Key Takeaways & Executive Findings
- •• • Exposure to 5 mg·L−1 DBP significantly reduced embryonic heart rate (P < 0.0001), causing 100% hatching failure and mortality, indicating a lethal threshold for early-life-stage fish. • • At 500 μg·L−1 DBP, hatching rate and survival rate were significantly reduced (P < 0.01 and P < 0.0001, respectively), demonstrating sublethal developmental toxicity at environmentally relevant concentrations. • • DBP exposure induced dose-dependent malformations including cardiovascular hemorrhage, spinal curvature, and yolk sac edema, with significant inhibition of larval swimming behavior, compromising fitness and survival. • • Molecular analyses revealed significant upregulation of oxidative stress genes (cat, gpx2, gsta) and estrogenic markers (vtg1, erβ1, chgl), alongside downregulation of neuroendocrine genes (trha, mbp, elavl3), indicating multi-system toxicity at transcriptional level.
Abstract
Dibutyl phthalate (DBP) is a ubiquitous environmental pollutant posing potential risks to aquatic ecosystems. This study assessed the developmental toxicity of DBP in Japanese medaka (Oryzias latipes) embryos. Embryos were exposed to gradient DBP concentrations (1, 5, 50, 500 μg·L−1, and 5 mg·L−1) for 15 days. Endpoints included embryonic heart rate, hatching time, survival rate, larval swimming behavior, and expression of genes related to cardiovascular, nervous, thyroid, antioxidant systems, and estrogenic effects. Results showed that 5 mg·L−1 DBP significantly reduced embryonic heart rate (P < 0.0001), leading to hatching failure and mortality. Exposure to 500 μg·L−1 DBP significantly reduced hatching rate (P < 0.01) and survival rate (P < 0.0001). DBP exposure caused developmental delay, cardiovascular hemorrhage, spinal curvature, yolk sac edema, and inhibited larval swimming behavior. At the molecular level, DBP significantly altered expression of atrap, dkk1, bnpa, fx, and dvl mRNA, affecting cardiovascular development; downregulated trha, mbp, and elavl3 mRNA, indicating endocrine disruption and neurotoxicity; upregulated cat, gpx2, and gsta mRNA, inducing oxidative stress; and upregulated vtg1, erβ1, and chgl mRNA, demonstrating estrogenic effects. This study demonstrates that DBP exposure adversely affects growth, development, hatching, survival, swimming behavior, and gene expression in Japanese medaka embryos, highlighting ecological risks of DBP pollution in aquatic environments.
1. Introduction
Dibutyl phthalate (DBP) is a widely used plasticizer that leaches into aquatic environments, posing chronic exposure risks to fish populations. Existing ecotoxicological assessments have largely focused on adult endpoints, leaving critical windows of embryonic development underexplored. The lack of comprehensive data on sublethal molecular and behavioral effects hinders accurate ecological risk assessment for DBP in freshwater systems.
This study addresses this gap by employing a Japanese medaka embryo-larval assay, a standard model for developmental toxicity. By integrating apical endpoints (heart rate, hatching, survival, behavior) with targeted gene expression analysis across multiple physiological systems, we provide a holistic view of DBP's toxic mode of action. The findings reveal concentration-dependent adverse outcomes, including cardiovascular, neuroendocrine, and oxidative stress effects, which are critical for deriving water quality criteria and informing regulatory decisions.
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DONG Zhongdian, GAO Jiahao, ZHANG Guiming, CHEN Zuchun, LIAO Jian, GUO Yusong, WANG Zhongduo, ZHANG Ning (2026). Toxicity Effects of Dibutyl Phthalate on Embryonic and Juvenile Stages of Japanese Medaka (Oryzias latipes). Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2025012501
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Frequently Asked Questions
What is the lowest observed effect concentration (LOEC) for DBP in this study, and what endpoint was most sensitive?
The LOEC was 500 μg·L−1, which significantly reduced hatching rate (P < 0.01) and survival rate (P < 0.0001). The most sensitive endpoint was survival, with a 15-day exposure causing significant mortality at this concentration.
How does DBP exposure affect the cardiovascular system at the molecular level?
DBP exposure significantly altered expression of atrap, dkk1, bnpa, fx, and dvl mRNA, which are involved in cardiac development and Wnt signaling. These changes correlated with reduced heart rate and cardiovascular hemorrhage observed at higher concentrations.
What evidence supports the estrogenic effect of DBP in this study?
DBP exposure significantly upregulated vtg1, erβ1, and chgl mRNA expression in larvae, indicating estrogenic activity. This is consistent with known endocrine-disrupting properties of phthalates and suggests potential reproductive impairment.
Are the observed oxidative stress responses adaptive or indicative of toxicity?
Upregulation of cat, gpx2, and gsta mRNA suggests an adaptive antioxidant response to DBP-induced ROS. However, at higher concentrations (500 μg·L−1 and above), the system becomes overwhelmed, leading to oxidative damage and mortality, as evidenced by reduced survival.
What are the implications of these findings for environmental risk assessment of DBP?
The study demonstrates that DBP concentrations as low as 500 μg·L−1 can cause significant developmental toxicity in fish embryos. Given that DBP is frequently detected in surface waters, these results highlight the need for stricter regulations and monitoring to protect aquatic ecosystems.
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