An evaluation of human sperm as indicators of chemically induced alterations of spermatogenic function. A report of the U.S. Environmental Protection Agency Gene-Tox Program

To evaluate the utility of sperm tests as indicators of chemical effects on human spermatogenesis, the literature on 4 sperm tests used to assess chemically induced testicular dysfunction was reviewed. The tests surveyed included sperm count, motility, morphology (seminal cytology), and double Y-body (a fluorescence-based test thought to detect Y-chromosomal nondisjunction). There were 132 papers that provided sufficient data for evaluation. These reports encompassed 89 different chemical exposures: 53 were to single agents; 14 to complex mixtures; and 22 to combinations of 2 or more identified agents. Approximately 85% of the exposures were to experimental or therapeutic drugs, 10% were to occupational or environmental agents, and 5% were to drugs for personal use. The most common sperm parameter studied was sperm count (for 87 of the 89 exposures reviewed). Sperm motility was evaluated for 59 exposures, morphology for 44, and double Y-bodies for only 4. The 89 exposures reviewed were grouped into 4 classes: those which adversely effected spermatogenesis, as measured by one or more of the sperm tests (52); those suggestive of improving semen quality (11); those showing inconclusive evidence of adverse effects from exposure (14); and those showing no significant changes (12). Since the reviewed reports had a large variety of study designs, and since every attempt was made to include all reports with interpretable data, these classifications were based on reviewing committee decisions rather than on uniform statistical criteria. This review gives strong evidence that human sperm tests can be used to identify chemicals that affect sperm production, but because of our limited understanding of underlying mechanisms, the extent to which they can detect mutagens, carcinogens or agents that affect fertility remains uncertain. For the very few agents studied with both human and mouse sperm tests, similar test-responses were seen; thus sperm tests in mice and other laboratory mammals may have a potential role in hazard identification. An overall comparison of the 4 human sperm tests suggests that no one test is biologically more responsive than another; all of them may thus be needed when testing for chemically induced changes from agents of unknown activity. This review also gives evidence that sperm tests can be used to assess the extent and the potential reversibility of induced spermatogenic damage. The reviewing committee recommends further studies to determine (a) the dose-response characteristics of the human sperm tests, (b) details of the reversibility of induced changes with time after exposure, (c) the relative responses in the 4 sperm tests in exposed individuals, (d) the mechanism of action, (e) the biological and genetic implications of chemically induced effects, and (f) the comparison of responses among different species for risk assessment. The reviewing committee outlines specific considerations for planning new sperm studies on chemically exposed men.     

Pulmonary function in persons who are professionally exposed to formaldehyde fumes

The present study examines long-term effects of occupational exposure to formaldehyde fumes on lung function. Forced spirometry and diffusing lung capacity were measured in 16 health-service professionals (8 medical doctors and 8 laboratory technicians) working at the pathoanatomic laboratory for at least 4 years with daily exposure 8 +/- 1 hours. Control group employed 16 males, which were matched by age and stature to members of the exposed group. Only non-smokers were included in the study. Spirometric parameters in study participants exposed to formaldehyde fumes compared to control group were not significantly different indicating absence of restrictive and/or obstructive deterioration of lung function in exposed group. The only parameter differing in two groups was blood volume of pulmonary capillaries (Vc') which was significantly larger in a group exposed to formaldehyde fumes. The possibility that the hyperemic lung reaction is the consequence of the exposure to formaldehyde fumes should be further explored.     

Genetic monitoring of aluminum workers exposed to coal tar pitch volatiles

A group of 50 workers exposed to coal tar pitch volatiles (CTPV) in an aluminum reduction plant and a group of 50 non-exposed workers were selected to evaluate the genotoxic effects of CTPV exposure. A battery of tests was performed on 3 different body fluids; urine, blood and semen. Urine samples were evaluated for mutagenic constituents using the Ames/Salmonella assay. Cultured lymphocytes from blood samples were used to perform cytogenetic analysis. Semen samples were used to measure sperm count, percent abnormal sperm morphology and frequency of sperm carrying double fluorescent bodies (2-F). 14 of 28 (50%) exposed workers and 7 of 36 (19.4%) non-exposed workers had mutagenic urine. This difference was significant (p less than 0.01). Among the non-smokers a significantly higher percentage of workers who were exposed had positive urine (36%) compared to the non-exposed workers (5%) (p less than 0.05). Among the exposed group, more mechanics had mutagenic urine than did other types of workers. Overall chromosome aberration rates were similar in both exposed and non-exposed workers. Among exposed workers a significant inverse correlation (p less than 0.05) between age and chromatid aberration rate was observed. Results of semen analysis failed to detect differences between exposed and non-exposed workers. Results of these tests lend support to a battery approach to genetic monitoring and suggest a link between exposure to CTPV and genotoxic effects. Detection of exposure to mutagens at an early time offers an opportunity for disease prevention by the reduction of exposure.     

Genotoxic risk assessment of pathology and anatomy laboratory workers exposed to formaldehyde by use of personal air sampling and analysis of DNA damage in peripheral lymphocytes

A study was conducted to evaluate the genotoxic effect of occupational exposure to formaldehyde on pathology and anatomy laboratory workers. The level of exposure to formaldehyde was determined by use of passive air-monitoring badges clipped near the breathing zone of 59 workers for a total sampling time of 15min or 8h. To estimate DNA damage, a chemiluminescence microplate assay was performed on 57 workers before and after a 1-day exposure. Assessment of chromosomal damage was carried out by use of the cytokinesis-blocked micronucleus assay (CBMN) in peripheral lymphocytes of 59 exposed subjects in comparison with 37 controls matched for gender, age, and smoking habits. The CBMN assay was combined with fluorescent in situ hybridization with a pan-centromeric DNA probe in 18 exposed subjects and 18 control subjects randomized from the initial populations. Mean concentrations of formaldehyde were 2.0 (range <0.1-20.4ppm) and 0.1ppm (range <0.1-0.7ppm) for the sampling times of 15min and 8h, respectively. No increase in DNA damage was detected in lymphocytes after a one-workday exposure. However, the frequency of binucleated micronucleated cells was significantly higher in pathologists/anatomists than in controls (16.9 per thousand+/-9.3 versus 11.1 per thousand+/-6.0, P=0.001). The frequency of centromeric micronuclei was higher in exposed subjects than in controls (17.3 per thousand+/-11.5 versus 10.3 per thousand+/-7.1) but the difference was not significant. The frequency of monocentromeric micronuclei was significantly higher in exposed subjects than in controls (11.0 per thousand+/-6.2 versus 3.1 per thousand+/-2.4, P<0.001), while that of the acentromeric micronuclei was similar in exposed subjects and controls (3.7 per thousand+/-4.2 and 4.1 per thousand+/-2.7, respectively). The enhanced chromosomal damage (particularly chromosome loss) in peripheral lymphocytes of pathologists/anatomists emphasizes the need to develop safety programs.     

Evaluation of propylene oxide for mutagenic activity in 3 in vivo test systems

Propylene oxide (CAS No. 75-56-9) was tested for mutagenic activity following vapor exposure using 3 in vivo test systems. Rat dominant lethal and mouse sperm-head morphology assays were conducted using males exposed to propylene oxide at 300 ppm in a dynamic exposure chamber for 7 h per day on 5 consecutive days. A sex-linked recessive lethal test in Drosophila melanogaster employed a 24-h static exposure to propylene oxide at 645 ppm. Male mice were killed 1, 3, 5, 7, and 9 weeks post-exposure for evaluation of sperm-head morphology. Propylene oxide exposure did not result in an increase in abnormal forms. Male rats were mated with 2 virgin females per week for 6 weeks following exposure. A statistically significant increase in preimplantation losses and a statistically significant reduction in the number of living implants in the first post-exposure week did not appear to be treatment related. A highly significant increase in sex-linked recessive lethal mutations was observed in two germ cell stages (mature sperm and developing spermatocytes). These results warrant continued caution in potential human exposure to propylene oxide.     

Evaluation of long-term occupational exposure to styrene vapor on olfactory function

The primary sensory neurons of the olfactory system are chronically exposed to the ambient environment and may therefore be susceptible to damage from occupational exposure to many volatile chemicals. To investigate whether occupational exposure to styrene was associated with olfactory impairment, we examined olfactory function in 2 groups: workers in a German reinforced-plastics boat-manufacturing facility having a minimum of 2 years of styrene exposure (15-25 ppm as calculated from urinary metabolite concentrations, with historical exposures up to 85 ppm) and a group of age-matched workers from the same facility with lower styrene exposures. The results were also compared with normative data previously collected from healthy, unexposed individuals. Multiple measures of olfactory function were evaluated using a standardized battery of clinical assessments from the Monell-Jefferson Chemosensory Clinical Research Center that included tests of threshold sensitivity for phenylethyl alcohol (PEA) and odor identification ability. Thresholds for styrene were also obtained as a measure of occupational olfactory adaptation. Styrene exposure history was calculated through the use of past biological monitoring results for urinary metabolites of styrene (mandelic acid [MA], phenylglyoxylic acid [PGA]); current exposure was determined for each individual using passive air sampling for styrene and biological monitoring for styrene urinary metabolites. Current mean effective styrene exposure during the day of olfactory testing for the group of workers who worked directly with styrene resins was 18 ppm styrene (standard deviation [SD] = 14), 371 g/g creatinine MA + PGA (SD = 289) and that of the group of workers with lower exposures was 4.8 ppm (SD = 5.2), 93 g/g creatinine MA+PGA (SD = 100). Historic annual average exposures for all workers were greater by a factor of up to 6x. No differences unequivocally attributable to exposure status were observed between the Exposed and Comparison groups or between performance of either group and normative population values on thresholds for PEA or odor identification. Although odor identification performance was lower among workers with higher ongoing exposures, performance on this test is not a pure measure of olfactory ability and is influenced by familiarity with the stimuli and their sources. Consistent with exposure-induced sensory adaptation, however, elevated styrene thresholds were significantly associated with higher occupational exposures to styrene. In summary, the present study found no evidence among a cross-section of reinforced-plastics workers that current or historical exposure to styrene was associated with a general impairment of olfactory function. When taken together with prior studies of styrene-exposed workers, these results suggest that styrene is not a significant olfactory toxicant in humans at current exposure levels.     

Combined action of X-rays and nonylphenol on mouse sperm

The aim of this study was to assess the effects of 2-weeks’ X-ray and/or nonylphenol (NP) exposure on male mice’s sperm count and quality. Pzh:SFIS mice were exposed to X-rays (0.05 Gy, 0.10 Gy, 0.20 Gy) or to nonylphenol (25 mg/kg bw, 50 mg/kg bw, 100 mg/kg bw) or to both agents (0.05 Gy + 25 mg/kg bw NP, 0.10 Gy + 50 mg/kg bw NP). At 24 h and 5 weeks after the end of exposure the sperm count, morphology and frequency of DNA damage in the male germ cells were estimated. Each agent alone diminished sperm count and morphology. The dose of 0.05 Gy of X-rays decreased the frequency of DNA damage. Combined exposure to lower doses of both agents significantly improved sperm morphology and decreased the level of DNA damage compared to one agent alone. Combined exposure to higher doses reduced the frequency of DNA damage compared to the effect of the appropriate dose of NP. Results of combined exposure to low doses of both agents suggest that 0.05 Gy of X-rays stimulate the DNA damagecontrol system and in consequence repair of DNA caused by X-rays and NP. It may be correlated with increased antioxidant capacity.     

Genetic injury in hybrid male mice exposed to low doses of 60Co gamma-rays or fission neutrons. III. Frequencies of abnormal sperm and reciprocal translocations measured during and following long-term weekly exposures

Male B6CF1 mice were exposed to either fission neutrons or 60Co gamma-rays at once-weekly doses approaching occupational levels for periods up to 60 weeks. Both during and after the irradiation sequence, the mice were screened to determine the incidence of abnormal epididymal sperm and of reciprocal chromosome translocations in metaphase spermatocytes. Abnormal sperm frequencies equilibrated with dose/week by 10 weeks and also showed an additive nonlinear seasonal increment. The relative biological effectiveness (RBE) for these damages is 12 +/- 1. After exposures ended, sperm frequencies in gamma-irradiated mice quickly returned to near-normal levels. Neutron-irradiated males showed a significantly elevated level of abnormalities for approximately 30 weeks--a paradoxical finding--as no clear evidence of cumulative injury was seen during exposure. When assayed at 10 and 25 weeks of exposure but not later, translocation frequencies demonstrated an increment, significant in the neutron series, attributed to irradiated spermatocytes. Dose-response analysis with cumulative dose up to the 60-week maximum gave an RBE of 45 +/- 10. Post exposure, the incidence of translocations subsided slightly, but the RBE remained above 30.     

Assessment of local genotoxic effects of formaldehyde in humans measured by the micronucleus test with exfoliated buccal mucosa cells

Volunteers (10 women, 11 men) were exposed to formaldehyde (FA) vapors for 4h per day over a period of 10 working days under strictly controlled conditions. Exposure varied randomly each day from constant 0.15 ppm up to 0.5 ppm with four peaks of 1.0 ppm for 15 min each (13.5 ppm h cumulative exposure over 10 working days). FA was masked on four days by co-exposure to ethyl acetate. During exposure, subjects had to perform bicycle exercises (about 80 W) three times for 15 min. Buccal smears were prepared 1 week before the start of the study (control 1), at the start of the study before the first exposure (control 2), at the end of the exposure period of 10 days and 7, 14 and 21 days thereafter. Two thousand cells per data point were analyzed for the presence of micronuclei (MN) and the frequency of MN per 1000 cells was determined on slides coded by an independent quality-assurance unit. No significant increase in the frequency of MN was measured at any time point after the end of the exposure. Twenty-one days after the end of the exposure MN frequencies were significantly lower in comparison with control 1. This study, which was performed under GLP-like conditions, clearly indicates that FA does not induce MN in buccal mucosa cells after peak exposures up to 1 ppm and a cumulative exposure of 13.5 ppm h over 2 weeks.     

New methodology for specific inhalation challenges with occupational agents

Background

Inhalation challenges are used for diagnosing occupational asthma (OA). The initial methodology consisted of a "realistic" exposure without monitoring nor controlling exposure. Our aim was to design an equipment, called the GenaSIC, that allows the generation of various agents regardless of the formulation and to assess the feasibility of its use in patients investigated for OA.

Results

GenaSIC can generate lactose, flour, malt, isocyanates, formaldehyde and N-butyl acetate with precise and fairly stable concentrations. Using N-butyl-acetate as a control agent and real time measurement, we show that normal breathing has a negligible effect on the concentration. We exposed forty-four different subjects to a control agent and/or to a suspected occupational agent. Nineteen of the subjects were only exposed to N-butyl acetate as a control agent without experiencing any significant irritant effect (no significant changes in spirometry thereafter). Eight subjects who were exposed to both N-butyl acetate and formaldehyde did not show significant reactions. Seven subjects were exposed to dry particles (flour in six instances, malt in the other) and five showed immediate asthmatic reactions which changes in FEV1 from 20% to a maximum of 28%. Finally, ten subjects were exposed to isocyanates, four of whom showed a positive reaction, including one subject with immediate maximum changes in FEV1 of 22%.

Conclusion

GenaSIC offers the possibility of reliable and safe exposures to dry particles, formaldehyde and isocyanates in the investigation of OA.     

Multigenerational exposure to uranium changes morphometric parameters and global DNA methylation in rat sperm

There is increasing evidence that environmental exposures early in fetal development influence phenotype and give rise to disease risk in the next generations. We previously found that lifelong exposure to uranium, an environmental contaminant, induced subtle testicular and hormonal defects; however, its impact on the reproductive system of multiple subsequent generations was unexplored. Herein, rats were exposed to a supra-environmental and non-nephrotoxic concentration of natural uranium (U, 40 mg·L⁻¹ of drinking water) from postnatal life to adulthood (F0), during fetal life (F1), and only as the germ cells from the F1 generation (F2). General parameters (reproductive indices, epididymal weight) and sperm morphology were assessed in the three generations. In order to identify the epigenetic effects of U, we analyzed also the global DNA methylation profile and described for the first time the mRNA expression levels of markers involved in the (de)methylation system in rat epididymal spermatozoa. Our results showed that the F1 generation had a reduced pregnancy rate. Despite the sperm number being unmodified, sperm morphology was affected in the F0, F1 and F2 generations. Morphometric analysis for ten parameters was detailed for each generation. No common parameter was detected between the three generations, but the head and the middle-piece were always modified in the abnormal sperms. In the F1 U-exposed generation, the total number of abnormal sperm was significantly higher than in the F0 and F2 generations, suggesting that fetal exposure to uranium was more deleterious. This effect could be associated with the pregnancy rate to produce the F2 generation. Interestingly, global DNA methylation analysis showed also hypomethylation in the sperm DNA of the last F2 generation. In conclusion, our study demonstrates that uranium can induce morphological sperm defects and changes in the DNA methylation level after multigenerational exposure. The epigenetic transgenerational inheritance of U-induced reproductive defects should be assessed in further experiments.     

Cytogenetic analysis of nasal mucosa cells and lymphocytes from high-level long-term formaldehyde exposed workers and low-level short-term exposed waiters

The evidence for genotoxic potential of formaldehyde (FA) in humans is insufficient and conflicting. We previously reported a higher frequency of micronuclei in nasal and oral exfoliative cells from students exposed to formaldehyde vapor for short-term. To further evaluate the genetic effects of long-term occupational exposure to FA and short-term exposure to FA of indoor sources, the frequencies of micronuclei (MN) in nasal mucosa cells, sister chromatid exchanges (SCEs) of peripheral lymphocytes, and the lymphocyte subsets were evaluated in 18 non-smoking workers (mean exposure duration was 8.6 years) in an FA factory and 16 non-smoking waiters exposed to FA for 12 weeks in a ballroom. A non-smoking student group without occupational exposure (n=23) to FA was used as control. The 8h time-weighted average (TWA) concentrations of formaldehyde was 0.985+/-0.286 mg/m3 with the ceiling exposure concentration of 1.694 mg/m3 in the workshop, and 0.107+/-0.067 mg/m3 in the ballroom (5 h TWA). Higher frequencies of micronuclei per thousand cells in nasal mucosa cells of workers versus control (2.70+/-1.50 versus 1.25+/-0.65, p<0.05) and higher frequency of SCEs in peripheral lymphocytes of workers group (8.24+/-0.89 versus 6.38+/-0.41, p<0.05) were observed. Increased frequency of micronuclei in nasal mucosa cells or SCE in peripheral lymphocytes was not found among waiters group. The results suggest that the genotoxic potential of high level FA exposure may have occupational risks in long-term exposure groups.     

Measurement of plasma or urinary metabolites and Hprt mutant frequencies following inhalation exposure of mice and rats to 3-butene-1,2-diol

Studies were performed to determine if the detoxification pathway of 1,3-butadiene (BD) through 3-butene-1,2-diol (BD-diol) is a major contributor to mutagenicity in BD-exposed mice and rats. First, female and male mice and rats (4-5 weeks old) were exposed by nose-only for 6h to 0, 62.5, 200, 625, or 1250 ppm BD or to 0, 6, 18, 24, or 36 ppm BD-diol primarily to establish BD and BD-diol exposure concentrations that yielded similar plasma levels of BD-diol, and then animals were exposed in inhalation chambers for 4 weeks to BD-diol to determine the mutagenic potency estimates for the same exposure levels and to compare these estimates to those reported for BD-exposed female mice and rats where comparable blood levels of BD-diol were achieved. Measurements of plasma levels of BD-diol (via GC/MS methodology) showed that (i) BD-diol accumulated in a sub-linear fashion during single 6-h exposures to >200 ppm BD; (ii) BD-diol accumulated in a linear fashion during single or repeated exposures to 6-18 ppm BD and then in a sub-linear fashion with increasing levels of BD-diol exposure; and (iii) exposures of mice and rats to 18 ppm BD-diol were equivalent to those produced by 200 ppm BD exposures (with exposures to 36 ppm BD-diol yielding plasma levels approximately 25% of those produced by 625 ppm BD exposures). Measurements of Hprt mutant frequencies (via the T cell cloning assay) showed that repeated exposures to 18 and 36 ppm BD-diol were significantly mutagenic in mice and rats. The resulting data indicated that BD-diol derived metabolites (especially, 1,2-dihydroxy-3,4-epoxybutane) have a narrow range of mutagenic effects confined to high-level BD (>or=200 ppm) exposures, and are responsible for nearly all of the mutagenic response in the rat and for a substantial portion of the mutagenic response in the mouse following high-level BD exposures.     

Chemical process-based reconstruction of exposures for an epidemiological study. Part II. Estimated exposures to chloroprene and vinyl chloride

In a four-facility occupational epidemiology study of chloroprene monomer and polymer production workers, the chloroprene (CD) and vinyl chloride monomer (VCM) exposures were modeled for plant specific job title classes. In two facilities an acetylene-based process was used and in the other two plants only a butadiene-based process was used in the monomer synthesis. In the Acetylene process VCM was an undesirable by-product to be removed. In the newer butadiene-based process, VCM was not involved and the exposures to CD were considerably lower than they were in the earlier years. One of the limiting factors was the operator rotation within a number of job titles. This rotation and inability to differentiate between job titles subsumed in job classifications recorded in the work histories required an exposure classification scheme based on an order of magnitude separation of exposure classes. In the four facilities with considerable variation in the mix of the production methods, the CD exposures were remarkably similar in both calculated and measured values. The reductions in exposures were much more dependent upon the improvement of the production methods, rather than deliberate exposure control for occupational hygiene considerations. This is reasonable since the exposures were generally lower than the coeval exposure limits and/or guidelines. The estimated exposures were less than 100 ppm in the pre-1960 era and less than 10 ppm in the 1960-1980 era, less than 1 ppm 1980-1990 era and less than 0.5 ppm thereafter. The exposures were categorized in four classes for VCM and six classes for CD. The characteristic class exposure values were used to cumulate individual exposures over time with a quantification of the potential range for exposures that are reasonably certain to ascribe correct ranking to job classes.     

Characterization of semen collected from beagles and captive Japanese black bears (Ursus thibetanus japonicus)

This study characterized semen collected from the Japanese black bear, Ursus thibetanus aponicus, to provide information on semen cryopreservation for artificial breeding. Preliminary studies using a beagle dog as the model species showed that sperm concentration and total sperm count were lower in semen collected by electroejaculation than in semen collected by digital manipulation, but that sperm motility, viability and morphology were similar. Characterization of semen obtained from Japanese black bears by electroejaculation under general anesthesia revealed that semen volume and total number of spermatozoa collected were lower; but that sperm concentration, motility, viability and morphology were equivalent to those reported in other ursids. When semen was collected via a catheter inserted into the urethra during the stimulation for ejaculation, the sperm concentration, total sperm count and motility were relatively higher than when semen was collected directly in a test tube. Specific normal semen characteristics (mean +/- SEM) were pH, 7.6 +/- 0.0; volume, 0.212 +/- 0.038 mL; sperm concentration, 361 +/- 100 x 10(6)/mL; total sperm count, 84.0 +/- 32.2 x 106; +++ motility, 30 +/- 5%; motility, 77 +/- 3%; viability 77 +/- 2%; and abnormal morphology, 11+/- 2%. These results suggest that semen can be collected from Japanese black bears by electroejaculation.     

Developmental toxicity of ethylene glycol monopropyl ether in the rat

In order to determine the potential developmental toxicity of ethylene glycol monopropyl ether (EGPE), pregnant rats were exposed to vapor concentrations of 100, 200, 300, or 400 ppm of the compound for 6 hours per day on days 6-15 of gestation. Maternal effects included a slight reduction in red blood cell count and increased mean corpuscular volume and mean corpuscular hemoglobin at the 200-, 300-, and 400-ppm concentrations. Reticulocyte counts and polychromasia of the red blood cells were increased at all exposure levels, while anisocytosis was increased at 300 and 400 ppm and macrocytosis was increased at 200, 300, and 400 ppm. Hematocrit, hemoglobin concentration, platelet, and total and differential white blood cell counts were comparable to those of the controls. Red urine was seen in the females after the first and second exposures to 200, 300, and 400 ppm of EGPE, but not after subsequent exposures. Absolute and relative spleen weights were increased by 200, 300, and 400 ppm EGPE. Histologic changes were seen in the maternal spleen, liver, and thymus, particularly after exposure to 300 and 400 ppm. Kidneys, bone marrow, and mesenteric lymph nodes were normal. Pregnancy rate, number of corpora lutea, implantation sites and viable fetuses per dam, the incidence of resorptions per litter, and the mean fetal body weights were comparable to those of the controls. Gross external, internal soft tissue, and skeletal examinations of the fetuses revealed that EGPE did not produce teratogenicity or significant embryo/fetotoxicity in the rat at vapor concentrations as high as 400 ppm. Variations in the ossification of certain skeletal elements and the incidence of 14th thoracolumbar rudimentary ribs were increased by exposure to 200, 300, and 400 ppm EGPE.     

Biomarkers in styrene-exposed boatbuilders.

14 fiberglass-reinforced plastics (FRP) boatbuilders were compared with 9 unexposed controls with respect to several chemical specific and nonspecific biomarkers measured in peripheral blood. Biomarkers included styrene-hemoglobin adducts (styrene-Hb), sister-chromatid exchanges (SCEs), micronuclei (MN), single-strand breaks (SSBs) and N-acetoxy-2-acetylaminofluorene-induced DNA binding (NA-AAF binding) as a measure of susceptibility to DNA damage. Workers' exposures averaged 11 ppm (8-h TWA; geometric mean) and ranged from 0.6 to 44 p.p.m. Mandelic acid levels were measured in end-of-shift urine samples and reflected an average styrene exposure equivalent to 15 p.p.m. There was a large though not significant difference in levels of styrene-Hb adducts among exposed workers and controls, largely the consequence of a single heavily-exposed individual with an extremely high level of adducts. Significant differences between biomarker levels in exposed workers and controls were observed with MN, SSBs and NA-AAF binding. No significant differences were seen in mean levels of SCEs nor in the incidence of cells with a high frequency of SCEs. The data suggest that exposure to levels of styrene in occupational settings near or below the current OSHA standard (50 p.p.m.) can induce damage at the cellular/molecular level. Appropriately-selected panels of biomarkers can be useful in identifying potentially harmful exposures.     

Semen Abnormalities,Sperm DNA Damage and Global Hypermethylation in Health Workers Occupationally Exposed to Ionizing Radiation

Background

Cytogenetic studies have demonstrated that low levels of chronic radiation exposure can potentially increase the frequency of chromosomal aberrations and aneuploidy in somatic cells. Epidemiological studies have shown that health workers occupationally exposed to ionizing radiation bear an increased risk of hematological malignancies.

Objectives

To find the influence of occupational radiation exposure on semen characteristics, including genetic and epigenetic integrity of spermatozoa in a chronically exposed population.

Methods

This cross sectional study included 134 male volunteers of which 83 were occupationally exposed to ionizing radiation and 51 were non-exposed control subjects. Semen characteristics, sperm DNA fragmentation, aneuploidy and incidence of global hypermethylation in the spermatozoa were determined and compared between the non-exposed and the exposed group.

Results

Direct comparison of the semen characteristics between the non-exposed and the exposed population revealed significant differences in motility characteristics, viability, and morphological abnormalities (P<0.05–0.0001). Although, the level of sperm DNA fragmentation was significantly higher in the exposed group as compared to the non-exposed group (P<0.05–0.0001), the incidence of sperm aneuploidy was not statistically different between the two groups. However, a significant number of hypermethylated spermatozoa were observed in the exposed group in comparison to non-exposed group (P<0.05).

Conclusions

We provide the first evidence on the detrimental effects of occupational radiation exposure on functional, genetic and epigenetic integrity of sperm in health workers. However, further studies are required to confirm the potential detrimental effects of ionizing radiation in these subjects.     

A study on specific behavioral effects of formaldehyde in the rat

It has been reported that single exposure of rats of low-level formaldehyde vapor concentrations causes significant alteration in their motor activity in the inhalation chamber. In this study, we determined the effects of formaldehyde on the locomotor activity and behavior of adult male and female Lew. 1K rats in an open field two hours after termination of a single two hours lasting inhalative exposure to approximately 0.1, 0.5, or 5 ppm. Following behavioral parameters were quantitatively examined: numbers of crossed floor squares, occurrence frequencies of air and floor sniffing, grooming, rearing, and wall climbing, as well as the incidence of fecal boli. In the open field situation, the males of all formaldehyde groups crossed significantly lower numbers of floor squares. Furthermore, significant decrease in the occurrence frequencies of floor sniffing, rearing, and wall climbing were observed. Within the female rat groups exposed to 0.5 or 5 ppm formaldehyde, a significantly decreased numbers of crossed squares were registered, while this parameter remained unchanged in the 0.1 ppm group. Other parameters were also affected by the formaldehyde inhalation (e.g. significant increase in the occurrence frequencies of air sniffing in the 0.1 and 0.5 ppm groups and significant decrease in the numbers of floor sniffing in the 0.5 and 5 ppm groups, respectively). The incidence of fecal boli was not affected in any exposure group neither in males nor in females. It is concluded from the results obtained that formaldehyde significantly affects the locomotor behavior of adult male and female rats in the open field after a single inhalative exposure to the above mentioned concentrations.     

Cytogenetic effects of microwave irradiation on male germ cells of the mouse

Hybrid male mice were exposed to 2.45 GHz microwaves for 30 min/day, 6 days a week for two consecutive weeks at power densities of 1.0, 100 or 400 W m-2, with sham-exposed controls. Rectal temperatures before and after exposure were measured on days 1, 6 and 12. Measurements made on day 1 were treated with caution because of heterogeneity in rectal temperatures taken before exposure between the groups of mice given different treatments. On days 6 and 12, rectal temperatures rose by approximately 1 degree C in mice sham exposed, or exposed to 1 W m-2 or 100 W m-2. Only in the group of mice exposed to 400 W m-2 was the mean rise in rectal temperature during exposure (about 3 degrees C) significantly increased above the sham value. In groups killed 2-3 days after treatment (mainly meiotic exposure) frequencies of chromosome aberrations in spermatocytes showed no significant heterogeneity although the highest frequency of 1.5 per cent was at the highest (400 W m-2) power density. Another group killed 30 days after 100 W m-2 exposures (spermatogonial sampling) showed no significant increase over controls in chromosome aberration frequency. There was a small but significant increase in sperm count with increasing power density in mice killed 12-13 days after exposure, but a non-significant one in those exposed as spermatogonia (killed 41 days later). Thus effects were markedly less severe than those reported previously by Manikowska-Czerska et al. (1985) with a very similar radiation regime and were probably caused by the temperature enhancement.