Genomic damages in peripheral blood lymphocytes and association with polymorphisms of three glutathione S-transferases in workers exposed to formaldehyde

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.

Incidence of lung cancer among healthcare workers in Hunan Province and analysis of related risk factors

Background

The prevalence of lung cancer, a major type of malignant tumor, has been increasing over the years greatly impacting the health of Chinese residents. This study investigates the epidemiological characteristics of lung cancer among healthcare workers in the Hunan Province, as well as the occupational risk factors.

Methods

The data analyzed in this study was collected from the largest tumor hospital in the province: the Hunan Provincial Tumor Hospital affiliated with Central South University, School of Medicine. The data collected encompasses input collected between the years of 2004 to 2013 of the population of healthcare workers who were hospitalized for lung cancer treatments. Information was obtained through statistical analysis and telephonic interviews.

Results

The prevalence of lung cancer among healthcare workers was much higher than that of the general population, as revealed by the difference between number of healthcare worker cases per 1,000 cases and number of healthcare workers per 1,000 population in the decade from 2004 to 2013. Analysis of the data further demonstrates that lung cancer prevalence among healthcare workers increases exponentially with age. Although smoking has been shown to increase the incidence of lung cancer to some extent, it is most likely not the main cause of lung cancer. In addition, it appears that the highest rates of lung cancer incidence occurs in mainly in primary general practitioners, medical radiologists, and nurses. The lack of awareness of personal safety measures may place healthcare workers at a greater risk of lung cancer.

Association of glutathione-S-transferase polymorphism with genetic damage in paint workers

BACKGROUND

Occupational exposure to toluene causes serious health problems ranging from drowsiness to lethal diseases such as cancer. Paint workers are exposed to toluene through inhalation or the dermal route, which can induce genetcic damage. The increased DNA damage could be linked to genetic polymorphism. Therefore, we evaluated the association of glutathione-S-transferase polymorphism with DNA damage in paint workers.

METHODS

First, we included skilled paint workers (n = 30) as exposed and healthy individuals (n = 30) as control belonging to the same socio-economic strata. The genotoxicity biomarkers, Cytokinesis-block micronucleus (CBMN), and single-cell gel electrophoresis (SCGE)/Comet assay were used to assess genotoxicity while Multiplex-PCR and PCR-RFLP were used to assess polymorphism in glutathione-s-transferase (GST) genes. Using linear curve regression analysis, we assessed the association between genetic damage and polymorphism in the glutathione-s-transferase (GST) gene in the exposed and control subjects.

RESULTS

A significantly higher frequency of CBMN (4.43 ± 1.50) and tail moment (TM) (11.23 ± 1.0) respectively in paint workers as compared to the control(1.50 ± 0.86 and (0.54 ± 0.37) underlined significantly high genetic damage in paint workers.Regression curve analysis reveals that polymorphism in the GST gene is significantly associated with higher MN and TM in paint workers.

CONCLUSION

Overall, our study provides a strong rationale for identifying a clear association between glutathione-S-transferase polymorphism and genetic damage in paint workers.

The Carcinogenic Effects of Formaldehyde Occupational Exposure: A Systematic Review

BACKGROUND

Formaldehyde, classified as a carcinogen in 2004, as of today is widely used in many work activities. From its classification, further studies were performed to evaluate its carcinogenicity. The aim of the systematic review is to update the evidence on occupational exposure to formaldehyde and cancer onset.

METHODS

The review, in accordance with the PRISMA statement, includes articles in English reporting original results of studies conducted on workers exposed to formaldehyde, considering all types of cancer, published from 1 January 2000 to 30 July 2021 and selected from the Pubmed and Scopus databases. The studies' quality was assessed by the Newcastle-Ottawa Scale.

RESULTS

A total of 21 articles were included, conducted in different European, American, and Asian countries. The most investigated occupational areas are those characterized by a deliberate use of formaldehyde. Some studies evaluated all types of cancer, whereas others focused on specific sites such as thyroid and respiratory, lymphohematopoietic, or central nervous systems. The results showed weak associations with lung cancer, nasopharyngeal cancer, leukemia, and non-Hodgkin's lymphoma.

CONCLUSIONS

The results demonstrate the need for further original studies carried out on representative samples of workers exposed to measured levels of FA. These studies should be designed to reduce the bias due to co-exposure to other carcinogens.

Oxidative damage, inflammation, genotoxic effect, and global DNA methylation caused by inhalation of formaldehyde and the purpose of melatonin

Formaldehyde (FA) exposure has been proven to increase the risk of asthma and cancer. This study aimed to evaluate for 28 days the FA inhalation effects on oxidative stress, inflammation process, genotoxicity, and global DNA methylation in mice as well as to investigate the potential protective effects of melatonin. For that, analyses were performed on lung, liver and kidney tissues, blood, and bone marrow. Bronchoalveolar lavage was used to measure inflammatory parameters. Lipid peroxidation (TBARS), protein carbonyl (PCO), non-protein thiols (NPSH), catalase activity (CAT), comet assay, micronuclei (MN), and global methylation were determined. The exposure to 5-ppm FA resulted in oxidative damage to the lung, presenting a significant increase in TBARS and NO levels and a decrease in NPSH levels, besides an increase in inflammatory cells recruited for bronchoalveolar lavage. Likewise, in the liver tissue, the exposure to 5-ppm FA increased TBARS and PCO levels and decreased NPSH levels. In addition, FA significantly induced DNA damage, evidenced by the increase of % tail moment and MN frequency. The pretreatment of mice exposed to FA applying melatonin improved inflammatory and oxidative damage in lung and liver tissues and attenuated MN formation in bone marrow cells. The pulmonary histological study reinforced the results observed in biochemical parameters, demonstrating the potential beneficial role of melatonin. Therefore, our results demonstrated that FA exposure with repeated doses might induce oxidative damage, inflammatory, and genotoxic effects, and melatonin minimized the toxic effects caused by FA inhalation in mice.

Occupational exposure to formaldehyde and early biomarkers of cancer risk, immunotoxicity and susceptibility

Formaldehyde (FA) is a high-volume production chemical manufactured worldwide to which many people are exposed to both environmentally and occupationally. FA was recently reclassified as a human carcinogen. Several epidemiological studies have revealed an increased risk of cancer development among workers exposed to FA. Although FA genotoxicity was confirmed in a variety of experimental systems, data from human studies are conflicting. The aim of the present study was to evaluate the occupational exposure to FA in a multistage approach relating the exposure with different biomarkers (dose and effect) and individual susceptibility. Air monitoring was performed to estimate the level of exposure to FA during shift work. Eighty-five workers from hospital anatomy-pathology laboratories exposed to FA and 87 controls were tested for cytogenetic alterations in lymphocytes (micronucleus, MN; sister-chromatid exchange, SCE) and T-cell receptor (TCR) mutation assay. The frequency of MN in exfoliated buccal cells, a first contact tissue was also assessed. Percentages of different lymphocyte subpopulations were selected as immunotoxicity biomarkers. The level of formic acid in urine was investigated as a potential biomarker of internal dose. The effects of polymorphic genes of xenobiotic metabolising enzymes and DNA repair enzymes on the endpoints studied were determined. The mean level of FA exposure was 0.38 ± 0.03 ppm. MN (in lymphocytes and buccal cells) and SCE were significantly increased in FA-exposed workers compared to controls. MN frequency positively correlated with FA levels of exposure and duration. Significant alterations in the percentage of T cytotoxic lymphocytes, NK cells and B lymphocytes were found between groups. Polymorphisms in CYP2E1, GSTP1 and FANCA genes were associated with increased genetic damage in FA-exposed subjects. The obtained information may provide new important data to be used by health and safety care programs and by governmental agencies responsible for setting the acceptable levels for occupational exposure to FA.

Modulatory role of GSTT1 and GSTM1 in Punjabi agricultural workers exposed to pesticides

Glutathione S-transferases are important detoxification enzymes involved in the metabolism of endogenous as well as exogenous compounds. Individuals differ in metabolic capacity due to inherited genetic variations. Due to the polymorphism exhibited by GSTT1 and GSTM1 that results in the complete loss of function, the present study was aimed towards the determination of the frequency distribution of GSTT1 and GSTM1 in agricultural workers in Punjab, India. The study aimed to investigate their contribution in susceptibility to increased disease risk. A total of 513 subjects were included in this study, out of which 250 were agriculture workers and 263 were non-exposed occupationally. GSTT1 and GSTM1 null-genotype distribution was analyzed through multiplex-PCR method. Complete gene deletion in either of the genes was strongly associated with an increased risk (OR = 1.8; 95% CI = 1.3-2.6; p < 0.0008) of DNA/cytogenetic damage, cancer, infertility, and many other serious health effects. Therefore, homozygous deletion in GSTT1 or GSTM1 could play a modulatory role in health of workers with long-term exposure to pesticides.

Re-evaluation of the WHO (2010) formaldehyde indoor air quality guideline for cancer risk assessment

In 2010, the World Health Organization (WHO) established an indoor air quality guideline for short- and long-term exposures to formaldehyde (FA) of 0.1 mg/m3 (0.08 ppm) for all 30-min periods at lifelong exposure. This guideline was supported by studies from 2010 to 2013. Since 2013, new key studies have been published and key cancer cohorts have been updated, which we have evaluated and compared with the WHO guideline. FA is genotoxic, causing DNA adduct formation, and has a clastogenic effect; exposure-response relationships were nonlinear. Relevant genetic polymorphisms were not identified. Normal indoor air FA concentrations do not pass beyond the respiratory epithelium, and therefore FA's direct effects are limited to portal-of-entry effects. However, systemic effects have been observed in rats and mice, which may be due to secondary effects as airway inflammation and (sensory) irritation of eyes and the upper airways, which inter alia decreases respiratory ventilation. Both secondary effects are prevented at the guideline level. Nasopharyngeal cancer and leukaemia were observed inconsistently among studies; new updates of the US National Cancer Institute (NCI) cohort confirmed that the relative risk was not increased with mean FA exposures below 1 ppm and peak exposures below 4 ppm. Hodgkin's lymphoma, not observed in the other studies reviewed and not considered FA dependent, was increased in the NCI cohort at a mean concentration ≥0.6 mg/m3 and at peak exposures ≥2.5 mg/m3; both levels are above the WHO guideline. Overall, the credibility of the WHO guideline has not been challenged by new studies.

Modulatory role of GSTM1 null genotype on the frequency of micronuclei in pesticide-exposed agricultural workers

In this study, we aimed to investigate the extent of genotoxic risk and the association between null GSTM1/GSTT1 and GSTP1 Ile105Val variants and cellular DNA damage, as measured by micronucleus (MN) assay in a group of agricultural workers from Denizli, Turkey. Peripheral blood samples were collected from 116 subjects, including 58 workers who were occupationally exposed to pesticides and 58 healthy unexposed controls. The MN frequencies of each individual were assessed by cytokinesis-blocked micronuclei assays on lymphocytes. Genotypes for different GST variants were determined using polymerase chain reaction-based methods. A significant 3.4-fold increase in MN frequency was observed in workers compared with the controls ( p < 0.001). Among the GST genotypes, only the GSTM1 null genotype was found to be significantly associated with an increased MN frequency in workers ( p = 0.01). Individuals with a concomitant null GSTM1/GSTT1 genotype demonstrated a significant ( p = 0.01) increase in MN frequency compared with those with functional isozymes in the exposed worker group. The association of the GSTM1 null genotype with higher MN frequency suggests that it may be a modifier of genotoxic risk in individuals exposed to pesticides and may thus be a candidate susceptibility biomarker for human biomonitoring studies.

Reassessment of MTBE cancer potency considering modes of action for MTBE and its metabolites

A 1999 California state agency cancer potency (CP) evaluation of methyl tert-butyl ether (MTBE) assumed linear risk extrapolations from tumor data were plausible because of limited evidence that MTBE or its metabolites could damage DNA, and based such extrapolations on data from rat gavage and rat and mouse inhalation studies indicating elevated tumor rates in male rat kidney, male rat Leydig interstitial cells, and female rat leukemia/lymphomas. More recent data bearing on MTBE cancer potency include a rodent cancer bioassay of MTBE in drinking water; several new studies of MTBE genotoxicity; several similar evaluations of MTBE metabolites, formaldehyde, and tert-butyl alcohol or TBA; and updated evaluations of carcinogenic mode(s) of action (MOAs) of MTBE and MTBE metabolite's. The lymphoma/leukemia data used in the California assessment were recently declared unreliable by the U.S. Environmental Protection Agency (EPA). Updated characterizations of MTBE CP, and its uncertainty, are currently needed to address a variety of decision goals concerning historical and current MTBE contamination. To this end, an extensive review of data sets bearing on MTBE and metabolite genotoxicity, cytotoxicity, and tumorigenicity was applied to reassess MTBE CP and related uncertainty in view of MOA considerations. Adopting the traditional approach that cytotoxicity-driven cancer MOAs are inoperative at very low, non-cytotoxic dose levels, it was determined that MTBE most likely does not increase cancer risk unless chronic exposures induce target-tissue toxicity, including in sensitive individuals. However, the corresponding expected (or plausible upper bound) CP for MTBE conditional on a hypothetical linear (e.g., genotoxic) MOA was estimated to be ∼2 × 10(-5) (or 0.003) per mg MTBE per kg body weight per day for adults exposed chronically over a lifetime. Based on this conservative estimate of CP, if MTBE is carcinogenic to humans, it is among the weakest 10% of chemical carcinogens evaluated by EPA.

Association of polymorphisms in glutathione S-transferase genes (GSTM1, GSTT1, GSTP1) with idiopathic azoospermia or oligospermia in Sichuan, China

The reported effects of the glutathione S-transferase (GSTs) genes (GSTM1, GSTT1, and GSTP1) on male factor infertility have been inconsistent and even contradictory. Here, we conducted a case-control study to investigate the association between functionally important polymorphisms in GST genes and idiopathic male infertility. The study group consisted of 361 men with idiopathic azoospermia, 118 men with idiopathic oligospermia, and 234 age-matched healthy fertile male controls. Genomic DNA was extracted from the peripheral blood, and analyzed by polymerase chain reaction and restriction fragment length polymorphism analysis. There was a significant association between the GSTP1 variant genotype (Ile/Val + Val/Val) with idiopathic infertility risk (odds ratio [OR]: 1.53; 95% confidence interval [CI]: 1.11–2.11; P = 0.009). Similarly, a higher risk of infertility was noted in individuals carrying a genotype combination of GSTT1-null and GSTP1 (Ile/Val + Val/Val) (OR: 2.17; 95% CI: 1.43–3.31; P = 0.0002). These results suggest an increased risk of the GSTP1 variant genotype (Ile/Val + Val/Val) for developing male factor infertility. Our findings also underrate the significance of the effect of GSTM1 and/or GSTT1 (especially the former) in modulating the risk of male infertility in males from Sichuan, southwest China.

Increased levels of chromosomal aberrations and DNA damage in a group of workers exposed to formaldehyde

Formaldehyde (FA) is a commonly used chemical in anatomy and pathology laboratories as a tissue preservative and fixative. Because of its sensitising properties, irritating effects and cancer implication, FA accounts probably for the most important chemical-exposure hazard concerning this professional group. Evidence for genotoxic effects and carcinogenic properties in humans is insufficient and conflicting, particularly in regard to the ability of inhaled FA to induce toxicity on other cells besides first contact tissues, such as buccal and nasal cells. To evaluate the effects of exposure to FA in human peripheral blood lymphocytes, a group of 84 anatomy pathology laboratory workers exposed occupationally to FA and 87 control subjects were tested for chromosomal aberrations (CAs) and DNA damage (comet assay). The level of exposure to FA in the workplace air was evaluated. The association between genotoxicity biomarkers and polymorphic genes of xenobiotic-metabolising and DNA repair enzymes were also assessed. The estimated mean level of FA exposure was 0.38±0.03 ppm. All cytogenetic endpoints assessed by CAs test and comet assay % tail DNA (%TDNA) were significantly higher in FA-exposed workers compared with controls. Regarding the effect of susceptibility biomarkers, results suggest that polymorphisms in CYP2E1 and GSTP1 metabolic genes, as well as, XRCC1 and PARP1 polymorphic genes involved in DNA repair pathways are associated with higher genetic damage in FA-exposed subjects. Data obtained in this study show a potential health risk situation of anatomy pathology laboratory workers exposed to FA (0.38 ppm). Implementation of security and hygiene measures may be crucial to decrease risk. The obtained information may also provide new important data to be used by health care programs and by governmental agencies responsible for occupational health and safety.

Application of toxicogenomic profiling to evaluate effects of benzene and formaldehyde: from yeast to human

Genetic variation underlies a significant proportion of the individual variation in human susceptibility to toxicants. The primary current approaches to identify gene-environment (GxE) associations, genome-wide association studies and candidate gene association studies, require large exposed and control populations and an understanding of toxicity genes and pathways, respectively. This limits their application in the study of GxE associations for the leukemogens benzene and formaldehyde, whose toxicity has long been a focus of our research. As an alternative approach, our published work has applied innovative in vitro functional genomics testing systems, including unbiased functional screening assays in yeast and a near-haploid human bone marrow cell line. Through comparative genomic and computational analyses of the resulting data, human genes and pathways that may modulate susceptibility to benzene and formaldehyde were identified, and the roles of several genes in mammalian cell models were validated. In populations occupationally exposed to low levels of benzene, we applied peripheral blood mononuclear cell transcriptomics and chromosome-wide aneuploidy studies in lymphocytes. In this review, we describe our comprehensive toxicogenomic approach and the potential mechanisms of toxicity and susceptibility genes identified for benzene and formaldehyde, as well as related studies conducted by other researchers.

Oxidative DNA damage and formalin-fixation procedures

An experimental study on how formaldehyde-fixation is capable of inducing excess oxidative DNA damage in formalin-fixed paraffin-embedded tissues.

Bone marrow injury induced via oxidative stress in mice by inhalation exposure to formaldehyde

OBJECTIVE

Formaldehyde, a ubiquitous environmental pollutant has been classified as a human leukemogen. However, toxicity of formaldehyde in bone marrow, the target site of leukemia induction, is still poorly understood.

METHODOLOGY/PRINCIPAL FINDINGS

To investigate bone marrow toxicity (bone marrow pathology, hematotoxicity) and underlying mechanisms (oxidative stress, inflammation, apoptosis) in formaldehyde-exposed mice. Male Balb/c mice were exposed to formaldehyde (0, 0.5, and 3.0 mg/m(3)) by nose-only inhalation for 8 hours/day, over a two week period designed to simulate a factory work schedule, with an exposure-free "weekend" on days 6 and 7, and were sacrificed on the morning of day 13. Counts of white blood cells, red blood cells and lymphocytes were significantly (p<0.05) decreased at 0.5 mg/m(3) (43%, 7%, and 39%, respectively) and 3.0 mg/m(3) (52%, 27%, and 43%, respectively) formaldehyde exposure, while platelet counts were significantly increased by 109% (0.5 mg/m(3)) and 67% (3.0 mg/m(3)). Biomarkers of oxidative stress (reactive oxygen species, glutathione depletion, cytochrome P450 1A1 and glutathione s-transferase theta 1 expression), inflammation (nuclear factor kappa-B, tomour necrosis factor alpha, interleukin-1 beta), and apoptosis (activity of cysteine-aspartic acid protease 3) in bone marrow tissues were induced at one or both formaldehyde doses mentioned above.

CONCLUSIONS/SIGNIFICANCE

Exposure of mice to formaldehyde by inhalation induced bone marrow toxicity, and that oxidative stress, inflammation and the consequential apoptosis jointly constitute potential mechanisms of such induced toxicity.

Recent trend in risk assessment of formaldehyde exposures from indoor air

Studies about formaldehyde (FA) published since the guideline of 0.1 mg/m(3) by the World Health Organization (WHO) in 2010 have been evaluated; critical effects were eye and nasal (portal-of-entry) irritation. Also, it was considered to prevent long-term effects, including all types of cancer. The majority of the recent toxicokinetic studies showed no exposure-dependent FA-DNA adducts outside the portal-of-entry area and FA-DNA adducts at distant sites were due to endogenously generated FA. The no-observed-adverse-effect level for sensory irritation was 0.5 ppm and recently reconfirmed in hypo- and hypersensitive individuals. Investigation of the relationship between FA exposure and asthma or other airway effects in children showed no convincing association. In rats, repeated exposures showed no point mutation in the p53 and K-Ras genes at ≤15 ppm neither increased cell proliferation, histopathological changes and changes in gene expression at 0.7 ppm. Repeated controlled exposures (0.5 ppm with peaks at 1 ppm) did not increase micronucleus formation in human buccal cells or nasal tissue (0.7 ppm) or in vivo genotoxicity in peripheral blood lymphocytes (0.7 ppm), but higher occupational exposures were associated with genotoxicity in buccal cells and cultivated peripheral blood lymphocytes. It is still valid that exposures not inducing nasal squamous cell carcinoma in rats will not induce nasopharyngeal cancer or lymphohematopoietic malignancies in humans. Reproductive and developmental toxicity are not considered relevant in the absence of sensory irritation. In conclusion, the WHO guideline has been strengthened.

Glutathione S-transferase M1 and T1 genotypes and myocardial infarction

Myocardial infarction (MI), which is the most important manifestation of coronary artery disease, is the leading cause of morbidity and mortality in the world. Glutathione S transferases (GSTs) are enzymes responsible for the metabolism of numerous xenobiotics and are known to be polymorphic in humans. We investigated the association between the GSTM1 and GSTT1 gene polymorphisms and MI. The study consists of 296 healthy controls and 324 consecutive patients who had undergone coronary angiography for suspicion of coronary artery disease and with a past history of myocardial infarction. DNA was extracted from whole blood of patient and control. GSTM1 and GSTT1 gene polymorphisms were examined using multiplex PCR. We found that the null GSTM1 was associated with protective effect on MI, although this increase was not significant for GSTM1 (p < 0.054). However, GSTT1 genotype was associated with an increase in the risk of developing MI. In addition to after adjusting other all coronary risk factors, the interactive effect of GSTT1 null genotype remained statistically significant (p < 0.001) for MI disease but GSTM1 null genotype was not statistically significant. Patients, who smoke having the null genotypes of GSTM1, were at a higher risk for developing MI (p < 0.001, OR = 0.41, 95 % CI = 0.240-0.207). There was an effect of interaction of GSTM1 null genotype and smoking on MI development between patient and control groups (p < 0.001). Our results showed that individuals with the null genotypes for GSTM1 had protective effect, while GSTT1 was at a higher risk for MI disease. In addition, there was additional effects of smoking when smoking and non-smoking groups were compared.

Association of the Glutathione S-transferases M1 and T1 polymorphism with male infertility: a meta-analysis

BACKGROUND

Genes of different pathways regulate spermatogenesis, and the complexity of the spermatogenic process indicates that polymorphisms or mutations in these genes could cause male infertility. Published data on the association between the GSTM1 and GSTT1 polymorphism and male infertility risk are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed.

METHODS

A total of 11 studies regarding GSTM1 and 9 studies regarding GSTT1 between 1999 and 2012 were identified through researching MEDLINE, EMBASE and the Chinese Biomedical Database. It was performed to obtain summary estimated odd ratios and 95 % confidence intervals of GSTM1 and GSTT1 for male infertility, with attention to study quality and publication bias.

RESULTS

Overall, a significant association was seen between GSTM1 (OR=1.20, 95 % CI=1.02-1.40, P(heterogeneity) =0.000, P=0.027) genotypes and male infertility. Significant associations were also observed in subgroups of Caucasian populations (OR=1.65, 95 %CI=1.16-2.34, P(heterogeneity) =0.006, P=0.005), but were not observed in Asian populations (OR=1.09, 95 % CI=0.72-1.65, P(heterogeneity) =0.054, P=0.697) when stratified by ethnicity. While there was no significant association was seen between GSTT1 (OR=1.00, 95 % CI=0.74-1.35, P(heterogeneity) =0.000, P=0.980) null genotypes and male infertility. Simultaneously, significant associations were not observed in subgroups of Caucasian populations (OR=0.94, 95 %CI=0.44-2.00, P(heterogeneity) =0.000, P=0.867) and Asian populations (OR=0.93, 95 % CI=0.46-1.87, P(heterogeneity) =0.002, P=0.838) when stratified by ethnicity.

CONCLUSION

Our results suggest the GSTM1 null genotype contributes to male infertility susceptibility, while GSTT1 gene polymorphisms are not associated with male infertility in our study.

Genotoxic biomonitoring of tobacco farmers: Biomarkers of exposure, of early biological effects and of susceptibility

Tobacco farming presents several hazards to those who cultivate and harvest the plant. The genotoxic and mutagenic effects in tobacco farmers were investigated. In order to verify the relationship between genetic susceptibility and biomarkers GSTT1, GSTM1, GSTP1, CYP2A6, PON, OGG1, RAD51, XRCC1, and XRCC4 genes polymorphism were evaluated. Oxidative stress markers and trace elements content were determined. Peripheral blood cells samples were collected from 111 agricultural workers during pesticides application and leaf harvest, and 56 non-exposed subjects. Results show that farmers are exposed to mixture of substances with genotoxic and cytotoxic potential. Only GSTM1 null and CYP2A6*9 showed significant associations with cytokinesis-blocked micronuclei assay results. In pesticide application an increase in trace elements content was observed. The results indicated that exposure to pesticides and nicotine can influence antioxidant enzymes activity. Our study drives the attention once more to the need for occupational training on safe work environment for farm workers.

Investigations of potential susceptibility toward formaldehyde-induced genotoxicity

Blood samples were taken from three groups of volunteers (30 male smokers, 30 female non-smokers, and 30 school children) and tested for ex vivo susceptibility toward formaldehyde (FA)-induced genotoxicity. Blood samples were exposed to 150 μM FA for 2 h, and the induction of DNA-protein crosslinks (DPX) in leukocytes was measured by a modification of the alkaline comet assay (i.e., reduction of γ-irradiation induced DNA migration). Removal of DPX was determined by the abolition of FA-induced reduction in DNA migration within 4 h after the end of the exposure. Induction and persistence of FA-induced DNA lesions was also measured by the sister chromatid exchange (SCE) test with cultured lymphocytes after treatment of whole blood cultures with FA (150 μM). Furthermore, the expression (mRNA level) of the GSH-dependent formaldehyde dehydrogenase (FDH, identical to alcohol dehydrogenase 5; ADH5) was measured in leukocytes by quantitative real-time RT-PCR with TaqMan probes. The subjects were also analyzed for the GSTM1 and GSTT1 metabolic gene polymorphisms and a correlation analysis with the investigated genetic endpoints for FA-induced genotoxicity was performed. The results indicate that there are no biologically relevant differences between the three study groups with regard to the various indicators of cellular sensitivity toward FA-induced genotoxic effects and the expression of FDH. The induced genotoxic effects were not associated with polymorphisms in GSTM1 and GSTT1. None of the study groups showed particular mutagen sensitivity toward FA-induced genotoxicity. These results suggest that a low scaling factor to address possible human inter-individual differences in FA-induced genotoxicity could be reasonable.

Re-evaluation of a reported increased micronucleus frequency in lymphocytes of workers occupationally exposed to formaldehyde

A replicate evaluation of increased micronucleus (MN) frequencies in peripheral lymphocytes of workers occupationally exposed to formaldehyde (FA) was undertaken to verify the observed effect and to determine scoring variability. May-Grünwald-Giemsa-stained slides were obtained from a previously performed cytokinesis-block micronucleus test (CBMNT) with 56 workers in anatomy and pathology laboratories and 85 controls. The first evaluation by one scorer (scorer 1) had led to a highly significant difference between workers and controls (3.96 vs 0.81 MN per 1000 cells). The slides were coded before re-evaluation and the code was broken after the complete re-evaluation of the study. A total of 1000 binucleated cells (BNC) were analysed per subject and the frequency of MN (in ‰) was determined. Slides were distributed equally and randomly between two scorers, so that the scorers had no knowledge of the exposure status. Scorer 2 (32 exposed, 36 controls) measured increased MN frequencies in exposed workers (9.88 vs 6.81). Statistical analysis with the two-sample Wilcoxon test indicated that this difference was not significant (p=0.17). Scorer 3 (20 exposed, 46 controls) obtained a similar result, but slightly higher values for the comparison of exposed and controls (19.0 vs 12.89; p=0.089). Combining the results of the two scorers (13.38 vs 10.22), a significant difference between exposed and controls (p=0.028) was obtained when the stratified Wilcoxon test with the scorers as strata was applied. Interestingly, the re-evaluation of the slides led to clearly higher MN frequencies for exposed and controls compared with the first evaluation. Bland-Altman plots indicated that the agreement between the measurements of the different scorers was very poor, as shown by mean differences of 5.9 between scorer 1 and scorer 2 and 13.0 between scorer 1 and scorer 3. Calculation of the intra-class correlation coefficient (ICC) revealed that all scorer comparisons in this study were far from acceptable for the reliability of this assay. Possible implications for the use of the CBMNT in human biomonitoring studies are discussed.

Influence of CYP2C9, GSTM1, GSTT1 and NAT2 genetic polymorphisms on DNA damage in workers occupationally exposed to organophosphate pesticides

Previous studies have revealed that organophosphate pesticides (OPs) are primarily metabolized by xenobiotic metabolizing enzymes (XMEs). Very few studies have explored genetic polymorphisms of XMEs and their association with DNA damage in pesticides-exposed workers. Present study was designed to determine the influence of CYP2C9, GSTM1, GSTT1 and NAT2 genetic polymorphisms on DNA damage in workers occupationally exposed to OPs. We examined 268 subjects including 134 workers occupationally exposed to OPs and an equal number of normal healthy controls. The DNA damage was evaluated using alkaline comet assay and genotyping was done using individual polymerase chain reaction (PCR) or polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Acetylcholinesterase and paraoxonase activity were found to be significantly lowered in workers as compared to control subjects which were analyzed as biomarkers of toxicity due to OPs exposure (p<0.001). Workers showed significantly higher DNA tail moment (TM) compared to control subjects (14.32±2.17 vs. 6.24±1.37 tail % DNA, p<0.001). GSTM1 null genotype was found to influence DNA TM in workers (p<0.05). DNA TM was also found to be increased with concomitant presence of NAT2 slow acetylation and CYP2C9*3/*3 or GSTM1 null genotypes (p<0.05). DNA TM was found increased in NAT2 slow acetylators with mild and heavy smoking habits in control subjects and workers, respectively (p<0.05). The results of this study suggest that GSTM1 null genotypes, and an association of NAT2 slow acetylation genotypes with CYP2C9*3/*3 or GSTM1 null genotypes may modulate DNA damage in workers occupationally exposed to OPs.

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.

Is exposure to formaldehyde in air causally associated with leukemia?--A hypothesis-based weight-of-evidence analysis

Recent scientific debate has focused on the potential for inhaled formaldehyde to cause lymphohematopoietic cancers, particularly leukemias, in humans. The concern stems from certain epidemiology studies reporting an association, although particulars of endpoints and dosimetry are inconsistent across studies and several other studies show no such effects. Animal studies generally report neither hematotoxicity nor leukemia associated with formaldehyde inhalation, and hematotoxicity studies in humans are inconsistent. Formaldehyde's reactivity has been thought to preclude systemic exposure following inhalation, and its apparent inability to reach and affect the target tissues attacked by known leukemogens has, heretofore, led to skepticism regarding its potential to cause human lymphohematopoietic cancers. Recently, however, potential modes of action for formaldehyde leukemogenesis have been hypothesized, and it has been suggested that formaldehyde be identified as a known human leukemogen. In this article, we apply our hypothesis-based weight-of-evidence (HBWoE) approach to evaluate the large body of evidence regarding formaldehyde and leukemogenesis, attending to how human, animal, and mode-of-action results inform one another. We trace the logic of inference within and across all studies, and articulate how one could account for the suite of available observations under the various proposed hypotheses. Upon comparison of alternative proposals regarding what causal processes may have led to the array of observations as we see them, we conclude that the case for a causal association is weak and strains biological plausibility. Instead, apparent association between formaldehyde inhalation and leukemia in some human studies is better interpreted as due to chance or confounding.

Genetic polymorphisms of GSTM1, GSTT1 and GSTP1 and susceptibility to DNA damage in workers occupationally exposed to organophosphate pesticides

GSTM1, T1 and P1 are important enzymes of glutathione S-transferases (GSTs), involved in the metabolism of many endogenous and exogenous compounds. Individual genetic variation in these metabolizing enzymes may influence the metabolism of their substrates. The present study was designed to determine the genotoxic effects using DNA damage and its association with GSTM1, GSTT1, and GSTP1 (Ile105Val) genetic polymorphisms in workers occupationally exposed to organophosphate pesticides (OPs). We examined 230 subjects including 115 workers occupationally exposed to OPs and an equal number of normal healthy controls. The DNA damage was evaluated using the alkaline comet assay and genotyping was done using individual PCR or PCR-RFLP. Significantly higher DNA tail moment (TM) was observed in workers as compared to control subjects (14.41 ± 2.25 vs. 6.36 ± 1.41 tail % DNA, p<0.001). The results revealed significantly higher DNA TM in workers with GSTM1 null genotype than those with GSTM1 positive (15.18 vs. 14.15 tail % DNA, p=0.03). A significantly higher DNA TM was also observed in workers with homozygous Ile-Ile GSTP1 genotype than heterozygous (Ile-Val) and mutant (Val-Val) GSTP1 genotype (p=0.02). In conclusion, the results show that null deletion of GSTM1 and homozygote wild GSTP1 genotype could be related to inter-individual differences in DNA damage arises from the gene-environment interactions in workers occupationally exposed to OPs.

Assessment of genotoxic effects and changes in gene expression in humans exposed to formaldehyde by inhalation under controlled conditions

Forty-one volunteers (male non-smokers) were exposed to formaldehyde (FA) vapours for 4 h/day over a period of five working days under strictly controlled conditions. For each exposure day, different exposure concentrations were used in a random order ranging from 0 up to 0.7 p.p.m. At concentrations of 0.3 and 0.4 p.p.m., four peaks of 0.6 or 0.8 p.p.m. for 15 min each were applied. During exposure, subjects had to perform bicycle exercises (∼80 W) four times for 15 min. Blood samples, exfoliated nasal mucosa cells and nasal biopsies were taken before the first and after the last exposure. Nasal epithelial cells were additionally sampled 1, 2 and 3 weeks after the end of the exposure period. The alkaline comet assay, the sister chromatid exchange test and the cytokinesis-block micronucleus test were performed with blood samples. The micronucleus test was also performed with exfoliated nasal mucosa cells. The expression (mRNA level) of the glutathione (GSH)-dependent formaldehyde dehydrogenase (FDH, identical to alcohol dehydrogenase 5; ADH5; EC 1.2.1.46) was measured in blood samples by quantitative real-time reverse transcription-polymerase chain reaction with TaqMan probes. DNA microarray analyses using a full-genome human microarray were performed on blood samples and nasal biopsies of selected subgroups with the highest FA exposure at different days. Under the experimental conditions of this study, inhalation of FA did not lead to genotoxic effects in peripheral blood cells and nasal mucosa and had no effect on the expression of the FDH gene. Inhalation of FA did also not cause alterations in the expression of genes in a microarray analysis with nasal biopsies and peripheral blood cells.

The in vivo or ex vivo origin of micronuclei measured in human biomonitoring studies

The micronucleus test (MNT) is a well-established assay in genotoxicity testing and human biomonitoring. The cytokinesis-block micronucleus test (CBMNT) is the preferred method for measuring MN in cultured human lymphocytes from human subjects exposed to genotoxins. However, it is unclear to what extent mutagen exposure either leads to the formation of MN already in vivo or to the formation of MN ex vivo during cell culture as a consequence of persisting DNA damage. MN that were already induced in vivo can be determined by scoring MN in mononuclear lymphocytes 24 h after the start of the lymphocyte culture (i.e. in lymphocytes that did not divide yet). Results obtained for cancer patients after chemotherapy suggest that mutagen exposure in vivo mainly leads to the formation of MN during ex vivo proliferation of lymphocytes as a consequence of mis-repair of persistent damage. If these results also apply to other kinds of mutagen exposure, increased MN frequencies in the CBMNT can only be expected for exposures leading to a sufficient amount of damage that persists during ex vivo lymphocyte culture. For a better understanding of the origin of increased MN frequencies and the correct interpretation of results obtained with the CBMNT, further research is recommended: MN in mononuclear lymphocytes should be additionally scored 24 h after the start of the cultures, comparative investigation with the CBMNT and the MNT with reticulocytes should be performed and the kinetics of MN formation in lymphocyte cultures and the repair capacity of lymphocytes for different kinds of DNA damage should be characterised.

Combined analysis of chromosomal aberrations and glutathione S-transferase M1 and T1 polymorphisms in pathologists occupationally exposed to formaldehyde

The formaldehyde (FA) genotoxic potential in occupationally exposed individuals is conflicting. A relevant indoor-air FA pollution was found in hospitals and scientific institutions where FA is used as a bactericide and tissue preservative. In the present study, we evaluated the frequency of chromosomal aberrations (CAs) in peripheral blood lymphocytes from workers in pathology wards who have been exposed to FA, compared with a group of unexposed subjects. The subjects were also analyzed for the GSTM1 and GSTT1 metabolic gene polymorphisms. The exposed subjects showed a significant increase in the frequency of CA per cell and in the percentage of cells with aberrations compared to control subjects. The different GST genotypes did not affect the level of cytogenetic damage since CA frequencies were not statistically different between the GST "null" genotypes and the GST "positives". The generalized linear models showed that the number of CAs and cells with CAs increased with age, but, independent of age, it was significantly higher in the experimental rather than in the control group. Cubic-spline regression confirmed the linear relationship between CAs and age, but it provided evidence for a non-linear relationship between CAs and the number of years of FA exposure. Similar results were observed when the model included the number of cells with CAs as dependent variables. Our results demonstrate that air FA induces CAs even consequently to low levels of daily exposure, indicating an increased risk of genetic damage for workers exposed to this air pollutant.

Occupational exposure to formaldehyde: genotoxic risk evaluation by comet assay and micronucleus test using human peripheral lymphocytes

Formaldehyde (FA) is a world high-production compound with numerous applications ranging from production of resins to medicines. Due to its sensitizing properties, irritating effects and potential cancer hazard FA is of great environmental health concern. Numerous studies in humans and experimental animals demonstrated that inhaled FA produced toxicity, genotoxicity, and cancer at distal sites. IARC, based on sufficient data, reclassified FA as a human carcinogen. The highest level of human exposure to this aldehyde occurs in occupational settings, namely, in pathology and anatomy laboratories, where FA is commonly used as a fixative and tissue preservative. Several studies consistently showed that the levels of airborne FA in anatomy laboratories exceeded recommended exposure criteria. In order to assess the genotoxic effects of chronic occupational exposure to FA, a group of pathology/anatomy workers was assessed using a micronucleus (MN) test and comet assay. The level of exposure to FA was also determined and the time-weighted average (TWA) of exposure was calculated for each subject. The TWA mean value for FA exposed workers was 0.43 ± 0.06 ppm, exceeding national and international recommended limit levels of 0.3 ppm. Both MN frequency and comet assay parameters were significantly higher in exposed subjects. Data obtained confirm a correlation between genetic damage and occupational exposure to FA. These data, along with recent implications of human carcinogenicity, point out the need for close monitoring of occupational exposure to FA. Implementation of security and hygiene measures as well as good practices campaigns may be crucial to decrease risk.