Environmental contaminants, ranging from persistent organic pollutants (POPs) to emerging chemicals of concern, continue to pose escalating risks to human health and ecosystems. Yet our capacity to evaluate their toxic potential remains constrained by fragmented and siloed testing systems. Traditional toxicology still relies heavily on animal models such as mice and zebrafish, as well as some in vitro assays such as two-dimensional (2D) cell cultures. These approaches, while historically foundational, often fail to recapitulate the complexity of human biology and therefore provide limited predictive value. (1) Meanwhile, regulatory momentum is shifting. The European Union has reaffirmed its commitment to reducing animal testing, and the U.S. Environmental Protection Agency (EPA) has begun phasing out mammalian testing for chemical safety evaluations. (2,3) These policy shifts, therefore, highlight the urgent need for integrated, human-relevant, and mechanistically informative models in toxicology.

Innovative three-dimensional (3D) culture systems, including organoids, spheroids, and matrix-embedded cultures, represent an important step beyond conventional cell systems by better simulating the architecture and physiology of human tissues. (4) Among these, organoids have emerged as a transformative technology in both biomedical and environmental research. (5) Derived from pluripotent stem cells (PSCs), adult stem cells (ASCs), or primary patient samples, organoids self-organize into 3D structures that preserve organ-specific architecture, cellular heterogeneity, and functional activity. (6,7) Importantly, the cellular origin of an organoid fundamentally influences its toxicological relevance. PSC-derived organoids, generated from embryonic stem cells or induced pluripotent stem cells, (8) are especially powerful for modeling early developmental processes, lineage specification, and organogenesis. These features make them particularly suited for the studies of developmental and life-course toxicity. (9,10) However, PSC-based organoids often exhibit immature, fetal-like phenotypes, incompletely developed xenobiotic metabolism and transporter functions, and limited preservation of donor-specific epigenetic states. (11) As a result, their ability to model chronic, low-dose, or age-dependent exposures remains constrained. In contrast, ASC-derived organoids more faithfully preserve tissue-specific differentiation programs, mature metabolic capacity, donor-associated epigenetic and transcriptional landscapes, and currently represent the most widely adopted platforms in translational toxicology and disease modeling. (12) These attributes make ASC-derived organoids well suited for toxicological questions centered on adult organ function, including gastrointestinal, hepatic, renal, and endocrine responses to sustained exposures...

Figure 1. Timeline of organoid generation and their comparative functional advantages. (A) Schematic representation of the generation timeline for different types of organoids. (B) Comparison of 2D cell cultures, organoids, and animal models in environmental toxicology applications.

Figure 2. Organoid applications bridge mechanistic, causal, and personalized insights in environmental toxicology. Organoids recapitulate tissue architecture and cellular interactions, enabling mechanistic studies of differentiation and developmental toxicity inaccessible in 2D cultures or animal models. Under controlled exposures, they link molecular perturbations to tissue- and organ-level outcomes, supporting causal inference and facilitating personalized assessments of susceptibility to environmental pollutants.

Figure 3. Emerging next-generation strategies in organoid-based environmental toxicology. Three complementary approaches are highlighted: Interconnected and vascularized organoid systems that integrate multiple organ types, vascularization, and cocultures with immune or microbial components to better recapitulate human physiology and interorgan interactions; Integration with single-cell omics analyses enables high-resolution mapping of pollutant-induced perturbations across diverse cell populations, pathways, and regulatory networks; and high-throughput organoid platforms, integrating automated imaging and AI-driven analytics for scalable screening, mechanistic discovery, and predictive toxicology.