Exposure of thermoelectric power-plant workers to volatile organic compounds from fuel oil: genotoxic and cytotoxic effects in buccal epithelial cells

Thermoelectric power-plant workers are constantly exposed to high levels of potentially genotoxic gaseous substances, such as volatile organic compounds (VOCs) from the combustion of fuel oil or the processing of naphtha. The aim of the present study was to estimate the association between such occupational exposure and the frequency of micronucleated cells and cells with other nuclear anomalies. Buccal epithelial cells were collected from a total of 44 power-plant workers (exposed group) and 47 administrative workers (non-exposed group), and examined for the frequency of micronucleated cells (MNC) and of cells with other nuclear anomalies (ONA: pyknosis, karyolysis, and karyorrhexis) by means of the micronucleus assay. The frequencies of MNC and ONA per 1000 cells in the exposed group (1.8‰ and 82.4‰, respectively) were significantly higher than in the non-exposed group (0.2‰ and 58.3‰, respectively). The exposed group had a twelve-fold increase in risk for formation of MNC compared with non-exposed individuals (RR=12.1; 95% CI, 5.0-29.2; P<0.001). The confounding factors analyzed (age, smoking status, alcohol consumption, and mouthwash use) did not show any significant association with the frequency of MNC or ONA. The findings of this study show that workers from power plants exposed to VOCs have a significantly elevated risk for DNA damage. Therefore, bio-monitoring of DNA damage is recommended for this group of workers.     

Cytogenetic analysis of peripheral blood lymphocytes in workers exposed to benzene

In the present study, the method of cytogenetic analysis of peripheral blood lymphocytes was used to investigate 66 workers exposed to benzene, and 20 individuals selected from general population from the same locality, not exposed to particular mutagenic or carcinogenic agents (control group). Altogether, 8,600 metaphases were analysed. Frequencies of aberrant cells, including chromatide and chromosomal breaks, and chromatide and chromosomal exchanges, were scored in both groups. A very slight increase in aberrant cell frequencies (2.152% aberrant cells) was observed in the professional exposure group as compared to the control group (1.6% aberrant cells). Increased frequencies of aberrant cells were found in smokers of both the benzene-exposed and the control group. The differences were however not significant. In addition to cytogenetic examination, the workers underwent a general examination of their health condition (preventive examination). Benzene exposure seemed to have no injurious effect on the state of health of exposed workers. Biochemical and haematological tests gave normal values.     

Assessment of EEG frequency dynamics using complex demodulation.

The complex demodulation (CD) approach was applied to human EEG recorded during a cognitive task performance, including voluntary goal-directed movements. The standard CD algorithm was extended by a simple procedure using frequency histograms and power spectra to select the characteristic frequencies of EEG segments around the task performance. In the majority of records, amplitude modulation was found, which decreased or disappeared in the period prior to and at the very beginning of the task performance. It was found that the decrease of modulation in fast beta and gamma components begins approximately one second before that of the alpha components. Frequency modulation appeared in some records at the end of the task in beta and gamma components. The results showed that a cognitive task performance is accompanied by non-linear processes in the frequency components of EEG. These dynamic changes could extend the findings of event-related desynchronization obtained by linear methods.     

Cytogenetic study of a group of workers exposed to thinner

The frequency of sister-chromatid exchanges (SCE) was evaluated in a group of 24 workers exposed to thinner in a luminous advertisements factory and in three workshops for painting sheet metal in Mexico City. 50 metaphases for each exposed individual and each control were analysed; air samples of the working places were also studied; it was observed that among all the components of thinner, only benzene exceeded advisable limits. The cytogenetic data were subject to one-way analyses of variance indicating that no significant differences existed between both groups; also, there are no significant differences among workers with a long exposure time and those with fewer than 5 years of exposure. Nevertheless, use of tobacco increased significantly the SCE frequencies among the exposed group, but did not increase SCE in the control group.     

Functional asymmetry of the neocortex electrical activity during food conditioning in dogs

Four dogs were trained to perform a conditioned alimentary response to a sound stimulus. The EEG was recorded from six pairs of chronically implanted neocortical electrodes. The EEG spectra and coherence functions between the neighboring derivations of each of the hemispheres were analyzed in the theta, alpha, beta 1 and beta 2 frequency ranges. At the first stages of conditioning, the percent of cases increased when the highest mean values of EEG frequency were localized in the left hemisphere. Later on the percent of cases, when the mean coherence values in the left hemisphere were higher than in the right hemisphere, also increased. At the stage of conditioned response stabilization, this asymmetry either disappeared or the right hemisphere became more active than the left one. The spatial localization of the maximal values of the EEG frequency was different for different frequency ranges. The highest values in the beta 1 range were more frequently registered in the posterior cortical regions and in the beta 2 range they were revealed, predominantly, in the anterior areas. The maximal values of coherence dominated in the anterior regions and their spatial distribution was similar for different frequencies. Thus, the initial stages of conditioning are accompanied by activation of the left hemisphere.     

Monitoring protein expression by proteomics: human plasma exposed to benzene

Low levels and long term exposure to benzene is associated with hematotoxicity including aplastic anemia, acute myelogenous leukemia, and lymphoma. Current biomonitoring methods such as urinary phenol, S-phenylmercapturic acid, and trans-trans muconic acid were found to be unreliable as analytical methods to detect benzene exposure. Therefore, to search for a specific protein for biomonitoring benzene exposure, we investigated plasma proteins from workers (n = 50) at a printing company who were exposed to benzene, by two-dimensional gel electrophoresis. The protein profiles are significantly different (p < 0.05) between benzene exposed and unexposed groups, as identified by matrix-assisted laser desorption ionization/time of flight mass spectrometry and confirmed by Western blot analyses. T cell receptor beta chain (TCR beta), FK506-binding protein, and matrix metalloproteinase-13 were expressed only in benzene exposed workers. In addition, interleukin-4 receptor alpha chain and T cell surface glycoprotein CD1b precursor were found to be up-regulated in the plasma of benzene exposed workers. When we treated Jurkat cells with benzene (10 microM-10 mM), TCR beta expression was increased in the membrane more than 6-9-fold compared to untreated cells. In addition, the amount of TCR beta released into the culture media, at benzene concentrations greater than 50 microM, increased up to 10 mM. Therefore, TCR beta levels in plasma could be used as a biomarker and a possible therapeutic target for benzene exposure.     

Effect of low frequency modulated microwave exposure on human EEG: individual sensitivity

The aim of this study was to evaluate the effect of modulated microwave exposure on human EEG of individual subjects. The experiments were carried out on four different groups of healthy volunteers. The 450 MHz microwave radiation modulated at 7 Hz (first group, 19 subjects), 14 and 21 Hz (second group, 13 subjects), 40 and 70 Hz (third group, 15 subjects), 217 and 1000 Hz (fourth group, 19 subjects) frequencies was applied. The field power density at the scalp was 0.16 mW/cm(2). The calculated spatial peak SAR averaged over 1 g was 0.303 W/kg. Ten cycles of the exposure (1 min off and 1 min on) at fixed modulation frequencies were applied. All subjects completed the experimental protocols with exposure and sham. The exposed and sham-exposed subjects were randomly assigned. A computer also randomly assigned the succession of modulation frequencies. Our results showed that microwave exposure increased the EEG energy. Relative changes in the EEG beta1 power in P3-P4 channels were selected for evaluation of individual sensitivity. The rate of subjects significantly affected is similar in all groups except for the 1000 Hz group: in first group 3 subjects (16%) at 7 Hz modulation; in second group 4 subjects (31%) at 14 Hz modulation and 3 subjects (23%) at 21 Hz modulation; in third group 3 subjects (20%) at 40 Hz and 2 subjects (13%) at 70 Hz modulation; in fourth group 3 subjects (16%) at 217 Hz and 0 subjects at 1000 Hz modulation frequency.     

Proteomic analysis of plasma proteins of workers exposed to benzene

In this study, we analyzed the proteins in plasma of workers exposed to benzene by two-dimensional gel electrophoresis, in the hope of finding a specific protein suitable for the biomonitoring of benzene exposure. Comet assays were also carried out to evaluate lymphocytes DNA damage. Fifty workers from a printing company and 38 matched unexposed healthy subjects were enrolled in the study. DNA damage was found to be significantly higher in the exposed workers than in the controls. The tail moments of the two groups were 2.07 +/- 0.35 and 1.48 +/- 0.41, respectively (P < 0.0001). The mean values of trans, trans-muconic acid (t,t-MA) in workers exposed to benzene and in unexposed subjects were 1.011 +/- 0.249 and 0.026 +/- 0.028 mg/g creatinine, respectively. Protein profiles were significantly different (P < 0.05) in the two groups, as identified by matrix-assisted laser desorption ionization/time of flight (MALDI-TOF) mass spectrometry and confirmed by Western blot. T cell receptor beta chain (TCR beta), FK506-binding protein (FKBP51) and matrix metalloproteinase-13 (MMP13) were found to be up-regulated in the benzene-exposed workers. In addition, the correlation between TCR beta and the tail moments of lymphocytes was statistically significant (r-value, 0.428). We conclude that TCR beta in plasma could be used for the early detection of exposure to benzene.     

Cytogenetic biomonitoring of workers from laboratories of clinical analyses occupationally exposed to chemicals

A cytogenetic monitoring study was carried out on a group of workers in clinical analysis laboratories to investigate the risk of occupational exposure to chronic low levels of chemicals.Thirty-four clinical laboratories have been involved in the study. In these laboratories, toxicants and analytical procedures utilized have been characterized. The individual occupational exposure of workers was assessed by use of a questionnaire concerning the chemical substances utilized. About 300 different chemicals have been identified.Cytogenetic analyses (chromosomal aberration and micronucleus tests) were carried out on a strictly selected group of 50 workers enrolled from these laboratories and compared to 53 controls (healthy blood donors) matched for gender and age.The exposed group shows a significantly higher frequency of genetic damage than the control group. Both chromatid and chromosome aberration frequencies in workers appear significantly higher than in controls. Similarly, comparison between micronucleated cells rates of exposed and unexposed groups show significantly higher frequencies of binucleated cells with micronucleus (BNMN) and of total micronuclei (MN tot) in workers than in controls.     

Cytogenetic biomonitoring of workers from laboratories of clinical analyses occupationally exposed to chemicals

A cytogenetic monitoring study was carried out on a group of workers in clinical analysis laboratories to investigate the risk of occupational exposure to chronic low levels of chemicals.Thirty-four clinical laboratories have been involved in the study. In these laboratories, toxicants and analytical procedures utilized have been characterized. The individual occupational exposure of workers was assessed by use of a questionnaire concerning the chemical substances utilized. About 300 different chemicals have been identified.Cytogenetic analyses (chromosomal aberration and micronucleus tests) were carried out on a strictly selected group of 50 workers enrolled from these laboratories and compared to 53 controls (healthy blood donors) matched for gender and age.The exposed group shows a significantly higher frequency of genetic damage than the control group. Both chromatid and chromosome aberration frequencies in workers appear significantly higher than in controls. Similarly, comparison between micronucleated cells rates of exposed and unexposed groups show significantly higher frequencies of binucleated cells with micronucleus (BNMN) and of total micronuclei (MN tot) in workers than in controls.     

Cytogenetic alterations in field workers routinely exposed to pesticides in Bogota flowers farms

Frequency of cytogenetic alterations (micronuclei and chromosome aberrations), DNA repair deficiencies and acetylcholinesterase activity was determined for field workers in Bogotá, Colombia. These workers were regularly exposed to organophosphate and carbamate insecticides while employed on farms for flower growing. Interviews were conducted with 31 workers associated with occupational risk of pesticides exposure and 30 without exposure. A standard cytogenetic assay was used to determine chromosome aberrations and micronuclei frequencies. In addition, a challenge assay assessed response to gamma-rays as an indication of DNA repair deficiencies--cells were exposed to gamma-rays in vitro and the frequencies of chromosome aberrations in post-irradiation metaphase cells were quantified. The data were evaluated for percentage of aberrant cells, cells with chromosome aberrations and frequencies of chromatid breaks per 100 metaphase cells in each worker. The exposed group had a significantly higher frequency of cells with chromosome aberrations and micronuclei as compared with the non-exposed group (p = 0.02). However, the challenge assay did not indicate a significant difference (p > 0.1). These findings require confirmation by further analytical studies involving larger sample. Cytogenetic and toxicological studies, in conjunction with thorough clinical examination are recommended.     

Effects of environmental benzene: micronucleus frequencies and haematological values in traffic police working in an urban area

Among the toxic chemicals present in the ambient air of urban centres, benzene raises particular concern due to its haematoxicity and leukaemogenic hazards, probably related to clastogenic factors. However, little is known about the health risks associated with environmental--rather than industrial--exposure to benzene. We analysed micronucleus (MN) frequencies in peripheral lymphocytes by use of the cytokinesis-block technique, and haematological parameters among 49 traffic police and 36 indoor workers (controls) in the city of Bologna. The analysis of urban air provided by a municipal air-quality monitoring station indicated that the levels of environmental benzene were often above the recommended threshold level (10 microg/m3) whereas other pollutants--nitrogen oxides, polycyclic aromatic hydrocarbon compounds, total suspended particulate matter, carbon monoxide, sulfur dioxide--did not exceed the maximum atmospheric concentration established for air-quality standards. Mean levels of individual airborne benzene exposure--as measured by personal devices worn during 4-h morning work-shifts--were six-fold higher in the traffic police than in controls (P=0.001). While no significant difference in haematological parameters was found between the two groups, MN frequency was significantly higher among the traffic police than in indoor workers (P=0.001). Among the study population, MN frequency was found to increase with age, but no influence was observed for gender or smoking. Although it cannot be excluded that the increase of MN frequency observed in traffic police could also depend, apart from benzene, on the complex mixture of pollutants encountered in urban air, our data indicate that elevated personal benzene exposure could represent a genetic risk. The analysis of biomarkers of genetic damage in subjects particularly exposed to environmental benzene deserves careful study.     

Variation in the number of presacral vertebrae in bantu-speaking South African Negroes

Variation in number of presacral vertebrae (PSV) was examined in 462 vertebral columns in four populations drawn from tribal groups of Southern African Negroes. The total incidence of numerical variants (23 PSV and 25 PSV) was 19% in males and 12.1% in females. Males have a higher frequency of 25 PSV and females a higher frequency of 23 PSV, a sex difference reported by previous workers. Significant differences in the incidence of 25 PSV in males were present between S.A. Negroes, American Negroes and other racial groups. The total number of variants (23 PSV and 25 PSV) is significantly higher in S.A. Negro males (and higher but not significantly in females) than in the other groups; owing mainly to the findings in the Nguni-speaking sub-samples of the S.A. Negro. These findings support a previous suggestion based on combined-sex data that the frequency of numerical variations of PSV are characteristic of a population. It is suggested here that such frequencies are even more characteristic when males and females are considered separately.     

Heritability of human brain functioning as assessed by electroencephalography.

To study the genetic and environmental contributions to individual differences in CNS functioning, the electroencephalogram (EEG) was measured in 213 twin pairs age 16 years. EEG was measured in 91 MZ and 122 DZ twins. To quantify sex differences in the genetic architecture, EEG was measured in female and male same-sex twins and in opposite-sex twins. EEG was recorded on 14 scalp positions during quiet resting with eyes closed. Spectral powers were calculated for four frequency bands: delta, theta, alpha, and beta. Twin correlations pointed toward high genetic influences for all these powers and scalp locations. Model fitting confirmed these findings; the largest part of the variance of the EEG is explained by additive genetic factors. The averaged heritabilites for the delta, theta, alpha and beta frequencies was 76%, 89%, 89%, and 86%, respectively. Multivariate analyses suggested that the same genes for EEG alpha rhythm were expressed in different brain areas in the left and right hemisphere. This study shows that brain functioning, as indexed by rhythmic brain-electrical activity, is one of the most heritable characteristics in humans.     

Advantages of Repeated Low Dose against Single High Dose of Kainate in C57BL/6J Mouse Model of Status Epilepticus: Behavioral and Electroencephalographic Studies

A refined kainate (KA) C57BL/6J mouse model of status epilepticus (SE) using a repeated low dose (RLD) of KA (5 mg/kg, intraperitoneal; at 30 min intervals) was compared with the established single high dose (SHD) of KA (20 mg/kg, intraperitoneal) model. In the RLD group, increased duration of convulsive motor seizures (CMS, Racine scale stage ≥3) with a significant reduction in mortality from 21% to 6% and decreased variability in seizure severity between animals/batches were observed when compared to the SHD group. There was a significant increase in the percentage of animals that reached stage-5 seizures (65% versus 96%) in the RLD group. Integrated real-time video-EEG analysis of both groups, using NeuroScore software, revealed stage-specific spikes and power spectral density characteristics. When the seizures progressed from non-convulsive seizures (NCS, stage 1–2) to CMS (stage 3–5), the delta power decreased which was followed by an increase in gamma and beta power. A transient increase in alpha and sigma power marked the transition from NCS to CMS with characteristic ‘high frequency trigger’ spikes on the EEG, which had no behavioral expression. During SE the spike rate was higher in the RLD group than in the SHD group. Overall these results confirm that RLD of KA is a more robust and consistent mouse model of SE than the SHD of KA mouse model.     

Aging-related changes of EEG synchronization during a visual working memory task

Differences of EEG synchronization between normal old and young people during a working memory (WM) task were investigated. The synchronization likelihood (SL) is a novel method to assessed synchronization in multivariate time series for non-stationary systems. To evaluate this method to study the mechanisms of WM, we calculated the SL values in brain electrical activity for both resting state and task state. EEG signals were recorded from 14 young adults and 12 old adults during two different states, respectively. SL was used to measure EEG synchronization between 19 electrodes in delta, theta, alpha1, alpha2 and beta frequency bands. Bad task performance and significantly decreased EEG synchronization were found in old group compared to young group in alpha1, alpha2 and beta frequency bands during the WM task. Moreover, significantly decreased EEG synchronization in beta band in the elder was also detected during the resting state. The findings suggested that reduced EEG synchronization may be one of causes for WM capacity decline along with healthy aging.     

Cognitive network interactions and beta 2 coherence in processing non-target stimuli in visual oddball task

Spatiotemporal dynamics of event-related potentials (ERP) evoked by non-target stimuli in a visual oddball experiment and the presence of coherent oscillations in beta 2 frequency band of decomposed EEG records from peristimulus period were investigated by means of intracranial electrodes in humans. Twenty-one patients with medically intractable epilepsy participated in the study. The EEG signal was recorded using platinum electrodes implanted in several cortical and subcortical sites. Averaged 2 s EEG records were analyzed. Task-specific EEG changes were found in each patient, ERPs were derived from 92 electrodes used (96 % of possible cases). In the majority of analysed cases, ERPs were composed of several distinct components, and their duration was mostly longer than 1 s. The mean onset of the first ERP component was 158+/-132 ms after the stimulus (median 112 ms, minimum value 42 ms, maximum value 755 ms), and large variability of these onset times was found in all the investigated structures. Possible coherence between neural activities of remote brain sites was investigated by calculating running correlations between pairs of decomposed EEG records (alpha, beta 1, beta 2 frequency bands were used, total number of correlated pairs was 662 in each frequency band). The record pairs exhibiting highly correlated time segments represented 23 % of all the investigated pairs in alpha band, 7 % in beta 1 band, and 59 % in beta 2 band. In investigated 2 s record windows, such segments were distributed evenly, i.e. they were also found before the stimulus onset. In conclusion, the results have implicated the idea that a lot of recorded ERPs was more or less by-products of chance in spreading a signal within the neuronal network, and that their functional relevance was somewhat linked with the phenomenon of activity synchronization.     

Spectrum of chromosomal aberrations in peripheral lymphocytes of hospital workers occupationally exposed to low doses of ionizing radiation

Chromosome aberrations frequency was estimated in peripheral lymphocytes from hospital workers occupationally exposed to low levels of ionizing radiation and controls. Chromosome aberrations yield was analyzed by considering the effects of dose equivalent of ionizing radiation over time, and of confounding factors, such as age, gender and smoking status. Frequencies of aberrant cells and chromosome breaks were higher in exposed workers than in controls (P = 0.007, and P = 0.001, respectively). Seven dicentric aberrations were detected in the exposed group and only three in controls, but the mean frequencies were not significantly different. The dose equivalent to whole body of ionizing radiation (Hwb) did appear to influence the spectrum of chromosomal aberrations when the exposed workers were subdivided by a cut off at 50 mSv. The frequencies of chromosome breaks in both subgroups of workers were significantly higher than in controls (< or =50 mSv, P = 0.041; >50 mSv, P = 0.018). On the other hand, the frequency of chromatid breaks observed in workers with Hwb >50 mSv was significantly higher than in controls (P = 0.015) or workers with Hwb < or =50 mSv (P = 0.046). Regarding the influence of confounding factors on genetic damage, smoking status and female gender seem to influence the increase in chromosome aberration frequencies in the study population. Overall, these results suggested that chromosome breaks might provide a good marker for assessing genetic damage in populations exposed to low levels of ionizing radiation.     

Study of the frequency parameters of EEG influenced by zone-dependent local ELF-MF exposure on the human head

It has been reported that human subjects exposed to electromagnetic fields exhibit changes in human EEG signals at the frequency of stimulation. The aim of the present study was to expose different parts of the brain to extremely low-frequency magnetic fields locally and investigate EEG power spectrum alters at the frequency of stimulation. EEG relative power spectrum were evaluated at 3, 5, 10, 17, and 45 Hz frequencies at T4, T3, F3, Cz, and F4 points, respectively, when these points were exposed to magnetic fields with similar frequencies and 100 μT intensity. The paired t-test results showed that power value of EEG did not alter significantly at the frequency of stimulation (P<0.05). Further, significant changes in different EEG bands caused by locally exposing to ELF-MF in different points of brain were observed. The changes in the EEG bands were not limited necessarily to the exposure point.     

Cytogenetic damage in workers exposed to ethylene oxide

Sister-chromatid exchanges (SECs) and chromosomal aberrations (CAs) were detected in the peripheral lymphocytes of 41 sanitary workers exposed to ethylene oxide (EO) in the sterilizing units of 8 hospitals in the Venice Region. The first group (19 workers) was exposed to 10.7 +/- 4.9 ppm EO, expressed as the time-weighted average concentration for an 8-h working day (TWA/8 h conc.), and the second group (22 workers) to 0.35 +/- 0.12 ppm. Each exposed worker was paired with a control of similar age and smoking habits. A highly significant (P less than 0.001) increase in the mean frequency of SCEs was found in the higher exposure group, 14 (74%) exposed subjects having significantly increased levels of SCEs compared to their matched controls. In the lower exposure group, the increase in mean frequency of SCEs was lower, though still significant (P less than 0.05): 7 (33%) exposed subjects had higher and 1 (5%) had a lower SCE level than the matched controls. From the first group, 10 subjects, 7 of whom had increased SCE levels, were reanalysed 12-18 months after their exposure had been lowered or interrupted: in only 2 of them the SCE level was significantly decreased. A statistically significant correlation between SCE frequency and level of EO exposure (TWA/8 h conc.), as well as a multiple correlation between SCE level and EO exposure, smoking and age were found. However, no interaction could be detected between EO exposure and smoking in the induction of SCEs. In controls, SCE frequency was correlated with smoking and age. In the higher exposure group, the number of both chromatid- and chromosome-type aberrations, independent of gaps, was significantly increased, whereas in the lower exposure group only the frequency of chromosome-type aberrations, excluding gaps, was statistically higher than in controls. The level of CAs remained to a great extent unchanged in the 10 subjects re-examined at a later stage after lowering or halting exposure. Taking the group as a whole, the frequency of cells with total CAs was found to be weakly (P = 0.05) correlated with EO exposure, and was not correlated with smoking, age or SCE frequency.