Effects of the workplace on fertility and related reproductive outcomes

The Minderoo-Monaco Commission on Plastics and Human Health

Background

Plastics have conveyed great benefits to humanity and made possible some of the most significant advances of modern civilization in fields as diverse as medicine, electronics, aerospace, construction, food packaging, and sports. It is now clear, however, that plastics are also responsible for significant harms to human health, the economy, and the earth's environment. These harms occur at every stage of the plastic life cycle, from extraction of the coal, oil, and gas that are its main feedstocks through to ultimate disposal into the environment. The extent of these harms not been systematically assessed, their magnitude not fully quantified, and their economic costs not comprehensively counted.

Goals

The goals of this Minderoo-Monaco Commission on Plastics and Human Health are to comprehensively examine plastics' impacts across their life cycle on: (1) human health and well-being; (2) the global environment, especially the ocean; (3) the economy; and (4) vulnerable populations-the poor, minorities, and the world's children. On the basis of this examination, the Commission offers science-based recommendations designed to support development of a Global Plastics Treaty, protect human health, and save lives.

Report Structure

This Commission report contains seven Sections. Following an Introduction, Section 2 presents a narrative review of the processes involved in plastic production, use, and disposal and notes the hazards to human health and the environment associated with each of these stages. Section 3 describes plastics' impacts on the ocean and notes the potential for plastic in the ocean to enter the marine food web and result in human exposure. Section 4 details plastics' impacts on human health. Section 5 presents a first-order estimate of plastics' health-related economic costs. Section 6 examines the intersection between plastic, social inequity, and environmental injustice. Section 7 presents the Commission's findings and recommendations.

Plastics

Plastics are complex, highly heterogeneous, synthetic chemical materials. Over 98% of plastics are produced from fossil carbon- coal, oil and gas. Plastics are comprised of a carbon-based polymer backbone and thousands of additional chemicals that are incorporated into polymers to convey specific properties such as color, flexibility, stability, water repellence, flame retardation, and ultraviolet resistance. Many of these added chemicals are highly toxic. They include carcinogens, neurotoxicants and endocrine disruptors such as phthalates, bisphenols, per- and poly-fluoroalkyl substances (PFAS), brominated flame retardants, and organophosphate flame retardants. They are integral components of plastic and are responsible for many of plastics' harms to human health and the environment.Global plastic production has increased almost exponentially since World War II, and in this time more than 8,300 megatons (Mt) of plastic have been manufactured. Annual production volume has grown from under 2 Mt in 1950 to 460 Mt in 2019, a 230-fold increase, and is on track to triple by 2060. More than half of all plastic ever made has been produced since 2002. Single-use plastics account for 35-40% of current plastic production and represent the most rapidly growing segment of plastic manufacture.Explosive recent growth in plastics production reflects a deliberate pivot by the integrated multinational fossil-carbon corporations that produce coal, oil and gas and that also manufacture plastics. These corporations are reducing their production of fossil fuels and increasing plastics manufacture. The two principal factors responsible for this pivot are decreasing global demand for carbon-based fuels due to increases in 'green' energy, and massive expansion of oil and gas production due to fracking.Plastic manufacture is energy-intensive and contributes significantly to climate change. At present, plastic production is responsible for an estimated 3.7% of global greenhouse gas emissions, more than the contribution of Brazil. This fraction is projected to increase to 4.5% by 2060 if current trends continue unchecked.

Plastic Life Cycle

The plastic life cycle has three phases: production, use, and disposal. In production, carbon feedstocks-coal, gas, and oil-are transformed through energy-intensive, catalytic processes into a vast array of products. Plastic use occurs in every aspect of modern life and results in widespread human exposure to the chemicals contained in plastic. Single-use plastics constitute the largest portion of current use, followed by synthetic fibers and construction.Plastic disposal is highly inefficient, with recovery and recycling rates below 10% globally. The result is that an estimated 22 Mt of plastic waste enters the environment each year, much of it single-use plastic and are added to the more than 6 gigatons of plastic waste that have accumulated since 1950. Strategies for disposal of plastic waste include controlled and uncontrolled landfilling, open burning, thermal conversion, and export. Vast quantities of plastic waste are exported each year from high-income to low-income countries, where it accumulates in landfills, pollutes air and water, degrades vital ecosystems, befouls beaches and estuaries, and harms human health-environmental injustice on a global scale. Plastic-laden e-waste is particularly problematic.

Environmental Findings

Plastics and plastic-associated chemicals are responsible for widespread pollution. They contaminate aquatic (marine and freshwater), terrestrial, and atmospheric environments globally. The ocean is the ultimate destination for much plastic, and plastics are found throughout the ocean, including coastal regions, the sea surface, the deep sea, and polar sea ice. Many plastics appear to resist breakdown in the ocean and could persist in the global environment for decades. Macro- and micro-plastic particles have been identified in hundreds of marine species in all major taxa, including species consumed by humans. Trophic transfer of microplastic particles and the chemicals within them has been demonstrated. Although microplastic particles themselves (>10 µm) appear not to undergo biomagnification, hydrophobic plastic-associated chemicals bioaccumulate in marine animals and biomagnify in marine food webs. The amounts and fates of smaller microplastic and nanoplastic particles (MNPs <10 µm) in aquatic environments are poorly understood, but the potential for harm is worrying given their mobility in biological systems. Adverse environmental impacts of plastic pollution occur at multiple levels from molecular and biochemical to population and ecosystem. MNP contamination of seafood results in direct, though not well quantified, human exposure to plastics and plastic-associated chemicals. Marine plastic pollution endangers the ocean ecosystems upon which all humanity depends for food, oxygen, livelihood, and well-being.

Human Health Findings

Coal miners, oil workers and gas field workers who extract fossil carbon feedstocks for plastic production suffer increased mortality from traumatic injury, coal workers' pneumoconiosis, silicosis, cardiovascular disease, chronic obstructive pulmonary disease, and lung cancer. Plastic production workers are at increased risk of leukemia, lymphoma, hepatic angiosarcoma, brain cancer, breast cancer, mesothelioma, neurotoxic injury, and decreased fertility. Workers producing plastic textiles die of bladder cancer, lung cancer, mesothelioma, and interstitial lung disease at increased rates. Plastic recycling workers have increased rates of cardiovascular disease, toxic metal poisoning, neuropathy, and lung cancer. Residents of "fenceline" communities adjacent to plastic production and waste disposal sites experience increased risks of premature birth, low birth weight, asthma, childhood leukemia, cardiovascular disease, chronic obstructive pulmonary disease, and lung cancer.During use and also in disposal, plastics release toxic chemicals including additives and residual monomers into the environment and into people. National biomonitoring surveys in the USA document population-wide exposures to these chemicals. Plastic additives disrupt endocrine function and increase risk for premature births, neurodevelopmental disorders, male reproductive birth defects, infertility, obesity, cardiovascular disease, renal disease, and cancers. Chemical-laden MNPs formed through the environmental degradation of plastic waste can enter living organisms, including humans. Emerging, albeit still incomplete evidence indicates that MNPs may cause toxicity due to their physical and toxicological effects as well as by acting as vectors that transport toxic chemicals and bacterial pathogens into tissues and cells.Infants in the womb and young children are two populations at particularly high risk of plastic-related health effects. Because of the exquisite sensitivity of early development to hazardous chemicals and children's unique patterns of exposure, plastic-associated exposures are linked to increased risks of prematurity, stillbirth, low birth weight, birth defects of the reproductive organs, neurodevelopmental impairment, impaired lung growth, and childhood cancer. Early-life exposures to plastic-associated chemicals also increase the risk of multiple non-communicable diseases later in life.

Economic Findings

Plastic's harms to human health result in significant economic costs. We estimate that in 2015 the health-related costs of plastic production exceeded $250 billion (2015 Int$) globally, and that in the USA alone the health costs of disease and disability caused by the plastic-associated chemicals PBDE, BPA and DEHP exceeded $920 billion (2015 Int$). Plastic production results in greenhouse gas (GHG) emissions equivalent to 1.96 gigatons of carbon dioxide (CO2e) annually. Using the US Environmental Protection Agency's (EPA) social cost of carbon metric, we estimate the annual costs of these GHG emissions to be $341 billion (2015 Int$).These costs, large as they are, almost certainly underestimate the full economic losses resulting from plastics' negative impacts on human health and the global environment. All of plastics' economic costs-and also its social costs-are externalized by the petrochemical and plastic manufacturing industry and are borne by citizens, taxpayers, and governments in countries around the world without compensation.

Social Justice Findings

The adverse effects of plastics and plastic pollution on human health, the economy and the environment are not evenly distributed. They disproportionately affect poor, disempowered, and marginalized populations such as workers, racial and ethnic minorities, "fenceline" communities, Indigenous groups, women, and children, all of whom had little to do with creating the current plastics crisis and lack the political influence or the resources to address it. Plastics' harmful impacts across its life cycle are most keenly felt in the Global South, in small island states, and in disenfranchised areas in the Global North. Social and environmental justice (SEJ) principles require reversal of these inequitable burdens to ensure that no group bears a disproportionate share of plastics' negative impacts and that those who benefit economically from plastic bear their fair share of its currently externalized costs.

Conclusions

It is now clear that current patterns of plastic production, use, and disposal are not sustainable and are responsible for significant harms to human health, the environment, and the economy as well as for deep societal injustices.The main driver of these worsening harms is an almost exponential and still accelerating increase in global plastic production. Plastics' harms are further magnified by low rates of recovery and recycling and by the long persistence of plastic waste in the environment.The thousands of chemicals in plastics-monomers, additives, processing agents, and non-intentionally added substances-include amongst their number known human carcinogens, endocrine disruptors, neurotoxicants, and persistent organic pollutants. These chemicals are responsible for many of plastics' known harms to human and planetary health. The chemicals leach out of plastics, enter the environment, cause pollution, and result in human exposure and disease. All efforts to reduce plastics' hazards must address the hazards of plastic-associated chemicals.

Recommendations

To protect human and planetary health, especially the health of vulnerable and at-risk populations, and put the world on track to end plastic pollution by 2040, this Commission supports urgent adoption by the world's nations of a strong and comprehensive Global Plastics Treaty in accord with the mandate set forth in the March 2022 resolution of the United Nations Environment Assembly (UNEA).International measures such as a Global Plastics Treaty are needed to curb plastic production and pollution, because the harms to human health and the environment caused by plastics, plastic-associated chemicals and plastic waste transcend national boundaries, are planetary in their scale, and have disproportionate impacts on the health and well-being of people in the world's poorest nations. Effective implementation of the Global Plastics Treaty will require that international action be coordinated and complemented by interventions at the national, regional, and local levels.This Commission urges that a cap on global plastic production with targets, timetables, and national contributions be a central provision of the Global Plastics Treaty. We recommend inclusion of the following additional provisions:The Treaty needs to extend beyond microplastics and marine litter to include all of the many thousands of chemicals incorporated into plastics.The Treaty needs to include a provision banning or severely restricting manufacture and use of unnecessary, avoidable, and problematic plastic items, especially single-use items such as manufactured plastic microbeads.The Treaty needs to include requirements on extended producer responsibility (EPR) that make fossil carbon producers, plastic producers, and the manufacturers of plastic products legally and financially responsible for the safety and end-of-life management of all the materials they produce and sell.The Treaty needs to mandate reductions in the chemical complexity of plastic products; health-protective standards for plastics and plastic additives; a requirement for use of sustainable non-toxic materials; full disclosure of all components; and traceability of components. International cooperation will be essential to implementing and enforcing these standards.The Treaty needs to include SEJ remedies at each stage of the plastic life cycle designed to fill gaps in community knowledge and advance both distributional and procedural equity.This Commission encourages inclusion in the Global Plastic Treaty of a provision calling for exploration of listing at least some plastic polymers as persistent organic pollutants (POPs) under the Stockholm Convention.This Commission encourages a strong interface between the Global Plastics Treaty and the Basel and London Conventions to enhance management of hazardous plastic waste and slow current massive exports of plastic waste into the world's least-developed countries.This Commission recommends the creation of a Permanent Science Policy Advisory Body to guide the Treaty's implementation. The main priorities of this Body would be to guide Member States and other stakeholders in evaluating which solutions are most effective in reducing plastic consumption, enhancing plastic waste recovery and recycling, and curbing the generation of plastic waste. This Body could also assess trade-offs among these solutions and evaluate safer alternatives to current plastics. It could monitor the transnational export of plastic waste. It could coordinate robust oceanic-, land-, and air-based MNP monitoring programs.This Commission recommends urgent investment by national governments in research into solutions to the global plastic crisis. This research will need to determine which solutions are most effective and cost-effective in the context of particular countries and assess the risks and benefits of proposed solutions. Oceanographic and environmental research is needed to better measure concentrations and impacts of plastics <10 µm and understand their distribution and fate in the global environment. Biomedical research is needed to elucidate the human health impacts of plastics, especially MNPs.

Summary

This Commission finds that plastics are both a boon to humanity and a stealth threat to human and planetary health. Plastics convey enormous benefits, but current linear patterns of plastic production, use, and disposal that pay little attention to sustainable design or safe materials and a near absence of recovery, reuse, and recycling are responsible for grave harms to health, widespread environmental damage, great economic costs, and deep societal injustices. These harms are rapidly worsening.While there remain gaps in knowledge about plastics' harms and uncertainties about their full magnitude, the evidence available today demonstrates unequivocally that these impacts are great and that they will increase in severity in the absence of urgent and effective intervention at global scale. Manufacture and use of essential plastics may continue. However, reckless increases in plastic production, and especially increases in the manufacture of an ever-increasing array of unnecessary single-use plastic products, need to be curbed.Global intervention against the plastic crisis is needed now because the costs of failure to act will be immense.

Elderberry Diet Restores Spermatogenesis in the Transient Scrotal Hyperthermia-Induced Mice

Over the past years, several studies have also reported the adverse effects of hyperthermia on normal testicular tissues in several species including mice, rats, and humans. These deleterious impacts include temporarily drop in relative weight of testis along with a temporary partial or complete infertility. Sambucus nigra, also known as elderberry or sweet elder, is a source of bioactive compounds that has drawn growing attention for its potential beneficial effects in preventing and treating several diseases. This experimental research divided 30 mice into the following three groups: (1) control, (2) hyperthermia, and (3) hyperthermia receiving elderberry diet for 35 days. Scrotal hyperthermia was induced by water bath with 43 °C for 30 min. Then, the mice were euthanized, and their sperm samples were collected for sperm parameters analysis. Then, we took the testis samples for histopathological experimentations, immunohistochemistry against TNF-α and caspase-3 and serum testosterone, FSH and LH levels. Our outputs indicated that elderberry diet could largely improve the sperms parameters and stereological parameters, like spermatogonia, primary spermatocyte, round spermatid, and Leydig cells together with an increasing level of the serum testosterone compared to the scrotal hyperthermia induced mice. In addition, it was found that the expression of TNF-α and caspase-3 significantly decreased in the treatment groups by elderberry diet compared to the scrotal hyperthermia-induced mice. In conclusion, it could be concluded that elderberry diet may be regarded as an alternative treatment for improving the spermatogenesis process in the scrotal hyperthermia induced mice.

Assessment of semen quality of taxi drivers exposed to whole body vibration

Whole body vibration (WBV) is a recognized occupational hazard for many workers such as drivers and operators of heavy and light machinery and exposure to it is accompanied by physical and mental repercussions. Only the limited studies have been done on the effects of vibration exposure on reproductive indices, however vibration exposure has been indicated as being a hazardous agents with the potential of being able to directly affect the reproductive system. Considering the importance of infertility, the present study was conducted with the aim of investigating semen quality among taxi drivers in Tehran and determine the effect of exposure to WBV on sperm parameters. The study population consisted of 70 taxi drivers and 70 office employee who attended infertility clinics for diagnostic purposes in the past year. The participants had to meet the entry criteria of the study while also being willing to recruit. Data was collected in the form of demographic questionnaires and general health questionnaires as well as sperm analysis conducted in an infertility clinic according to standard laboratory guidelines. The 8-hour time-weighted average (TWA) exposure to of WBV in automobile was measured as per ISO 2631-1. The TWA exposure to WBV among the taxi drivers and office employees were 0.697 ± 0.13 m/s² and 0.068 ± 0.09 m/s² respectively (P < 0.05). A statistically significant difference in total sperm count, progressive motility, non-progressive motility and total motility was observed between the taxi drivers and the office employees (P < 0.05). According to the univariate analysis of variance, exposure to WBV had negative effect on sperm concentration, progressive motility and normal morphology (P > 0.05); moreover exposure to WBV resulted in the larger effect size (B) on sperm parameters than the demographic variables (P > 0.05). Being taxi drivers increase the chance of the decreased semen quality (P > 0.05). It is difficult to draw definitive conclusions regarding the effects of WBV while intervening factors exist, such as psychological stressors, quality of sleep, background issues as well as environmental factors such as chemical pollutants (heavy metals) or ergonomic factors (body posture and working while sitting down).

Relationship between occupational exposure to whole-body vibration and noise with sex hormone levels: An empirical assessment in an automobile parts manufacturing plant

The present study investigated the relationship between occupational exposure to noise and whole-body vibration (WBV) with the levels of sex hormones in an automobile parts manufacturing plant. The level of workers' exposure (n = 162) to each of the mentioned stressors was measured through standard methods, and the time-weighted average of exposure was calculated for each person. In order to determine serum sex hormones (free testosterone, luteinizing hormone, and follicle-stimulating hormone), blood samples were taken from all participants after 8-10 h of fasting between 7 and 9 am and then the blood samples were analyzed by an enzyme-linked immunosorbent assay method. In general, regarding testosterone as the main male sex hormone, only 49% of the participants were in the normal range. In a total of three sections, the lowest mean testosterone levels were observed in the third exposure group (WBV > 1.93 m/s²; noise >92.69 dB) of the studied stressor; however, only the difference in testosterone levels between the three different groups of exposure to noise was statistically significant (p = 0.001). The relationship between demographic variables and levels of noise and WBV exposure with sex hormones was not linear and only the relationship between noise exposure and testosterone levels was statistically significant (R = -0.201, p = 0.013). According to the results of logistic regression, the WBV had the greatest effect on testosterone levels. However, according to the results of the correlation test, only the relationship between noise exposure and testosterone levels was statistically significant.

Occupational manganese exposure, reproductive hormones, and semen quality in male workers: A cross-sectional study

It has been found that exposure to manganese (Mn) could induce reproductive dysfunction, but its occupational risk in male workers is unclear. This study aims to assess the association of occupational Mn exposure with reproductive hormones and semen quality in a cross-sectional study. Urinary Mn, semen quality, and reproductive hormones were explored in 84 male workers occupationally exposed to Mn and 92 referents. Multiple linear regression analyses were used to assess the relationship. Urinary Mn levels in Mn-exposed workers ranged from 0.56 to 34.25 µg/L, and the average level was 15.92 ± 8.49 µg/L. Compared with the control group, gonadotropin-releasing hormone (GnRH) levels and luteinizing hormone (LH) levels increased significantly and the levels of testosterone (TSTO) decreased significantly in the Mn-exposed group. There was a significant positive linear association between urinary Mn and GnRH and LH, while the linear association between urinary Mn and TSTO was negative. Sperm progressive motility and total motility decreased significantly in the Mn-exposed group. There was a significantly negative linear association between urinary Mn and sperm progressive motility and total motility. In conclusion, occupational Mn exposure was inversely associated with reproductive health of male workers, resulting in the abnormality of hormones secretion and decrease of sperm motility.

Pectinase-treated Panax ginseng protects against chronic intermittent heat stress-induced testicular damage by modulating hormonal and spermatogenesis-related molecular expression in rats

Background

Elevated testicular temperature disrupts spermatogenesis and causes infertility. In the present study, the protective effect of enzymatically biotransformed Panax ginseng Meyer by pectinase (GINST) against chronic intermittent heat stress-induced testicular damage in rats was investigated.

Methods

Male Sprague–Dawley rats (4 wk old, 60–70 g) were divided into four groups: normal control (NC), heat-stress control (HC), heat-stress plus GINST-100 mg/kg (HG100), and heat-stress plus GINST-200 mg/kg (HG200) treatment groups. Each dose of GINST (100 mg/kg and 200 mg/kg) was mixed separately with a regular pellet diet and was administered orally for 24 wk. For inducing heat stress, rats in the NC group were maintained at 25°C, whereas rats in the HC, HG100, and HG200 groups were exposed to 32 ± 1°C for 2 h daily for 6 mo. At week 25, the testes and serum from each animal were analyzed for various parameters.

Results

Significant (p < 0.01) changes in the sperm kinematic values and blood chemistry panels were observed in the HC group. Furthermore, spermatogenesis-related molecules, sex hormone receptors, and selected antioxidant enzyme expression levels were also altered in the HC group compared to those in the NC group. GINST (HS100 and HS200) administration significantly (p < 0.05) restored these changes when compared with the HC group. For most of the parameters tested, the HG200 group exhibited potent effects compared with those exhibited by the HG100 group.

Conclusion

GINST may be categorized as an important medicinal herb and a potential therapeutic for the treatment of male subfertility or infertility caused by hyperthermia.

Adverse effects of parental smoking during pregnancy in urban and rural areas

Background

Parental smoking during pregnancy is associated with lower birthweight and gestational age, as well as with the risks of low birthweight (LBW) and preterm birth. The present study aims to assess the association of parental smoking during pregnancy with birth outcomes in urban and rural areas.

Methods

This was a secondary analysis of data collected in the Indonesia Family Life Survey, between 1993 and 2007, the first national prospective longitudinal cohort study in Indonesia. Retrospective data of parental smoking habits, socioeconomic status, pregnancy history and birth outcomes were collected from parents with children aged 0 to 5 years (n = 3789). We assessed the relationships between the amount of parental smoking during pregnancy with birthweight (LBW) and with gestational age (preterm birth).

Results

We found a significant reduction in birthweight to be associated with maternal smoking. Smoking (except for paternal smoking) was associated with a decrease in the gestational age and an increased risk of preterm birth. Different associations were found in urban area, infants born to smoking fathers and both smoking parents (>20 cigarettes/day for both cases) had a significant reduction in birthweight and gestational age as well as an increased risk of LBW and preterm birth.

Conclusions

Residence was found to be an effect modifier of the relation between parental smoking during pregnancy, amount of parental smoking, and birth outcomes on their children. Smoking cessation/reduction and smoking intervention program should be advised and prioritized to the area that is more prone to the adverse birth outcomes.

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.

Association between sperm DNA integrity and seminal plasma antioxidant levels in health workers occupationally exposed to ionizing radiation

There is a paucity of data regarding the association between occupational radiation exposure and risk to human fertility. Recently, we provided the first evidence on altered sperm functional characteristics, DNA damage and hypermethylation in radiation health workers. However, there is no report elucidating the association between seminal plasma antioxidants and sperm chromatin integrity in occupationally exposed subjects. Here, we assessed the seminal plasma antioxidants and lipid peroxidation level in 83 men who were occupationally exposed to ionizing radiation and then correlated with the sperm chromatin integrity. Flow cytometry based sperm chromatin integrity assay revealed a significant decline in αt value in the exposed group in comparison to the non-exposed group (P<0.0001). Similarly, both total and reduced glutathione levels and total antioxidant capacity in the seminal plasma were significantly higher in exposed group than the non-exposed group (P<0.01, 0.001 and 0.0001, respectively). However, superoxide dismutase level and malondialdehyde level, which is an indicator of lipid peroxidation in the seminal plasma, did not differ significantly between two groups. The total antioxidant capacity (TAC) and GSH level exhibited a positive correlation with sperm DNA integrity in exposed subjects. To conclude, this study distinctly shows that altered sperm chromatin integrity in radiation health workers is associated with increase in seminal plasma antioxidant level. Further, the increased seminal plasma GSH and TAC could be an adaptive measure to tackle the oxidative stress to protect genetic and functional sperm deformities in radiation health workers.

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.

The effects of chronic ingestion of mercuric chloride on fertility and testosterone levels in male Sprague Dawley rats

Although male infertility is well researched, the effects of inorganic mercury on male reproduction and fertility are less well known. Studies pertaining to mercury and male fertility identified reduced concentration of testosterone in the serum of male workers, a toxic influence on fertility of organic mercury compounds within concentrations at the workplace, and increased days to pregnancy. We evaluated the effect of chronic mercuric chloride (HgCl₂) exposure in male rats on reproductive endpoints. Thirty-day old male Sprague Dawley rats (n = 31) were exposed to 0.0, 1.0, or 2.0 mg/kg/day of HgCl₂ via gavage. After 60 days exposure, they were housed with nonexposed females for 21 days. A survivor analysis revealed the exposed animals took longer to impregnate the females and had a lower rate of impregnation. Further statistical analysis revealed a lower correlation between testicular testosterone levels and days to impregnate, and also lower sperm counts in the epididymis head and body of the exposed males. The results indicate that HgCl₂ exposure had significant adverse effects on male rat reproduction endpoints including fertility at a dose that was not clinically toxic.

Occupational reproductive function abnormalities and bladder cancer in Korea

The purpose of this study was to review occupational reproductive abnormalities and occupational bladder cancer in Korea and to discuss their toxicological implications. Reproductive dysfunction as a result of 2-bromopropane poisoning was first reported in Korean workers. In 1995, 23 of the 33 workers (25 female and 8 male workers) who were exposed to 2-bromopropane during the assembly of tactile switch parts developed reproductive and/or hematopoietic disorders. A total of 17 (68%) workers were diagnosed with ovarian failure. Two of the eight male workers experienced azoospermia and four workers experienced some degree of oligospermia or reduced sperm motility. In summary, 2-bromopropane poisoning caused severe reproductive effects in Korean workers. The prognosis was poor for reproductive dysfunction. A few cases of occupational bladder cancer have been reported in Korea, whereas other cancers of the urinary tract have not been reported after occupational exposure. A few cases of benzidine-induced cancer have been reported in Korea and 592 workers in Japan have received compensation for benzidine and β-naphthylamine-induced cancer. In conclusion, a few cases of benzidine-induced occupational bladder cancer have been reported in Korea. However, benzidine-induced bladder cancer will likely be an important occupational health issue in Korea in the coming years.

Time-to-pregnancy and pregnancy outcomes in a South African population

BACKGROUND

Time-to-pregnancy (TTP) has never been studied in an African setting and there are no data on the rates of adverse pregnancy outcomes in South Africa. The study objectives were to measure TTP and the rates of adverse pregnancy outcomes in South Africa, and to determine the reliability of the questionnaire tool.

METHODS

The study was cross-sectional and applied systematic stratified sampling to obtain a representative sample of reproductive age women for a South African population. Data on socio-demographic, work, health and reproductive variables were collected on 1121 women using a standardized questionnaire. A small number (n = 73) of randomly selected questionnaires was repeated to determine reliability of the questionnaire. Data was described using simple summary statistics while Kappa and intra-class correlation statistics were calculated for reliability.

RESULTS

Of the 1121 women, 47 (4.2%) had never been pregnant. Mean gravidity was 2.3 while mean parity was 2.0 There were a total of 2467 pregnancies; most (87%) resulted in live births, 9.5% in spontaneous abortion and 2.2% in still births. The proportion of planned pregnancies was 39% and the median TTP was 6 months. The reliability of the questionnaire for TTP data was good; 63% for all participants and 97% when censored at 14 months. Overall reliability of reporting adverse pregnancy outcomes was very high, ranging from 90 - 98% for most outcomes.

CONCLUSION

This is the first comprehensive population-based reproductive health study in South Africa, to describe the biologic fertility of the population, and provides rates for planned pregnancies and adverse pregnancy outcomes. The reliability of the study questionnaire was substantial, with most outcomes within 70 - 100% reliability index. The study provides important public information for health practitioners and researchers in reproductive health. It also highlights the need for public health intervention programmes and epidemiological research on biologic fertility and adverse pregnancy outcomes in the population.

Male reproductive organs are at risk from environmental hazards

Male reproductive disorders that are of interest from an environmental point of view include sexual dysfunction, infertility, cryptorchidism, hypospadias and testicular cancer. Several reports suggest declining sperm counts and increase of these reproductive disorders in some areas during some time periods past 50 years. Except for testicular cancer this evidence is circumstantial and needs cautious interpretation. However, the male germ line is one of the most sensitive tissues to the damaging effects of ionizing radiation, radiant heat and a number of known toxicants. So far occupational hazards are the best documented risk factors for impaired male reproductive function and include physical exposures (radiant heat, ionizing radiation, high frequency electromagnetic radiation), chemical exposures (some solvents as carbon disulfide and ethylene glycol ethers, some pesticides as dibromochloropropane, ethylendibromide and DDT/DDE, some heavy metals as inorganic lead and mercury) and work processes such as metal welding. Improved working conditions in affluent countries have dramatically decreased known hazardous workplace exposures, but millions of workers in less affluent countries are at risk from reproductive toxicants. New data show that environmental low-level exposure to biopersistent pollutants in the diet may pose a risk to people in all parts of the world. For other toxicants the evidence is only suggestive and further evaluation is needed before conclusions can be drawn. Whether compounds as phthalates, bisphenol A and boron that are present in a large number of industrial and consumer products entails a risk remains to be established. The same applies to psychosocial stressors and use of mobile phones. Finally, there are data indicating a particular vulnerability of the fetal testis to toxicants-for instance maternal tobacco smoking. Time has come where male reproductive toxicity should be addressed form entirely new angles including exposures very early in life.

Low blood lead concentration in association with infertility in women

This study investigated the relationship between low-level lead exposure and risk of infertility in women. Study participants consisted of 64 cases recruited at a private infertility clinic and 83 control women from the postpartum clinic unit at a medical center in Kaohsiung, Taiwan. With informed consent, venous blood samples were obtained from subjects, during their early follicular phases (the 1st to 5th days of the menstrual cycle), for measuring concentrations of lead and hormones. Information on other potential risk factors associated with infertility, including reproductive history, Chinese herbal Medicine use, dairy product consumption, residential environment, and sociodemographic status, was obtained during an in-person interview. The mean blood lead level (BLL) in infertile women was significantly higher than that in controls (3.55 vs 2.78 microg/dL, P=0.007). Compared to women with BLL < or = 2.5 microg/dL, women with BLL>2.5 microg/dL were associated with a threefold increased risk for infertility (adjusted odds ratio=2.94, 95% confidence interval 1.18-7.34), after controlling for age, body mass index, smoking, Chinese herbal Medicine use, and irregular menstruation. Women's BLL was a significant predictor of the serum estradiol concentration also. These findings suggest an important role of very low BLL in the risk of infertility in women.

Carbaryl inhibits basal and FSH-induced progesterone biosynthesis of primary human granulosa-lutein cells

Carbaryl is known to impede female reproductive function, however, the mechanisms through which the adverse effects are mediated are not clearly elucidated. In order to get insight into the mechanisms, this study was conducted to raise fresh concerns about the potential effects of carbaryl on steroidogenesis by primary human granulosa-lutein cells (hGLCs) and explore the possible nature of this action. hGLCs were co-incubated with various concentrations of carbaryl at 0, 1, 5, 25, 125 micromol/L for 24 h to examine effects of this carbamate pesticide on progesterone accumulation. We observed that the carbaryl inhibited basal and FSH-induced progesterone production in a dose-dependent manner. We also investigated the effects of carbaryl on 22(R)-hydroxycholesterol (22R-HC)-stimulated progesterone yield, basal and FSH-stimulated StAR gene expression and cyclic adenosine monophosphate (cAMP) production, as well as forskolin (non-specific activator of adenylyl cyclase)-induced progesterone and cAMP production of hGLCs. We found that the decreased progesterone biosynthesis was accompanied with a reduced cAMP abundance on both basal and FSH-induced condition. Furthermore, our results demonstrated that the 22R-HC could remove the carbaryl-induced restraint of progesterone biosynthesis, suggesting that carbaryl caused a disruption of cholesterol transport across mitochondrial membranes, which was further confirmed by the observation that carbaryl inhibited the gene expression of steroidogenic acute regulatory protein (StAR). In addition, the inhibitory effects of carbaryl on progesterone and cAMP production were completely reversed by addition of forskolin to the cell culture, which indicated a repaired site on the upstream components of adenylate cyclase or adenylate cyclase per se by carbaryl in the cAMP-mediated signal pathway. All the effects mentioned above were not due to a detrimental action of carbaryl on cell viability by MTS assay. In conclusion, carbaryl may inhibit steroidogenesis, at least in part, by obstructing the delivery of cholesterol over mitochondrial membranes and attenuating cAMP generation.

Reproductive toxicology in occupational settings: an update

OBJECTIVE

This article mainly attempts to review the recent human literature on the adverse effects of occupational factors on fertility, developmental effects and genetic changes in the germ line, which lead to genetic malformations or to genetic disease. The secondary study aim is to answer whether occupational exposures are quantitative momentously for 15% involuntarily childless couples, 10-20% spontaneous abortions and 3% birth defects.

METHODS

A literature survey was conducted for publications on these subjects focusing on the latest publications. PubMed (Medline. 2005) was used for this literature search.

RESULTS

Publication bias and a large amount of confounding factors, which have to be controlled, make the design of human fertility studies difficult. Epidemiologic studies using time to conception techniques have been useful in identifying substances and exposure scenarios with proven toxic effect on fertility. The collected studies suggest that the exposure to the following substances or occupational settings may affect fertility function: lead, organic mercury compounds, manganese, carbon disulfide, 2-bromopropane and dibromochloropropane, welding, professional driving and working with heat. Concerning developmental effects even for methyl mercury, which was in group A of the German MAK list, to date no reliable evidence of the damaging effect on the human fetus under actual work conditions has been obtained. It is also difficult to classify substances according to their mutagenic potential for the germ cell, since no direct evidence of an association between exposure against a physical or chemical pollutant and the occurrence of a hereditary disorder has been found yet.

CONCLUSION

In conclusion there are only a few substances which may affect reproductive function in the workplace without a doubt. The decreasing fertility of women in Western countries can be explained by the increasing female reproduction age, rather than by occupational exposures. Also the rates for spontaneous abortions and birth defects cannot be explained by industrial exposures at the workplace.

Environmental and occupational factors affecting fertility and IVF success

Reproductive function has been shown to be sensitive to changes in the physical, psychosocial and chemical environments. Although reproductive effects of occupational exposure to hazardous chemicals have been well documented in the literature, the potential effects of chemical contaminants at levels representative of contemporary exposures in the general population are much less certain. Evidence for adverse effects of exposure to environmental contaminants is more conclusive among the lower animals than for humans where considerable controversy remains. In addition to potential reproductive hazards of exposure to environmental contaminants, there is also evidence for adverse reproductive effects of the physical and psychosocial environments. In this review we focus on the difficulties involved in linking exposure to putative hazardous substances in environmental and occupational settings to adverse reproductive outcomes, especially success of IVF procedures. We highlight the plausibility of adverse events through animal and cell studies and the application of these results to the interpretation of human data. We consider both the male and female partners since it is essentially their combined contributions of gametes which may be affected by chemicals, which lead to successful outcomes.

Genotoxic Effects on Spermatozoa of Carbaryl-Exposed Workers

Carbaryl, one of the most important insecticides, is widely produced and used. To explore carbaryl-induced genotoxic effects of spermatozoa, particularly DNA damage and chromosome aberrations (CA), we first examined conventional semen parameters, the progression and motion parameters of the spermatozoa among 16 carbaryl-exposed workers and 30 internal and external control individuals. Sperm DNA damage represented as positive percentage of DNA fragmentation was detected by a modified terminal deoxy-nucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) assay. Then numerical CA of chromosome X, Y, and 18 were investigated by multicolor fluorescence in situ hybridization (FISH). The results showed significant differences in the percentage of sperm abnormality between carbaryl-exposed group and the external control group (p = 0.008). Mean (+/-SD) percentage of spermatozoa with fragmented DNA in carbaryl-exposed group (21.04 +/- 8.88%) was significantly higher than those in the internal (13.36 +/- 12.17%) and external control groups (13.92 +/- 7.15%), respectively (p = 0.035 and p = 0.030). Using FISH, we observed the frequency of sperm sex chromosome disomy was 0.661 +/- 0.238% in the exposed group, which was significantly higher than that in the external control group (0.386 +/- 0.140%) (p = 0.001), and the carbaryl-exposed group (0.276 +/- 0.126%) had an elevated chromosome 18 disomy compared with the internal (0.195 +/- 0.094%) and external control groups (0.124 +/- 0.068%), respectively (p < 0.05 and p < 0.01). In addition, carbaryl-exposed donors had significantly higher sperm nullisomic frequencies of sex chromosomes and chromosome 18 than the external controls (p < 0.01) but not the internal controls. In summary, the frequencies of aneuploidy and numerical CA showed significant differences between exposed group and control groups (p < 0.05 and/or p < 0.01). Moreover, positive correlations were found between sex chromosome disomy, aneuploidy rate, and morphologic abnormalities in spermatozoa of all donors (r = 0.564 and r = 0.555, p < 0.01). Our findings suggested that carbaryl might induce morphologic abnormalities and genotoxic defects of spermatozoa among exposed workers by causing DNA fragmentation and numerical CA in spermatogenesis as a potential genotoxicant. The evidence also indicated that the spermatotoxicity induced by carbaryl exposure might be related to adverse reproductive outcomes.

Occupational reproductive hazards

Although the causes of many reproductive disorders remain unknown, scientific evidence is accumulating to implicate occupational agents in fertility disorders and adverse pregnancy outcomes. Effective assessment and management of workers exposed to reproductive hazards often involves a team-based approach. By identifying potential reproductive hazards, making appropriate referrals, and by educating and advocating for patients, clinicians can play an important part in safeguarding the reproductive health of workers.

A comparative study of chemically induced DNA damage in isolated human and rat testicular cells

Testicular cells prepared from human organ transplant donors or from Wistar rats were used to compare 15 known reproductive toxicants with respect to their ability to induce DNA damage, measured as single-strand DNA breaks and alkali labile sites (ssDNA breaks) with alkaline filter elution. The compounds tested included various categories of chemicals (i.e., pesticides, industrial chemicals, cytostatics, and mycotoxins) most of which are directly acting genotoxicants (i.e., reacting with DNA either spontaneously or via metabolic activation). In addition, a few indirect genotoxic and nongenotoxic reproductive toxicants were included. Six of the chemicals induced no significant levels of ssDNA breaks in human and rat testicular cells; methoxychlor (10 to 100 microM, human and rat), benomyl (10 to 100 microM, human and rat), thiotepa (10 to 1000 microM, human and rat), cisplatin (30 to 1000 microM, human; 100 to 1000 microM, rat), Cd2+ (30 to 1000 microM, human; 100 to 1000 microM, rat), and acrylonitrile (30 to 1000 microM, human; 30 to 300 microM, rat). Four chemicals induced significant levels of ssDNA breaks in testicular cells from both species: styrene oxide (> or = 100 microM, rat and human), 1,2-dibromoethane (EDB) (> or = 100 microM, rat; 1000 microM human), thiram (> or = 30 microM, rat; > or = 100 microM, human), and chlordecone (300 microM, rat; > or = 300 microM, human). Finally, five chemicals induced ssDNA breaks in one of the two species. Four chemicals induced significant ssDNA breaks in rat testicular cells only: 1,2-dibromo-3-chloropropane (DBCP) (> or = 10 microM), 1,3-dinitrobenzene (1,3-DNB) (> or = 300 microM), Cr6+ (1000 microM), and aflatoxin B1 (> or = 100 microM), the last two of these produced only a minor positive response. One chemical, acrylamide, induced a marginal increase in ssDNA breaks in human at 1000 microM, but not in rat testicular cells. Although based on a limited number of donors, the data indicate a close correlation between the induction of DNA damage in human and rat testicular cells in vitro. For some chemicals, however, there appears to be differences in the susceptibility to chemically induced ssDNA breaks of isolated testicular cells from the two species. The data indicate that the parallel use of human and rat testicular cells provides a valuable tool in the assessment of human testicular toxicity.

Spontaneous Abortions of Known Karyotype Related to Occupational and Environmental Factors: A Case-Referent Study

The aim of the study was to examine the roles of occupational and environmental factors in relation to spontaneous abortions with known karyotypes. A case-referent study was performed among 793 women hospitalized for spontaneous abortion and 808 referents attending ultrasound screening at 17-18 weeks of pregnancy. Chromosomal analysis were obtained for 371 abortuses and 679 referent newborns. Significantly elevated odds ratios (ORs) for abortions with abnormal chromosomes were found for maternal psychological strain at work (OR:1.8), exposure to anesthetic gases (OR:6.9), video display unit work >/= 1/2 working day (OR:1.9), and sales work (OR:2.0). An association with paternal security work (OR:3.0) was possibly confounded by maternal exposure to psychological strain. Abortuses with normal chromosomes were associated with maternal sales work (OR:1.9) and psychological (OR:2.3) and physical (OR:1.6) strain at home, and with paternal construction work (OR:2.1) and physical strain at home (OR:1.9). No relationship between air pollution and spontaneous abortion was observed regardless of karyotype.

Occupational hazards for the male reproductive system

The etiology of male infertilities is largely undetermined, and our knowledge of exogenous factors affecting the male reproductive system is still limited. In particular, the role of specific environmental and occupational factors is incompletely elucidated. Various occupational (physical and chemical) agents have been shown to affect male reproductive functions in animals, but large differences in reproductive function and/or xenobiotic handling between species limit extrapolation to humans. When available, human data are often conflicting and, except in a few instances, usually refer to broad and heterogenous occupational categories or to groups of agents (e.g., solvents). It is often difficult to elucidate the role of a single agent because occupational exposure conditions are often complex and various confounding factors related to lifestyle (smoking, alcohol, and diet) or socioeconomic state may also affect sperm quality, fertility, or pregnancy outcomes. The objective of this work is to summarize the main epidemiological and, where relevant, experimental findings pertaining to agents (physical and chemical) encountered in the occupational environment that might affect the male reproductive system (sperm count, motility and morphology, libido, and fertility) and/or related pregnancy outcomes (spontaneous abortion, stillbirth, low birth weight, and birth defects and childhood malignancy in offspring). Some methodological issues related to research on the reproductive effects of toxicants are also discussed briefly.

Environmental effects on human reproduction: the basis for new efforts in eastern Europe

Increasing data are becoming available to implicate toxic environmental effects on the reproductive process in animals and man. Political changes in Central and Eastern Europe have provided new opportunities to study reproductive health in an area where environmental effects may be marked. Eastern European health has been affected by environmental transgressions, but other factors, including life style, have played a role in recent changes in life expectancy in the region. While a few programs worldwide are actively pursuing the implications of environmental toxins on reproduction, human data remain sparse. Further research in this field on a global basis is needed. A new center in Copenhagen has begun to pursue such activities, additionally supported by wider World Health Organization (WHO) programs to promote greater communication between eastern and western scientists working in reproductive health.

Acute cadmium exposure and ovarian steroidogenesis in cycling and pregnant rats

The purpose of this study was to evaluate the effect(s) of acute in vivo cadmium (Cd) exposure on steroidogenesis in rat ovaries during different reproductive states. Sprague-Dawley rats were injected subcutaneously on the day of diestrus, or on day 7 or 16 of gestation with a single dose of 0, 3, or 5 mg Cd/kg bw, and evaluated 24 h later. Serum progesterone and estradiol concentrations were determined. Whole-ovary culture was used to evaluate Cd effects on the production of progesterone, testosterone, and estradiol. Liver, kidney, spleen, ovary, placenta, and blood were analyzed for Cd and iron (Fe) concentrations. No general toxic effects, no disruption of estrous cyclicity, and no change in fetal viability were seen. Histologic evaluation revealed moderate Cd-related thecal congestion in ovaries of pregnant rats. The highest Cd concentrations, except for liver, were found in the fetal portion of the placenta. Interestingly, Cd-related decreases in Fe concentration were found in several tissues from rats in proestrus and on gestation day 8, and in fetal placenta from rats on gestation day 17. Cadmium appears to interfere with normal steroidogenesis at a number of sites in the biosynthetic pathway with serum estradiol concentration and ovarian estradiol production the most affected. Acute Cd effects on steroidogenesis are most severe in rats evaluated in proestrus or in early pregnancy, while in late pregnancy steroidogenesis is relatively unaffected.