Children's exposure to environmental pollutants and biomarkers of genetic damage. II. Results of a comprehensive literature search and meta-analysis

The present review is based on findings from 178 publications retrieved through an extensive search of the MedLine/PubMed database for a 25 years time period (1980-2004) and 10 manually identified papers. Among the cytogenetic biomarkers that are frequently used in field studies, chromosome aberrations (CA) and micronuclei (MN) but not sister chromatid exchanges (SCE) were found consistently increased in children exposed to environmental pollutants. Meta-analysis of the studies reporting SCE in cord blood showed similar levels of SCE in exposed and in non-exposed newborns. Exposure to airborne pollutants, soil and drinking water contaminants, mostly increased CA and, to a lesser extent, MN levels in children. The effect of exposure to airborne urban pollutants was consistently reported by field studies measuring DNA, albumin and hemoglobin adducts. Prenatal (in utero) and postnatal exposure (environmental tobacco smoke, ETS) to tobacco smoke compounds were associated with increased frequencies of DNA and hemoglobin adducts and CA. The limited number of field studies measuring DNA fragmentation (Comet assay), hypoxanthine-guanine phosphoribosyltransferase (HPRT) and the glycophorinA (GPA) mutation frequency in environmentally exposed children precluded a meaningful evaluation of the usefulness of these assays. Meta-analyses performed in children exposed to ETS and in newborns exposed in utero to their mothers' smoke showed 1.3 and 7 times higher levels of hemoglobin adducts compared to referent subjects, respectively. These increases are consistent with the epidemiological evidence of higher lung cancer risks reported in adults who had never smoked and were exposed to ETS during childhood and with 7-15 times higher lung cancer risks reported in smokers than in non-smokers. Higher levels of PAH-DNA adducts were found in fetal than in maternal tissue, suggesting a specific susceptibility of the fetus to this class of ubiquitous environmental pollutants. According to these findings, future research and biomonitoring programs on children would greatly benefit from the inclusion of selected biomarkers that could provide biologically based evidence for the identification of intervention priorities in environmental health.     

Prolongation of occult damage to the liver after cessation of chronic gamma irradiation

A study was made of the effect of continuous gamma-irradiation on changes in the mitotic index (MI), the ratio of the number of metaphases to that of prophases (M/P), and the frequency of chromosome aberrations at the post-metaphase in the regeneration rat liver. The data obtained indicate that the injury to the intact liver of exposed rats persists throughout the entire period of observation which is displayed by a relative stability of M/P ratio and the frequency of chromosome aberrations. On the other hand, the MI changes indicate the trend toward the repair of the injury.     

The effect of the spontaneous level of the chromosome aberration rate on its alterations after a single local irradiation

With X-ray examinations of the stomach and duodenum, changes in chromosomal aberration frequencies in peripheral blood lymphocytes were shown to depend on the spontaneous level of these aberrations in patients exposed to a single local irradiation by 25 R. The cytogenetic efficiency of radiation exposure was found to be local in patients with the lower frequency of spontaneous chromosomal aberrations. A genetic genesis of the revealed dependence is supposed. The effect of irradiation on the correlation between radiosensitivity and radioresistance of the cytogenetic process is regarded as a possible mechanism of the appearance of the observed dependence.     

Genetic effect of low doses of radiation in occupationally exposed workers in coal mines and in coal fired plants

Summary Analyses of structural aberrations of chromosomes and of the body burden of lead-210 were carried out in a group of workers occupationally exposed to chemical pollutants and low doses of ionizing radiation during a technological process in which coal is used as fuel. A parallel study was performed in a control group of workers.In the exposed group the percentage of chromatid and chromosome aberrations and the results of radiochemical analyses were higher than in the control group.This paper is based on work performed under International Atomic Energy Agency contract No. 2346/RB     

The correlation between the frequency of micronuclei and specific chromosome aberrations in human lymphocytes exposed to microwave radiation in vitro.

Human whole-blood samples were exposed to continuous microwave radiation, frequency 7.7 GHz, power density 0.5, 10 and 30 mW/cm2 for 10, 30 and 60 min. A correlation between specific chromosomal aberrations and the incidence of micronuclei after in vitro exposure was observed. In all experimental conditions, the frequency of all types of chromosomal aberrations was significantly higher than in the control samples. In the irradiated samples the presence of dicentric and ring chromosomes was established. The incidence of micronuclei was also higher in the exposed samples. The results of the structural chromosome aberration test and of the micronucleus test were comparatively analyzed. The values obtained showed a positive correlation between micronuclei and specific chromosomal aberrations (acentric fragments and dicentric chromosomes). The results of the study indicate that microwave radiation causes changes in the genome of somatic human cells and that the applied tests are equally sensitive for the detection of the genotoxicity of microwaves.     

Comparative investigation of structural and gene somatic mutations in workers of nuclear chemical plants. I. A study of stable and unstable chromosome aberrations

A study of frequency of unstable chromosome aberrations in 50 workers of nuclear chemical plants in remote period after beginning or finishing professional contact with ionizing radiation was carried out. 14 persons from this cohort were mainly whole-body exposed to external gamma-rays and 36 were exposed to combined external and internal radiation from incorporated Pu nuclides. In results of this irradiating practically every subject had a chronical radiation sickness. In the 1-st group the frequency of unstable aberrations varied from 0.2 to 3.6 per 100 cells and exceeded reliably control level in 5 persons. In the 2-nd group the frequency of unstable aberrations varied from 0 to 11.6 per 100 cells and exceeded reliably control level in 20 examined workers. The FISH study of frequency of stable aberrations was performed in 13 subjects who were exposed to combined external and internal radiation. Total frequency of complete and incomplete translocations varied from 0.6 to 18.5 aberrations per genome per 100 cells and reliable exceeded control level in 9 subjects. Non-random participation in exchange rearrangements (translocations) was revealed for used set of chromosomes (2, 3 and 8).     

Effect of novobiocin on the frequencies of chromatid-type aberrations and sister-chromatid exchanges following gamma-irradiation

The effect of novobiocin on the frequencies of chromatid-type aberrations and SCEs was examined in Chinese hamster V79 cells which were exposed to gamma-rays and post-treated with novobiocin. While no chromatid aberrations were induced in the unirradiated cells by novobiocin, the frequency of SCEs was slightly increased by treatment with novobiocin alone. Irradiation of G2 cells produced multiple chromatid-type aberrations and post-treatment of the irradiated cells with novobiocin resulted in a significant increase of the aberrations, including chromatid gaps and breaks. In contrast, novobiocin failed to increase the frequency of SCEs induced by gamma-rays when the irradiated cells were post-treated with novobiocin.     

Multiyear dynamics of cytogenetic abnormalities in adolescents from a large industrial city

Long-term cytogenetic monitoring was carried out in adolescents of the town of Kemerovo. In total, aberrant metaphase frequency increased from 1.53% in 1992 to 4.40% in 1996 in Kemerovo adolescents, being significantly higher than a control frequency from 1993 to 1996. In all samples, chromosome aberrations mostly included acentric fragments, while exchanges were rare. The highest number of aberrations per aberrant metaphase was 2 in Kemerovo adolescents and 1 in the control sample. The observed increase in total number of chromosome aberrations suggests that the mutagenic effect of chemical environmental pollutants on Kemerovo adolescents increased over the five years.     

Long-Term Monitoring of Cytogenetic Aberrations in Adolescents of a Large Industrial Town

Long-term cytogenetic monitoring was carried out in adolescents of the town of Kemerovo. In total, aberrant metaphase frequency increased from 1.53% in 1992 to 4.40% in 1996 in Kemerovo adolescents, being significantly higher than a control frequency from 1993 to 1996. In all samples, chromosome aberrations mostly included acentric fragments, while exchanges were rare. The highest number of aberrations per aberrant metaphase was 2 in Kemerovo adolescents and 1 in the control sample. The observed increase in total number of chromosome aberrations suggests that the mutagenic effect of chemical environmental pollutants on Kemerovo adolescents increased over the five years.     

Analysis of chromosomal aberration frequencies in the peripheral blood lymphocytes of smokers exposed to uranyl compounds

One hundred fifteen smokers working in a nuclear fuel manufacturing facility were analysed for various types of chromosomal aberrations. They experienced exposure for a period of 1-25 years. Their age ranges from 23 to 52 years. A total of 94 smokers and 118 non-smokers who were not exposed to uranyl compounds or to any other known mutagens and belong to the same age group formed the control subjects. The results showed that there is a significant increase in the frequency of chromosomal aberrations in the exposed smokers when compared to the control smokers. In the control group, the smokers showed a high frequency of chromosomal aberrations when compared to non-smokers suggesting clastogenic effect of smoking. Chromosomal aberrations observed in the exposed smokers could be due to the cumulative effect of both smoking and exposure to uranyl compounds.     

Chromosome damage in rat pulmonary alveolar macrophages following ozone inhalation

To determine whether ozone is clastogenic at environmentally relevant exposure levels, rats were exposed for 6 h to 0.0, 0.12, 0.27, or 0.80 ppm ozone. The alveolar macrophages were isolated from animals sacrificed 28 h after the end of the exposure. The mitotic index and frequency of chromosome aberrations were determined. No change in the mitotic index was detected following 0.12 ppm ozone exposure. A significant decrease in mitotic index was observed after exposure to 0.27 ppm ozone; a significant (4-fold) increase in the frequency of dividing macrophages was detected following exposure to 0.8 ppm ozone. Only chromatid-type aberrations were observed. There was a significant increase in the frequency of cells with chromatid gaps and in the frequency of cells with chromatid deletions. Animals exposed to 0.27 ppm ozone had the highest proportion of cells with chromatid deletions (0.172) relative to background level (0.028). No exchanges or chromosome-type aberrations were detected in any of the animals. These data suggest that ozone, at relatively low levels, is clastogenic in macrophages from exposed rats.     

Retrospective dose estimation in remote period after exposure using different biological methods

Investigation of application of chromosome aberrations of lymphocytes in peripheral blood for biological dosimetry purposes in remote (up to 40 years) period after acute exposure to doses of 1 Gy and more was carried out. The comparative analysis of frequency of unstable and stable (using FISH and G-banding methods) aberrations was performed for 24 subjects accidentally exposed to radiation on nuclear submarines during 1961-1985. Statistically significant increasing of frequency of dicentrics and centric rings was determined in the exposed subjects in remote period after exposure to compare with controls. Their sum frequency in the exposed group varied depending on ARS heaviness from 0.1 to 1.0 aberrations per 100 cells. In control group it was from 0 to 0.2 correspondingly. Translocation frequency (complete + incomplete) fixed by FISH method (2, 4, and 12 chromosomes) varied within the limits of 0.2-16.0 for exposed subjects and 0.3-1.26 translocations per genome per 100 cells for controls. Some examined persons (5 subjects) exposed to accident in 1985 had results of analysis of unstable chromosome aberration in acute period after exposure that allow to estimate obtained doses by dicentrics frequency which having good correlation with ARS heaviness. Individual dosed using traslocation frequency were defined retrospectively in 11 from 21 exposed persons. They correlate with calculated physics doses and doses estimated by haematolotical parameters in acute period and also doses obtained by ESR spectroscopy of tooth enamel in remote period.     

Protective roles of exogenous polyamines on chromosomal aberrations in <Emphasis Type="Italic">Hordeum vulgare</Emphasis> exposed to salinity

The effects of exogenous polyamines (PAs): spermine (Spm), spermidine (Spd), cadaverine (Cad) and putrescine (Put) on mitotic activity and chromosomal aberrations in root meristem cells of Hordeum vulgare L. (barley) seeds exposed to salinity were analyzed. The PAs significantly inhibited cell division in distilled water. Furthermore, most of these PAs (except for Spd) caused a significant increase in the frequency of chromosomal aberrations as compared to control group. Seeds treated with Put caused the highest percentage of mitotic abnormalities in total. The negative effect of salinity on mitotic index and the frequency of chromosomal aberrations increased with increasing salt concentration. PAs studied could not be successful in ameliorating of the negative effect of salinity on mitotic activity. Particularly, exposure to Cad and 0.40 M NaCl caused a complete block of cell division in total. However, most of the PA studied showed a perfectly performance in alleviating the detrimental effects of increasing salinity on chromosomal aberrations.     

The effects of post-treatments with caffeine during S and G2 on the frequencies of chromosomal aberrations induced by thiotepa in root tips of Vicia faba and in human lymphocytes in vitro

The effects of post-treatments with caffeine on the frequencies of chromosomal aberrations induced by the trifunctional alkylating agent thiotepa were studied in human lymphocytes and in root tips of Vicia faba. In lymphocytes the frequency of aberrations induced in G0 or G1 was most strongly increased when the caffeine post-treatments were given during G2. In Vicia faba, on the other hand, the frequency of aberrations induced in early interphase was unaffected by post-treatments with caffeine during G2, but strongly increased when the root tips were exposed to caffeine during the S phase.     

Chromosomal aberrations in human amniotic cells after intermittent exposure to fifty hertz magnetic fields

Our recent studies have shown a significant increase in the frequency of chromosomal aberrations in human amniotic cells after exposure to a sinusoidal 50 Hz, 30 μT (rms) magnetic field. To evaluate further interactions between chromosomes and electromagnetic fields, we have analyzed the effects of intermittent exposure. Amniotic cells were exposed for 72 h to a 50 Hz, 30 μT (rms) magnetic field in a 15 s on and 15 s off fashion. Eight experiments with cells from different fetuses were performed. The results show a 4% mean frequency of aberrations among exposed cells compared to 2% in sham-exposed cells. The difference is statistically significant, with P < 0.05 both excluding and including gaps. In another series of eight experiments, the cells were exposed in the same way but with the field on for 2 s and off for 20 s. Also in these experiments a similar increase in the frequency of chromosomal aberrations was seen, but only when the analysis included gaps. Continuous exposure for 72 h to 300 μT, 50 Hz, did not increase the frequency of chromosomal aberrations. The background electromagnetic fields at different locations within the two incubators used was carefully checked and was nowhere found to exceed 120 nT. Likewise, the background level of chromosomal aberrations in cells cultured at different locations in the incubators showed no significant interculture differences. © 1994 Wiley-Liss, Inc.     

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.     

The effect of low-dose irradiation and of age on the in vitro radiosensitivity of human lymphocytes

The effect of low-dose irradiation and of age on the radiosensitivity of human lymphocytes was studies in two groups: control (67 people) and exposed to uncontrolled low-dose irradiation in past (165 people). Radiosensitivity of lymphocytes was estimated by the level of chromosome aberrations induced in vitro by gamma-radiation Cs137 at the dose 1.5 Gy. In exposed children the frequency of induced chromosome aberrations was higher and in the exposed adults--lower in comparison to the coresponding controls. To investigate an age response of the number of chromosome aberrations three statistical approaches were used: the correlation analysis of individual data, the correlation analysis of means for 10-years intervals, the comparison of 3 age groups. In control group no significant alteration in the level of induced chromosome aberrations with age was found. However the significant negative correlation between these two parameters was revealed in exposed group, which likely is due to the opposite direction of differences in radiosensitivity of exposed children and adults from the corresponding controls.     

The relationship between colony-forming ability, chromosome aberrations and incidence of micronuclei in V79 Chinese hamster cells exposed to microwave radiation

Cultured V79 Chinese hamster fibroblast cells were exposed to continuous radiation, frequency 7.7 GHz, power density 0.5 mW/cm2 for 15, 30 and 60 min. The effect of microwave radiation on cell survival and on the incidence and frequency of micronuclei and structural chromosome aberrations was investigated. The decrease in the number of irradiated V79 cell colonies was related to the power density applied and to the time of exposure. In comparison with the control samples there was a significantly higher frequency of specific chromosome aberrations such as dicentric and ring chromosomes in irradiated cells. The presence of micronuclei in irradiated cells confirmed the changes that had occurred in chromosome structure. These results suggest that microwave radiation can induce damage in the structure of chromosomal DNA.     

Chromosomal analysis in mouse eggs fertilized in vitro with sperm exposed to ultraviolet light (UV) and methyl and ethyl methanesulfonate (MMS and EMS)

Chromosome aberrations were analyzed at the first-cleavage metaphase of mouse eggs fertilized in vitro with sperm exposed to ultraviolet light (UV) as well as to methyl and ethyl methanesulfonate (MMS and EMS). The frequencies of chromosome aberrations markedly increased with dose of UV as well as with concentration of MMS and EMS. In the UV-irradiation group, the frequency of chromosome-type aberrations was much higher than that of chromatid-type aberrations. About 90% of chromosome aberrations observed in the eggs following MMS and EMS treatment to sperm were chromosome type in which the frequency of chromosome fragments was the highest. The effects of UV on the induction of chromosome aberrations were clearly potentiated by post-treatment incubation of fertilized eggs in the presence of Ara-C or caffeine, but the effects of MMS and EMS were not pronounced by post-treatment of Ara-C or caffeine. The results indicate a possibility that UV damage induced in mouse sperm DNA is reparable in the eggs during the period between the entry of sperm into the egg cytoplasm and the first-cleavage metaphase.     

Clastogenic effect of pesticides in peripheral lymphocytes of cotton-field workers.

We studied clastogenic effects in peripheral lymphocytes of cotton-field workers who were exposed to different pesticides. All the cells were grown in RPMI 1640 medium for 48 and 72 h. The type of aberrations observed in the exposed group are gaps, breaks, dicentrics, exchanges, rings and polyploidy. The frequency of total chromosomal aberrations increased significantly in male pesticide applicators when compared to controls. A significant decrease in mitotic index was observed in the exposed group as compared to the control group. The 48-h cultures showed high incidence of chromosomal aberrations and low mitotic index when compared to 72-h cultures. The difference in chromosomal aberrations between 48- and 72-h cultures was not significant. 24 out of 26 individuals showed ill health effects such as severe giddiness and nervous disorders.