The buccal micronucleus cytome assay: New horizons for its implementation in human studies.

In this report we provide a summary of the presentations and discussion of the latest knowledge regarding the buccal micronucleus (MN) cytome assay. This information was presented at the HUMN workshop held in Malaga, Spain, in connection with the 2023 European, Environmental Mutagenesis and Genomics conference. The presentations covered the most salient topics relevant to the buccal MN cytome assay including (i) the biology of the buccal mucosa, (ii) its application in human studies relating to DNA damage caused by environmental exposure to genotoxins, (iii) the association of buccal MN with cancer and a wide range of reproductive, metabolic, immunological, neurodegenerative and other age-related diseases, (iv) the impact of nutrition and lifestyle on buccal MN cytome assay biomarkers; (v) its potential for application to studies of DNA damage in children and obesity, and (vi) the growing prospects of enhancing the clinical utility by automated scoring of the buccal MN cytome assay biomarkers by image recognition software developed using artificial intelligence. The most important knowledge gap is the need of prospective studies to test whether the buccal MN cytome assay biomarkers predict health and disease.

Occupational Health Aspects with Special Focus on Physiological Differences between Office and Metalworkers.

Physical workload adversely impacts inflammation, oxidative stress and mood in heavy workers. We compared these risk parameters between metalworkers (n = 20) and office workers (n = 30), including gender differences. Blood samples were analyzed with thirty parameters to overview endocrinology, inflammation, and psychological and oxidative stress. Despite an adequate antioxidative supply, oxidative stress occurred in metalworkers, as indicated by significantly increased peroxide and homocysteine (Hcy) levels. Moreover, increased concentrations were observed in this group regarding psychological stress and diet-related parameters. Sex-specific differences were determined for physical dimensions, dehydroepiandrosterone sulfate (DHEAS), Hcy, uric acid, triglycerides, osmolality, anti-Mullerian hormone (AMH) and testosterone. Age-associated differences were observed for DHEAS, glycosylated hemoglobin, adrenaline, AMH and testosterone. In male office workers, the body mass index was associated with increased LDL-HDL, cholesterol-HDL and homeostatic model assessment of insulin resistance (HOMA-IR). In conclusion, these results indicate increased oxidative stress and psychological stress in heavy workers independently of adequate antioxidant sustenance. The sedentary occupation of office workers, in turn, favored diseases of affluence. This might be particularly relevant for long-term occupied persons and older workers due to a hormonal shift coming along, given the risk for oxidative stress-related diseases such as cardiovascular disease, particularly in the case of males, based on their lifestyle habits.

Induction of DNA damage as a consequence of occupational exposure to crystalline silica: A review and meta-analysis.

About 40 million workers are occupationally exposed to crystalline silica (CS) which was classified as a human carcinogen by the IARC. It is assumed that damage of the genetic material via inflammation and reactive oxygen species by CS lead to formation of malignant cells. We conducted a systematic literature search to find out if inhalation of CS containing dusts at workplaces causes damage of the genetic material. Thirteen studies were found eligible for this review, in most of them (n = 9) micronuclei (MN) which reflect structural/numerical chromosomal aberrations were monitored in lymphocytes and/or in exfoliated buccal cells. In 5 investigations DNA damage was measured in blood cells in single cell gel electrophoresis (comet) experiments. Frequently studied groups were potters, stone cutters, miners and construction workers. Results of meta-analyses show that exposure to CS causes formation of MN and DNA breaks, the overall ratio values were in exposed workers 2.06- and 1.96-fold higher than in controls, respectively. Two studies reported increased levels of oxidized guanine, and higher levels of DNA adducts with malondialdehyde indicating that exposure to CS leads to oxidative damage. The exposure of the workers to CS was quantified only in two studies, information concerning the size and chemical structures of the particles is lacking in most investigations. Therefore, it is not possible to use the results to derive occupational exposure limits of workers to CS which vary strongly in different countries. Nevertheless, the evaluation of the current state of knowledge shows that biomonitoring studies in which damage of the genetic material is measured in CS exposed workers can contribute to assess adverse health effects as consequence of DNA instability in specific occupations.

The Single-Cell Gel Electrophoresis Genotoxin Sensitivity Assay.

The single-cell gel electrophoresis-based genotoxin sensitivity assay (GSA) is an ex vivo approach which enables to study the impact of a variety of dietary factors, occupational exposures, and diseases on the sensitivity of humans towards genotoxic chemicals which cause adverse health effects such as cancer, accelerated aging, and infertility.

The First Lactate Threshold Is a Limit for Heavy Occupational Work.

Long-term heavy physical work often leads to early retirement and disability pension due to chronic overload, with a need to define upper limits. The aim of this study was to evaluate the value of the first lactate threshold (LTP1) as a physiological marker for heavy occupational work. A total of 188 male and 52 female workers performed an incremental cycle ergometer test to determine maximal exercise performance and the first and second lactate (LTP1; LTP2) and ventilatory thresholds (VT1; VT2). Heart rate (HR) recordings were obtained during one eight-hour shift (HR8h) and oxygen uptake was measured during 20 minutes of a representative work phase. Energy expenditure (EE) was calculated from gas-exchange measures. Maximal power output (Pmax), maximal oxygen consumption (VO2 max) and power output at LTP1 and LTP2 were significantly different between male and female workers. HR8h was not significantly different between male and female workers. A significant relationship was found between Pmax and power output at LTP1. HR8h as a percentage of maximum HR significantly declined with increasing performance (Pmax:r = -0.56; p < 0.01; PLTP1:r = -0.49; p < 0.01). Despite different cardio-respiratory fitness-levels; 95.4% of all workers performed their usual work below LTP1. It is therefore suggested that LTP1 represents the upper limit for sustained heavy occupational work; which supports its use to determine work capability and assessing the limits of heavy occupational work.

Induction of chromosomal damage in exfoliated buccal and nasal cells of road markers.

Road markers are exposed to various chemicals and particles. The aim of this study was to determine whether road worker exposure induceschromosomal damage which is indicative for increased cancer risks. Micronucleus (MN) cytome assays were thus conducted with exfoliated nasal and buccal cells collected from 42 workers and 42 matched controls. The frequencies of MN (reflecting chromosomal aberrations), nuclear buds (NBuds; reflecting gene amplifications) and binucleated cells (BN; reflecting disturbed mitosis) were scored. Further, the rates of nuclear anomalies indicative of acute cytotoxicity (condensed chromatin, karyorrhexis, karyolysis, pyknosis) were evaluated. Data demonstrated marked induction of MN, NBuds, and BN by 1.34-fold, 1.24-fold and 1.14-fold in buccal cells. In nasal cells, only MN frequencies were elevated, 1.23-fold. These effects were paralleled by increased rates of condensed chromatin, karyorrhexis and karyolysis in both cell types. The effects were more pronounced in individuals who had worked for more than 10 years while smoking did not produce synergistic responses. This is the first investigation concerning the induction of genetic damage in road markers and the results are suggestive for enhanced cancer risks. It is conceivable that exposure to silica dust (known to induce cancer and genetic damage) and/or benzoyl peroxide which forms reactive radicals may be associated with the observed genetic damage in road workers. Further investigations of the cancer risks of these workers are warranted.

Impact of extended working periods on genomic and telomeric DNA and on inflammatory markers: Results of an intervention study with office workers and carpenters.

Aim of this study was to clarify if extension of the work phase has an impact on DNA- stability, telomere lengths and inflammatory markers. We conducted an intervention trial with office workers (n = 24) and carpenters (n = 10), who changed their working schedule from 8 to 12 h per day over a period of 3 months. The work of both groups involved only moderate physical activity. We found no evidence for induction of double strand breaks (measured in γH2AX assays) and relative telomere lengths (relTL_36B4 and ALB) in lymphocytes in the two study groups. Furthermore, no overall changes of the levels of C-reactive protein (CRP), interleukin-6 (IL-6) and thiobarbituric acid reactive substances (TBARS) in plasma were detected. However, we found in agreement with earlier investigations a moderate (not significant) increase of the CRP levels with age. Furthermore, significant higher CRP concentrations (P = 0.03) were detected in young individuals (21-30 years) as a consequence of the extended working period. Taken together our findings indicate that prolongation of the working hours has no pronounced impact on DNA stability, telomere shortening and inflammatory markers; but the increase of the CRP concentrations in young workers may be indicative for adverse health effects in this subgroup.

Work Intensity, Low-Grade Inflammation, and Oxidative Status: A Comparison between Office and Slaughterhouse Workers.

Limited knowledge exists about the impact of physical workload on oxidative stress in different occupational categories. Thus, we aimed to investigate the oxidative and inflammatory status in employees with different physical workloads. We enrolled a total of 79 male subjects, 27 office workers (mean age 38.8 ± 9.1 years) and 52 heavy workers, in a slaughterhouse (mean age 40.8 ± 8.2 years). Fasting blood was drawn from an antecubital vein in the morning of the midweek before an 8-hour or 12-hour work shift. The antioxidative capacity was assessed measuring total antioxidant capacity (TAC), uric acid, total polyphenols (PPm), and endogenous peroxidase activity (EPA). Total peroxides (TOC), malondialdehyde (MDA), and myeloperoxidase (MPO) were analyzed as prooxidative biomarkers, and an oxidative stress index (OSI) was calculated. In addition, hsCRP, interleukin-6 (IL-6), MDA-LDL IgM antibodies, galectin-3, adrenocorticotropic hormone (ACTH), and the brain-derived neurotrophic factor (BDNF) were measured as biomarkers of chronic systemic inflammation and emotional stress. TOC (p = 0.032), TAC (p < 0.001), ACTH (p < 0.001), OSI (p = 0.011), and hsCRP (p = 0.019) were significantly increased in the heavy workers group, while EPA, BDNF (p < 0.001), and polyphenols (p = 0.004) were significantly higher in office workers. Comparison between 8 and 12 h shifts showed a worse psychological condition in heavy workers with increased levels for hsCRP (p = 0.001) and reduced concentration of BDNF (p = 0.012) compared to office workers. Oxidative stress and inflammation are induced in heavy workers and are particularly pronounced during long working hours, that is, 12-hour versus 8-hour shifts.

Genotoxic and Cytotoxic Effects in Exfoliated Buccal and Nasal Cells of Chromium and Cobalt Exposed Electroplaters.

Results of a number of studies indicate that electroplaters have increased cancer risks as a consequence of exposure to genotoxic metals such as chromium (VI) and nickel. These effects may be due to induction of damage of the genetic material which plays a key role in the etiology of cancer, and it was found that workers in galvanization factories exhibited increased levels of DNA damage. The aim of the present study was to investigate genetic stability in workers of a bright plating factory who are exposed to chromium (Cr) and cobalt (Co). Exfoliated cells were collected from the buccal and nasal mucosa of workers (n = 42) and matched controls (n = 43) and analyzed for induction of micronuclei (MN) which are formed as a consequence of chromosomal aberrations. In addition, other nuclear anomalies namely nuclear buds (Nbuds) which are formed as a consequence of gene amplification and markers indicating different stages of cell death (condensed chromatin, karyorrhexis, karyolysis, and pyknosis) were also assessed. No evidence was noted for induction of MN, but significantly increased rates of Nbuds in cells from both, buccal and nasal mucosa, were found. Parameters which are indicative for cytotoxic effects were more pronounced in nasal cells and rose with duration of employment period. Overall, our findings indicated that no apparent chromosomal damage occurred in bright electroplaters. However, data demonstrated that acute cytotoxic effects may lead to inflammations and/or lesions in epithelia of the respiratory tract of the workers.

Use of the lymphocyte cytokinesis-block micronucleus assay in occupational biomonitoring of genome damage caused by in vivo exposure to chemical genotoxins: Past, present and future.

This article concerns the use of the lymphocyte cytokinesis-block micronucleus (CBMN) assay in biomonitoring of occupational and environmental exposures to genotoxic agents. Furthermore, we evaluated the use of this method in different exposure scenarios, in comparison to other DNA damage biomarkers and its regional distribution. So far ca. 400 studies have been published and the number increased substantially in the last years. The most frequently investigated groups are hospital personnel, followed by workers in the chemical industry and agricultural workers. The lymphocyte CBMN assay is more frequently used in occupational studies than MN assays with epithelial cells and other methods, such as chromosomal aberration analyses, Comet assay and DNA-adduct measurements. The use of probes which enable the discrimination between MN containing chromosome fragments and whole chromosomes allows the identification of the molecular mechanisms of MN formation. Most studies were performed in Europe and Asia (ca. 65% and 25%, respectively). Important future developments will be the evaluation of the biological consequences of formation of additional nuclear endpoints (e.g. nucleoplasmic bridges), the improvement of the understanding of the health consequences of their formation, and the use of automated scoring devices. Future applications of the CBMN assay should address new emerging problems, e.g. the potential genotoxic damage induced by the use of nanoparticles and mobile phones. The control of occupational exposures to chemical genotoxins is currently based on chemical measurements which do not reflect interactions of individual factors and the inclusion of the lymphocyte CBMN assay in routine surveillance of workers could contribute substantially to the prevention of adverse health effects.

Results of micronucleus assays with individuals who are occupationally and environmentally exposed to mercury, lead and cadmium.

Millions of humans are exposed occupationally and environmentally to lead, mercury and cadmium compounds. Mercury compounds are less abundant but some of them belong to the most toxic chemicals which are known. We evaluated the literature to find out if these metals act in humans as genotoxic carcinogens and if their health effects can be predicted by use of micronucleus (MN) assays with lymphocytes and/or with other genotoxicity tests. Numerous studies showed that lead and mercury induce cancer in humans and also in animals, in vitro experiments with cultured cells indicate that they cause DNA damage via different molecular mechanisms including release of reactive oxygen species and interactions with DNA repair processes. Also in most human studies, positive results were obtained in MN tests with lymphocytes (all 15 occupational studies with lead yielded positive results, with mercury 6 out of 7 investigations were positive). For cadmium, there is clear evidence that it causes cancer in humans; however, induction of chromosomal damage was only seen in high dose experiments with mammalian cells while results of animal and human studies yielded conflicting results (only in 2 of 5MN trials with humans positive findings were reported). Possibly, non-genotoxic mechanisms such as inhibition of apoptosis and interaction with signaling pathways account for the carcinogenic properties of cadmium species. The findings of MN studies with lead and mercury are in excellent agreement with results which were obtained with other endpoints (e.g. chromosomal aberrations and comet formations) and it is evident that this approach can be used for occupational and environmental monitoring of exposed individuals. Important future tasks will be the realization of larger studies with a uniform standardized protocol, the additional evaluation of anomalies other than MN (nuclear buds and bridges) and the combination of such trials with investigations which allow to define the molecular mechanisms relevant for exposed humans.

The Impact of Visual Guided Order Picking on Ocular Comfort, Ocular Surface and Tear Function.

PURPOSE: We investigated the effects of a visual picking system on ocular comfort, the ocular surface and tear function compared to those of a voice guided picking solution. DESIGN: Prospective, observational, cohort study. SETTING: Institutional. STUDY POPULATION: A total of 25 young asymptomatic volunteers performed commissioning over 10 hours on two consecutive days. MAIN OUTCOME MEASURES: The operators were guided in the picking process by two different picking solutions, either visually or by voice while their subjective symptoms and ocular surface and tear function parameters were recorded. RESULTS: The visual analogue scale (VAS) values, according to subjective dry eye symptoms, in the visual condition were significantly higher at the end of the commissioning than the baseline measurements. In the voice condition, the VAS values remained stable during the commissioning. The tear break-up time (BUT) values declined significantly in the visual condition (pre-task: 16.6 sec and post-task: 9.6 sec) in the right eyes, that were exposed to the displays, the left eyes in the visual condition showed only a minor decline, whereas the BUT values in the voice condition remained constant (right eyes) or even increased (left eyes) over the time. No significant differences in the tear meniscus height values before and after the commissioning were observed in either condition. CONCLUSION: In our study, the use of visually guided picking solutions was correlated with post-task subjective symptoms and tear film instability.

Impact of exposure to wood dust on genotoxicity and cytotoxicity in exfoliated buccal and nasal cells.

Wood dust was classified by the IARC as a human carcinogen which causes sinonasal tumours. However, the exposure in different industries varies strongly and the risks of workers depend on the specific situation which can be assessed by the use of biomonitoring methods. The aim of this study was to investigate the workers who are exposed to low dust levels (below the permitted concentrations) with cytogenetic and biochemical methods. Micronuclei (MNi) which are indicative for genomic damage, nuclear buds which reflect gene amplification, binucleated cells which are caused by mitotic disturbances and acute cytotoxicity parameters (pyknosis, karyorrhexis, condensed chromatin, karyolysis) were monitored in buccal and nasal cells of workers of a veneer factory (n = 51) who are exposed to volatile wood-derived compounds, in carpenters of a furniture factory which use no synthetic chemicals (n=38) and in a control group (n = 65). Additionally, markers were measured in blood plasma which reflect inflammations (C-reactive protein, CRP) and the redox status, namely malondialdehyde (MDA) and oxidised low density proteins (oxLDL). No induction of micronucleated cells was observed in both epithelia in the two exposure groups while all other nuclear anomalies except pyknosis were increased; also one health-related biochemical marker (MDA) was significantly elevated in the workers. Taken together, the results of our study show that exposure to low levels of wood dust does not cause formation of MNi indicating that the cancer risks of the workers are not increased as a consequence of genetic damage while positive results were obtained in earlier studies with workers who are exposed to high dust levels. However, our findings indicate that wood dust causes cytotoxic effects which may lead to inflammations.

Micronucleus assay with urine derived cells (UDC): a review of its application in human studies investigating genotoxin exposure and bladder cancer risk.

The first micronucleus (MN) study with urine derived cells (UDC) appeared 30 years ago. So far, 56 investigations have been published with this method and it was shown that it can be used for the detection of chromosomal damage caused by environmental and lifestyle factors as well as by occupational exposures and certain diseases This approach may be also useful as a diagnostic tool for the detection and prognosis of bladder cancer. The test system has been improved in the last years, i.e., it was shown that, apart from MN also other nuclear anomalies can be evaluated in UDC which are found in other types of epithelial cells as well (e.g., in oral and nasal cells) and are indicative for acute toxicity (pyknosis, karyorrhexis, karyolysis, condensed chromatin) and genomic instability (nuclear buds, binucleates). Furthermore, an improved protocol with Carnoy I fixation and Papanicolaou stain was developed which enables the discrimination between cells which originate from the cervix and those from the urothelium. The evaluation of the currently available results indicates that exposures and health conditions which are associated with increased cancer rates in the bladder (and possibly also in other organs) lead to positive results in MN-UDC assays and a limited number of studies indicate that this method may be equally sensitive as other more frequently used human biomonitoring assays. The major shortcoming of the UDC-MN method is the lack of standardization; the evaluation of the current data shows that a variety of staining and fixation methods are used and that the numbers of evaluated cells vary over a broad range. These inconsistencies may account for the large inter-laboratory variations of the background frequencies. In order to improve the reliability of the method, further standardization and validation is required. Therefore an international program should be initiated in which a similar strategy could be used as in previous validation/standardization projects concerning MN-cytome assays with lymphocytes and buccal cells.

The sensitivity of biomarkers for genotoxicity and acute cytotoxicity in nasal and buccal cells of welders.

Welders are inhalatively exposed to fumes which contain genotoxic carcinogens and it was found in epidemiological studies that they have increased cancer rates which may be causally related to DNA damage. In order to assess their health risks and to find out which chemicals cause the adverse effects, bioassays can be performed which enable the detection of genetic damage. The aim of the present study was a comparative investigation with exfoliated buccal and nasal cells in regard to induction of chromosomal alterations and acute cytotoxicity in welders and unexposed controls (n=22 per group). To elucidate the factors which account for genotoxic and cytotoxic effects, additional biochemical parameters were monitored reflecting the redox status as well as concentrations of different metals and 1-hydroxypyrene (1-OHP) in body fluids. We found in the nasal cells significant induction of alterations which are indicative for DNA damage, i.e. of micronuclei (MNi) and nuclear buds, while elevated rates of nuclear anomalies reflecting cytotoxic effects (condensed chromatin, karyorrhexis, karyolylsis) were detected in cells from both organs. The levels of certain metals (Cr, Cu, Mn, Mo, Ni), but not markers of oxidative damage were significantly higher in the body fluids of the welders. Multivariate Poisson regression analyses indicate that exposure to Mo (15% MNi increase by one standard deviation increase of Mo in serum), Ni (9% increase) and Mn (14% increase) are positively associated with the induction of MNi in nasal cells while Ni was associated with cytotoxic effects in both types of cells (12 and 16% increase). Taken together, our findings indicate that epithelial cells from the respiratory tract are suitable for the detection of DNA-damaging and cytotoxic effects in welders and can be used to assess health risks associated with genomic instability.

Induction of nuclear anomalies in exfoliated buccal cells of coca chewers: results of a field study.

The leaves of coca (Erythroxylum coca var. coca), a South American shrub which contains cocaine, other alkaloids and phenolics are widely used by indigenous populations of the Andes. It is currently not known if coca consumption causes genotoxic effects in humans. This information is important to predict potential long-term toxic effects such as cancer induction. Therefore, the buccal cytome assay was used to analyze oral cells from 45 uni- and bilateral chewers and 23 controls living in the Altiplano of the Peruvian Andes. In total, 123,471 cells were evaluated from chewers and 57,916 from controls. Information concerning the consumption levels and habits and also use of lime were collected with questionnaires. Chewing of the leaves did not induce nuclear anomalies reflecting genetic damage such as micronuclei (MNi) and nuclear buds; in the highest exposure group (but not in the overall group) even a significant decrease in the frequencies of cells with MNi (by 64 %) was observed. However, we found significantly elevated levels of other nuclear anomalies (karyorrhexis and karyolysis) which reflect cytotoxic effects in the coca users. The frequencies of these anomalies increased with the daily consumption and when lime was used to improve the release of the alkaloids. In contrast to other chewing habits (betel, tobacco and khat), consumption of coca leaves does not induce genetic instability in cells from the oral cavity and our findings indicate that no adverse health effects take place in chewers which are associated with DNA damage. However, the significant increase in certain anomalies shows that acute toxic effects are caused by coca consumption.

Formation of micronuclei and other nuclear anomalies in exfoliated nasal and oral cells: results of a human study with workers in a power plant processing poultry litter.

Handling of chicken litter leads to exposure to toxic gases, endotoxins and airborne microorganisms. Aim of this study was to investigate if this results in acute cytotoxicity and to damage of the genetic material which is involved in the etiology of various diseases including cancer. Nuclear anomalies which reflect genotoxic and cytotoxic effects were monitored in exfoliated buccal and nasal cells which were collected from workers (n = 25) of a power plant which processes chicken manure and from controls (n = 21). Furthermore, biochemical parameters of the redox status (malondialdehyde, oxLDL and TEAC) and C-reactive protein (CRP) in plasma and the concentrations of toxic gases and endotoxins in the air were determined. No increase of anomalies which reflect chromosomal damage (micronuclei, binucleates, nuclear buds) but significantly higher rates of nuclear aberrations which are indicative for cytotoxicity (karyolysis, karyorrhexis, condensed chromatin) were found in the workers. These effects were in nasal cells more pronounced as in buccal cells. MDA, oxLDL and CRC levels were in both study groups similar. Chemical analyses show that the workers are exposed to high concentrations of NO and endotoxins, while the levels of NO2, NH3 and H2S were below the MAK levels. Taken together, the results show that anomalies that are due to cytotoxicity are increased in the workers and suggest that the exposure may lead to inflammations in the respiratory tract. However, the lack of induction of anomalies that reflect chromosomal damage indicate that no health effects will take place which are due to instability of the genetic material.

Governmental regulations for early retirement by means of energy expenditure cut offs.

OBJECTIVES: Long-term heavy work impairs employees, and they may retire prematurely by law. We investigated the value of energy expenditure (EE) during work shifts as a means to define heavy workload. METHODS: The study comprised 79 male [mean age 32.2 (standard deviation [SD] 7.5) years] and 33 female [33.5 (SD 11.2) years] employees in different occupations classified as "heavy work" (EE of 1400 and 2000 kcal for women and men, respectively). Cycle ergometry determined exercise performance. Gas exchange measures were performed during selected phases of work, and heart rate (HR) recordings were obtained for a complete work shift. EE was calculated from gas exchange measures. RESULTS: Male and female subjects differed significantly for maximal power output (P(max)) [men=206.3 (SD 47.3) watts; women=149.6 (SD 36.1) watts] and maximal oxygen consumption (VO(2max)) [men=2.965 (SD 0.63) l/min; women= 1.958 (SD 0.50) l/min] in the cycle ergometer test. Shift HR (HR(Sh)) was found between 102 (SD 14) b/min [57.6 (SD 8.5) % HR(max)] and 99 (SD 10) b/min [55.5 (SD 5.9) % HR(max)] dependent on tasks and groups. Working EE was found between 1864 (SD 732) kcal and 1249 (SD 609) kcal for men and women, respectively, but approximately 60% of subjects were well below the legal limits. CONCLUSIONS: The legal definition of heavy workload by mean working EE per 8-hour work shift applies to all investigated occupations; however, a substantial proportion of workers may not fulfill the criterion if applied individually. Alternative definitions of heavy workload in terms of absolute oxygen consumption or EE relative to cardiorespiratory fitness lead to similar classification results of the investigated occupations.

Use of nasal cells in micronucleus assays and other genotoxicity studies.

Genotoxicity experiments with exfoliated nasal mucosa cells are a promising minimally invasive approach for the detection of DNA-damaging compounds in ambient air. Results of single cell gel electrophoresis (SCGE) assays with individual cells and organ cultures from bioptic material show that DNA damage caused by compounds such as nitrosamines, polycyclic aromatic hydrocarbons and pesticides can be detected. Biochemical studies indicate that enzymes involved in the metabolism of environmental mutagens are represented in nasal cells. Several protocols for experiments with nasal cells have been developed and it was shown that formaldehyde, metals, styrene and crystalline silica induce DNA damage in SCGE and/or in micronucleus studies; furthermore, it was also found that polluted urban air causes DNA instability in nasal epithelial cells. Comparisons of these data with results obtained in lymphocytes and buccal cells indicate that nasal cells are in general equally sensitive. Broad variations in the baseline levels, differences of results obtained in various studies as well as the lack of information concerning the impact of confounding factors on the outcome of experiments with these cells indicate the need for further standardisation of the experimental protocols.

Genotoxic effects of occupational exposure measured in lymphocytes of waste-incinerator workers.

Workers of solid-waste incinerators are exposed to a variety of pollutants such as dioxins, polycyclic aromatic hydrocarbons and heavy metals. It has been shown that the emissions and the fly ash produced by incineration have mutagenic properties. To our knowledge, no studies have been conducted in which genotoxic effects were investigated in exposed workers. Therefore, we monitored DNA damage by means of the single-cell gel electrophoresis (SCGE) and micronucleus (MN) assays in lymphocytes of individuals (n=23) who were temporarily (1-11 months) conducting maintenance works of an incinerator and in unexposed controls (n=19). Additionally, we measured the urinary concentrations of selected metals (Cr, Mn, Ni, As) with atomic absorption resonance. We found no differences in the levels of DNA migration and in the MN frequencies between different exposure groups and controls. Likewise, we also failed to find differences in the metal concentrations. Taken together, our results indicate that incinerator workers at the site investigated here have no increased health risks due to DNA damage.