Plastic Pollution’s Hidden Danger: Hormone-Disrupting Chemicals Leaching Inside Seabirds
The pervasive presence of plastic waste in the world’s oceans has long been recognized as a significant environmental threat, affecting marine ecosystems and their inhabitants. However, recent groundbreaking research reveals an alarming and previously underestimated biological impact: plastics ingested by seabirds can leach harmful chemicals that directly interfere with their hormonal systems. According to a newly published study in the renowned Environmental Pollution journal, scientists from the University of California, Santa Cruz, and the San Diego Zoo Wildlife Alliance have provided compelling species-specific evidence showing that plastics swallowed by northern fulmars, a seabird species native to the North Atlantic and North Pacific Oceans, release endocrine-disrupting chemicals inside their bodies, impairing critical physiological processes.
This investigation, which marks the second collaborative project between UC Santa Cruz and the San Diego Zoo Wildlife Alliance focusing on the hidden risks of oceanic plastics, highlights the insidious nature of plastic pollution. Endocrine disruption — alterations to hormone systems caused by exogenous chemicals — is known to affect reproductive success, development, behavior, and ultimately species survival. Despite long-standing suspicion of plastics’ role in such effects, this study is the first to demonstrate directly how chemicals extracted from ingested plastic interact with hormone receptors of a wild seabird species, thus solidifying the causal link in a real-world context.
Lead researcher Dr. Liesbeth Van Hassel, whose doctoral work at UC Santa Cruz was integral to this effort, notes the shift in understanding plastic pollution, stating, “While the physical harms of ingesting plastics—such as blockages or internal injuries—have been acknowledged, this study reveals deeper, biological consequences that operate at the molecular level. Notably, these chemicals are not merely transient contaminants; they bind and modulate hormone receptors, causing disruption that can cascade through physiological pathways.” Such molecular interference is particularly troubling because hormones regulate critical functions including metabolism, growth, reproduction, and stress responses.
In their methodology, the research team meticulously collected plastic debris from northern fulmars’ stomachs, subsequently applying chemical solvents to extract substances embedded within the plastic matrix. The extracted chemical cocktails were then applied to cloned hormone receptor proteins specific to the northern fulmar species. Utilizing receptor assays, the scientists monitored alterations in receptor activation or inhibition, finding that almost half of the birds studied (13 out of 27) carried plastics that released chemicals capable of either stimulating or blocking these hormonal pathways. This finding underscores the prevalence and potency of endocrine-disrupting compounds within marine plastic debris.
A particularly striking outcome of the study was the parallelism between fulmar hormone receptors and those in humans. The extracted chemicals triggered similar receptor responses in both species, elevating concerns about the broad ecological ramifications. The authors hypothesized that it is not the plastic polymers themselves but rather the additive chemicals — such as bisphenol A (BPA) and phthalates, well-documented endocrine disruptors in humans — responsible for this hormonal interference. These additives, incorporated during plastic manufacturing to enhance flexibility, durability, or color, appear to leach continuously once in contact with bodily fluids.
The persistence of this leaching phenomenon emerged as another worrying aspect. Co-author Christopher Tubbs, Associate Director of Reproductive Sciences at the San Diego Zoo Wildlife Alliance, emphasizes that “some plastic samples continued to leach biologically active chemicals for at least two weeks in lab conditions.” This indicates a prolonged internal exposure period for seabirds continuously ingesting plastic fragments, likely resulting in sustained disruption of endocrine signaling rather than isolated or transient effects.
Given the keystone role that seabirds like northern fulmars play in marine food webs, these findings carry larger ecosystem implications. Endocrine disruption can influence reproductive success and population dynamics, potentially destabilizing predator-prey relationships and nutrient cycles within ocean habitats. Moreover, the biochemical similarity in receptor responses across vertebrates raises alarms about possible parallel threats to other marine and terrestrial species, including mammals, fish, and potentially humans exposed to contaminated marine environments.
The study’s intersection of ecotoxicology, molecular biology, and conservation science exemplifies the innovative approaches necessary to unravel the complex impacts of plastic pollution. By employing species-specific receptor assays alongside traditional ecological fieldwork, the researchers have paved the way for targeted future investigations into pollutant effects across a diversity of wildlife. This research also underscores the critical need to re-examine plastic additives’ safety and regulation frameworks, as many legacy chemicals recognized as endocrine disruptors continue to be prevalent in consumer plastics worldwide.
The collaboration between the San Diego Zoo Wildlife Alliance and UC Santa Cruz exemplifies the powerful synergy between academic institutions and conservation organizations. Through shared expertise and resources, they have exposed a hidden dimension of the plastic pollution crisis and are galvanizing efforts to protect vulnerable wildlife. The Alliance continues to champion partnerships geared toward unveiling and mitigating emerging environmental threats using rigorous scientific tools, strengthening species conservation on a global scale.
Overall, this study provides an urgent call to action to address ocean plastic pollution not only as a visible material hazard but also as a chemically active threat with ripple effects on hormonal health and wildlife resilience. As plastics degrade and disperse throughout marine systems, they form complex chemical mixtures internalized by animals, delivering hormone-altering compounds that jeopardize biological integrity from cellular to ecosystem levels. Closing this knowledge gap is vital for guiding policy, conservation planning, and public awareness initiatives aiming to stem and remediate plastic contamination in our oceans.
Subject of Research: Endocrine disruption caused by chemicals leaching from ingested ocean plastics in northern fulmars (seabirds).
Article Title: Plastic pollution releases hormone-disrupting chemicals inside seabirds, new research warns.
News Publication Date: April 30, 2025.
Web References: https://www.sciencedirect.com/science/article/abs/pii/S0269749125005184
Image Credits: Liesbeth Van Hassel / San Diego Zoo Wildlife Alliance.
Keywords: Endocrine disruptors, Pollution, Seabirds, Environmental toxicology, Marine biology, Oceans
