Sperm chromatin structure and semen quality following occupational styrene exposure. Asclepios.
Explore the source record for details and available documents.
Biomarkers↗
Biomedical subjects
H A Kolstad
Publications and source records attributed to H A Kolstad.
Change in semen quality and sperm chromatin structure following occupational styrene exposure. ASCLEPIOS.
OBJECTIVES: Organic solvents have been suspected to exert detrimental effects on human spermiogenesis. Styrene, which is both mutagenic and neurotoxic, was selected as a suitable organic solvent for further assessment of a possible effect on semen quality and sperm DNA damage. SUBJECTS AND METHODS: Semen samples were collected from 23 reinforced plastics workers at the time of employment and after 6 months of styrene exposure and from 21 nonexposed farmers. Intra-individual changes in conventional semen parameters and sperm-DNA denaturation patterns were related to the internal dose of styrene exposure as measured by postshift urinary mandelic acid. RESULTS: A statistically significant decline in sperm density was seen during styrene exposure from 63.5 to 46.0 million sperm/ml, whereas no decline was seen in the nonexposed subjects. The total sperm count was almost halved from an initial value of 175 million sperm/ejaculate. However, no relationship was apparent when the sperm parameters were related to internal levels of exposure. However, an exposure-response relationship was shown for DNA-denaturation patterns, but the numbers were small. CONCLUSION: A declining sperm count following styrene exposure is suggested. However, the findings of the internal and external comparisons are inconsistent, and this may be due to the high intraindividual variability of semen parameters and the limited study size but may also be attributable to a weak internal exposure gradient. Spermatogenesis may be vulnerable to styrene exposure. However, due to the small numbers these findings are only preliminary.
Adult↗
Job strain and time to pregnancy.
OBJECTIVES: The association between fertility and job strain defined as high job demands and low job control has not previously been studied. A follow-up study was conducted with prospective collection of information on job strain among women, achievement of pregnancy, and potential confounding variables. METHODS: A total of 297 Danish couples without previous reproductive experience was followed for a maximum of 6 menstrual cycles from termination of birth control until pregnancy. Job demand and job control were measured by a questionnaire developed by Karasek and his co-workers. RESULTS: The odds ratio and 95% confidence interval (95% CI) for conception per menstrual cycle for women with high job strain was 0.9 (95% CI 0.5-1.5) when compared with that of women in low-strain jobs. Only in secondary analyses restricted to couples with no suspected competitive causes of reduced fertility was a statistically significant reduced odds found for women with high-strain jobs compared with all other jobs. CONCLUSIONS: The main finding of this study did not corroborate a hypothesis of a substantial detrimental effect of job strain on fecundability.
Adult↗
Year of birth and sperm count in 10 Danish occupational studies.
OBJECTIVES: Several reports indicate a secular decline of human sperm counts. It is still not known if these findings are artifacts related to shortcomings in the data and applied methodologies. Even less is known about possible mechanisms, but it has been proposed that potential changes may be related to disruption of the hormonal regulation of testicular development in prenatal life. The objective of this study was to examine whether sperm count was related to year of birth. METHODS: An analysis was made of the sperm count of 1196 men participating in 10 cross-sectional occupational sperm studies in 3 regions of Denmark from 1986 through 1995. RESULTS: The median sperm concentration was 63 million per milliliter for men born in 1937-1949 and 52 million per milliliter for men born in 1970 or later, and the median total sperm was 206 million and 117 million, respectively. The inverse relationship between sperm concentration and year of birth was statistically significant even after adjustment for duration of sexual abstinence, season of the year, and study population. However, bias because of differential participation related to age and fertility or lack of comparability across the populations cannot be ruled out. CONCLUSIONS: The apparent decline of sperm count with increasing year of birth is compatible with the hypothesis of a common risk factor for male reproductive health operating in prenatal life or early childhood, but the evidence is circumstantial. Age-related selection bias is an alternative and perhaps not a less likely explanation.
Adult↗
Clonal chromosome aberrations in myeloid leukemia after styrene exposure.
OBJECTIVES: The purpose of the study was to determine the risk of myeloid leukemia subclassified according to clonal chromosome aberrations in styrene-exposed workers. METHODS: A nested case-referent study was carried out on 19 myeloid leukemia patients, of which 12 showed clonal chromosome aberrations, and 57 referents ascertained within the Danish reinforced plastics industry and similar industries with no styrene exposure. RESULTS: A 2.5-fold increased risk for myeloid leukemia with clonal chromosome aberrations (95% confidence interval 0.2-25.0) was found among workers of companies with styrene exposure. CONCLUSIONS: The results suggest that styrene may cause leukemia through a clastogenic effect. But similar findings could also have been found if the exposure was associated with a specific subtype of leukemia prone to develop the chromosome aberrations in question. Due to the few observations and the lack of detailed exposure data, additional studies are needed to corroborate or refute the present suggestive findings.
Adult↗
Exposure to styrene and chronic health effects: mortality and incidence of solid cancers in the Danish reinforced plastics industry.
OBJECTIVES: To study the occurrence of non-malignant diseases and solid cancers in workers exposed to styrene in the Danish reinforced plastics industry. METHODS: All 36,610 workers of 386 reinforced plastics companies and 14,293 workers not exposed to styrene from similar industries were followed up from 1970 to 1990. This industry is characterised by simple exposure conditions, exposure to high concentrations of styrene, and a high proportion of small companies, and the exposure assessment was based on experts' classification on a company level. The mortality from non-malignant causes and the incidence of solid cancers were compared with the national rates. Poisson models were used for internal comparisons. RESULTS: A total of 3031 deaths and 1134 newly diagnosed cases of solid cancer were reported in the workers in the reinforced plastics industry. In companies where 50% or more of the workers produced reinforced plastics an increased mortality rate ratio (MRR) for degenerative disorders of the nervous system (multiple sclerosis, parkinsonism, and motor neurone disease; MRR 1.8, 16 cases, 95% confidence interval (95% CI) 0.9-3.8) and an increased incidence rate ratio (IRR) for pancreatic cancer (IRR 2.2, 17 cases, 95% CI 1.1-4.5) was found. For both disease categories increased occurrence was also found among long term workers, workers of the 1960s (the period with the highest exposure to styrene), and workers with a latent period of more than 10 years after the start of employment. No other non-malignant diseases or solid cancers showed these patterns. CONCLUSION: The findings have to be interpreted with caution, due to the company based exposure assessment, but the possible association between exposures in the reinforced plastics industry, mainly styrene, and degenerative disorders of the nervous system and pancreatic cancer, deserves attention.
Cause of Death↗
Incidence of lymphohematopoietic malignancies among styrene-exposed workers of the reinforced plastics industry.
OBJECTIVES: The goal of this study was to determine the risk of lymphohematopoietic malignancies for workers exposed to styrene. METHODS: This was a historical cohort study. The observed numbers of newly diagnosed cases of lymphohematopoietic malignancies in the study population were compared with expected numbers based on the national rates. The study took place in the Danish reinforced plastic industry, in which high exposure levels of styrene occur frequently in an environment free of most other suspected carcinogens. Altogether 36,525 male employees of 386 companies producing reinforced plastics and 14,254 nonstyrene exposed employees of similar industries were studied. RESULTS: An insignificantly increased standardized incidence ratio (SIR) of 1.22 [95% confidence interval (95% CI) 0.88-1.65] was found for leukemia among all employees of the reinforced plastics industry. Workers employed in the 1960s (the period with the highest recorded styrene levels) or in companies with the highest exposure probability showed increased SIR values of 1.54 (95% CI 1.04-2.19) and 1.38 (95% CI 0.75-2.32), respectively. Both estimates increased when a 10-year latency period was considered. CONCLUSIONS: An increased risk of leukemia was shown for workers in the early phase of the reinforced plastics industry in Denmark. If this association is not due to chance or confounding, the most likely cause is styrene exposure.
Cohort Studies↗
Cancer incidence in the Danish reinforced plastics industry.
Increased occurrences of malignancies of the lymphatic and haematopoietic tissues have been reported from industries in which employees are potentially exposed to styrene. The aim of the study reported here was to describe cancer incidence in the reinforced plastics industry in Denmark. A total of 64,000 employees of 552 Danish companies assessed to have produced reinforced plastics at any time since the 1960s were identified from a public administrative registry of all Danish employers and wage earners. Cancer incidence in the population was compared with similar rates for the population at large. No excess risk for all neoplasms was observed. Among male employees, increased risks were found for cancer of the lung (396 cases; relative risk [RR], 1.15; 95% confidence interval, 1.04-1.27), of the pleura (20 cases; RR, 2.33; 1.42-3.60), of the nasal cavities (nine cases; RR, 1.55; 0.71-2.94), of non-Hodgkin's lymphoma (61 cases; RR, 1.27; 0.97-1.63) and for leukaemia (61 cases; RR, 1.15; 0.88-1.48). Among female employees, a reduced risk for non-Hodgkin's lymphoma was observed (one case; RR, 0.16; 0.00-0.88). Some support was thus found for previous reports of increased risk for respiratory cancers and for malignancies of the lymphatic and haematopoietic tissues. The results must be interpreted with caution, however, owing to shortcomings in the design of the study.
Denmark↗
[Bladder tumors in West Lolland. A case-control study of occupational exposure in a risk region].
The Danish Cancer Register recorded a significant excess incidence of bladder tumours among men in West Lolland during the period 1970 and 1979. No corresponding excess incidence of cancer of the lung was recorded. This might suggest that causes other than increased prevalence of smokers explain the recorded findings. A case-control investigation was carried out to illustrate possible occupational causal factors with the aid of the Cancer Register database concerning cancer and occupation which is based on linking of the Cancer Register with the Supplementary Pension Fund (additional pensions supplementary pension fund awarded via the Labour Market.) Increased risks of bladder tumours were demonstrated in several occupations which are recognized as involving a risk for this disease. A significantly increased risk was demonstrated in the transport occupation. No evidence was found to suggest that the peculiar occupational structure of the region could explain the excess risk registered.
Case-Control Studies↗
[Chlorinated solvents and fetal damage. Spontaneous abortions, low birth weight and malformations among women employed in the dry-cleaning industry].
Workers in the dry-cleaning industry are exposed to vapours from the cleaning fluids, primarily perchlorethylene, which is a chlorinated solvent. Animal experiments, short-term tests for mutagenic effects and epidemiological investigations have raised the suspicion that perchlorethylene may cause reproductive failure. This investigation is an attempt to assess the risk for reproductive failure in 886 women exposed to dry-cleaning solvents while employed in dry-cleaning establishments. Twelve spontaneous abortions occurred, one infant was born with malformations and ten infants had low birth weights. A non-significant risk for spontaneous abortion was found among women with the greatest exposure. This estimate is, however, uncertain and the result must be interpreted with care.
Abortion, Legal↗
A follow-up study of male exposure to welding and time to pregnancy.
The aim of this study was to estimate whether male welding has an impact on couple fecundability (the probability of conceiving in a menstrual cycle). A sample of Danish couples without previous reproductive experience was recruited nationwide by postal letters to members of the union of metal workers and three other trade unions. Among 430 included couples, 201 males were metal workers and 130 were welders. The couples were followed for a maximum of six menstrual cycles from termination of birth control until a clinical pregnancy was detected. Compared with nonwelding metal workers the fecundability odds ratio (OR) of male exposure to welding was 0.86 (95% confidence interval [CI] 0.58-1.28). An interaction between male smoking and welding was found; within smokers the OR for welding was 0.40 (95% CI 0.17-0.95) and within nonsmokers it was 1.22 (95% CI 0.74-1.99). Previous welding exposure was negatively related to fecundability among smokers (OR 0.84 per year with mild steel welding, OR 0.76 per year with stainless steel welding). No significant results were found when comparing with an external group of nonmetal workers. Decreased fecundability among smoking welders attributable to both current and previous welding exposure is possible, but these findings were the results of subanalyses that were not part of the a priori hypothesis.
Adult↗
Semen quality and sex hormones with reference to metal welding.
Welding may involve hazards to the male reproductive system, but previous studies of semen quality have produced inconsistent results. We studied the effects of welding on markers of semen quality in a Danish nationwide sample of 430 first-time pregnancy planners without earlier reproductive experience. Couples were recruited among members of the union of metal workers and three other trade unions and were followed from termination of birth control until pregnancy for a maximum of six menstrual cycles. The males provided semen samples in each cycle. Median sperm density for welders was 56 x 10(6)/mL (52.5 x 10(6)/mL and 50.0 x 10(6)/mL in two reference groups). No statistically significant differences attributable to welding were found in proportions of morphologically normal sperm, sperm motility assessed by computer-aided sperm analysis, or sex hormones (testosterone, follicle-stimulating hormone, and luteinizing hormone). These negative findings may not apply to populations with high-level exposure to welding fume or to welders exposed to other putative hazards, e.g., heat.
Adult↗