Xenoestrogens earn their name from their structural resemblance to endogenous estrogens, the natural hormones that guide far more than reproduction. In the brain, estrogen signaling shapes neuronal differentiation, synaptic plasticity, neurotransmitter release, and the organization of sexually dimorphic circuits. Because xenoestrogens can bind estrogen receptors and hijack these pathways, they can mimic, amplify, or scramble hormonal instructions at concentrations far below those traditionally used in toxicological testing. The review emphasizes that these compounds frequently display non-monotonic dose-response curves, meaning that low doses can produce effects that are different, or even opposite, to those seen at high doses. That property upends a foundational assumption of classical toxicology, which has long held that the dose makes the poison.

The chemicals in question are everywhere. Bisphenol A, or BPA, leaches from plastic containers, food-can linings, and thermal receipts. Phthalates, added to plastics to make them flexible and durable, shed from personal care products, building materials, and countless household items. Polychlorinated biphenyls, or PCBs, were banned decades ago yet persist in soil, water, and animal tissue, bioaccumulating as they move up the food chain. Natural xenoestrogens such as phytoestrogens, found in certain plants, add a further layer of complexity. The result, the authors note, is chronic, low-dose, real-world exposure to a shifting cocktail of compounds whose combined effects remain poorly understood.

At the molecular level, the review describes several converging mechanisms of harm. BPA and certain PCBs bind estrogen receptors ERα and ERβ, triggering both genomic and rapid non-genomic signaling through pathways such as MAPK and PI3K/AKT, which govern cell proliferation, apoptosis, and differentiation. Xenoestrogens also disrupt the synthesis, transport, and metabolism of endogenous hormones by interfering with the hypothalamic-pituitary-gonadal axis, tilting the hormonal milieu that the developing brain depends on. Beyond receptor binding, these compounds perturb calcium signaling and glutamatergic neurotransmission by modulating NMDA receptor expression, a shift that can push neurons toward excitotoxicity and impair the precise wiring of synaptic connections.

Perhaps the most unsettling mechanism is epigenetic. Xenoestrogen exposure can induce aberrant DNA methylation and histone modifications, chemically rewriting the instructions that govern gene expression without changing the underlying DNA sequence. Among the genes affected are BDNF, SHANK3, and RELN, all of which are central to synaptic function and have been implicated in neurodevelopmental disorders such as autism spectrum disorder and attention-deficit/hyperactivity disorder. The downstream consequences include defects in synaptic pruning, neuronal migration, and myelination, the very processes that sculpt a mature, functional brain. Because epigenetic marks can be inherited, the review raises the possibility that today’s exposures may predispose future generations to neurodevelopmental vulnerability, a transgenerational shadow that conventional risk assessments have barely begun to address.

The behavioral evidence spans the laboratory and the wild. In rodent models, perinatal exposure to BPA, PCBs, and the synthetic estrogen diethylstilbestrol disrupts mating behavior by deranging the hypothalamic-pituitary-gonadal axis and altering estrogen and testosterone levels. Male rodents exposed to BPA early in life show reduced mounting and intromission frequencies, while females display altered estrous cyclicity and diminished lordosis responses. The sexually dimorphic nucleus of the preoptic area, normally larger in males, shrinks following early-life exposure to estrogenic disruptors, accompanied by disturbances in dopamine and oxytocin signaling that underpin sexual and affiliative behavior. In aquatic species, estrogenic pollutants have feminized male fish and amphibians, collapsing courtship behavior and reproductive success, with one landmark study documenting the collapse of an entire fish population after exposure to a synthetic estrogen.

Cognitive and emotional effects are equally well documented. The review links xenoestrogen exposure to impairments in learning, memory, and executive function, with implications for academic and professional performance, and to heightened anxiety, depression, and mood dysregulation, likely reflecting disruption of the limbic system. Social behavior is also affected, with altered social recognition, interaction, and communication observed across studies. Critically, many of these effects are sex-specific. Estrogen receptor subtypes are distributed differently in male and female brains, particularly in the hypothalamus, hippocampus, and amygdala, and male neurodevelopment depends heavily on the aromatization of testosterone into estradiol, creating distinct points of vulnerability. Prenatal BPA exposure, for example, has been associated with hypomethylation of the estrogen receptor alpha gene in the prefrontal cortex of female rodents but not males, correlating with increased anxiety-like behavior in females. The authors call for sex-stratified analyses to become standard practice in this field.

Timing magnifies the danger. The developing brain passes through tightly choreographed windows, spanning prenatal life, infancy, early childhood, and adolescence, when hormonal signals orchestrate the construction of neural circuits. Exposure during these periods can permanently alter brain structure, neuronal connectivity, and neurotransmitter systems, and the review links prenatal and early-childhood exposures to neurodevelopmental disorders, cognitive deficits, and behavioral abnormalities that persist into adulthood. Fetuses and infants are especially susceptible because their detoxification systems are immature and their brains are maximally plastic, while adolescents face risks during the extensive cortical reorganization of that stage. Regulatory frameworks, the authors argue, have lagged badly behind the science. Agencies such as the United States Food and Drug Administration and Environmental Protection Agency have restricted some compounds, and the European Union and World Health Organization have taken steps of their own, but critics contend these measures are insufficient. Most regulations still test chemicals one at a time and at high doses, missing the low-dose and mixture effects that define real-world exposure, and industry-conducted safety assessments raise conflicts of interest. The pattern of regrettable substitution is a case in point: when BPA was phased out, structurally similar analogs such as BPS and BPF moved in, potentially carrying comparable endocrine-disrupting activity. Legacy pollutants like DDT and PCBs continue to circulate decades after their bans.

What can be done? The review outlines a prevention agenda that spans individual action and structural reform. Reducing exposure means choosing products free of known xenoestrogens, improving manufacturing practices, and strengthening waste management. Public education can empower families, clinicians, and policymakers to make informed choices, while targeted interventions, including dietary modifications and environmental remediation, may help protect the most vulnerable. On the research frontier, the authors identify priorities that include characterizing emerging xenoestrogens, deploying sensitive tools such as neuroimaging and epigenetic profiling, testing whether pharmacological or nutritional therapies can mitigate harm, and untangling the synergistic effects of chemical mixtures. They also flag persistent methodological hurdles: non-monotonic dose responses that defy standard modeling, species differences that complicate extrapolation to humans, and the difficulty of sustaining longitudinal studies long enough to capture chronic and transgenerational outcomes. The bottom line, the authors conclude, is that safeguarding the neurological health of current and future generations demands a coordinated, precautionary response, one that combines rigorous independent research, evidence-based policymaking, international collaboration, and honest public engagement with the invisible chemical landscape that now surrounds every developing brain.

Subject of Research: Neurobehavioral and developmental toxicity caused by xenoestrogen endocrine-disrupting chemicals

Article Title: An overview of neurobehavioral and developmental toxicity induced by xenoestrogens

Article References: Shaw, R., Kamath, A. S., & Chaube, R. (2025). An overview of neurobehavioral and developmental toxicity induced by xenoestrogens. Discover Toxicology, 2(1), Article 10. https://doi.org/10.1007/s44339-025-00025-x

Image Credits: AI Generated

DOI: 10.1007/s44339-025-00025-x

Keywords: xenoestrogens, endocrine-disrupting chemicals, bisphenol A, phthalates, PCBs, estrogen receptors, neurodevelopment, epigenetics, developmental toxicity, neurobehavioral effects, brain development, public health

The problem the review addresses is both vast and largely invisible. Compounds with estrogenic activity, including natural steroid estrogens excreted by humans and livestock, synthetic hormones from contraceptives, and a sprawling family of industrial chemicals known as xenoestrogens such as bisphenol A, nonylphenol, phthalates, and organotin compounds, are continuously released into ecosystems through industrial activity, agriculture, and domestic wastewater. Conventional chemical analysis can identify and quantify these substances, but it cannot by itself answer the question that matters most ecologically: are the compounds present in a given water body biologically available and actively interfering with the endocrine systems of living organisms? That is where bioassays, tests using living organisms or their tissues to measure biological effect, come in, and where the review makes its case for snails.

The authors conducted a systematic search of the scientific literature using relevant keywords, screened the resulting manuscripts according to predefined criteria, and extracted data from the selected studies. Their synthesis shows that snails have now been used to assess estrogenic activity across a striking range of aquatic settings: drinking water, river and lake water, rice fields, and waste liquids both before and after treatment. In each of these contexts, snail-based endpoints provided a readout of estrogenic pressure that complemented, and in some cases exceeded, the information available from chemical measurement alone. The breadth of environments covered is significant, because it suggests that a single, relatively simple test organism can be deployed across the full spectrum of water quality monitoring, from pristine sources to heavily impacted effluents.

Why snails? Part of the answer lies in their biology. Mollusks are extremely sensitive to endocrine-active compounds, and their reproductive output is easy to observe and count. Many freshwater gastropods reproduce prolifically under laboratory conditions, laying eggs in predictable patterns, which means that changes in the rate of reproduction, the number of eggs or embryos produced, or the timing of breeding can be quantified without sophisticated equipment. The review highlights that some assessments, such as the rate of increase in reproduction, are simple enough to be carried out by laboratories that lack advanced analytical instrumentation. This simplicity is precisely what makes the authors recommend deploying snail bioassays in sensitive environments such as urban and industrial treatment plants, where a fast, cheap, and biologically meaningful indicator of estrogenic activity would be most valuable.

The underlying literature assembled in the review illustrates how this sensitivity plays out in practice. Studies on the freshwater snail Biomphalaria alexandrina established the species as a model organism for assessing the endocrine-disrupting effects of 17β-estradiol, the primary natural estrogen, while other work documented endocrine-disruptor effects of the herbicides atrazine and glyphosate on the same genus. In Europe, researchers used the mudsnail Potamopyrgus antipodarum in in situ cage experiments, placing the animals directly into rivers and lakes to capture real-world exposure, and in effect-directed analysis of riverine sediments to confirm endocrine disruption in vivo. Caged mudsnails deployed as an integrated field biomonitoring tool have revealed reprotoxic effects of water column contamination that would be difficult to reconstruct from spot samples of water chemistry alone.

Other studies reviewed by the authors extend the picture to different species and settings. The snail Physella acuta was used in an in situ bioassay across three Iberian river basins to ask whether its reproduction was affected by endocrine-disrupting compounds, and the golden apple snail Pomacea canaliculata showed alterations of biochemical indicators in its hepatopancreas in paddy fields in Taiwan, demonstrating the value of snails in agricultural monitoring. Work on the freshwater snail Parafossarulus striatulus characterized an estrogen receptor and its expression profiles under both laboratory and field exposure, while single-molecule real-time sequencing of freshwater snails exposed to estrogens and androgens has begun to reveal the molecular responses that underlie the whole-organism effects. Even bisphenol A has been traced from river water around a secure landfill into the tissues of freshwater snails collected on site, closing the loop between environmental occurrence and biological uptake.

The review also situates snail bioassays within the broader toolkit of endocrine disruption assessment, and in doing so exposes a gap. Much of the regulatory and scientific attention to estrogenic pollution has focused on fish, where the production of vitellogenin, an egg-yolk precursor protein, serves as the canonical biomarker of estrogen exposure. Yet recent cross-laboratory surveys have highlighted methodological challenges in fish vitellogenin analysis, and questions have been raised about whether changes in vitellogenin concentrations in fish are always reliable indicators of chemically induced endocrine activity. Snails offer an alternative and complementary endpoint: direct measurement of reproductive output in an organism that is often easier and cheaper to maintain, and whose responses integrate exposure over time in a way that a single blood sample from a fish cannot.

None of this means that snails are a perfect or complete solution, and the review is careful to frame them as one component of a monitoring strategy rather than a replacement for chemical analysis. The molecular machinery of estrogen signaling in mollusks differs in important ways from that of vertebrates, and the evolutionary history of estrogen receptors across the animal kingdom remains an active area of research. Some studies reviewed found no substantial changes in estrogen receptor or estrogen-related receptor gene transcription in the snail Marisa cornuarietis exposed to estrogenic chemicals, a reminder that responses can be species-specific and that transcriptional endpoints do not always track reproductive outcomes. The strength of the snail approach lies in its whole-organism, population-relevant endpoints, such as fecundity and embryo production, which are directly tied to ecological consequences even when the precise molecular pathway remains unresolved.

The practical implications of the review are considerable. Wastewater treatment plants are a critical control point for estrogenic pollution, because natural and synthetic estrogens, bisphenol analogues, alkylphenols, and pharmaceuticals pass through conventional treatment with variable efficiency. Advanced treatment processes such as ozonation and activated carbon filtration have been shown to reduce in vitro endocrine activity, yet studies using in vivo test batteries have found that reproductive toxicity is not always eliminated, underscoring the need for biological verification rather than reliance on chemical removal targets alone. A snail bioassay deployed at the outfall of a treatment plant, or upstream and downstream of an industrial discharge, would provide a direct measure of whether the effluent is biologically active, at a cost and complexity that many facilities could realistically absorb. The same logic applies to drinking water, where the occurrence of natural estrogens and bisphenol analogues in treatment plants has been documented, and to rice fields and livestock wastewaters, where estrogens from animal husbandry enter surface waters.

What emerges from this systematic review is a picture of an underused tool on the verge of wider adoption. The evidence base now spans multiple snail species, multiple continents, and multiple classes of estrogenic compounds, from steroid hormones to industrial xenoestrogens, and it consistently supports the conclusion that snails can be used to assess the estrogenic activity of different aquatic environments. Because the most informative endpoints are simple, reproducible, and ecologically meaningful, the authors argue that the deployment of these bioassays should be actively encouraged in sensitive settings, particularly urban and industrial treatment plants where the stakes for downstream ecosystems and human water supplies are highest. In an era when endocrine-disrupting chemicals are increasingly recognized as threats to reproductive health in wildlife and humans alike, the humble snail may prove to be one of the most effective early-warning systems that environmental science has overlooked for too long. The shells, it turns out, were listening all along.

Subject of Research: Using snail bioassays to assess estrogenic pollutants in aquatic environments

Article Title: Assessment of estrogenic pollutants in aquatic environments with snail (bio)tests: a systematic review

Article References: Basaran, B., Ghazi-Khansari, M., Akbari, N., Gholami-Ahangaran, M., Bekheir, S. A., & Sadighara, P. (2026). Assessment of estrogenic pollutants in aquatic environments with snail (bio)tests: a systematic review. Environmental Monitoring and Assessment, 198(10), Article 1089. https://doi.org/10.1007/s10661-026-15931-9

Image Credits: AI Generated

DOI: 10.1007/s10661-026-15931-9

Keywords: snails, estrogenic compounds, endocrine disruptors, bioassay, water quality, wastewater treatment, ecotoxicology, freshwater mollusks, xenoestrogens, environmental monitoring, reproductive toxicity, Potamopyrgus antipodarum