Toxicity of microplastics and nanoplastics: invisible killers of female fertility and offspring health

The effects of exposure to microplastics on female reproductive health and pregnancy outcomes: A systematic review and meta-analysis

Microplastic pollution is one of the most important challenges to public health. The current study aimed to assess the impact of microplastic accumulation on female reproductive health and pregnancy outcomes. A comprehensive search was conducted in databases, including ISI Web of Science, PubMed, Scopus, and Google Scholar, to evaluate the effects of microplastic contamination on reproductive health and fetal outcomes. Thirteen studies met our criteria. Microplastic pollution was found in samples of placenta, meconium, amniotic fluid, and feces. In total, 10 polymers were identified, among which polystyrene, polyurethane, and polyamide polymers were the most abundant. The average size of the microplastics was 2.1-100 micrometers. The contamination rate with microplastics was measured at about an event rate of 87 % (95 % CI: 80.0-91.2). It was found that microplastic content in human reproductive tissue has nothing to do with the mode of delivery. Also, the results showed that consuming food in plastic containers increased the chance of contamination with microplastics in pregnant women (95 % CI: 1.32-21.9; OR: 5.39). The clinical elevation of microplastic accumulation with adverse pregnancy outcomes has shown a significant correlation between microplastic content in the placenta and gestational age (95 % CI: 0.03-0.22; OR: 0.89). In addition, microplastic pollution in the placenta significantly increases the risk of intrauterine growth restriction (IUGR) (95 % CI: 2.07-8.06; OR: 5.06). Microplastics may be a risk factor that contributes to human reproductive health issues and pregnancy-related outcomes; further large-scale investigations are needed to confirm the current findings.

Polystyrene nanoplastics chronic exposure cause zebrafish visual neurobehavior toxicity through TGFβ-crystallin axis

The ubiquitous presence of micro-and nanoplastics (MNPs) in the environment and everyday products has attracted global attention for their hazardous risks. However, the effects and underling mechanisms of MNPs chronic exposure on behavioral/visual changes of the adult and offspring remain unclear. The present study investigated the impact of polystyrene (PS) nanoplastics of 80, 200 and 500 nm diameters on zebrafish visual behaviors at an environmentally relevant concentration of 0.1 mg/L. Exposure to PS resulted in zebrafish hyperactivity, enhanced aggression, compacted shoaling and less sociability, and especially suppressed the adult optokinetic response (OKR) and offspring larval phototactic behavior, with the 500 nm PS being the most detrimental. Histopathological analysis showed 500 nm PS caused significant structural damage to the retina's pigment epithelium (RPE), photoreceptor cells (PRC), and crystalline lens. Fluorescence observation found PS accumulation in retinal layers correlated with reduced oligodendrocyte transcription factor 2 (Olig2) in optic nerve. Further transcriptomic analysis of the adult eye tissue revealed that 500 nm PS affected the transforming growth factor β (TGFβ) and phototransduction signaling pathways, dysregulated visual perception and lens development, potentially leading to dysopia in zebrafish. Specifically, TGFβ and its regulated-extracellular matrix/inflammatory factors and crystallin genes were increased, but the visual perception genes were decreased, suggesting the TGFβ-crystallin axis disorders contribute to the eye dysfunction induced by PS exposure. Collectively, our results provide new evidence revealing the molecular mechanisms of PS-induced visual toxicity and neurobehavioral changes highlighting that MNPs may pose a risk to vision health.

Implications of plastic-derived endocrine disruptors on human health

Endocrine-disrupting chemicals (EDCs), such as bisphenol A (BPA), bisphenol S (BPS), phthalates, and micro- and nanoplastics, present substantial environmental and health hazards because of their potential to disrupt hormonal systems. Micro- and nanoplastics can release EDCs that disrupt reproductive and developmental processes, potentially affecting future generations. BPA, a common plasticizer and resin component, mimics estrogen and disrupts thyroid hormone metabolism, contributing to obesity, diabetes, and cardiovascular issues. BPS, a BPA substitute, exhibits similar endocrine-disrupting properties and persists longer in the environment. Phthalates, which are widely used as plasticizers, are associated with reproductive issues, metabolic conditions, and developmental issues in children. Combined exposure to multiple EDCs can amplify health risks, underscoring the need for further research on the synergistic impacts of these chemicals. This review underscores the urgent need for effective regulatory measures and further investigations into the health impacts of EDCs to mitigate their harmful impacts on the health of humans and the environment.

A case-control study on the link between trace element exposure in follicular fluid and premature ovarian insufficiency

Premature ovarian insufficiency (POI), affecting 3.5 % of women under 40, significantly impacts reproductive health. The unknown etiology in over 50 % of POI cases impedes accurate diagnosis and treatment. Evidence shows that environmental agents can adversely affect health and reduce fertility. Trace elements are critical pollutants impacting human health. However, research on populations with POI and their links to these elements is limited. We enrolled 367 female patients, dividing them into a POI group and a control group. We employed ICP-MS to measure 25 trace elements in follicular fluid. Bayesian kernel machine regression analyzed combined exposure effects and restricted cubic splines evaluated the relationships between individual trace elements and ovarian reserve markers, focusing on anti-Müllerian hormone (AMH) and basal FSH (bFSH). Logistic regression assessed the association between specific element concentrations and POI occurrence, and the posterior inclusion probability model tested the robustness of key driving factors. The study identified 24 trace elements in follicular fluid samples, revealing significant differences in 23 elements between the two groups. There were positive correlations between Cu, I, Se, and Zn with AMH levels, while negative correlations were observed for Ca, Co, Li, and AMH. Nonlinear relationships were noted for Ba, Cd, Fe, Mg, Mn, Mo, and Pb. Ca, Li, and Ni showed a significant positive correlation with bFSH, while Cu, I, Mg, Se, and Zn demonstrated a significant negative correlation with bFSH. Additionally, Ba, Mn, and Pb exhibited a nonlinear correlation with bFSH. Individuals in the medium and high tertiles for Cu, I, Pb, Se, and Zn were less likely to develop POI. In contrast, those in the medium and high tertiles for Ba, Ca, Cd, Li, Mn, and Ni had an increased likelihood of POI. Our study addresses a crucial gap by examining trace element exposure in follicular fluid and its link to POI risk, enhancing understanding of their effects on female ovarian function. This study lays a foundation for monitoring female fertility and emphasizes the importance of environmental pollutants on reproductive health.

Micro- and Nanoplastics and Fetal Health: Challenges in Assessment and Evidence from Epidemiological Studies

The usage of plastics in life and industrial applications has led to global environmental pollution by micro- and nanoplastics (MPs/NPs). Despite their widespread occurrence in the environment, little is known about their presence in humans and the potential implications for human health, particularly maternal and fetal health during the prenatal and neonatal periods. Studies on experimental animals indicate that exposure to MPs/NPs can lead to neurological abnormalities in offspring and hemodynamic alterations in the placenta and fetal cerebral arteries. These findings underscore the need for further epidemiological studies that examine the effects of MPs/NPs on fetal health during pregnancy, a critical period for neurological development. This review summarizes the existing knowledge on the effects of prenatal exposure to MPs/NPs on fetal development and birth outcomes in humans and provides a detailed overview of the challenges encountered in contamination prevention, quality assurance and quality control in analytical procedures. It also discusses the sampling and digestion methods used for the extraction of MPs/NPs from biological samples of maternal and fetal origin, highlighting the difficulties associated with accurately quantifying these particles in complex biological matrices, identifying the gaps in current research, and suggesting recommendations to improve methodologies for assessing the risks associated with prenatal MP/NP exposure.

Low-dose exposure to microplastics retards meiotic maturation via HDAC3 insufficiency

Microplastics (MPs) are considered one of the main causes of male and female infertility. However, the reproductive toxicity and its related mechanisms are currently understood primarily through animal models with acute exposure to MPs. In this study, we demonstrate that low-dose exposure to polystyrene microplastics (PSMPs) leads to severely abnormal reproduction in females, manifested by oocyte meiotic maturation defect. Mechanistically, PSMPs exposure induce the overactivation of cell metabolism pathways, insufficient HDACs, and H4K16 hyperacetylation in oocytes both in vivo and in vitro. When an HDAC3 inhibitor is added, the oocyte maturation defect, overactivation of cell metabolism pathways, and H4K16 hyperacetylation are recapitulated. Conversely, the overexpression of HDAC3 can rescue the defects in meiotic maturation induced by PSMPs. Our observations suggest a direct link between the maturation defects caused by PSMPs and HDAC3 insufficiency. Thus, we propose potential treatments to address the meiotic maturation defect of oocytes in women highly exposed to MPs by activating or supplying HDAC3.

Environmental Concentrations of Polystyrene Nanoplastics Induce Low-Dose Tamoxifen Toxicity Through Oxidative Stress in Caenorhabditis elegans

In recent years, significant focus has been placed on the negative impacts of nanoplastics on living organisms. However, nanoplastics at environmental concentrations may interact with drugs, leading to more severe side effects in organisms. This study used Caenorhabditis elegans (C. elegans) to investigate how environmental levels (μg/L) of polystyrene nanoparticles (PS-NPs) influence tamoxifen toxicity and its mechanisms. Combined exposure to tamoxifen and PS-NPs significantly impaired locomotion, pumping, brood size, growth, and induced oxidative stress in both parents and offspring compared to single exposures. DAF-2 mutations conferred resistance, while DAF-16 mutations increased susceptibility. The combined exposure promoted DAF-16::GFP nuclear translocation and decreased SOD-3::GFP and HSP-16.2::GFP fluorescence, indicating toxicity through the DAF-2/DAF-16 IIS pathway. Bacterial metabolism was also linked to the toxic effects, feeding C. elegans metabolically inactivated OP50 significantly reduced the toxicity associated with the combined exposure of PS-NPs and tamoxifen. Additionally, dietary N-acetyl-L-cysteine significantly improved resistance to combined PS-NP and tamoxifen exposure. In summary, this study highlights how long-term exposure to environmental nanoplastic levels can enhance drug side effects, providing new insights into nanoplastics' role in drug interactions.

First evidence of microplastics in human ovarian follicular fluid: An emerging threat to female fertility

Several studies have assessed the presence of microplastics (MPs) in human biological fluids and tissues highlighting potential health risks associated to oxidative stress, inflammation, immune dysfunction, neurotoxicity and reprotoxicity. However, only few studies have evaluated MP presence and effects in ovarian tissues of mammalians and, to date, no studies have detected MPs in human ovarian follicular fluids. Based on these premises, in this study, 18 women (undergoing assisted reproductive treatment at In Vitro Fertilisation center in Salerno, Southern Italy) were selected to assess the presence of MPs in follicular fluid. Plastic particles < 10 µm were measured using Scanning Electron Microscopy (SEM) coupled with an EDX (X Energy Dispersion) detector. MPs (size <10 µm) were detected in 14 out of 18 samples of follicular fluid, with an average concentration of 2191 particles/mL (0-7181particles/mL) and with a mean diameter of 4.48 µm (3.18-5.54 µm). Moreover, a significant correlation between MP concentration in follicular fluid samples and Follicle-Stimulating Hormone (FSH) (p-value <0.05), as well as a weak (non-significant) correlation with Body Mass Index (BMI), age and 17β-estradiol (E2), was found. On the contrary, no correlation with anti-Müllerian Hormone (AMH), fertilization outcomes, miscarriages, or live birth was observed. Since several studies on animal models have demonstrated the negative effects of MPs on ovarian function, the present study, that verified for the first time the presence of MPs in human follicular fluid, is of great significance for the scientific community in terms of raising awareness of the impact that these increasingly pervasive emerging contaminants have on reproductive function and human health.

Polystyrene microplastics exposition on human placental explants induces time-dependent cytotoxicity, oxidative stress and metabolic alterations

Introduction

Microplastics (MPs) are environmental pollutants that pose potential risks to living organisms. MPs have been shown to accumulate in human organs, including the placenta. In this study, we investigated the biochemical impact of 5 μm polystyrene microplastics (PS-MPs) on term placental chorionic villi explants, focusing on cytotoxicity, oxidative stress, metabolic changes, and the potential for MPs to cross the placental barrier.

Methods

Term placental chorionic explants were cultured for 24 hours with varying concentrations of PS-MPs, with MTT assays used to determine the appropriate concentration for further analysis. Cytotoxicity was assessed using the lactate dehydrogenase (LDH) release assay over a period of up to 72 hours. Reactive oxygen species formation and antioxidant activity were evaluated using biochemical assays. Metabolomic profiling was performed using proton nuclear magnetic resonance (1H NMR).

Results

Placental explants exposed to 100 μg/mL of PS-MPs showed a significant increase in cytotoxicity over time (p < 0.01). Levels of mitochondrial and total superoxide anion (p < 0.01 and p < 0.05, respectively) and hydrogen peroxide (p < 0.001) were significantly elevated. PS-MP exposure resulted in a reduction in total sulfhydryl content (p < 0.05) and the activities of antioxidant enzymes superoxide dismutase (p < 0.01) and catalase (p < 0.05), while glutathione peroxidase activity increased (p < 0.05), and the oxidized/reduced glutathione ratio decreased (p < 0.05). Markers of oxidative damage, such as malondialdehyde and carbonylated proteins, also increased significantly (p < 0.001 and p < 0.01, respectively), confirming oxidative stress. Metabolomic analysis revealed significant differences between control and PS-MP-exposed groups, with reduced levels of alanine, formate, glutaric acid, and maltotriose after PS-MP exposure.

Discussion

This study demonstrates that high concentrations of PS-MPs induce time-dependent cytotoxicity, oxidative stress, and alterations in the TCA cycle, as well as in folate, amino acid, and energy metabolism. These findings highlight the need for further research to clarify the full impact of MP contamination on pregnancy and its implications for future generations.

Concerning influences of micro/nano plastics on female reproductive health: focusing on cellular and molecular pathways from animal models to human studies

The female reproductive system can face serious disorders and show reproductive abnormalities under the influence of environmental pollutants. Microplastics (MPs) and nanoplastics (NPs) as emerging pollutants, by affecting different components of this system, may make female fertility a serious challenge. Animal studies have demonstrated that exposure to these substances weakens the function of ovaries and causes a decrease in ovarian reserve capacity. Also, continuous exposure to micro/nano plastics (MNPs) leads to increased levels of reactive oxygen species, induction of oxidative stress, inflammatory responses, apoptosis of granulosa cells, and reduction of the number of ovarian follicles. Furthermore, by interfering with the hypothalamic-pituitary-ovarian axis, these particles disturb the normal levels of ovarian androgens and endocrine balance and delay the growth of gonads. Exposure to MNPs can accelerate carcinogenesis in the female reproductive system in humans and animal models. Animal studies have determined that these particles can accumulate in the placenta, causing metabolic changes, disrupting the development of the fetus, and endangering the health of future generations. In humans, the presence of micro/nanoplastics in placenta tissue, infant feces, and breast milk has been reported. These particles can directly affect the health of the mother and fetus, increasing the risk of premature birth and other pregnancy complications. This review aims to outline the hazardous effects of micro/nano plastics on female reproductive health and fetal growth and discuss the results of animal experiments and human research focusing on cellular and molecular pathways.

Molecular and Cellular Effects of Microplastics and Nanoplastics: Focus on Inflammation and Senescence

Microplastics and nanoplastics (MNPs) are ubiquitous environmental contaminants. Their prevalence, persistence, and increasing industrial production have led to questions about their long-term impact on human and animal health. This narrative review describes the effects of MNPs on oxidative stress, inflammation, and aging. Exposure to MNPs leads to increased production of reactive oxygen species (ROS) across multiple experimental models, including cell lines, organoids, and animal systems. ROS can cause damage to cellular macromolecules such as DNA, proteins, and lipids. Direct interaction between MNPs and immune cells or an indirect result of oxidative stress-mediated cellular damage may lead to increased production of pro-inflammatory cytokines throughout different MNP-exposure conditions. This inflammatory response is a common feature in the pathogenesis of neurodegenerative, cardiovascular, and other age-related diseases. MNPs also act as cell senescence inducers by promoting mitochondrial dysfunction, impairing autophagy, and activating DNA damage responses, exacerbating cellular aging altogether. Increased senescence of reproductive cells and transfer of MNPs/induced damages from parents to offspring in animals further corroborates the transgenerational health risks of the tiny particles. This review aims to provoke a deeper investigation into the notorious effects these pervasive particles may have on human well-being and longevity.

Role of Humic Substances in the (Bio)Degradation of Synthetic Polymers under Environmental Conditions

Information on the detection of the presence and potential for degradation of synthetic polymers (SPs) under various environmental conditions is of increasing interest and concern to a wide range of specialists. At this stage, there is a need to understand the relationship between the main participants in the processes of (bio)degradation of SPs in various ecosystems (reservoirs with fresh and sea water, soils, etc.), namely the polymers themselves, the cells of microorganisms (MOs) participating in their degradation, and humic substances (HSs). HSs constitute a macrocomponent of natural non-living organic matter of aquatic and soil ecosystems, formed and transformed in the processes of mineralization of bio-organic substances in environmental conditions. Analysis of the main mechanisms of their influence on each other and the effects produced that accelerate or inhibit polymer degradation can create the basis for scientifically based approaches to the most effective solution to the problem of degradation of SPs, including in the form of microplastics. This review is aimed at comparing various aspects of interactions of SPs, MOs, and HSs in laboratory experiments (in vitro) and environmental investigations (in situ) aimed at the biodegradation of polymers, as well as pollutants (antibiotics and pesticides) that they absorb. Comparative calculations of the degradation velocity of different SPs in different environments are presented. A special place in the analysis is given to the elemental chemical composition of HSs, which are most successfully involved in the biodegradation of SPs. In addition, the role of photo-oxidation and photoaging of polymers under the influence of the ultraviolet spectrum of solar radiation under environmental conditions on the (bio)degradation of SPs in the presence of HSs is discussed.

[Climate and environmental crisis impacts on women's health: What specificities? What can be done?]

OBJECTIVE

Pollution is one of the world's largest risk factors for disease and premature death. In Europe, it is responsible for approximately 20% of mortality. Chemicals exposure can occur by inhalation, ingestion or skin contact and begins in utero. Pollutants can be divided into three categories: endocrine disruptors (pesticides, PFAS, plastics, dioxins, etc.), heavy metals (cadmium, mercury and lead…) and nanomaterials. Climate change and air pollution are other main health threats.

METHODS

Literature review using PubMed and ResearchGate databases and institutional websites.

RESULTS

Endocrine disruptors are identified as significant risk factors for the reproductive health with negative documented impacts following prenatal or adult exposure. Climate change and air pollution can cause gender-based health disparities. Numerous scientific arguments show that chemical pollution and climate change disproportionately impact women, both on a social and biological level. Populations in precarious situations among which women are over-represented suffer the most severe social consequences including in France. There are several gender-specific domestic or occupational exposures to pollutants, most often to the disadvantage of women compared to men. Finally, although very few gendered data exist in environmental health, there are sexual-based physiological vulnerabilities concerning the metabolism of pollutants and the capacity to adapt to heat.

CONCLUSION

Facing this threat of gender inequity in sexual and reproductive health and rights' width, women's health professionals have a major role to play in initiating new ways to assess and reduce the environmental health burden in women.

Nanoplastic at environmentally relevant concentrations induces toxicity across multiple generations associated with inhibition in germline G protein-coupled receptor CED-1 in Caenorhabditis elegans

Nanoplastics at environmentally relevant concentrations (ERCs) could cause transgenerational toxicity on organisms. Caenorhabditis elegans is an important model for the study of transgenerational toxicology of pollutants. Nevertheless, the underlying mechanisms for the control of transgenerational nanoplastic toxicity by germline signals remain largely unclear. In C. elegans, exposure to 1-100 μg/L polystyrene nanoparticle (PS-NP) decreased expression of germline ced-1 encoding a G protein-coupled receptor at parental generation (P0-G). After PS-NP exposure at P0-G, transgenerational decrease in germline ced-1 expression could be detected. Meanwhile, the susceptibility to transgenerational PS-NP toxicity was observed in ced-1(RNAi) animals. After PS-NP exposure at P0-G, germline RNAi of ced-1 increased expressions of met-2 and set-6 encoding histone methylation transferases. The susceptibility of ced-1(RNAi) to transgenerational PS-NP toxicity could be inhibited by RNAi of met-2 and set-6. Moreover, in PS-NP exposed met-2(RNAi) and set-6(RNAi) nematodes, expressions of ins-39, wrt-3, and/or efn-3 encoding secreted ligands were decreased. Therefore, our results demonstrated that inhibition in germline CED-1 mediated the toxicity induction of nanoplastics at ERCs across multiple generations in nematodes.

Plastic induced urinary tract disease and dysfunction: a scoping review

INTRODUCTION

In 2019 the World Health Organisation published a report which concluded microplastics in drinking water did not present a threat to human health. Since this time a plethora of research has emerged demonstrating the presence of plastic in various organ systems and their deleterious pathophysiological effects.

METHODS

A scoping review was undertaken in line with recommendations from the Johanna Briggs Institute. Five databases (PubMed, SCOPUS, CINAHL, Web of Science and EMBASE) were systematically searched in addition to a further grey literature search.

RESULTS

Eighteen articles were identified, six of which investigated and characterised the presence of microplastics and nanoplastics (MNPs) in the human urinary tract. Microplastics were found to be present in kidney, urine and bladder cancer samples. Twelve articles investigated the effect of MNPs on human cell lines associated with the human urinary tract. These articles suggest MNPs have a cytotoxic effect, increase inflammation, decrease cell viability and alter mitogen-activated protein kinases (MAPK) signalling pathways.

CONCLUSION

Given the reported presence MNPs in human tissues and organs, these plastics may have potential health implications in bladder disease and dysfunction. As a result, institutions such as the World Health Organisation need to urgently re-evaluate their position on the threat of microplastics to public health.

IMPACT STATEMENT

This scoping review highlights the rapidly emerging threat of microplastic contamination within the human urinary tract, challenging the World Health Organisation's assertion that microplastics pose no risk to public health. The documented cytotoxic effects of microplastics, alongside their ability to induce inflammation, reduce cell viability and disrupt signalling pathways, raise significant public health concerns relating to bladder cancer, chronic kidney disease, chronic urinary tract infections and incontinence. As a result, this study emphasises the pressing need for further research and policy development to address the challenges surrounding microplastic contamination.

Polystyrene nanoplastics induce apoptosis, autophagy, and steroidogenesis disruption in granulosa cells to reduce oocyte quality and fertility by inhibiting the PI3K/AKT pathway in female mice

BACKGROUND

Nanoplastics (NPs) are emerging pollutants that pose risks to living organisms. Recent findings have unveiled the reproductive harm caused by polystyrene nanoparticles (PS-NPs) in female animals, yet the intricate mechanism remains incompletely understood. Under this research, we investigated whether sustained exposure to PS-NPs at certain concentrations in vivo can enter oocytes through the zona pellucida or through other routes that affect female reproduction.

RESULTS

We show that PS-NPs disrupted ovarian functions and decreased oocyte quality, which may be a contributing factor to lower female fertility in mice. RNA sequencing of mouse ovaries illustrated that the PI3K-AKT signaling pathway emerged as the predominant environmental information processing pathway responding to PS-NPs. Western blotting results of ovaries in vivo and cells in vitro showed that PS-NPs deactivated PI3K-AKT signaling pathway by down-regulating the expression of PI3K and reducing AKT phosphorylation at the protein level, PI3K-AKT signaling pathway which was accompanied by the activation of autophagy and apoptosis and the disruption of steroidogenesis in granulosa cells. Since PS-NPs penetrate granulosa cells but not oocytes, we examined whether PS-NPs indirectly affect oocyte quality through granulosa cells using a granulosa cell-oocyte coculture system. Preincubation of granulosa cells with PS-NPs causes granulosa cell dysfunction, resulting in a decrease in the quality of the cocultured oocytes that can be reversed by the addition of 17β-estradiol.

CONCLUSIONS

This study provides findings on how PS-NPs impact ovarian function and include transcriptome sequencing analysis of ovarian tissue. The study demonstrates that PS-NPs impair oocyte quality by altering the functioning of ovarian granulosa cells. Therefore, it is necessary to focus on the research on the effects of PS-NPs on female reproduction and the related methods that may mitigate their toxicity.

Impact of Microplastics on Pregnancy and Fetal Development: A Systematic Review

Microplastic (MP) pollution is a growing global concern because of its potential to impair human health, particularly with regard to fetal development. However, the origins of prenatal MP exposure and its effects on fetal development have not been well studied. This study aimed to provide a systematic review of the literature regarding the impact of microplastics on pregnancy and fetal development. PubMed, Embase, ScienceDirect, Web of Science, Scopus, and Google Scholar were searched from 2010 until March 2024. Original publications exploring the impact of microplastics on pregnancy and fetal development were included in the study. After selecting papers, two independent reviewers extracted data regarding study characteristics, microplastics identified, and reproductive impacts. The quality of studies was assessed using the Critical Appraisal Checklists for Studies created by the Joanna Briggs Institute (JBI). Twelve studies, including 234 subjects, were selected from a total of 2,809 citations for the final qualitative analysis. Articles were published between 2021 and 2024, and most were conducted in China. The results of the included studies confirmed the existence of microplastics with varying sizes (2.1 to 100 micrometers) in the placenta and the fetal body. Studies revealed correlations between lifestyle choices and the presence of microplastics in the placenta. They also reported correlations between the level of microplastics and diminished microbiome diversity, reduced birthweights, affected gestational age, and fetal growth and development. Microplastics may be detrimental to a developing fetus during pregnancy. Nonetheless, more thorough research is required to comprehend the impact of microplastic exposure on pregnancy and fetal development.

What is driving the global decline of human fertility? Need for a multidisciplinary approach to the underlying mechanisms

An intense period of human population expansion over the past 250 years is about to cease. Total fertility rates are falling dramatically all over the world such that highly industrialized nations, including China and the tiger economies of SE Asia, will see their populations decline significantly in the coming decades. The socioeconomic, geopolitical and environmental ramifications of this change are considerable and invite a multidisciplinary consideration of the underlying mechanisms. In the short-term, socioeconomic factors, particularly urbanization and delayed childbearing are powerful drivers of reduced fertility. In parallel, lifestyle factors such as obesity and the presence of numerous reproductive toxicants in the environment, including air-borne pollutants, nanoplastics and electromagnetic radiation, are seriously compromising reproductive health. In the longer term, it is hypothesized that the reduction in family size that accompanies the demographic transition will decrease selection pressure on high fertility genes leading to a progressive loss of human fecundity. Paradoxically, the uptake of assisted reproductive technologies at scale, may also contribute to such fecundity loss by encouraging the retention of poor fertility genotypes within the population. Since the decline in fertility rate that accompanies the demographic transition appears to be ubiquitous, the public health implications for our species are potentially devastating.