Reproductive toxicology in occupational settings: an update

Efficacy of antioxidant therapy on sperm quality measurements after varicocelectomy: A systematic review and meta-analysis

Antioxidants were proved to be efficient to improve the quality of spermatozoa after varicocelectomy. We carried out a systematic review and performed a meta-analysis to evaluate the efficacy of antioxidant therapy in sperm parameters' quality after varicocelectomy during 3 or 6 months' treatment cycle. During research, randomised controlled trials were searched by MEDLINE, EMBASE and the Cochrane Controlled Trials Register, and necessary parameters were compared between two groups after varicocelectomy. Finally, six studies including 576 patients were included in our meta-analysis. As for sperm parameters, significant improvements of sperm concentration (p < .0001), sperm motility (p = .03), progressive sperm motility (p < .00001) and sperm morphology (p < .00001) were existed in antioxidant group 3 months after varicocelectomy. With regard to the 6 months' outcomes, sperm parameters were improved as well except sperm motility (p = .72) and progressive sperm motility (p = .57). Referring to pregnancy rate, no significant difference was existed between two groups (p = .36), and the FSH level of antioxidant group was lower than placebo group 3 or 6 months after varicocelectomy (3 months, p = .02; 6 months, p = .03). In conclusion, compared with the placebo, the antioxidant therapy after varicocelectomy can improve the quality of sperm parameters and construct a favourable living condition for spermatozoa by reducing FSH level.

ACOG Committee Opinion No. 733: Employment Considerations During Pregnancy and the Postpartum Period

In the United States, it is common for women, including mothers and pregnant women, to work outside the home. Working during pregnancy is generally safe. For those in high-risk occupations or with medically complicated pregnancies, work accommodations often can allow for continued safe employment. The major employment issues concerning pregnant women include pregnancy-related discrimination, work accommodations that allow continued employment, job-protected leave, and wage replacement while on leave. Workplace discrimination related to being pregnant and pregnancy-related harassment, including discrimination in the hiring process, is prohibited by federal and state law. There is no federal law guaranteeing comprehensive accommodations for pregnant and postpartum workers. Current federal and state laws provide protection for some pregnant women, but not others, because of eligibility requirements and state-by-state differences. By writing appropriate notes to employers, obstetrician-gynecologists and other obstetric care providers can be instrumental in obtaining accommodations for their patients who are able to continue working. Accommodations that allow a woman to keep working are the most reliable way to guarantee pay, benefits, and job protection. Obstetrician-gynecologists and other obstetric care providers also can assist pregnant women and their partners by providing them with information and resources that might help them better understand their employment rights. However, in cases for which potential job discrimination has occurred, accommodations are denied, extended medical leave is necessary, or when other complex employment questions arise, legal assistance should be obtained.

Chemical and biological work-related risks across occupations in Europe: a review

BACKGROUND

Work-related health inequalities are determined to some extent by an unequal exposure to chemical and biological risk factors of disease. Although their potential economic burden in the European Union (EU-25) might be substantial, comprehensive reviews focusing on the distribution of these risks across occupational groups are limited. Thus, the main objective of this review is to provide a synopsis of the exposure to chemical and biological hazards across occupational groups. In addition, main industrial applications of hazardous substances are identified and some epidemiological evidence is discussed regarding societal costs and incidence rates of work-related diseases.

METHODS

Available lists of carcinogens, sensitisers, mutagens, reprotoxic substances and biological hazards were consulted. For each work-related hazard the main industrial application was identified in order to assess which ISCO occupational groups may be associated with direct exposure. Where available, information on annual tonnage production, risk assessment of the substances and pathogens, and other relevant data were collected and reported.

RESULTS

Altogether 308 chemical and biological hazards were identified which may account to at least 693 direct exposures. These hazards concentrate on the following major occupational groups: technicians (ISCO 3), operators (ISCO 8), agricultural workers (ISCO 6) and workers in elementary occupations (ISCO 9). Common industrial applications associated with increased exposure rates relate among others to: (1) production or application of pigments, resins, cutting fluids, adhesives, pesticides and cleaning products, (2) production of rubber, plastics, textiles, pharmaceuticals and cosmetics, and (3) in agriculture, metallurgy and food processing industry, Societal costs of the unequal distribution of chemical and biological hazards across occupations depend on the corresponding work-related diseases and may range from 2900 EUR to 126000 EUR per case/year.

CONCLUSIONS

Risk of exposure to chemical and biological risks and work-related disease incidence are highly concentrated on four occupational groups. The unequal burden of exposure across occupations is an important contributing factor leading to health inequalities in society. The bulk of societal costs, however, are actually being borne by the workers themselves. There is an urgent need of taking into account the health impact of production processes and services on workers' health.

Occupational exposure to pesticides and consequences on male semen and fertility: a review

Exposure to pesticides affects many body organs including reproductive system. Disorder of the reproductive system leads to infertility and therefore has been in the center of attention within the recent decades. Pesticides are one of the compounds that might reduce the semen quality in the exposed workers according to current knowledge. Although many underlying mechanisms have been proposed, the mechanisms of action are not clarified yet. The object of the present review was to criticize all the results of studies which evaluated the pesticide effects on male reproductive system. Results indicate that semen changes are multifactorial in the workers exposed to pesticides as there are numerous factors affecting sperm quality in occupational exposures. Majority of pesticides including organophosphoruses affect the male reproductive system by mechanisms such as reduction of sperm density and motility, inhibition of spermatogenesis, reduction of testis weights, reduction of sperm counts, motility, viability and density, and inducing sperm DNA damage, and increasing abnormal sperm morphology. Reduced weight of testes, epididymis, seminal vesicle, and ventral prostate, seminiferous tubule degeneration, change in plasma levels of testosterone, follicle-stimulating hormone (FSH), and luteinizing hormone (LH), decreased level and activity of the antioxidant enzymes in testes, and inhibited testicular steroidogenesis are other possible mechanisms. Moreover, DDT and its metabolites have estrogenic effects on males. Although effect of pesticides on sperm quality is undeniable, well-designed long-term studies are needed to elucidate all the possible affecting variables such as socioeconomic, cultural, nutritional, occupational, physical, and clinical characteristics alongside pesticides.

Chemical exposure in occupational settings and related health risks: a neglected area of research in Pakistan

In Pakistan a huge number of workers is routinely exposed to various types of chemical contaminants but there is a dearth of information as to the impact of these agents, due to a lack of a routine surveillance system and proper reporting. Prolonged and sometimes acute occupational exposures to varied organic chemicals may result in numerous health related problems. Studies from all over the world have shown adverse health outcomes of chemicals that are commonly used in various occupations. Such chemical exposures are not just confined to the workplace, but the residents surrounding industrial sites also face significant health risks due to indirect chemical exposure. Occupational exposure is a multidimensional risk factor that varies from one occupation to another, and is associated with health decline in workers. Common determinants of workplace hazards include improper, or lack of use of self-protective equipment, active and passive exposure to cigarette smoke as well as the socio-demographic and economic background of workers. There may be more than one cause of occupational stress and psychophysical disturbance among workers such as workload, lower salaries, and lack of social and medical facilities; indeed, their general health is poor. Therefore, in Pakistan, it is particularly important to focus on these issues and set rules and regulations to create occupational hazard awareness among workers, which will promote health safety at work places. If priorities are given to the correct use of self-protective equipment, adopting proper hygiene at the workplace and to avoid smoking, occupational exposures and consequent health risks may be minimized significantly.

Predictors of pregnancy and live birth after insemination in couples with unexplained or male-factor infertility

OBJECTIVE

To identify risk factors for pregnancy outcomes in couples treated with intracervical or intrauterine insemination, with or without superovulation for unexplained or male-factor infertility.

DESIGN

Secondary analysis of data from a randomized superovulation and intrauterine insemination trial.

SETTING

Academic medical centers.

INTERVENTION(S)

Treatment continued for four cycles unless pregnancy was achieved.

PATIENT(S)

Out of 932 couples randomized to four treatment groups, 664 couples who had completed the lifestyle questionnaires were assessed for occurrence of pregnancy and live birth.

MAIN OUTCOME MEASURE(S)

Pregnancy and live birth.

RESULT(S)

The pregnancy and live birth rates were significantly higher in couples in which the female partners reported that they had consumed coffee or tea in the past or drank alcoholic beverages in the past (past users) compared with those who had never consumed coffee, tea, or alcoholic beverages. Past users also had significantly higher pregnancy and live birth rates than those currently consuming coffee or tea or alcoholic beverages. Demographic, occupational exposure, and other lifestyle factors were not significant.

CONCLUSION(S)

Couples in which the female partners drank coffee, tea, or alcoholic beverages in the past had higher pregnancy and live birth rates compared with never or current users. When discontinuing these habits, they might have made other lifestyle changes to improve the pregnancy outcome.

Working conditions associated with ovarian cycle in a medical center nurses: a Taiwan study

AIM

Decreased basal body temperature measurements predict ovulation with an accuracy of 74%. The anovulatory cycle exhibits an ovarian monophasic pattern. This study evaluated the relationship between ovarian cycle pattern and sociodemographic characteristics, menstrual history and work characteristics of nurses in a Taiwan medical center.

METHODS

Of 200 nurses recruited, 151 were analyzed. Each subject completed questionnaires and provided life recordings and daily basal body temperature measurements during the 14-week study.

RESULTS

The analytical results demonstrated that work place (P = 0.014) and work shift (P = 0.048) are significantly related to ovarian cycle pattern. Nurses who worked in emergent care units and wards had a higher prevalence of irregular ovarian cycle pattern. Approximately 53% of nurses who worked rotating shifts exhibited irregular ovarian cycle pattern.

CONCLUSIONS

Nurses who either had rotating shift work or worked in emergent care units and wards should be concerned with their own ovarian cycle pattern for their health.

Evaluation of testicular degeneration induced by low-frequency electromagnetic fields

The population exposure to electromagnetic fields (EMF) has been growing in recent decades. The generation, distribution and use of electric energy can generate low-frequency electromagnetic fields. The present study investigates the effects of EMF (60 Hz and 1 mT) on spermatogenesis of rats during different periods of maturation. Wistar rats were exposed to EMF from day 13 of gestation to postnatal day 21 or 90 in three daily applications of 30 min. Plasma testosterone concentration was not changed by EMF exposure; however, histopathological and histomorphometrical analyses of the testes showed testicular degeneration in a subset of animals exposed to EMF. The magnitude of the degenerative process varied between those individuals affected, indicating different individual sensitivity to EMF. The main alterations observed through transmission electron microscopy were highly electron-dense mitochondria with loss of their organization and cristae. Exposure to 60 Hz and 1 mT EMF can disturb spermatogenesis and may produce subfertility or infertility.

Industrial differences in female fertility treatment rates--a new approach to assess differences related to occupation?

AIMS

Infertility is highly prevalent and 16-26% of women trying to achieve a pregnancy experience infertility in one or more periods. Several exposures in the work environment have been hypothesized to affect female reproduction. This study aimed to estimate relative rates (RR) of female fertility treatment in the 57 industrial groups in Denmark.

METHODS

The closed cohort of all 20-39 year old economically active women in Denmark by January 2001 (n = 567,816) were followed-up for hospital contacts due to infertility from 2001 to 2005 as registered in the Danish Occupational Hospital Register. Age-standardized relative rates for being diagnosed as infertile were estimated by industry. Further standardization with respect to socioeconomic status was also performed.

RESULTS

In total, 12,575 women were diagnosed with infertility during the follow-up period. Three industries presented with statistically significant elevations in age-standardized RRs: hospitals (RR = 1.27, 95% confidence interval (CI): 1.20-1.35), general and dental practice (RR = 1.17, 95% CI: 1.02-1.35) and other health care (RR = 1.24, 95% CI: 1.09-1.41). Standardization for socioeconomic status rendered two industries that were statistically significantly elevated: manufacture of wood and wood products (RR = 1.20, 95% CI: 1.02-1.42) and hospitals (RR = 1.17, 95% CI: 1.10-1.24).

CONCLUSIONS

Interpretation of the results is complex, since the relative contributions to the observed inequalities of the work environment and, for example, differences in inclination to start a family or in proneness to seek treatment are difficult to resolve. Withstanding shortcomings and limitations, register data of fertility treatment offers a possibility to suggest industries for further investigation of reproductive health.

The effects of carbon disulfide on male sexual function and semen quality

A cross-sectional study was initiated to clarify whether the current level of exposure to carbon disulphide (CS(2)) is low enough to prevent occurrence of subclinical health impairments. This paper describes the effects of exposure to CS(2) on male sexual function and semen quality in a baseline observation. The effects of CS(2) on male sexual function were evaluated, including number of sexual encounters and length of sexual encounters related to solvents in 80 male workers exposed to CS(2) and 49 reference workers from the filature and cotton pulp departments of a fabric factory in China. And the semen samples were obtained from 43 of the exposed and 35 of the control. Adjustment was made for potential confounding factors such as age or alcohol drinking. Exposure to CS(2) was dichotomized by job type. The rate of sexual dysfunction was higher, number of sexual encounters was lower, and length of sexual encounters was shorter compared with the control (p < 0.001). It was indicated that exposed workers had fewer semen quantity, longer liquefaction time, lower acrosomal membrane integrity rate, vitality and density, and more deformity of semen than the control (p < 0.01). The age and type of work played the most important roles in sexual dysfunction by the multinomial logistic regression analysis (p < 0.01).The duration of exposure had the effect on sexual function and semen quality but no statistical significance (p > 0.05). Clinical effects on the male sexual function and semen quality were found in the workers exposed to CS(2).

Radiofrequency electromagnetic fields; male infertility and sex ratio of offspring

Concern is growing about exposure to electromagnetic fields and male reproductive health. The authors performed a cross-sectional study among military men employed in the Royal Norwegian Navy, including information about work close to equipment emitting radiofrequency electromagnetic fields, one-year infertility, children and sex of the offspring. Among 10,497 respondents, 22% had worked close to high-frequency aerials to a "high" or "very high" degree. Infertility increased significantly along with increasing self-reported exposure to radiofrequency electromagnetic fields. In a logistic regression, odds ratio (OR) for infertility among those who had worked closer than 10 m from high-frequency aerials to a "very high" degree relative to those who reported no work near high-frequency aerials was 1.86 (95% confidence interval (CI): 1.46-2.37), adjusted for age, smoking habits, alcohol consumption and exposure to organic solvents, welding and lead. Similar adjusted OR for those exposed to a "high", "some" and "low" degree were 1.93 (95% CI: 1.55-2.40), 1.52 (95% CI: 1.25-1.84), and 1.39 (95% CI: 1.15-1.68), respectively. In all age groups there were significant linear trends with higher prevalence of involuntary childlessness with higher self-reported exposure to radiofrequency fields. However, the degree of exposure to radiofrequency radiation and the number of children were not associated. For self-reported exposure both to high-frequency aerials and communication equipment there were significant linear trends with lower ratio of boys to girls at birth when the father reported a higher degree of radiofrequency electromagnetic exposure.

Background, approaches and recent trends for setting health-based occupational exposure limits: a minireview

The setting of occupational exposure limits (OELs) are founded in occupational medicine and the predictive toxicological testing, resulting in exposure-response relationships. For compounds where a No-Observed-Adverse-Effect-Level (NOAEL) can be established, health-based OELs are set by dividing the NOAEL of the critical effect by an overall uncertainty factor. Possibly, the approach may also be used for carcinogens if the mechanism is epigenetic or the genetic effect is secondary to effect from reactions with proteins such as topoisomerase inhibitors, and mitotic and meiotic spindle poisons. Additionally, the NOAEL approach may also be used for compounds with weak genotoxic effect, playing no or only a minor role in the development of tumours. No health-based OEL can be set for direct-acting genotoxic compounds where the life-time risks may be estimated from the low-dose linear non-threshold extrapolation, allowing a politically based exposure level to be set. OELs are set by several agencies in the US and Europe, but also in-house in major chemical and pharmaceutical companies. The benchmark dose approach may in the future be used where it has advantage over the NOAEL approach. Also, more attention should be devoted to sensitive groups, toxicological mechanisms and interactions as most workplace exposures are mixtures.

Proceedings of the Summit on Environmental Challenges to Reproductive Health and Fertility: executive summary

The 2007 Summit on Environmental Challenges to Reproductive Health and Fertility convened scientists, health care professionals, community groups, political representatives, and the media to hear presentations on the impact of environmental contaminants on reproductive health and fertility, and to discuss opportunities to improve health through research, education, communication, and policy. Environmental reproductive health focuses on exposures to environmental contaminants, particularly during critical periods of development, and their potential effects on future reproductive health, including conception, fertility, pregnancy, adolescent development, and adult health. Approximately 87,000 chemical substances are registered for commercial use in the United States, with ubiquitous human exposures to environmental contaminants in air, water, food, and consumer products. Exposures during critical windows of susceptibility may result in adverse effects with lifelong and even intergenerational health impacts. Effects can include impaired development and function of the reproductive tract and permanently altered gene expression, leading to metabolic and hormonal disorders, reduced fertility and fecundity, and illnesses such as testicular, prostate, uterine, and cervical cancers later in life. This executive summary reviews effects of pre- and postnatal exposures on male and female reproductive health, and provides a series of recommendations for advancing the field in the areas of research, policy, health care, and community action.

Proceedings of the Summit on Environmental Challenges to Reproductive Health and Fertility: executive summary

The 2007 Summit on Environmental Challenges to Reproductive Health and Fertility convened scientists, health care professionals, community groups, political representatives, and the media to hear presentations on the impact of environmental contaminants on reproductive health and fertility, and to discuss opportunities to improve health through research, education, communication, and policy. Environmental reproductive health focuses on exposures to environmental contaminants, particularly during critical periods of development, and their potential effects on future reproductive health, including conception, fertility, pregnancy, adolescent development, and adult health. Approximately 87,000 chemical substances are registered for commercial use in the United States, with ubiquitous human exposures to environmental contaminants in air, water, food, and consumer products. Exposures during critical windows of susceptibility may result in adverse effects with lifelong and even intergenerational health impacts. Effects can include impaired development and function of the reproductive tract and permanently altered gene expression, leading to metabolic and hormonal disorders, reduced fertility and fecundity, and illnesses such as testicular, prostate, uterine, and cervical cancers later in life. This executive summary reviews effects of pre- and postnatal exposures on male and female reproductive health, and provides a series of recommendations for advancing the field in the areas of research, policy, health care, and community action.

Effect of occupational safety measures on micronucleus frequency in semiconductor workers

OBJECTIVES

To examine whether semiconductor workers exposed to complex mixtures of chemical waste show an increase in genotoxic effects, and, if so, whether occupational safety measures protect these workers.

METHODS

To assess chemical exposure in the workplace, air monitoring of boron trifluoride and boron trichloride was performed and urinary concentrations of fluoride were measured. The cytokinesis-block micronucleus test on isolated lymphocytes was used for the detection of genotoxic effects. Two series of monitoring have been performed in order to assess the effect of implemented protection measures.

RESULTS

We found a significantly higher mean frequency of micronuclei in exposed workers than in controls, whereas air monitoring and measurement of urinary fluoride failed to detect chemical exposure of these workers. Twelve years after implementation of protective measures, the mean level of micronuclei in exposed individuals was found to be as low as those from controls.

CONCLUSIONS

These findings indicate that exposed workers in the semiconductor industry may have an increased risk of genotoxic effects from complex mixtures of chemical waste products. The decline of the mean level of micronuclei in exposed workers down to the base level of controls after implementation of protective measures points to the significance of adequate safety standards to protect against chromosomal damage in semiconductor personnel.