-level Pb signature demonstrated 100% sensitivity and specificity in the leave-one-out crossvalidation. These two signatures exhibited dose-specificity in their ability to predict Pb exposure and had little overlap in terms of constituent genes. The signatures also seemed to reflect current levels of Pb exposure rather than past exposure. Finally, the two doses showed differential activation of cellular pathways. Low-level Pb exposure increased activity of the interferon-gamma pathway, whereas high-level Pb exposure increased activity of the E2F1 pathway.

Genotoxicity of platinum in embryos of zebrafish (Danio rerio) and ramshorn snail (Marisa cornuarietis)

The metal platinum is inter alia used for industrial and medical purposes. Due to its application in automobile catalytic converters and as an anti-cancer drug, Pt enters the aquatic environment via road runoff and hospital sewage and raises concerns about its environmental impact and toxicity to organisms. Therefore, the genotoxicity of Pt at 0, 0.1, 1, 10, 50, 100 and 200μg/l PtCl(2) was tested on two freshwater organisms, zebrafish (Danio rerio) and ramshorn snail (Marisa cornuarietis) using the single cell gel electrophoresis, also called comet assay. PtCl(2) did not show any genotoxicity for D. rerio at the tested concentrations, whereas significantly elevated DNA damage was observed in M. cornuarietis at 1μg/l PtCl(2) and beyond. The results of the study suggest a high sensitivity of M. cornuarietis concerning the genotoxic impact of PtCl(2).

Lead, cadmium and cobalt (Pb, Cd, and Co) leaching of glass-clay containers by pH effect of food

Recent studies have shown that handcrafted glass-clay containers are a health risk because they can be contaminated by heavy metals, which can be transferred to food, thus reaching the human body to potentially cause illness. Therefore, in the present work, we evaluate the leaching of lead, cadmium, and cobalt from glass-clay containers into two types of food: tomato sauce (salsa), and chickpea puree. The containers were obtained from four regions in the Mexican state of Hidalgo. Repetitive extractions from the containers were carried out to quantify the leaching of the heavy metals into the salsa, the chickpea puree, and acetic acid using the technique proposed by the USFDA. The results show that greater use of the containers leads to more leaching of heavy metals into both types of food and into the acetic acid, with the greatest metal extraction recorded for the Ixmiquilpan vessels. These results indicate that the metals present in the glass-clay containers leach into the food and that increased reuse increases the risk to the people who use them in food preparation.

Aporrectodea caliginosa, a suitable earthworm species for field based genotoxicity assessment?

There is a growing interest for the application of biomakers to field-collected earthworms. Therefore we have evaluated the usability of native populations of endogeic, widely distributed earthworm Aporrectodea caliginosa in the assessment of soil genotoxicity using the Comet assay. Validation of the Comet assay on earthworm coelomocytes has been established using commercially available Eisenia fetida exposed to copper, cadmium, and pentachlorophenol, along with A. caliginosa exposed to copper in a filter paper contact test. Neutral red retention time (NRRT) assay was conducted on copper exposed and field-collected earthworms. Significant DNA and lysosomal damage was measured using Comet and NRRT assays in native populations of A. caliginosa sampled from the polluted soils in the urban area in comparison to the earthworms from the reference site. The results of this study confirm the employment of A. caliginosa as a suitable species for the in situ soil toxicity and genotoxicity field surveys.

Increased levels of lead in the blood and frequencies of lymphocytic micronucleated binucleated cells among workers from an electronic-waste recycling site

In recent years, adverse health effects of chemicals from electronic waste (e-waste) have been reported. However, little is known about the genotoxic effects of chemicals in e-waste. In the present study, air concentrations of the toxic metals at e-waste and control sites were analyzed using inductively-coupled plasma mass spectrometry. Levels of toxic metals (lead, copper and cadmium) in blood and urine were detected using atomic absorption spectrophotometry in 48 exposed individuals and 56 age- and sex-matched controls. The frequencies of lymphocytic micronucleated binucleated cells (MNBNCs) were determined using a cytokinesis-block micronucleus assay. Results indicated that blood lead levels were significantly higher in the exposed group (median: 11.449 μg/dL, 1st/3rd quartiles: 9.351-14.410 μg/dL) than in the control group (median: 9.104 μg/dL, 1st/3rd quartiles: 7.275-11.389 μg/dL). The exposed group had higher MNBNCs frequencies (median: 4.0 per thousand, 1st/3rd quartiles: 2.0-7.0 per thousand) compared with the controls (median: 1.0 per thousand, 1st/3rd quartiles: 0.0-2.0 per thousand). Additionally, MNBNCs frequencies and blood lead levels were positively correlated (r = 0.254, p<0.01). Further analysis suggested that a history of working with e-waste was a predictor for increased blood lead levels and MNBNCs frequencies in the subjects. The results suggest that both the living and occupational environments at the e-waste site may be risk factors for increased MNBNCs frequencies among those who are exposed.