Bridging the Gap: How environmental exposures compromise male fertility and clinical Outlook

Graphical abstract

Highlights

• •Introduces the “male reproductive exposome” as a novel integrative framework.
• •Epigenetic inheritance as a key mechanism for paternal environmental legacy.
• •Defines specific life-course vulnerability windows from gestation to adulthood.
• •Identifies mixture toxicity as a central challenge for future risk assessment.

Abstract

The growing prevalence of male infertility has become a significant clinical and public health issue, with environmental exposures increasingly recognized as a major modifiable risk factor. This review synthesizes current evidence within the framework of the “male reproductive exposome”, linking lifelong exposure to environmental toxicants—ranging from endocrine-disrupting chemicals to emerging contaminants—to clinically relevant outcomes such as impaired semen parameters, altered reproductive hormone profiles, and an increased risk of testicular dysfunction. We critically evaluate the concept of life-course vulnerability, highlighting how exposures during critical developmental windows—including prenatal, peripubertal, and adult stages—may program distinct pathological trajectories that manifest as reproductive disorders in later life. In addition to classical mechanisms of endocrine disruption, we emphasize oxidative stress and, particularly, epigenetic reprogramming of the germline as key biological pathways contributing to both immediate fertility impairments and potential transgenerational health effects. Furthermore, we discuss the translational importance of these insights, focusing on the development of mechanism-informed biomarker panels for early detection and risk stratification, as well as addressing the persistent challenge of assessing toxicity from complex chemical mixtures. Finally, we underscore the necessity of integrating epidemiological research, mechanistic toxicology, and clinical practice to advance preventive and clinical strategies. This integration requires overcoming methodological challenges in mixture exposure assessment, accelerating biomarker discovery for personalized risk prediction, and formulating evidence-based public health interventions. In a word, this review advocates for a proactive, science-driven approach to mitigate environmental threats to male reproductive health and protect the well-being of future generations.

1. Introduction

The integrity of male reproductive health is fundamental to public health and the continuity of the human species. However, compelling evidence indicates a concerning global decline, characterized by a greater than 50% reduction in average sperm counts over recent decades(Levine et al., 2023), along with increasing rates of testicular cancer and congenital genital abnormalities—collectively referred to as Testicular Dysgenesis Syndrome (TDS)(Xing and Bai, 2018). The survey(Liang et al., 2025) reveal a growing prevalence of infertility among individuals aged 15–49  years worldwide from 1990 to 2021, with an expected continued increase through 2040, leading to significant societal and health consequences. The rapid onset of these trends strongly implicates environmental and lifestyle factors as primary drivers(Mínguez-Alarcón et al., 2023, Mohammadzadeh et al., 2024, Mann et al., 2020), rather than purely genetic causes.

The male reproductive system is particularly susceptible to environmental insults. Spermatogenesis, a prolonged and highly complex biological process, is especially vulnerable to exogenous disruptions(Meng et al., 2025). Moreover, the male germline exhibits limited DNA repair capacity compared to somatic cells, and mature spermatozoa are particularly prone to oxidative stress due to their high content of polyunsaturated fatty acids(Hu et al., 2024). The Developmental Origins of Health and Disease (DOHaD)(Goyal et al., 2019) hypothesis suggests that exposures during critical developmental periods, particularly in utero, may induce irreversible alterations in the reproductive tract, thereby establishing a reduced baseline for adult fertility(Lombó and Herráez, 2021).

Despite significant advances, important knowledge gaps remain. Research has traditionally relied on a reductionist “one-chemical, one-outcome” paradigm, which fails to account for lifelong, concurrent exposure to complex mixtures of environmental chemicals(Peng and He, 2024). In addition, an emphasis on classical endocrine disruption mechanisms has led to insufficient attention being paid to other key pathways of toxicity, including oxidative stress and epigenetic modifications(Zhou et al., 2020). A comprehensive understanding of life stage–specific susceptibility in males remains incomplete; limiting the precision of public health interventions.

This review presents an integrative framework centered on the concept of the “male reproductive exposome”—defined as the totality of environmental exposures and corresponding biological responses across the lifespan—to address these limitations. Rather than merely cataloging individual toxicants, we synthesize evidence on how exposures from fetal development through adulthood collectively contribute to impaired fertility and adverse offspring outcomes. A central innovation lies in examining epigenetic mechanisms underlying transgenerational inheritance(Liao et al., 2025), offering a plausible biological basis for the heritable impact of paternal environmental exposures. By integrating epidemiological data with cutting-edge mechanistic toxicology, this review seeks to reframe the current discourse and emphasize the urgent need for preventive public health interventions and innovative translational research.

2. Methods

2.1. Selection criteria

Inclusion criteria were: (a) observational studies, including cross sectional, case-control, and longitudinal studies which investigated the association between environmental exposure and male reproductive health with sperm quality as a primary or secondary outcome; (b) mechanism research of in vivo and in vitro models; (c) male infertility diagnosed according to the latest international clinical diagnostic guidelines; (d) studies published in the English language. We excluded meta-analyses that examined intervention strategies.

2.2. Search strategy

This review was conducted by systematically searching the scientific literature by two investigators (HXC, XW) to identify relevant studies published primarily within the last five years (2020–2025). The primary databases utilized were PubMed/MEDLINE, Web of Science, and Scopus. The search strategy employed a combination of the following key terms and their variants: (“endocrine disrupting chemicals” OR EDCs OR “persistent organic pollutants” OR phthalates OR bisphenol OR PFAS OR “microplastics” OR “nanoplastics”) AND (“male reproductive health” OR “male infertility” OR “adult infertility” OR “sperm quality” OR “sperm count” OR “sperm DNA integrity”) AND (epidemiology OR cohort OR “cross-sectional” OR mechanism OR pathogenesis). The reference lists of retrieved articles were also manually screened for additional pertinent publications. The focus was placed on original research articles, meta-analyses, and seminal reviews in high-impact journals. The selection process prioritized human epidemiological studies and experimental models that provided mechanistic insights, with the overarching aim of synthesizing a contemporary and evidence-based perspective on the topic.

3. Epidemiological and toxicological evidence between male infertility and environmental exposures

An increasing prevalence of male infertility has been associated with greater exposure to a wide range of environmental chemicals, including heavy metals, phthalates, pesticides, and bisphenol A. Evidence from both human epidemiological studies and controlled animal experiments consistently demonstrates a correlation between biomarkers of endocrine-disrupting chemical (EDC) exposure and adverse outcomes such as reduced semen quality, hormonal imbalances, and impaired fertility (Stavros et al., 2025). This section presents a critical synthesis of data on major traditional endocrine-disrupting chemicals and emerging contaminants, with an emphasis on common mechanistic pathways underlying their detrimental effects.

3.1. Traditional Endocrine-Disrupting chemicals (EDCs): Established threats

3.1.1. Phthalates

As widely used plasticizers, phthalates are pervasive environmental contaminants, and their metabolites are consistently detected in human urine (Oh et al., 2025). Robust epidemiological and toxicological evidence—summarized in comprehensive reviews by Virant-Klun et al. (Virant-Klun et al., 2022) and Eales et al. (Eales et al., 2022)—demonstrates a statistically significant association between phthalate exposure (as measured by urinary metabolite concentrations) and adverse reproductive outcomes, including reduced semen quality and impaired sperm DNA integrity.

Epidemiological Evidence: Human studies have consistently demonstrated a worrying association between exposure to certain phthalates (particularly the anti-androgenic DEHP and its metabolites) and adverse male reproductive outcomes(Radke et al., 2018). Cross-sectional and longitudinal cohort studies(Lærkeholm Müller et al., 2023, Nowak et al., 2024) have linked higher urinary concentrations of these phthalates with a well-defined phenotype: the “Phthalate Syndrome” in adults. This is characterized by reduced sperm concentration and motility, increased sperm DNA fragmentation, and altered reproductive hormone levels (specifically, lowered testosterone and estradiol). Crucially, studies in infertile populations show a higher burden of phthalate exposure compared to fertile controls(Begum et al., 2021).

Animal Model Evidence: Animal studies have been instrumental in establishing causality and elucidating mechanisms. Prenatal or perinatal exposure to phthalates in rats (Štefánik et al., 2022)recapitulates the human TDS phenotype with remarkable fidelity, inducing cryptorchidism, hypospadias, and decreased anogenital distance. The mechanism is primarily anti-androgenic, involving the suppression of fetal testosterone synthesis in Leydig cells via disruption of steroidogenic gene expression. Adult exposure models (Wei et al., 2023)further confirm direct toxic effects on Sertoli cell function and the induction of oxidative stress in the seminiferous epithelium, leading to spermatogenic arrest.

3.1.2. Bisphenol A (BPA) and its structural analogues

Bisphenol A (BPA), a key monomer in the synthesis of polycarbonate plastics and epoxy resins, is a well-known xenoestrogen (Rubin and Seebacher, 2022). Beyond its estrogenic activity, BPA exhibits a complex, multi-modal mechanism of action, including interactions with nuclear and membrane-bound hormone receptors, as well as modulation of cellular signaling pathways(Guan et al., 2025). Although BPA undergoes rapid phase II metabolism—primarily glucuronidation—in humans, leading to short systemic half-life and challenges in exposure assessment, converging evidence from in vitro, in vivo, and epidemiological studies raises substantial concern regarding its potential adverse effects on endocrine, developmental, and metabolic health.

Epidemiological Evidence: The evidence for BPA is more complex due to its rapid metabolism, but a significant body of research points to detrimental effects. Numerous studies(Chen et al., 2022, Martínez et al., 2024, Ghayda et al., 2019) have reported associations between higher urinary BPA levels and poorer semen quality parameters, including reduced sperm count, motility, and vitality. Furthermore, BPA exposure has been linked to erectile dysfunction and decreased libido, suggesting broader endocrine disruption beyond the testis(Zhao et al., 2025). The concern for substitutes like BPS and BPF is growing, with early epidemiological data(Li et al., 2025) suggesting they may have similar or even greater toxicity.

Animal Model Evidence: Controlled animal experiments leave little doubt about BPA’s potential to harm the male reproductive system. Studies in mice and rats demonstrate that developmental exposure to low, environmentally relevant doses of BPA can lead to permanent alterations in the prostate and seminal vesicles, disrupt the hypothalamic-pituitary–gonadal (HPG) axis, and impair spermatogenesis(Castellini et al., 2020). Mechanistically, BPA acts as a xenoestrogen, binding to estrogen receptors and interfering with normal estrogen signaling, which is crucial for testicular development and function. It also induces oxidative stress and mitochondrial dysfunction in spermatozoa(Santiago et al., 2021).

3.1.3. Pesticides

Certain pesticides are among the most potent anti-androgenic EDCs identified(Castiello and Freire, 2021); such as Benomyl, vinclozolin, and prochloraz, which was confirmed by Robitaille et al. in the study(Robitaille et al., 2015) that pesticides may exert antiandrogenic effects through several mechanisms that are cell type-specific, including AR antagonism and down-regulation or catalytic inhibition of androgen biosynthetic enzymes, such as CYP17 and SRD5A1.

Epidemiological Evidence: Occupational studies in agricultural workers provide the most compelling human evidence(Knapke et al., 2022). Men with high exposure to organophosphate and carbamate pesticides consistently show significantly worse semen quality, lower testosterone levels, and a higher incidence of infertility. Studies in general populations, while assessing lower exposure levels, also suggest links between pesticide biomarkers and adverse reproductive outcomes, highlighting a potential risk even at background exposure levels(Dziewirska et al., 2019).

Animal Model Evidence: The power of animal models is vividly illustrated with pesticides like vinclozolin and prochloraz. These are classified as potent “anti-androgens” because they act as competitive antagonists of the androgen receptor(Kortenkamp, 2020). When administered during the critical fetal window of sexual differentiation, they produce a characteristic phenotype of male offspring with hypospadias, cryptorchidism, and, in adulthood, severely impaired fertility. The groundbreaking discovery from studies of vinclozolin is its ability to induce epigenetic transgenerational inheritance, where the effects on spermatogenesis and disease susceptibility are observed in the F3 generation (great-grand-offspring) that was never directly exposed(Beck et al., 2017).

3.2. Emerging Contaminants: The next frontier of risk

3.2.1. Per- and polyfluoroalkyl substances (PFAS): Mechanisms beyond accumulation.

Epidemiological Evidence: As “forever chemicals”, certain PFAS pose a long-term accumulation threat(Ajana et al., 2025). A growing number of human studies, particularly from highly exposed communities, report associations between serum levels of PFOA and PFOS and male reproductive dysfunction(Jane et al., 2022). The most consistent findings are a reduction in sperm motility and morphological abnormalities(Calvert et al., 2022). There is also emerging evidence for disruption of the hypothalamic-pituitary axis, leading to altered levels of reproductive hormones(Gaillard et al., 2025). Large-scale human studies have strengthened the link between PFAS exposure and clinically relevant semen parameter alterations. A 2022 multi-center European study reported a significant inverse association between serum levels of PFOA, PFOS, and PFNA and sperm motility and morphology(Hærvig et al., 2022), independent of other lifestyle factors. Crucially, newer research suggests that PFAS mixtures may be associated with altered sperm chromatin integrity and DNA methylation patterns in sperm, providing a plausible direct link to embryonic viability and potential transgenerational epigenetic effects(Maxwell et al., 2024).

Animal Model Evidence: Rodent studies confirm the reproductive toxicity of PFAS. Specifically, exposure to a mixture of PFOS、PFOA、PFNA、PFHxS、Genx leads to sperm abnormalities, Leydig cell tumors, and testicular degeneration(Maxwell et al., 2024). For PFOA and PFOS exposure, the mechanisms appear to be multifaceted, including induction of oxidative stress, perturbation of gap junction communication in the testis (vital for Sertoli-germ cell coordination), and disruption of peroxisome proliferator-activated receptor (PPAR) signaling, which is involved in lipid metabolism and energy homeostasis—critical processes for functional sperm production(Shi et al., 2024). Beyond confirming reproductive tract abnormalities and spermatogenic disruption, recent animal studies elucidate novel mechanisms. Exposure to GenX (a PFOA replacement) in mice was shown to induce testicular inflammation and disrupt the blood-testis barrier via activation of the NLRP3 inflammasome pathway(Fan et al., 2025). Furthermore, paternal exposure to PFOS in rodent models has been linked to metabolic dysregulation (e.g., glucose intolerance) in offspring, mediated through sperm-borne small non-coding RNA alterations, demonstrating a non-genetic inheritance pathway for paternal environmental legacy(Akhatova et al., 2025).

3.2.2. Micro- and nanoplastics (MNPs): From systemic Carriers to direct Toxins

Epidemiological Evidence: The reproductive toxicity of MNPs is a new and alarming frontier(Wang et al., 2025). Direct human evidence is still in its infancy due to analytical challenges in measuring MNP burden in tissues. However, ecological and indirect studies raise serious concerns(Martínez et al., 2024). The temporal correlation between the exponential increase in plastic production and the decline in sperm quality is suggestive. Furthermore, MNPs are known to act as vectors for adsorbed toxicants like heavy metals and persistent organic pollutants, potentially amplifying their delivery to sensitive tissues(Zhao et al., 2025). Direct human evidence remains a challenge, but a groundbreaking 2023 pilot study using pyrolysis–gas chromatography/mass spectrometry detected and quantified polyethylene and polystyrene particles in human testicular tissue and semen samples(Zhao et al., 2023). This provides the first direct evidence of MNPs reaching the human male reproductive system. A multi-site study in China indicated that men from regions with higher environmental plastic pollution showed a higher testicular MNP burden, which correlated negatively with sperm count(Zhang et al., 2024).

Animal Model Evidence: Animal studies provide the first direct causal links. Oral administration of polystyrene microplastics to mice results in their accumulation in the testis, inducing inflammation, oxidative stress, and disruption of the blood-testis barrier. This leads to meiotic arrest, apoptosis of spermatogenic cells, and significantly reduced sperm count and quality(Zhang et al., 2023). A particularly alarming finding is the potential for MNPs to induce gut microbiota dysbiosis, which can trigger systemic inflammation and further exacerbate testicular damage via the “gut-testis axis”(Zhang et al., 2024).

3.2.3. Novel Targets: Environmental Nanoparticles and Synthetic Phenols

Titanium Dioxide Nanoparticles (TiO2 NPs): TiO2 NPs are widely utilized in food products and consumer goods, raising increasing public health concerns. Although epidemiological evidence remains limited, animal studies demonstrate that chronic oral exposure to TiO2 NPs impairs spermatogenesis through oxidative stress-mediated apoptosis and disruption of the Keap1-Nrf 2 antioxidant signaling pathway in the testes. Recent mechanistic studies(Wang et al., 2025) further indicate that TiO2 NPs inhibit stress granule formation in germ cells under heat stress conditions and promote germ cell apoptosis by activating the ATM / p53 signaling pathway.

Bisphenol Substitutes (BPS, BPF): With growing regulatory restrictions on bisphenol A (BPA), human exposure to its analogues, such as BPS and BPF, has increased. Findings from the Led-Fertyl cross-sectional study (Martínez et al., 2024) show that BPF exposure is associated with reduced semen vitality in men, supporting an association between urinary bisphenol levels and impaired sperm quality. Animal models suggest that these substitutes exhibit endocrine-disrupting effects similar to BPA, yet may possess distinct toxicokinetic profiles and a higher potential for bioaccumulation. These characteristics underscore the need for urgent, compound-specific risk assessments.

3.2.4. Airborne particulate matter (PM)

Epidemiological Evidence: Large-scale epidemiological studies in regions with high air pollution have consistently demonstrated a significant association between exposure to fine particulate matter (PM_2.5) and poor semen quality, particularly sperm morphology and DNA integrity(Ma et al., 2024, Zhang et al., 2024). Time-series analyses show that acute spikes in air pollution can lead to a measurable decline in sperm function parameters(Zhang et al., 2023).The epidemiological evidence came from a case-control study (Peña-García et al., 2024) showed that one-year occupational PAH exposure was associated with lower antioxidant capacity and higher leukocyte infiltration in seminal plasma. However, one-year exposure to PAH did not have a negative impact on the sperm cellularity of the worker, either quantitatively (sperm count) or qualitatively (motility, vitality, morphology, or cellular DNA fragmentation).

Animal Model Evidence: Controlled inhalation or instillation studies in rodents provide mechanistic clarity. PM exposure induces systemic inflammation and a robust oxidative stress response(Talaie et al., 2025). In the testis, this leads to lipid peroxidation of sperm membranes and, most critically, direct fragmentation of sperm nuclear DNA. This DNA damage is a key contributor to infertility, miscarriage, and developmental abnormalities in offspring. These models unequivocally demonstrate that inhaled particles can have direct gonadotoxic effects(Zhao et al., 2025).

3.3. Synthesis of evidence (Table 1)

The convergence of human epidemiology and animal toxicology constitutes a robust and complementary foundation of evidence. Epidemiological studies identify associations observed in real-world populations, whereas animal experiments enable the establishment of causality and the elucidation of underlying biological mechanisms. For well-established endocrine-disrupting chemicals (EDCs), the body of evidence is substantial and compelling (Thacharodi et al., 2023). In the case of emerging contaminants such as per- and polyfluoroalkyl substances (PFAS) and micro- and nanoplastics (MNPs), data from animal models provide a clear and urgent warning of potential harm (Alex et al., 2025). A critical insight is that, despite their diverse molecular initiating events, these toxicants frequently converge on shared downstream pathways—namely, oxidative stress, germ cell apoptosis, and impaired Sertoli cell function—ultimately resulting in the production of spermatozoa with compromised functionality and DNA damage (Talaie et al., 2025) Table 1.

Table 1.

Synthesis of Epidemiological and Toxicological Evidence on Key Environmental Exposures.

Pollutant Class	Example Compounds	Key Epidemiological Evidence (Human)	Key Toxicological Evidence (Animal Models)	Primary Proposed Mechanisms
Traditional EDCs
Phthalates	DEHP, DBP, BBP	Inverse association with sperm concentration, motility, and testosterone; Shorter anogenital distance in sons of exposed mothers; Increased sperm DNA fragmentation	Fetal exposure induces Testicular Dysgenesis Syndrome (cryptorchidism, hypospadias); Anti-androgenic action via suppression of fetal testosterone synthesis; Adult exposure causes oxidative stress and Sertoli cell dysfunction	Endocrine disruption (anti-androgen); Oxidative stress; Germ cell apoptosis
Bisphenols	BPA, BPS, BPF	Associated with reduced sperm count, motility, and vitality; Linked to erectile dysfunction and altered hormone levels	Developmental exposure disrupts HPG axis and spermatogenesis; Acts as a xenoestrogen (ER agonist); Induces sperm oxidative stress and mitochondrial dysfunction	Endocrine disruption (estrogenic); Oxidative stress; Mitochondrial toxicity
Pesticides	Vinclozolin, Organophosphates	Occupational exposure linked to poor semen quality and lower testosterone; General population exposure associated with adverse trends	Fetal exposure to anti-androgens (e.g., vinclozolin) causes malformations and infertility; Epigenetic transgenerational inheritance of disease via sperm DNA methylation changes	Endocrine disruption (AR antagonism); Epigenetic reprogramming; Oxidative stress
Emerging Contaminants
PFAS	PFOA, PFOS, GenX	Associated with reduced sperm motility, abnormal morphology, and altered reproductive hormones; Emerging links to sperm DNA integrity;	Induces testicular inflammation, Leydig cell tumors, and spermatogenic disruption; Disrupts PPAR signaling and gap junction communication; Paternal exposure alters offspring metabolism via sperm RNAs	PPAR pathway disruption; Oxidative stress & inflammation; Intergenerational epigenetic/RNA-mediated effects
Micro-/Nanoplastics	Polystyrene, Polyethylene	First evidence of particles in human testis and semen; burden correlates with lower sperm count	Accumulates in testes, inducing inflammation, oxidative stress, and blood-testis barrier damage; Triggers germ cell ferroptosis; Disrupts spermatogenesis via the gut-testis axis (microbiota dysbiosis);	Physical tissue damage & inflammation; Oxidative stress; Systemic endocrine/metabolic disruption
Airborne Particulate Matter	PM2.5, PAHs	Exposure associated with poor sperm morphology, motility, and increased DNA fragmentation; Acute exposure can lower semen quality	Inhalation induces systemic and testicular oxidative stress; Directly causes sperm DNA damage and lipid peroxidation; Leads to spermatogenic cell apoptosis	Systemic inflammation; Oxidative stress; Direct DNA damage

Abbreviations.

EDCs: Endocrine-Disrupting Chemicals; DEHP: Di(2-ethylhexyl) phthalate; BPA: Bisphenol A; HPG: Hypothalamic-Pituitary-Gonadal; ER: Estrogen Receptor; AR: Androgen Receptor; PFAS: Per- and Polyfluoroalkyl Substances; PFOA: Perfluorooctanoic acid; PFOS: Perfluorooctanesulfonic acid; PPAR: Peroxisome Proliferator-Activated Receptor; PM_2.5: Fine Particulate Matter; PAHs: Polycyclic Aromatic Hydrocarbons.

Current research on emerging contaminants is advancing beyond the documentation of associations toward the investigation of complex, inter-organ mechanistic pathways (e.g., the gut-testis axis) and mechanisms of non-genetic inheritance. The capacity of these chemicals to directly alter sperm epigenetics and mitochondrial function positions them not only as key contributors to current infertility trends but also as mediators in the heritable transmission of environmentally induced disease risk. This highlights the imperative for proactive chemical safety assessment frameworks that incorporate endpoints related to reproductive health, epigenetic modulation, and transgenerational effects.

4. Windows of Vulnerability: A Life-Course perspective on exposome Dynamics

The concept of “windows of vulnerability” is central to elucidating the pathogenesis of environmentally induced male reproductive disorders. It asserts that the biological impact of an environmental exposure depends not only on its intensity or duration, but—more critically—on the developmental stage and physiological context of the male organism at the time of exposure (Braun, 2017). This section delineates the male life course into three temporally defined windows of susceptibility, integrating empirical evidence demonstrating that exposures occurring during each window differentially program distinct components of the observed reproductive pathology. Although this conceptual framework enjoys broad scientific acceptance, a rigorous appraisal identifies substantial knowledge gaps, persistent methodological limitations, and highlights the urgent need for a more mechanistically grounded and temporally refined application of the model—particularly in environmental risk assessment and clinical translation.

4.1. The foundational programming Window: Strength of evidence and translational challenges

This period, spanning fetal testis development and early infancy, represents the phase of highest and most consequential susceptibility(Svingen, 2025). The fundamental architecture of the reproductive system is established here, and insults during this time can cause permanent, life-long alterations—a classic example of the Developmental Origins of Health and Disease (DOHaD) paradigm(Conley et al., 2021).

4.1.1. Key processes and vulnerabilities

The primary events include primordial germ cell migration, gonadal sex determination, Sertoli and Leydig cell differentiation, the initiation of fetal testosterone production (the “mini-puberty”), and the formation of the testis cord structures. The fidelity of these processes is exquisitely sensitive to hormonal cues, particularly androgen and anti-Müllerian hormone signaling(Gladwell et al., 2026).

4.1.2. Evidence and consequences

Exposure to anti-androgenic chemicals during this window can disrupt this delicate hormonal milieu, leading to the manifestations of Testicular Dysgenesis Syndrome (TDS)(Barrett et al., 2023). The evidence is robust:

Animal Models: Seminal studies in rats showed that in utero exposure to phthalates (e.g., DEHP) or anti-androgenic pesticides (e.g., vinclozolin) reliably induces cryptorchidism, hypospadias, and permanently reduces the Sertoli cell population, which is a key determinant of ultimate sperm production capacity (Sharpe and Skakkebaek, 2008, Wu et al., 2020).

Human Correlates: While direct human experimental evidence is unavailable, compelling epidemiological links exist. Higher maternal urinary levels of phthalates during pregnancy are associated with a shorter anogenital distance (a sensitive biomarker of prenatal androgen action) in their sons, which in turn predicts poorer semen parameters in adulthood (Skinner et al., 2019).

4.1.3. Critical analysis and gaps

The primary challenge lies in the translational extrapolation of this evidence to human populations at common environmental exposure levels. While epidemiological studies(Lu et al., 2024) find associations between maternal urinary phthalates and shorter anogenital distance in sons—a validated biomarker of prenatal androgen action(Jain et al., 2018)—the direct causal link to adult infertility in humans remains inferential. The current evidence landscape is characterized by a “mechanistic certainty in animals, yet epidemiological correlation in humans”. Furthermore, this window is often treated as a monolithic phase, whereas emerging data(Liu et al., 2024) suggest distinct sub-windows (e.g., programming of Sertoli cells vs. germ cell maturation) with potentially different key mechanisms. Future research must prioritize longitudinal birth cohorts with deep phenotyping and exposure assessment, tracking individuals from womb to adulthood to solidify causal pathways and define exposure thresholds for adverse outcomes.

4.2. The pubertal Window: A critical phase of reproductive system Reorganization and functional activation

Puberty constitutes far more than a transient surge in gonadal hormone secretion; it represents a second major phase of testicular development, structural remodeling, and functional maturation (Barrett et al., 2023). This period functions as a temporally constrained window of heightened biological vulnerability—during which latent developmental perturbations originating in fetal life may become phenotypically manifest, and novel environmental insults may disrupt the final stages of reproductive system differentiation and functional calibration.

4.2.1. Key developmental processes and associated vulnerabilities

This phase is defined by the reactivation of the hypothalamic–pituitary–gonadal (HPG) axis, expansion of the spermatogonial stem cell (SSC) pool, initiation of complete spermatogenesis, and terminal maturation of Sertoli and Leydig cells. The concomitant high rates of cellular proliferation, extensive tissue remodeling, and establishment of new endocrine homeostatic set-points collectively render this developmental interval exceptionally sensitive to exogenous disruption.

4.2.3. Empirical evidence and functional consequences

Environmental exposures occurring during puberty can impair the final functional “calibration” of reproductive capacity (Naulé et al., 2021).

Animal Models: Peripubertal rodent studies (Lauridsen et al., 2017, Zhao et al., 2025) involving exposure to EDCs—including BPA and dioxins—demonstrate delayed pubertal onset, reduced testicular mass, and persistent deficits in sperm production and quality, even following cessation of exposure. Although these effects are often less overt than those observed after fetal exposure, they remain functionally consequential and mechanistically informative.

Human Data: Prospective epidemiological investigations in adolescent populations face methodological constraints—including ethical limitations on invasive sampling and challenges in precisely aligning exposure timing with individual pubertal staging—yet yield compelling associations. For example, adolescent exposure to specific agricultural pesticides or ambient air pollutants has been linked to altered pubertal tempo and diminished semen parameters in early adulthood (Cook et al., 2019). Moreover, this developmental window may critically influence the later emergence of adult-onset conditions such as varicocele or subclinical hypogonadism—disorders whose pathogenic origins may be rooted in incomplete or dysregulated pubertal maturation.

4.2.4. Conceptual Refinement: The “Unmasking” hypothesis

The pubertal window may be conceptualized as an endogenous physiological “stress test” for testicular integrity. A suboptimal developmental foundation established prenatally—such as reduced Sertoli cell number or compromised germ cell niche architecture—may remain clinically silent until puberty, when the system is physiologically challenged to achieve maximal functional output. Consequently, an environmental exposure that would be tolerated without consequence in adulthood may exert disproportionately deleterious effects during the intense proliferative and differentiative activity characteristic of puberty.

4.2.5. Critical appraisal and knowledge gaps

The empirical foundation supporting the pubertal window remains comparatively less robust than that for the fetal period. Human research is hindered by ethical restrictions on invasive biomonitoring in minors and difficulties in retrospectively reconstructing precise exposure windows relative to pubertal milestones. Much current evidence is therefore derived from animal models or retrospective adult cohort studies. A particularly underexplored yet pivotal concept is “unmasking”: puberty may not initiate de novo pathology but instead reveal latent vulnerabilities programmed during fetal development—such as an inadequate Sertoli cell reserve—when demand for functional capacity escalates. Accordingly, pubertal exposure may not generate new defects but rather precipitate clinical expression of preexisting, subclinical deficits. This paradigm carries significant implications for clinical practice: adolescent males with antecedent risk factors—including cryptorchidism, hypospadias, or other features of the testicular dysgenesis syndrome (TDS)—may represent a biologically distinct subgroup exhibiting heightened susceptibility to concurrent environmental stressors(Albadawi et al., 2024). Such individuals warrant prioritized counseling, longitudinal monitoring, and potentially tailored preventive strategies.

4.3. The adult Window: Direct insult and the clinically actionable Interface

Adult exposure predominantly disrupts ongoing spermatogenesis and post-testicular sperm function. The supporting evidence is robust and highly translatable to clinical practice, demonstrating consistent, dose-responsive associations between environmental exposures—including organic solvents, heavy metals, and ambient particulate matter—and adverse semen parameters, particularly elevated sperm DNA fragmentation index (SDF).

4.3.1. Key biological processes and vulnerabilities

The adult testis exhibits heightened susceptibility to exogenous insults that compromise critical structural and functional elements: (i) the intricate cellular architecture of spermatogenesis; (ii) the integrity and selective permeability of the blood–testis barrier; (iii) hypothalamic–pituitary–gonadal axis regulation of germ cell development; and (iv) epididymal sperm maturation and storage. Primary phenotypic outcomes in this window include quantifiable declines in conventional semen quality metrics and—of paramount clinical significance—persistent sperm DNA damage.

4.3.2. Evidence and consequences

The evidence for adult exposure effects is extensive and forms the basis of most occupational health studies (Huang et al., 2011, Huang et al., 2014).

Convergent Human and Preclinical Data: Exposure to endocrine-disrupting chemicals—including phthalates, bisphenol A (BPA), and fine particulate matter (PM_2.5)—is consistently associated with oligoasthenoteratozoospermia (OAT) and increased SDF across human cohort studies and controlled animal models (Corcini et al., 2025). Mechanistically, these effects are frequently mediated by oxidative stress, mitochondrial bioenergetic failure, and apoptosis of meiotic and haploid germ cells—processes that directly impair sperm genomic and functional integrity(Mohajer and Culty, 2025, Huang et al., 2025).

4.3.3. Conceptual Reframing

Sperm as a Dual-Function Biomarker—Sentinel and Transgenerational Vector.

The adult window introduces a paradigm-shifting duality: first, sperm quality serves as a sensitive, real-time sentinel of recent environmental perturbations, offering a dynamic biomarker of cumulative exposure burden; second—and more consequential—spermatozoa function as epigenetic and genetic vectors, transmitting environmentally acquired molecular alterations to the zygote. Critically, sperm DNA damage and exposure-associated epigenetic modifications (e.g., aberrant DNA methylation, histone retention, or non-coding RNA profiles) are not merely correlative markers of infertility but causally implicated in impaired embryonic development, increased miscarriage risk, and altered metabolic and neurodevelopmental trajectories in offspring(Siddeek et al., 2018). This reframes adult environmental exposures from a narrow fertility concern to a foundational issue in intergenerational public health.

4.3.4. Critical appraisal and knowledge gaps

A prevailing, yet increasingly untenable, assumption holds that adult-stage reproductive toxicity is inherently reversible. This warrants rigorous reassessment. Although spermatogenesis operates via cyclic renewal, certain insults—including genotoxic agents and epigenome-modifying compounds—may induce persistent damage to spermatogonial stem cells or heritable epigenetic reprogramming, resulting in long-term or irreversible deficits. Furthermore, the dual role of sperm—as both an exposure sentinel and a transgenerational vector—remains underappreciated in clinical practice. While sperm DNA fragmentation testing has gained traction as a diagnostic adjunct, the functional implications of environmentally induced sperm epigenome dysregulation for embryo viability and offspring health represent a critical frontier in translational reproductive science. Consequently, the adult window must be reconceptualized not solely through the lens of male fertility, but as a pivotal node in life-course and intergenerational health policy.

4.4. Synthesis and forward Path: Toward predictive susceptibility profiling

To advance beyond descriptive chronology, the “windows of vulnerability” framework must evolve into a predictive, individualized model of dynamic susceptibility. This transition necessitates:

4.4.1. Mechanism-Informed biomarkers of window Engagement

Development of molecular signatures—such as epigenetic clocks, histone modification patterns, or germ cell–specific transcriptomic profiles—that enable retrospective identification of active vulnerability windows (e.g., methylation-based biomarkers of pubertal onset or gonadarche timing(Lu et al., 2024).

4.4.2. Integration of Multilayered susceptibility Determinants

Temporal windows alone are insufficient. Individual susceptibility is modulated by intersecting factors—including polygenic risk scores for reproductive traits(Benonisdottir et al., 2024), micronutrient status (e.g., folate, zinc, antioxidants), microbiome composition, and co-exposure to psychosocial stressors or infectious agents. Future risk stratification must therefore adopt an integrated susceptibility profiling approach.

4.4.3. Clinical and public health implementation

For clinicians, this paradigm mandates comprehensive life-course andrological assessment—including structured inquiry into prenatal environment, childhood growth patterns, pubertal timing, and occupational history(Esteves, 2022). For public health systems, it underscores the necessity of stage-specific preventive interventions: safeguarding maternal health during pregnancy, delivering evidence-informed reproductive health education to adolescents, and enforcing stringent occupational exposure limits for working-age men. By grounding the windows-of-vulnerability model in mechanistic biology and individualized risk architecture, we can transform it into a scalable instrument for precision prevention and equitable, life-stage–targeted public health action.

In summary, the pathophysiological impact of the reproductive exposome is fundamentally governed by developmental timing. The fetal window establishes the foundational blueprint for gonadal development and germ cell reserve; the pubertal window orchestrates the activation and refinement of hypothalamic–pituitary–testicular signaling; and the adult window governs both immediate reproductive performance and the molecular fidelity of paternal contributions to the next generation. This life-course framework supersedes static toxicological paradigms, offering a dynamic, biologically grounded model for elucidating the etiology of male reproductive disorders. It affirms that safeguarding male reproductive health is not episodic—but a continuous, lifelong imperative.

5. Beyond hormone Disruption: Novel mechanistic insights and their translational promise

While the paradigm of receptor-mediated endocrine disruption has been instrumental in identifying many reproductive toxicants, it represents only the proverbial tip of the iceberg. A wealth of recent research has unveiled a more complex and insidious landscape of toxicity, where environmental chemicals hijack fundamental cellular processes within the male germline(Lombó and Herráez, 2021). These non-receptor-mediated mechanisms often operate at low, environmentally relevant doses and provide a more comprehensive explanation for the diverse pathologies observed, including those that are transgenerational in nature. The evolution of research from phenomenology to mechanism has been pivotal in understanding the male reproductive toxicity of environmental exposures. This section delves into the cutting-edge science that moves beyond traditional endocrine disruption to explore oxidative stress, mitochondrial dysfunction, and epigenetic reprogramming as central pillars of male reproductive toxicity(Skinner et al., 2010). Critically, these mechanisms do not merely explain pathology; they reveal actionable molecular footprints within the germline. This positions them as the foundation for a new generation of preclinical and clinical biomarkers, offering transformative potential for early detection, personalized risk stratification, and informed public health intervention.

5.1. Oxidative stress and sperm DNA Fragmentation: A quantifiable link to clinical outcomes

Oxidative stress is a convergent pathway for many toxicants, leading to sperm membrane lipid peroxidation and, most consequentially, sperm DNA fragmentation (SDF). High SDF is a well-established independent predictor of failed fertilization, impaired embryo development, and recurrent pregnancy loss, even in men with normal conventional semen parameters(Agarwal et al., 2020).

Spermatozoa are inherently vulnerable to oxidative attack due to their unique physiological composition: a plasma membrane rich in polyunsaturated fatty acids (PUFAs) and a limited cytoplasmic volume housing sparse antioxidant defenses. Many environmental toxicants, including phthalates, BPA, and particulate matter, induce oxidative stress either directly by generating reactive oxygen species (ROS) or indirectly by depleting antioxidant capacity(Hug et al., 2023).

From the biomarker connection view, the measurement of SDF (e.g., via TUNEL, SCSA, or SCD assays) has already transitioned from research to clinical practice. It serves as a direct functional biomarker of cumulative oxidative insult(Agarwal et al., 2024). Furthermore, specific oxidized DNA adducts like 8-hydroxy-2′-deoxyguanosine (8-OHdG) in sperm or seminal plasma provide a more precise chemical-specific fingerprint of oxidative damage(Moustakli et al., 2025). Their assessment moves andrology beyond morphology, offering a mechanistic explanation for idiopathic infertility and guiding clinical decisions towards antioxidant therapy or the selection of advanced reproductive techniques like ICSI with preimplantation genetic testing.

5.1.1. Lipid peroxidation and membrane integrity

The primary target of ROS is the sperm plasma membrane. The peroxidation of PUFAs leads to a loss of membrane fluidity and integrity, which is catastrophic for sperm function. This directly impairs the sperm’s ability to undergo the acrosome reaction and fuse with the oocyte, a key explanation for failed fertilization even in cases of normal sperm concentration(Fei et al., 2022).

5.1.2. Sperm DNA Fragmentation: A legacy of paternal Injury

Perhaps the most significant consequence of oxidative stress is the damage inflicted upon the sperm nuclear genome(Rashki Ghaleno et al., 2021). ROS, particularly the hydroxyl radical, can cause single- and double-strand DNA breaks, as well as the formation of oxidized base adducts like 8-hydroxy-2′-deoxyguanosine (8-OHdG)(Mottola et al., 2024). Unlike somatic cells, sperm have limited DNA repair capacity. This sperm DNA fragmentation (SDF) is thus carried into the oocyte. High SDF levels are strongly associated with impaired embryo development, increased rates of miscarriage, and a heightened risk of childhood diseases, including certain cancers, in the offspring (Borges et al., 2019). This establishes oxidative stress not just as a cause of infertility, but as a direct threat to the health of the next generation.

5.2. Mitochondrial Dysfunction: The bioenergetic biomarker of sperm health

Sperm motility is fundamentally dependent on mitochondrial adenosine triphosphate (ATP) production. The mitochondrion, serving as the primary energy source in sperm cells, plays a dual role as both a target and a mediator of toxic effects. Situated in the midpiece, sperm mitochondria generate the ATP required to sustain motility. Numerous environmental toxicants, including specific pesticides and perfluorodecanoic acid (PFDA), have been demonstrated to disrupt the mitochondrial electron transport chain, leading to impaired bioenergetic function(Widhalm et al., 2025).

5.2.1. Bioenergetic failure

Disruption of the electron transport chain impairs oxidative phosphorylation, leading to a critical deficit in ATP production. This results in asthenozoospermia (reduced sperm motility), effectively rendering sperm incapable of traversing the female reproductive tract(Durairajanayagam et al., 2021).

5.2.2. The vicious cycle of ROS production

A dysfunctional electron transport chain is also a prolific source of electron leakage and superoxide anion generation. This creates a vicious, self-propagating cycle: chemically-induced mitochondrial damage leads to increased ROS, which in turn causes further oxidative damage to mitochondrial DNA and membranes, exacerbating the bioenergetic failure and amplifying the oxidative assault on the sperm cell as a whole.This direct attack offers powerful diagnostic tools. Mitochondrial membrane potential (ΔΨm), measurable using fluorescent probes like JC-1, is a sensitive, real-time indicator of sperm metabolic competence. Assessment of mitochondrial membrane potential (ΔΨm) is now emerging as a more sensitive biomarker of sperm health than standard motility measures, reflecting this central role in cellular vitality(Zhang et al., 2016). A low ΔΨm strongly correlates with asthenozoospermia(Wang et al., 2025). Additionally, assays of sperm oxygen consumption rate provide a direct readout of mitochondrial respiratory function(Irigoyen et al., 2024). Integrating these bioenergetic profiles creates a “sperm metabolic fingerprint” that can identify subclinical toxicity long before motility is grossly affected, enabling earlier lifestyle or environmental interventions.

5.3. Epigenetic Reprogramming: The Herald of transgenerational risk

This mechanism represents a paradigm shift in the field of environmental reproductive toxicology. The term “epigenetics” refers to heritable changes in gene expression that occur without modifications to the underlying DNA sequence. The sperm epigenome—comprising DNA methylation, histone modifications, and non-coding RNAs—is now widely recognized as a key target of environmental exposures (Lismer and Kimmins, 2023), providing a plausible biological pathway through which a father’s environmental and lifestyle history can influence the phenotypic outcomes of his offspring, even in the absence of direct exposure.

A major mechanistic advancement lies in the recognition that environmental exposures can induce alterations in the sperm epigenome—the regulatory layer governed by DNA methylation, histone modifications, and non-coding RNAs. These changes are not limited to contributing to individual infertility; they are increasingly regarded as a primary vector for the paternal transmission of disease susceptibility across generations (Siklenka et al., 2015). Sperm epigenetic marks are unparalleled sentinel biomarkers of exposure. Unlike transient hormone levels, epigenetic alterations in sperm can provide a durable record of past environmental encounters. For instance:

5.3.1. DNA methylation

The establishment and maintenance of DNA methylation patterns are crucial for genomic imprinting and gene regulation. Exposure to a range of environmental agents, from vinclozolin to air pollutants, has been shown to alter the methylation status of specific genes in sperm. These include genes involved in development and metabolism. These aberrant methylation marks can be transmitted to the zygote, potentially silencing or activating genes in the developing embryo and leading to adult-onset diseases (Guerrero-Bosagna et al., 2010).

Specific differentially methylated regions (DMRs) in sperm have been linked to exposures like smoking, phthalates, and pesticides in human studies. These signatures could be developed into diagnostic panels for assessing an individual’s reproductive toxicant burden.

5.3.2. Histone retention and modifications

During spermatogenesis, most histones are replaced by protamines to achieve a highly compacted nucleus. However, about 1–15% of the genome in humans retains nucleosomes, enriched at genes critical for early development. Evidence(Zhu et al., 2020) now shows that exposures like BPA can disrupt the normal pattern of histone-to-protamine exchange and alter histone modifications (e.g., methylation, acetylation) at these key loci. This can dysregulate the embryonic transcription program post-fertilization.

5.3.3. Sperm-borne non-coding RNAs

An emerging body of evidence indicates that sperm carry a diverse repertoire of non-coding RNAs, including microRNAs (miRNAs), tRNA-derived small RNAs (tsRNAs), and PIWI-interacting RNAs (piRNAs). These molecules are not merely residual byproducts of spermatogenesis but function as bioactive regulators delivered to the oocyte during fertilization, where they modulate embryonic gene expression. Notably, the composition of small non-coding RNAs—particularly tRNA fragments and miRNAs—in sperm is highly responsive to paternal environmental factors such as diet, stress, and toxin exposure. Alterations in this RNA profile have been shown to be sufficient to induce changes in offspring phenotype in animal models. Consequently, the analysis of cell-free RNA in seminal plasma or the RNA content of sperm has emerged as a promising non-invasive biomarker for assessing both male fertility potential and the risk of metabolic and neurodevelopmental disorders in progeny. Remarkably, murine studies have demonstrated that paternal exposure to stress or a high-fat diet can significantly remodel the sperm RNA profiles(Tomar et al., 2024). Moreover, microinjection of these environmentally altered RNAs from exposed males into unexposed control oocytes recapitulates key metabolic and behavioral phenotypes in offspring (Chen et al., 2016), providing direct experimental evidence for a non-genetic, RNA-mediated mechanism linking paternal environmental exposures to offspring health outcomes.

These novel mechanisms are not mutually exclusive; they form an integrated, synergistic network of damage. A chemical like BPA can induce oxidative stress, which in turn can cause DNA damage and also inhibit the enzymes responsible for DNA methylation (DNA methyltransferases), leading to epigenetic alterations. Mitochondrial dysfunction amplifies oxidative stress, which can further damage both nuclear and mitochondrial DNA. This interconnectedness explains the pleiotropic effects of a single exposure and underscores why a multi-faceted analytical approach is essential for future risk assessment.

5.4. Synthesis and translational Vision: From mechanism to Multilevel biomarker panels

The clinical and public health value of these novel mechanisms lies in their measurability. We are progressing towards a multi-parametric diagnostic framework that complements standard semen analysis, seen in Table 2.

Table 2.

Translational Vision: From Novel Mechanisms to a Multi-tiered Biomarker Panel.

Tier	Targeted Mechanism	Specific Biomarkers	Clinical & Diagnostic Utility	Public Health & Preventive Value
Tier 1 Functional Damage	Oxidative Stress & Genomic Integrity	Sperm DNA Fragmentation (SDF) Index; Oxidized DNA adducts (e.g., 8-OHdG); Lipid peroxidation products (e.g., MDA) in seminal plasma	Diagnosis: Identifies idiopathic infertility and “hidden” sperm dysfunction beyond standard parameters; Prognosis: Predicts IVF/ICSI outcomes and risk of pregnancy loss; Management: Guides use of antioxidant therapy and selection of advanced ART (e.g., PICSI)	Biomonitoring: Population-level SDF data can indicate the impact of environmental oxidative stressors; Intervention Assessment: Measures the effectiveness of public health policies aimed at reducing exposure to pro-oxidant chemicals
Tier 2 Bioenergetic Capacity	Mitochondrial Dysfunction	Mitochondrial Membrane Potential (ΔΨm); OCR; ATP levels in sperm	Early Detection: Reveals subclinical toxicity affecting sperm metabolism before overt motility decline; Functional Assessment: Provides a direct measure of sperm energetic competence, explaining asthenozoospermia; Personalized Intervention: Monitors response to lifestyle or therapeutic interventions targeting cellular metabolism	Risk Profiling: Identifies populations or occupational groups with high exposure to mitochondrial toxicants; Chemical Safety: Sperm bioenergetic assays can serve as sensitive endpoints in toxicological testing of new compounds
Tier 3 Exposure Memory & Heritable Risk	Epigenetic Reprogramming	Sperm DNA methylation profiles (specific DMRs); Sperm-borne non-coding RNA signatures (e.g., tsRNAs, miRNAs); Histone retention/modification patterns	Exposure History: Acts as a “molecular ledger” for past environmental exposures (e.g., smoking, specific chemicals); Risk Stratification: Potentially predicts not only fertility outcomes but also offspring health risks (metabolic/neurological); Future Diagnostics: Envisioned for personalized pre-conception counselling based on paternal exposome	Sentinel Surveillance: Epigenetic signatures in sperm can be powerful biomarkers for population biomonitoring, assessing community-wide reproductive toxicity of environmental mixtures; Transgenerational Risk Assessment: Informs long-term public health policies by evaluating the heritable impacts of environmental exposures

Abbreviations.

8-OHdG: 8-hydroxy-2′-deoxyguanosine; MDA: Malondialdehyde; IVF: In Vitro Fertilization; ICSI: Intracytoplasmic Sperm Injection; ART: Assisted Reproductive Technology; PICSI: Physiological ICSI; DMRs: Differentially Methylated Regions; OCR: Oxygen Consumption Rate; tsRNAs: tRNA-derived small RNAs.

This integrated approach shifts the paradigm from describing infertility to predicting risk. It empowers clinicians to: i) identify men with high environmental risk profiles for targeted counselling, ii) monitor the efficacy of exposure-reduction strategies, and iii) make more informed prognoses for assisted reproduction. For public health, validated sperm epigenetic biomarkers could serve in biomonitoring programs to assess the reproductive toxicity of communities, guiding evidence-based policy to regulate harmful exposures. Thus, deciphering these “deep” mechanisms is not an academic exercise; it is the critical step towards developing the tools needed for preventive and personalized reproductive medicine.

6. Challenges and future Directions: Toward a predictive and translational framework

Despite substantial scientific progress, environmental male reproductive toxicology faces a pivotal moment. To translate rigorous evidence into meaningful clinical interventions and effective public health policies, the field must move decisively beyond observational associations toward predictive models grounded in mechanistic insight. Critical methodological limitations—including the limited physiological relevance of current in vitro systems compared with in vivo models, and insufficient analytical sensitivity for detecting low-dose exposures and complex environmental mixtures—must be systematically addressed. Advancing this agenda will require sustained investment in innovative technologies and concerted efforts to bridge the persistent gap between basic discovery and real-world application.

6.1. Deciphering the complex Exposure: The mixture Problem and the path to Real-World risk assessment

The greatest scientific hurdle remains the realistic simulation of human exposure to complex, low-dose chemical mixtures(Hu et al., 2022). Traditional models, which assess single agents in isolation, fail to capture potential additive, synergistic, or antagonistic interactions, likely underestimating true risk. The future lies in computational toxicology and advanced in vitro systems. Integrating high-throughput screening data (e.g., from ToxCast/Tox21) with Adverse Outcome Pathway (AOP) frameworks can help prioritize mixtures and identify key molecular initiating events(Kim and Choi, 2025). Furthermore, we must move beyond chemical-only mixtures to integrate physical and psychosocial stressors, truly embracing the holistic exposome concept(Gao, 2021). Additionally, the development of human-derived in vitro models, such as testicular organoids or microphysiological systems (“testis-on-a-chip”), offers unprecedented potential to study mixture effects on human tissue in a controlled setting(Gao et al., 2025). These systems will be crucial for moving beyond animal models to directly assess human-specific toxicity and for screening the vast number of untested chemicals in our environment.

6.2. Advancing biomonitoring and the development of predictive biomarkers

Accurate assessment of internal exposure levels and early biological responses is essential for timely intervention. Current practices that rely on single-point biomonitoring are limited in capturing longitudinal exposure patterns. Emerging technologies, such as passive sampling devices (e.g., silicone wristbands) (Yin et al., 2024), offer a promising alternative by enabling personalized, time-integrated monitoring of environmental exposures. Complementing these advances, there is a growing need to move beyond conventional semen parameters and identify sensitive molecular biomarkers (Dutta et al., 2024). The novel mechanisms outlined in Section 4 represent a valuable foundation for biomarker discovery. Future efforts must prioritize the rigorous clinical validation and standardization of these emerging tools. For the proposed multi-tiered biomarker panel (Table 2), large-scale, longitudinal cohort studies are required to establish definitive reference ranges, validate predictive utility for fertility outcomes and offspring health, and assess cost-effectiveness. Integrating multi-omics approaches—including epigenomics, metabolomics, and proteomics—with comprehensive exposure data can accelerate the identification of robust biological signatures. For example, conserved sperm DNA methylation patterns or distinct metabolic profiles in seminal plasma associated with specific exposures may serve as functional indicators of exposome impact. Furthermore, identifying a consistent set of sperm miRNA alterations linked to specific exposure classes (e.g., phthalates, pesticides) could provide a functional “molecular memory” of exposure, offering novel insights into underlying mechanisms and individual susceptibility (Klastrup et al., 2019, Oluwayiose et al., 2023). Large-scale collaborative initiatives, such as the Human Exposome Project (Hartung, 2023), are critical for generating the extensive data resources necessary to support these discoveries. Such biomarkers hold promise as early warning indicators of individual risk and as more sensitive endpoints in population-based research. A key frontier lies in exploring non-invasive or minimally invasive biomarkers, such as seminal plasma-derived extracellular vesicles (exosomes) containing protein or miRNA cargo from the reproductive tract, or urinary metabolites indicative of testicular oxidative stress. Concurrently, the application of artificial intelligence and machine learning to analyze complex multi-omics datasets (epigenomic, transcriptomic, metabolomic) will be instrumental in identifying high-fidelity biosignatures of specific exposures or pathological conditions, thereby advancing the goal of truly personalized risk assessment.

6.3. Closing the translational Gap: From scientific evidence to policy and clinical practice

A persistent disconnect exists between scientific findings and their implementation in regulatory policies and clinical guidelines. Bridging this gap requires coordinated, multi-faceted efforts:

6.3.1. Regulatory Reform

Regulatory frameworks should more explicitly incorporate the precautionary principle, particularly in the evaluation of novel chemicals. Mandatory testing for developmental, reproductive, and transgenerational epigenetic effects should be required prior to market approval(Yin et al., 2025).

6.3.2. Clinical innovation

The andrology clinic must evolve into a hub for preconception health. Based on the international cutting-edge research from 2023 to 2025, the scientific evidence on male reproductive health will be transformed into clinically actionable measures. The core lies in establishing a closed-loop path of “precise diagnosis − stratified intervention − comprehensive management”. This involves integrating validated environmental biomarkers (e.g., SDF) into diagnostic workflows and developing clear clinical guidelines for their interpretation and application in patient counseling. Routine measurement of sperm DNA fragmentation should be integrated into standard clinical evaluations as an indicator of both fertility potential and environmental insult(Adler et al., 2023). The concept of the “Paternal Preconception Visit” should be promoted, where history includes an environmental exposure assessment, empowering individuals with evidence-based strategies for exposure reduction. Notably, the key guarantee for clinical transformation lies in: (1) Establishing a “reproductive-metabolic” multidisciplinary collaboration (MDT) team, integrating resources from urology, endocrinology, and nutrition departments, to develop personalized plans for complex cases; (2) Providing Patient education tools: Provide a “Reproductive Health Action Checklist” (a visual table showing diet, exercise, and testing frequency) to enhance compliance. In the future, epigenetic profiling may support personalized counseling and risk stratification(De Jonge et al., 2024).

6.3.3. Public health interventions and scientific collaboration

There is an urgent need to modernize chemical risk assessment paradigms. Regulatory agencies must mandate testing for transgenerational epigenetic endpoints and require mixture risk assessments for new compounds(Yu et al., 2025). Public health initiatives should develop clear, accessible communication tools to translate research findings into actionable advice for the public, focusing on major exposure sources (diet, consumer products, air quality). Evidence derived from population-level studies should inform clear, practical guidance for reducing exposure through everyday choices (e.g., diet, personal care products)(Nian et al., 2025). Coupled with advocacy for green chemistry and safer material alternatives, such initiatives are essential for primary prevention. Digital health platforms and mobile applications could be designed to assist individuals in monitoring and managing their personal exposome according to lifestyle and environmental context(Sillé et al., 2025). Future research must be inherently interdisciplinary, fostering closer collaboration between epidemiologists, analytical chemists, reproductive biologists, clinicians, and data scientists. Large-scale citizen science projects or biobank studies(Ugai et al., 2022) with detailed exposure metadata and longitudinal follow-up will be invaluable resources.

In conclusion, the future of the field is not merely about documenting further associations but about building a predictive, preventive, and personalized framework. By confronting the complexity of the exposome with innovative tools, transforming mechanistic insights into validated clinical biomarkers, and deliberately building bridges to policy and practice, we can shift the paradigm from managing infertility to preserving and promoting male reproductive health across generations.

7. Conclusions

Compelling evidence has now established environmental exposures as a major modifiable determinant of the global decline in male reproductive health. This review synthesizes existing evidence through an integrative and forward-looking framework—the male reproductive exposome—demonstrating that the cumulative and interactive effects of chemical mixtures across the lifespan contribute to observed pathologies. A key advancement lies in identifying critical windows of vulnerability across the life course, during which exposures in specific developmental periods may program distinct adverse outcomes, ranging from testicular dysgenesis to adult infertility and impaired offspring health.

The scientific understanding has clearly evolved beyond classical endocrine disruption. We emphasize that environmental toxicants converge on fundamental cellular pathways, inducing oxidative stress, mitochondrial dysfunction, and, critically, epigenetic reprogramming of the germline. These mechanisms not only account for compromised sperm function but also offer a plausible explanation for the paternal transmission of disease risk across generations.

The translational potential of these findings hinges on their practical application. The identification of novel mechanisms reveals actionable molecular targets, enabling the development of a multi-tiered biomarker panel that bridges environmental exposure with clinical diagnosis. This paradigm shift—from descriptive associations toward predictive, mechanism-based assessments—is crucial for advancing personalized andrological care and informing evidence-based public health policies. Future research must prioritize addressing the complexity of real-world mixture exposures, validating next-generation biomarkers, and translating mechanistic insights into effective preventive strategies. Protecting male reproductive health is thus not solely a matter of fertility but a fundamental imperative for safeguarding the health of future generations.

Data availability

NA

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.