Chromosome and DNA damage analysis in individuals occupationally exposed to pesticides with relation to genetic polymorphism for CYP 1A1gene in Ecuador

The Comet Assay as a Tool in Human Biomonitoring Studies of Environmental and Occupational Exposure to Chemicals-A Systematic Scoping Review

Biomonitoring of human populations exposed to chemical substances that can act as potential mutagens or carcinogens, may enable the detection of damage and early disease prevention. In recent years, the comet assay has become an important tool for assessing DNA damage, both in environmental and occupational exposure contexts. To evidence the role of the comet assay in human biomonitoring, we have analysed original research studies of environmental or occupational exposure that used the comet assay in their assessments, following the PRISMA-ScR method (preferred reporting items for systematic reviews and meta-analyses extension for scoping reviews). Groups of chemicals were designated according to a broad classification, and the results obtained from over 300 original studies (n = 123 on air pollutants, n = 14 on anaesthetics, n = 18 on antineoplastic drugs, n = 57 on heavy metals, n = 59 on pesticides, and n = 49 on solvents) showed overall higher values of DNA strand breaks in the exposed subjects in comparison with the unexposed. In summary, our systematic scoping review strengthens the relevance of the use of the comet assay in assessing DNA damage in human biomonitoring studies.

Assessment of chromosomal aberrations among agricultural workers exposed to pesticides in Punjab, India

Chromosomal aberrations (CAs) are an important tool for assessment of exposure to pesticides. Genotoxic potential of pesticides is a principal risk factor for long-term health effects. The present study was aimed toward the assessment of CAs among agricultural workers exposed to pesticides and comparison with nonagricultural workers not exposed to pesticides. A total of 296 subjects were enrolled in the study: exposed (n = 148) and nonexposed subjects (n = 148) from Punjab. A significantly high frequency of aberrations was seen in peripheral blood lymphocytes of exposed subjects as compared with nonexposed ones. Most CAs were present as loss (aneuploidy) and were observed significantly in subjects having a history of alcohol consumption. It can be, thus, concluded that agricultural workers exposed to a mixture of pesticides, in addition to being alcoholic, are at a greater risk of genotoxic damage. It is highly recommended that the agricultural workers are educated regarding the potential hazards of occupational exposure to pesticides.

Characterization of risk factors for DNA damage among paddy farm worker exposed to mixtures of organophosphates

This is a cross-sectional study conducted among paddy farmers to characterize potential risk factors that influence levels of DNA damage from exposure to mixtures of organophosphates. Comet assay was used to determine the level of DNA damage by measuring the comet tail length from the exfoliated buccal mucosa. The result suggests that farmers who chronically exposure to a mixture of organophosphates has at least 2-fold significant increase of DNA damage as compared with control group. Factor analysis and linear regression both suggest that DNA damage reported by farmers may influence individual, occupational, and residential factors and are reported as significant predictor factors, whereas this effect is mainly caused by individual factors among the control group. The findings of the present study suggest that either farmer or control group bear certain extent of genotoxic burden contributed by different risk factors.

Evaluation of DNA damage in agricultural workers exposed to pesticides using single cell gel electrophoresis (comet) assay

BACKGROUND:

Pesticides are used in agriculture to protect crops, but they pose a potential risk to farmers and environment. The aim of the present study is to investigate the relation between the occupational exposure to various pesticides and the presence of DNA damage.

MATERIALS AND METHODS:

Blood samples of 210 exposed workers (after a day of intense spraying) and 50 control subjects belonging to various districts of Punjab (India) were evaluated using Comet assay. Sixty workers who showed DNA damage were selected for follow up at 5-6 months after the first sampling during a low or null spraying period.

RESULTS:

Significant differences were found in DNA damage between freshly exposed workers and controls and freshly exposed and followed up cases. There was significant increase in the comet parameters viz. mean comet tail length and frequency of cells showing migration in exposed workers as compared to controls (72.22 ± 20.76 vs. 46.92 ± 8.17, P<0.001; 31.79 vs. 5.77, P<0.001). In the second samples, followed up cases showed significant decrease in frequency of damaged cells as compared to freshly exposed workers of first sampling (P<0.05). The confounding factors such as variable duration of pesticide exposure, age, smoking, drinking and dietary habits etc which were expected to modulate the damage, were instead found to have no significant effect on DNA fragmentation.

CONCLUSION:

The evidence of a genetic hazard related to exposure resulting from the intensive use of pesticides stresses the need for educational programs for agricultural workers to reduce the use of chemicals in agriculture.

Genotoxicity studies performed in the ecuadorian population

Genotoxicity studies in Ecuador have been carried out during the past two decades. The focuses of the research were mainly the area of environmental issues, where the populations have been accidentally exposed to contaminants and the area of occupational exposure of individuals at the workplace. This paper includes studies carried out in the population of the Amazon region, a zone known for its rich biodiversity as well as for the ecological damage caused by oil spills and chemical sprayings whose consequences continue to be controversial. Additionally, we show the results of studies comprised of individuals occupationally exposed to toxic agents in two very different settings: flower plantation workers exposed to pesticide mixtures and X-ray exposure of hospital workers. The results from these studies confirm that genotoxicity studies can help evaluate current conditions and prevent further damage in the populations exposed to contaminants. As such, they are evidence of the need for biomonitoring employers at risk, stricter law enforcement regarding the use of pesticides, and increasingly conscientious oil extraction activities.

Role of genetic polymorphisms of CYP1A1, CYP3A5, CYP2C9, CYP2D6, and PON1 in the modulation of DNA damage in workers occupationally exposed to organophosphate pesticides

Organophosphate pesticides (OPs) are primarily metabolized by several xenobiotic metabolizing enzymes (XMEs). Very few studies have explored genetic polymorphisms of XMEs and their association with DNA damage in pesticide-exposed workers. The present study was designed to determine the role of genetic polymorphisms of CYP1A1, CYP3A5, CYP2C9, CYP2D6, and PON1 in the modulation of DNA damage in workers occupationally exposed to OPs. We examined 284 subjects including 150 workers occupationally exposed to OPs and 134 normal healthy controls. The DNA damage was evaluated using the alkaline comet assay and genotyping was done using PCR-RFLP. The results revealed that the PONase activity toward paraoxonase and AChE activity was found significantly lowered in workers as compared to control subjects (p<0.001). Workers showed significantly higher DNA damage compared to control subjects (14.37±2.15 vs. 6.24±1.37 tail% DNA, p<0.001). Further, the workers with CYP2D6*3PM and PON1 (QQ and MM) genotypes were found to have significantly higher DNA damage when compared to other genotypes (p<0.05). In addition, significant increase in DNA damage was also observed in workers with concomitant presence of certain CYP2D6 and PON1 (Q192R and L55M) genotypes which need further extensive studies. In conclusion, the results indicate that the PON1 and CYP2D6 genotypes can modulate DNA damage elicited by some OPs possibly through gene-environment interactions.

Biomonitoring of rural workers exposed to a complex mixture of pesticides in the municipalities of Tianguá and Ubajara (Ceará state, Brazil): genotoxic and cytogenetic studies

In recent years, the use of pesticides in agriculture has been steadily increasing, and associations between exposure to agricultural chemicals and DNA damage and cancer have been reported. Brazil is one of the world leaders in pesticide use; however, studies that evaluate the impact of pesticide exposure on cancer incidence and mortality are very scarce in the Brazilian population. The alkaline comet assay and the chromosome aberration (CA) test were used to evaluate primary DNA damage in the peripheral blood lymphocytes of workers exposed to a complex mixture of pesticides in two small rural communities in the municipalities of Tianguá and Ubajara, located in the western part of Ceará State (Northeast Brazil), which are among the largest agricultural areas of the state. The comet assay showed that the damage index and damage frequency observed in the exposed groups were significantly higher in relation to the controls (P < 0.05). On the other hand, no differences were detected regarding structural and numerical CAs in the communities evaluated. Additionally, the observed levels of DNA strand breaks and frequencies of CAs, stratified for exposure time, were not statistically different for individuals of either rural community. Our results suggest that the damages caused by pesticides in our study area were not great enough to induce permanent mutations or to interfere with mitotic apparatus formation; minimal pesticide damages could have undergone cellular repair, explaining the absence of structural and numerical CAs.

Health effects of persistent organic pollutants: the challenge for the Pacific Basin and for the world

Persistent organic pollutants include some organo-metals, such as methylmercury; lipophilic halogenated organics, such as dioxins, polychlorinated biphenyls, chlorinated pesticides, and polybrominated flame retardants; and perfluorinated compounds used as repellants. These compounds are resistant to degradation both in the environment and in the human body and tend to bioaccumulate within the food chain. Persistent organic pollutants cause a variety of adverse health effects, including cancer, immune system suppression, decrements in cognitive and neurobehavioral function, disruption of sex steroid and thyroid function, and at least some of them increase the risk of chronic diseases, such as hypertension, cardiovascular disease, and diabetes. Some compounds are byproducts of industry and combustion. Although the manufacture and use of most man-made chemicals has been reduced in recent years, the levels currently present in the population are still associated with an elevated risk of human disease. Others are still manufactured and used. These are dangerous chemicals that have contaminated even areas remote from the industrialized world, such as the polar regions.

Baseline determination in social, health, and genetic areas in communities affected by glyphosate aerial spraying on the northeastern Ecuadorian border

The northeastern Ecuadorian border has undergone aerial spraying with an herbicide mix that contains surfactants and adjuvants, executed by the Colombian Government. The purpose of this study was to diagnose social, health, and genetic aspects of the people affected by glyphosate. For this objective to be achieved, 144 people were interviewed, and 521 medical diagnoses and 182 peripheral blood samples were obtained. Genotyping of GSTP1 Ile105Val, GPX-1 Pro198Leu, and XRCC1 Arg399Gln polymorphisms were analyzed, using PCR-RFLP technique. The assessment of chromosomal aberrations was performed, obtaining 182 karyotypes. Malnutrition in children was 3%. Of the total population, 7.7% had children with malformations, and the percentage of abortions was 12.7%. Concerning genotyping, individuals with GSTP1 Val/Val obtained an odds ratio of 4.88 (p < 0.001), and Ile/Val individuals, together with Val/Val individuals, had an odds ratio of 2.6 (p < 0.05). In addition, GPX-1 Leu/Leu individuals presented an odds ratio (OR) of 8.5 (p < 0.05). Regarding karyotyping, the 182 individuals had normal karyotypes. In conclusion, the study population did not present significant chromosomal and DNA alterations. The most important social impact was fear. We recommend future prospective studies to assess the communities.

Genetic polymorphisms in apolipoprotein E and glutathione peroxidase 1 genes in the Ecuadorian population affected with Alzheimer's disease

INTRODUCTION

The main objective of this study is to determine the prevalence of apolipoprotein E (Apo E) and glutathione peroxidase 1 (GPX1) polymorphisms and their influence on the development of Alzheimer disease (AD) in the Ecuadorian population.

METHODS

The authors performed an analytic transversal case-control study. The study group (n = 39) consisted of patients with AD and dementia. The control group (n = 39) comprised elderly adults who have not been diagnosed with dementia and have the same age and education as the study group. Their inclusion period was from 2007 to 2008. Later on, after obtaining informed consent and after finishing a structural interview; the next step forward was to collect blood and extract DNA by standardized protocols. Besides, the authors performed polymerase chain reaction-restriction fragment length polymorphism technique to determine the genotype of each individual.

RESULTS

The authors found a positive association between ε4 and ε2 alleles of Apo E. The GPX1 gene shows an association of leu allele, whereas pro allele shows a negative association. The odds ratio test shows no significant relative risk.

CONCLUSIONS

Apo E is not a risk factor, nor a protective one for AD, whereas the leu allele of GPX1 is a possible risk factor for the disease.

Comet assay: a reliable tool for the assessment of DNA damage in different models

New chemicals are being added each year to the existing burden of toxic substances in the environment. This has led to increased pollution of ecosystems as well as deterioration of the air, water, and soil quality. Excessive agricultural and industrial activities adversely affect biodiversity, threatening the survival of species in a particular habitat as well as posing disease risks to humans. Some of the chemicals, e.g., pesticides and heavy metals, may be genotoxic to the sentinel species and/or to non-target species, causing deleterious effects in somatic or germ cells. Test systems which help in hazard prediction and risk assessment are important to assess the genotoxic potential of chemicals before their release into the environment or commercial use as well as DNA damage in flora and fauna affected by contaminated/polluted habitats. The Comet assay has been widely accepted as a simple, sensitive, and rapid tool for assessing DNA damage and repair in individual eukaryotic as well as some prokaryotic cells, and has increasingly found application in diverse fields ranging from genetic toxicology to human epidemiology. This review is an attempt to comprehensively encase the use of Comet assay in different models from bacteria to man, employing diverse cell types to assess the DNA-damaging potential of chemicals and/or environmental conditions. Sentinel species are the first to be affected by adverse changes in their environment. Determination of DNA damage using the Comet assay in these indicator organisms would thus provide information about the genotoxic potential of their habitat at an early stage. This would allow for intervention strategies to be implemented for prevention or reduction of deleterious health effects in the sentinel species as well as in humans.

Genotoxic evaluation of workers employed in pesticide production

Pesticides are widely used throughout the world in agriculture to protect crops and in public health to control diseases. Nevertheless exposure to pesticides can represent a potential risk to humans. Pesticide manufacturing unit workers are prone to possible occupational pesticide exposure. Therefore, this study was performed to evaluate the genotoxic effect of pesticide exposure in these workers. In the present investigation 54 pesticide workers and an equal number of control subjects were assessed for genome damage in blood lymphocytes utilizing the chromosomal aberration analysis and the buccal epithelial cell by adopting the micronucleus test. The results suggested that pesticide workers had a significantly increased frequency of chromosomal aberrations when compared with controls (mean+/-S.D., 8.43+/-2.36 versus 3.32+/-1.26; P<0.05). Similarly, the pesticides exposed workers showed a significant increase in micronucleated cells compared with controls (1.24+/-0.72 versus 0.32+/-0.26; P<0.05). Analysis of variance revealed that occupational exposure to pesticides had a significant effect on frequency of micronuclei (P<0.05), whereas smoking, age, gender and alcohol consumption had no significant effect on genetic damage (P>0.05). However, no association was found between years of exposure, smoking, age, gender, alcohol consumption and higher levels of genetic damage as assessed by the chromosomal aberration assay (P>0.05). Our findings indicate that occupational exposure to pesticides could cause genome damage in somatic cells.

Our recent experiences with sarin poisoning cases in Japan and pesticide users with references to some selected chemicals

Attention has been paid to neurobehavioral effects of occupational and environmental exposures to chemicals such as pesticides, heavy metals and organic solvents. The area of research that includes neurobehavioral methods and effects in occupational and environmental health has been called "Occupational and Environmental Neurology and Behavioral Medicine." The methods, by which early changes in neurological, cognitive and behavioral function can be assessed, include neurobehavioral test battery, neurophysiological methods, questionnaires and structured interview, biochemical markers and imaging techniques. The author presents his observations of neurobehavioral and neurophysiological effects in Tokyo subway sarin poisoning cases as well as in pesticide users (tobacco farmers) in Malaysia in relation to Green Tobacco Sickness (GTS). In sarin cases, a variety effects were observed 6-8 months after exposure, suggesting delayed neurological effects. Studies on pesticide users revealed that organophosphorus and dithiocarbamate affected peripheral nerve conduction and postural balance; subjective symptoms related to GTS were also observed, indicating the effects of nicotine absorbed from wet tobacco leaves. In addition, non-neurological effects of pesticides and other chemicals are presented, in relation to genetic polymorphism and oxidative stress.

Genetic polymorphisms and the effect of cigarette smoking in the comet assay

A potential genotoxic effect of cigarette smoking has repeatedly been investigated with the comet assay (alkaline single cell gel electrophoresis) and conflicting results have been reported. Besides differences in the methodology and the study design used, genetic differences between the subjects investigated might contribute to the variability of test results. Considering genetic polymorphisms of genes involved in metabolism or DNA repair has led to a better discrimination of smoking-related genotoxic effects in some cases but also led to discrepant results. We therefore evaluated our baseline comet assay effects obtained for nonsmokers and smokers in relation to selected genetic polymorphisms. Our study group comprised 52 nonsmokers and 51 smokers who were strictly selected to exclude potential confounding factors. We chose polymorphisms in the genes GSTM1 and CYP1A1 (Ile462Val) because they take part in the metabolism of genotoxins contained in tobacco smoke. In a subgroup of 32 nonsmokers and 31 smokers we also studied polymorphisms in XPD (Lys751Gln), XRCC1 (Arg399Gln) and XRCC3 (Thr241Val) because they are part of DNA repair pathways involved in the repair of tobacco-related DNA damage. Freshly collected peripheral whole blood samples were tested in the alkaline (pH > 13) comet assay. In all experiments a reference standard (untreated V79 cells) was included to correct for assay variability. An independent second evaluation was carried out for all experiments. None of these approaches revealed a significant difference between nonsmokers and smokers.