Anasayfa » The Impact of Microplastics on Male Fertility
Global infertility is a common human reproductive health problem affecting approximately 15% of couples, and men are generally found to be infertile no less than women; they contribute to 50% of infertility problems, and it is estimated that poor semen quality and abnormal sperm functions account for 50% of these males. Spermatogenesis in the seminiferous tubules of testes involves series of mitosis and meiosis stages that produce haploid sperm, and it requires a strictly controlled intratubular environment. This environment is based on regular progression of the seminiferous epithelial cycle and highly regulated signaling relationship among different kinds of somatic cells and germ cells. Any abnormal change in this relationship may trigger infertility. Currently, reproductive disorders are also becoming more common, such as undescended testis, hypospadias, and declining semen quality. Many studies have legalized that the occurrence of these diseases is closely related to environmental disturbance during early embryo development. In environmental contaminants, plasticizers, bisphenol, dioxins, and trace metals may mimic endocrine hormones and interfere with the reproductive system through different pathways. As long-chain polymer chains begin to disintegrate, plastics are broken down from the original condition. The current plastic debris floating in the ocean is undergoing continuous photochemical degradation, leading to the generation of a wide variety of small, plastic-like debris called microplastics, which have particles smaller than 5 mm. Due to difficulties in cleaning, treatment, or exploitation, microplastics can distribute in the entire habitat. They may gather microbial communities, act as vectors to introduce diseases into organisms, deliver pollutants to deep subsurfaces, or settle in the air, even across the blood/membrane of the gastrointestinal system, skin, and placenta. Furthermore, microplastics may act like endocrine disruptors and provoke cellular response of human cells in vitro, such as MTT, LDH, caspase-3 activity, superoxide dismutase, and inflammatory signal transduction factors. However, a number of studies which utilized different doses of microplastics as a point of departure to manifest whether environmentally realistic levels can affect males have presented contradictory results. The inherent mechanism of microplastics in male reproductive health has not yet been thoroughly elucidated.
The widespread use of plastics has posed a threat to both the terrestrial and aquatic environment. Plastic pollution is not solely a hook or ingestion concern, and the research on microplastic toxicity focused on various kinds of animals, such as marine animals, fish, and oyster, and presented that microplastics could cause harmful effects on marine species. In recent years, small-size microplastics have been recognized as an important category due to its accessibility to the whole body through different ways. These microplastics may bind to algal cells and zooplankton organisms, and then migrate to higher trophic levels through food chains, causing ecological risks. Furthermore, the damages of marine species may affect human health by collecting marine species as food. However, in addition to poisoning, there is still a third concern about the reproductive toxicity of microplastics, but this aspect has not been intensified to develop in discussions. Concerns about male infertility are also increasing.
In view of the above facts, not much attention has been attracted by organisms in the marine ecosystem in which reproductive malfunctions occur due to the concentration effect of residual microplastics. Recently, some information has been documented regarding the effects of microplastics in terrestrial species. Accordingly, in the present study, the authors demonstrate the possible mode of action of microplastics in inflicting reproductive malfunction in six different ways. Through TAM and assays, it has been demonstrated that the testicular cells become weakened due to the chronic effects of microplastics.
Wide varieties of small plastic entities, ranging in size from a few nanometres to a few micrometres, are called microplastics. These stay for a longer duration in environments due to resistance against degradation and pollution. In the marine ecosystem, microplastics are efficiently bio-accumulated and/or bio-concentrated. Concentration of microplastics in the environment is found to be 10^5 units/m^2 and it may be adjudged to predict the potential risk due to the exposure in general. In a normal scenario, exposure to microplastics is found to be noxious in the dentature development of marine organisms.
In order to investigate the tissue depositions of micro- and nanoplastics, we generated a histological examination procedure and were able to show that microplastic particles were found in close contact with the development lines of the spermatozoa in testicular tissue. No nanoplastics were detected in sections according to the developed method of the nanoplastic visualization. However, undetectability of nanoplastics could potentially be explained by the use of very young boars in the previous study of histologic testicular samples. In the present study, infertile and fertile men tissues could contain potential plastic deposits. During our experiments, no nanoplastics were detected according to the hematoxylin and eosin histochemical staining. Our modified plastic decontamination procedure with subsequent standard phloxine-picroindigo staining was validated on samples confirmed to contain nanoplastics. Then, micro- and nanoplastics presence was further confirmed using attenuated total reflection-Fourier transform infrared spectroscopy.
In order to study the effects of micro- and nanoplastic particles on male fertility, we first examined human testicular tissue. An important part of the procedure was the special care we took during our studies, as the risk of contamination during histological procedures involving plastic materials is very high. The pictures shown in this article clearly demonstrate that in the histological sections of the testes, microplastics were found in close contact with sperm-forming cell lines. However, during our experiments, no nanoplastics were detected in sections according to the developed method of the modified hematoxylin and eosin staining. Since preparation of the testicular samples involved orchiectomy, the next phase of the study will involve studies of exfoliated sperm to increase data on nanoplastics and to investigate the interaction of micro- and nanoplastics with the spermatozoa.
Humans consume microplastics not only via a number of sources, including air, food, and water, but also from the widespread use of such materials as food packaging. These days, the human population is living in the so-called “Age of Plastics,” prompted by the wide use of these materials in our everyday lives. However, the rapid consumption, storage, production, and degradation of such non-biodegradable materials have demonstrated their potential adverse impact on human and environmental health. In particular, a substantial number of studies have reported the presence of microplastics in the human diet by investigating seafood and bottled water. Although microplastics have entered the human body and consequently increased their concentration in the human digestive tract, as well as potentially damaging the reproductive system and influencing human fertility, the insufficient research conducted so far serves as an obstacle to the establishment of a comprehensive evaluation of the risks associated with microplastics on the reproductive health of human beings.
Fertility depends on both male and female health status, although society has traditionally associated fertility problems exclusively with women. However, male fertility problems are increasing, largely due to environmental exposure to endocrine disruptors, known as the “environmental vulnerability of the male,” which is currently high and increasing. Various environmental sources of microplastics have been previously described. These include both terrestrial environments, such as wastewater treatment plants, terrestrial sediments, and soils, and freshwater and marine environments, such as surface waters, tap water, estuaries, and beaches, among others. In particular, marine organisms are under threat from bioaccumulation and biomagnification. Drinking water, bottled water, honey, table salt, sugar, mussels, and beer, among others, represent other sources of microplastics.
There is still no clear evidence on the concentration of microplastics in the environment in order to understand the health risks related to human exposure. Different studies have been conducted on the environmental sources of microplastics, including wastewater treatment plant effluents, marine environments, drinking water, bottled water, honey, table salt, sugar, mussels, beer, seafood, and tap water. These sources may end up in the human body through different exposure sources. Although the environmental sources of microplastics are already described in a previous study, in order to understand the human exposure sources of microplastics to include them in the risk assessment studies, the main environmental sources of microplastics are described in this study.
As the central organ of human life maintenance, the study of the testis and the mechanisms of testicular development are of great significance for reproduction and genetic physiology. Testicular development is associated with many genes, some of which are specific to sperm production and determine genetic degradation. Testis-expressed mutants reduce the rate of genetic mutations because mutations are produced by these mutations in the human germ line, research could provide relevant information. In our study, we studied the relationship between microplastic exposure and testis damage. The analysis of the gene expression patterns of the testis also suggested that the mechanism of testis damage might be associated with bulkier metabolic processes.
Microplastics have been detected in foods such as fish, mussels, honey, sugar cake, and table salt, among others. These reports indicated that the entry of microplastics into the human body was mostly through the consumption of food. Therefore, the existence of microplastics in the diet deserves special attention. In our study, exposure by the dietary path showed that diet was one of the most important sources of microplastics. The content and distribution of microplastics in body tissues were influenced by the fabric type of the gut, which was related to the dietary microplastic concentration. Based on the content of microplastics and the Pearson’s correlation analysis, it has been shown that the diet could facilitate the transfer of microplastics through the digestive system to other tissues of the body.
Global contamination of the environment with microplastics is alarming. Microplastics risk function disorders by microtrauma due to hard body structures in arthropods and worm type invertebrates, salinity adaptation or excretion, cell division and regeneration disorders, redox balance disturbance, reproduction and development failures in all organisms, especially fish, and DNA damage. Microplastics also cause oxidative stress, neurotoxicity, genotoxicity, and inflammation in aquatic organisms. They cause reproductive disturbances, cellular injuries, diseases, life cycle disruption, and behavioral and physiological disorders in humans through endocrine disruptions. The accumulation of microplastics in the liver, spleen, and kidneys was proven to cause inflammation and damage in these tissues. Chronic inflammation caused by the accumulation of microplastics in the liver can lead to hepatocellular carcinoma in humans. Microplastics also have effects on the microbiological structure of the soils. Increased microplastic content has increased the number of pathogenic bacteria and decreased the number of bacteria retaining carbon and nitrogen cycles and characteristics.
Plastics are inexpensive and durable, and they have important physical, chemical, and biological properties. Plastics, on the other hand, are a two-sided coin. Plastics pose a serious pollution problem on the planet, and they generate microplastics as an effect of being used in billions of ton quantities. Microplastics generated from road tires, industrial and domestic waste, synthetic textiles, and cosmetics are an essential part of municipal and industrial wastewaters entering the environmental system through wastewater treatment facilities and directly to surface water, affecting especially the aquatics. Chemicals used during the production process, plastic additives such as antioxidants, flame retardants, UV stabilizers, plasticizers, lubricants, fillers, or pigments with the aim of increasing the quality of the plastics used trigger side effects, especially affecting living organisms. The chemicals desorbed from the microplastics produced by these agents cause endocrine, metabolic, and oxidative stress with hormone-simulating effects.
There are few human studies, but in men seeking fertility treatment, especially counts of morphologically normal sperm, appear to be adversely affected. The number of live births in IVF treatment with a male infertility factor, according to the WHO definition, is inversely related to the concentration of microplastics negatively affecting total sperm motility. At this juncture, human data on the levels of exposure to microplastics are few but suggest that, at least in Denmark’s urban and suburban areas, it is widespread. Overall, it is important to understand the implications of microplastic exposure in humans as soon as possible in order to design better standards for use.
The impact of microplastics on male fertility is an area of growing concern. Plastics are known to contain multiple additives, some of which are potential endocrine disruptors. The data are sparse, but regarding the least studied nanoplastic, the finding is that they display endocrine disruption. Animal studies show that male reproductive organs are sensitive to microplastics exposure. Spermatogenesis appears to be particularly vulnerable to exposure to certain microplastics. For example, multiple in vitro studies have shown that some microplastics impair the ability of sperm to fertilize an egg. Thus, there is a consistent body of data demonstrating that microplastics can negatively impact spermatogenesis and sperm quality in humans.
With the exclusion of some specific causes that can be treated surgically, the previously identified cases or any form of male factor infertility without a specific etiology give the answer that male factors are responsible for one-third of the infertility cases. Although there are many methods available to increase the motility or concentration impairments of the sperm, the necessary result is often not obtained. If it is not achieved after a long period of treatment or follow-up, solutions such as artificial insemination and in vitro fertilization are suggested. If the sperm is not available for any reason, micro-injection techniques come into play. In this case, the treatment is getting more expensive and stressful and the likelihood of achieving widely expected success with such high financial and spiritual charge is getting significantly lower. In light of all these data, one can see how important a complete male examination is in case of infertility.
Whereas the factors of infertility, if any, are identified and removed in women through a detailed physical examination and laboratory tests, this is not entirely possible or sufficient in men. Male infertility diagnosis does not include any relevant physical examination nor is there a special test with predictive power. The key issue in the male infertility diagnosis is the analysis of the semen. The analysis of the male sperm is performed through semen. The basic principle of the semen analysis is to detect the cause of the infertility due to the examination of various parameters. If the results of the semen analysis are below the values specified in the World Health Organization (WHO) publications, then male infertility is to be taken into account.
Characteristics of infertility change within biological, medical, and social life. The definition of infertility is still a controversial issue. The couples of reproductive age are considered infertile after one year of regular unprotected intercourse failing to occur pregnancy. Not only female but also male factors have an important place in the etiology of infertility.
Infertility has harmful impacts on men and women and can be devastating for their life. After a long time and many efforts spent in vain on trying to have a baby, many couples’ hope is implanted in the solution that our high-performance and advanced healthcare system may provide to them. However, infertility treatments are expensive, time-consuming, and not always successful with significant psychological pressure. This, in turn, can result in relationship deterioration or even lead to the breakdown of relationships. Thus, infertility is not only a health issue but also a major socioeconomic problem.
The World Health Organization (WHO) has set the sperm count of normal semen quality as 20 million sperm per milliliter or more. Anything less than that means below-normal fertility, but it alone does not indicate infertility. If you have an abnormally low sperm count, you may be having a genetic problem. A 2010 study suggested that azoospermia factor microdeletions have an especially high frequency of association with very-severe oligospermia. In any case, despite the significant decline in the seminal characteristics of men in the last few decades, the WHO has yet to define a separate norm for the parameters of the seminal characteristics. The significant decline might have aroused social attention, but not the scientific. That, in turn, might be delaying the perpetuation of policy changes for the protection of human reproductive health.
According to the immigration department, there were 118 urologists registered in the Hong Kong Special Administrative Region in 2021. The urologist is a medical specialist who diagnoses and treats diseases of the male and female urinary-tract system and the male reproductive organs. Treatment options can include both noninvasive and surgical approaches. When assessing infertility, a urologist would perform an examination of the genital area and ask questions regarding pain, problems with sexual function, and blocks within the tract system. In the past, the urologist would also suggest a semen analysis. The sample for this semen analysis is typically collected through masturbation three days after the last ejaculation, but it might also be collected during intercourse using a special condom. The biomedical information that helps to assess sperm pathology would be morphology, vitality, progression, and concentration.
Education and public awareness on how microplastics affect ecosystems, human health, and radiation protection is necessary. Public educational campaigns would increase awareness and reduce environmental contamination. Using other options might decrease environmental contamination levels, such as washing food in biodegradable or aluminum foil instead of using plastic bags, or buying products in glass containers instead of plastic packaging, which not only reduces microplastic contamination levels, but also promotes the use of materials with a lower risk of adverse health effects. More research is needed to understand the molecular mechanisms of microplastic toxicity and the impact on the male reproductive system, and long-term studies are vital to assess the impact scaling up to human populations. Furthermore, the factors causing the deterioration components are related to aging, lifestyle, and environmental chemicals; these factors can influence microplastic pollution sources or formation in testicles, thereby causing human epididymal sperm permanent depleting syndromes. Given the potential health risks of microplastics, it is necessary to constantly monitor human exposure to microplastics.
Currently, there is no effective strategy to remove microplastics from water bodies, air, and soils before they reach the testicles. Therefore, reducing microplastic pollution in the environment is the most effective long-term solution to protect male fertility. Personal human behavior can contribute to this solution through the use of reusable plastic products, such as kitchenware, bags, and tableware, and by promoting the adoption of biodegradable materials and products. Implementation of sound environmental policies, such as the phasing out of microplastics in cosmetics, commercial products, and industrial production, also plays a fundamental role in reducing and preventing the effects of microplastic pollution on male fertility, among others. The most effective policy should encourage manufacturers to develop alternative materials that mimic the same properties of microplastics without impacting human health and the environment. In addition, existing wastewater treatment plants must be retrofitted or added with proper filtration materials or devices that can directly remove microplastics.
initiatives should be taken to minimize the level of microplastics in drinking water after sewage treatment. For instance, Granados, M. et.al propose photocatalysis as a way to remove contaminant microplastics from drinking water. More research should be performed on tap water for microplastics as this is one avenue that scientists have yet to study in-depth. Evidence suggests widespread ubiquity. Tap drinking water must continue being heavily monitored. Furthermore, the public has every right to be aware of its safety. Additionally, although large microplastics are removed from sewage treatment plants, it is possible for the shredded filaments to release what remains from their original segments resulting in unaccounted quantities of microplastics being reintroduced to the environment. It is imperative to conduct continuous monitoring in order to report on any updates related to water safety.
Companies manufacture several different types of in-home water filters that the consumers can install. These water filter systems perform well when removing large particles like sediment, hard water minerals and chlorine. Presently, few at-home carbon filters are available that decrease plastic microfiber break-off in the wash, and none of them are guaranteed to remove all risk. Many researchers agree that point-of-use in-home water treatment should be improved. To prevent microplastic pollution from tap water, the active removal of microscopic plastics from effluent discharges is an important measure. Several researchers recommend incorporating interception technologies into the sewage infrastructure, but there is room for improvement in chosen methods and understanding expects.
https://weillcornell.org/news/microplastics-in-testicles-may-play-a-role-in-male-infertility-study-suggests
https://www.medicalnewstoday.com/articles/microplastics-in-testicles-may-play-a-role-in-male-infertility-study-suggests
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7967748/