Recycled plastics can affect hormone systems and metabolism
University of Gothenburg
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Recycled plastic pellets from polyethylene (PE) can be used when making a water bottle for instance. But we can never have full knowledge of what chemicals will end up in an item made of recycled plastic. Therefore the item could contain toxic chemicals that can leach out.
view moreCredit: Olof Lönnehed
A single pellet of recycled plastic can contain over 80 different chemicals. A new study with researchers from University of Gothenburg and Leipzig shows that recycled polyethylene plastic can leach chemicals into water causing impacts in the hormone systems and lipid metabolism of zebrafish larvae.
The plastic pollution crisis has reached global levels, threatening both planetary and human health, and recycling is proposed as one of the solutions to the plastics pollution crisis. However, as plastics contain thousands of chemical additives and other substances that can be toxic, and these are almost never declared, hazardous chemicals can indiscriminately end up in recycled products.
Increasing gene expressions
In a new study, researchers bought plastic pellets recycled from polyethylene plastic from different parts of the world and let the pellets soak in water for 48 hours. After which zebrafish larvae were exposed to the water for five days. The experimental results show increases in gene expression relating to lipid metabolism, adipogenesis, and endocrine regulation in the larvae.
“These short leaching times and exposure times are yet another indicator of the risks that chemicals in plastics pose to living organisms. The impacts that we measured show that these exposures have the potential to change the physiology and health of the fish,” says Azora König Kardgar, lead author and researcher in ecotoxicology at the University of Gothenburg.
“Never full knowledge”
Previous research has shown similar effects to humans, including threats to reproductive health and obesity, from exposure to toxic chemicals in plastics. Some chemicals used as additives in plastics and substances that contaminate plastics are known to disturb hormones, with potential impacts on fertility, child development, links to certain cancers, and metabolic disorders including obesity and diabetes.
“This is the main obstacle with the idea of recycling plastic. We never have full knowledge of what chemicals will end up in an item made of recycled plastic. And there is also a significant risk of chemical mixing events occuring, which render the recycled plastic toxic,” says Bethanie Carney Almroth, professor at the University of Gothenburg and principal investigator on the project.
Different chemicals
Apart from the study on the impact that recycled plastics have on zebra fish larvae, the researcher also conducted a chemical analysis of the chemicals leaching from the plastic pellets to the water. And they found a lot of different chemical compounds, but the mixture altered between different samples of pellets.
“We identified common plastics chemicals, including UV-stabilizers and plasticizers, as well as chemicals that are not used as plastics additives, including pesticides, pharmaceuticals and biocides. These may have contaminated the plastics during their first use phase, prior to becoming waste and being recycled. This is further evidence of the complicated issue of plastics waste flows, and of toxic chemicals contaminating recycled plastics,” says Eric Carmona, researcher at Department of Exposure Science, Helmholtz Centre for Environmental Research in Leipzig.
“Ban hazardous chemicals”
Representatives from the nations of the world are preparing to head to Geneva, Switzerland, in August, for what is planned to be the final negotiating meeting for a Global Plastics Treaty at the Intergovernmental Negotiating Committee under the United Nations Environmental Program. The authors of the work stress that negotiators and decision-makers must include provisions to ban or reduce hazardous chemicals in plastics, and to increase transparency and reporting along plastics value chains. Plastics cannot be recycled in a safe and sustainable manner if hazardous chemicals are not addressed.
“This work clearly demonstrates the need to address toxic chemicals in plastics materials and products, across their life cycle”, says Professor Bethanie Carney Almroth. “We cannot safely produce and use recycled plastics if we cannot trace chemicals throughout production, use and waste phases.”
Facts: Polyethylene (PE)
Polyethylene, abbreviated PE, is a type of plastic used in a lot of packaging materials like bottle caps, plastic bags, agricultural mulch films, insulation for wiring and cables, pipes, ropes, toys and household items. It is the most widely produced and used polymer. On plastic products made of polyethylene, the number in the recycling code is either 2 or 4.
Journal
Journal of Hazardous Materials
Method of Research
Experimental study
Subject of Research
Animals
Article Title
Effects of leachates from black recycled polyethylene plastics on mRNA expression of genes involved in adipogenesis and endocrine pathways in zebrafish embryos
Article Publication Date
23-Jun-2025
WVU student discovers widespread microplastic pollution in first-of-its-kind study of Appalachian streams and fish
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A WVU junior who researched pollution from microplastics in Appalachian streams and fish found tiny plastic particles that present potential human health risks in every sampled fish.
view moreCredit: WVU Photo
When West Virginia University biology undergraduate student Isabella Tuzzio tested fish from central Appalachian streams, her research revealed microplastics in every fish she sampled.
Tuzzio said her results from the study, which was the first of its kind in Appalachia, suggest significant environmental risks, as well as potential risks to human health.
Microplastics can disrupt hormones and carry harmful chemicals like heavy metals and antibiotics. Additionally, there is evidence they accumulate as they pass through the food chain, potentially reaching humans at high concentrations.
A junior from Shepherdstown in the WVU Eberly College of Arts and Sciences, Tuzzio found microplastics — plastic particles less than 5 millimeters in size — in juvenile northern hogsucker fish from seven streams across the Cheat, Monongahela and Ohio River watersheds. Each fish contained an average of 40 pieces of microplastics.
Tuzzio published her findings with WVU Davis College of Agriculture and Natural Resources faculty members Caroline Chaves Arantes, assistant professor of wildlife and fisheries, and Brent Murry, assistant professor of aquatic ecology. She found microplastics in 100% of the fish, and nearly 2,200 particles were documented across 55 samples.
“Microplastics are coming from everyday sources like synthetic fibers from laundry and plastic beads in exfoliating face washes,” she said. “They’re now everywhere, from our streams to remote deserts and even the human body.”
Big Sandy Creek in Preston County had the highest concentration of microplastics. Tuzzio said sites with the most contamination also had higher levels of E. coli bacteria in the water and were associated with agricultural land use, suggesting wastewater runoff from farms may play a role in getting microplastics into streams.
“These plastics are small, but their impact is massive,” Tuzzio said. “They carry pollutants, heavy metals and antibiotics. And while the microplastics are spread out in smaller fish, the bigger fish eat those smaller fish. As you work your way up the food chain, there are heavily concentrated levels of these plastics. It’s a problem for them and for us, too.”
In humans, microplastic concentrations interfere with biological systems and may be linked to chronic illnesses like diabetes and even congenital conditions that affect developing fetuses. Studies have found microplastics in placentas, brains and other human organs.
The particles Tuzzio’s team extracted from the fish included fibers, fragments, sheets and foams. Fibers accounted for 96% of all particles.
While past microplastic contamination studies have been done in saltwater environments, it’s not just an oceanic problem.
“Microplastics have been identified in animals throughout the world,” Murry said. “And we’re still really getting a handle on how extensive the problem is. Most work has been done on marine species that we eat, and much less work has been done in freshwater systems and even less throughout Appalachia.”
Next, the researchers plan to include additional fish species in the study and examine the potential role of precipitation or other deposits from the atmosphere in spreading microplastics throughout ecosystems.
Tuzzio said public awareness will be key to any solution for combatting microplastic pollution. Sustainable solutions for reducing microplastics in the watershed include recycling, choosing environmentally friendly detergents and installing filters on washing machines. Improving waste management and water treatment infrastructure can also help.
“I think it’s definitely an emerging contaminant,” she said. “People don’t know much about it, and we hope our research sparks conversations about sustainability and inspires action to protect the streams and communities of Appalachia.”
Arantes agreed.
“Isabella’s work not only fills a major gap in our understanding of microplastics in freshwater systems but also sheds light on links between land use, atmospheric deposition and pollutant exposure.”
Plastic particles less than five millimeters in size, microplastics come from everyday sources like synthetic fibers in laundry and can accumulate as they move through the food chain.
Credit
WVU
Journal
Sustainability
Article Title
Widespread Microplastic Pollution in Central Appalachian Streams: Implications for Freshwater Ecosystem Sustainability
Impact of co-exposure of bisphenol A and retinoic acid on brain development
Researchers report that bisphenol A potentiated the effect of retinoic acid to disrupt neurodevelopmental gene signaling
Ritsumeikan University
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Researchers demonstrate how the co-exposure of bisphenol A and retinoic acid (RA) potentiate the effect of RA signaling in early development.
view moreCredit: Prof. Tatsuyuki Takada from Ritsumeikan University, Japan
Synthetic chemicals and plastics are useful and indispensable in our lives. On the other hand, the world is grappling with plastic pollution—clogging oceans, threatening wildlife, and leaching into ecosystems. While eco-friendly alternatives are on the way, researchers have been trying to identify the various effects of the synthetic plastics present within the ecosystem.
Bisphenol A (BPA) is a common chemical used in synthetic plastics and is known to act as an endocrine disruptor. Upon exposure to the human body, it interacts with multiple steroid hormone receptors, including estrogen, androgen, and thyroid receptors, causing various damage to the reproductive system, immune system, and neuroendocrine system. However, its mechanisms of action remain incompletely understood. While BPA is commonly leached into water bodies, retinoic acid (RA), a nutrient derivative which is essential for organ development, has also been reported to be found in low levels in water sources.
To investigate a mechanistic link between BPA and a wide range of disorders, a team of researchers led by Professor Tatsuyuki Takada from the College of Pharmaceutical Sciences, Ritsumeikan University, Japan, along with Dr. Akira Hirasawa from Kyoto University, Japan, focused on RA signaling, which plays fundamental roles in early development and explored how co-exposure to these two substances affects early neurodevelopment. Their findings were published online in Environmental Health Perspectives on May 13, 2025.
By exposing human induced pluripotent stem cells (iPSCs) and zebrafish embryos to exogenous RA and BPA (alone and in combination), they found that the combination of BPA and RA triggered abnormal brain and facial development by overstimulating RA-responsive genes, particularly a group known as HOX genes.
“When cells were exposed to BPA and RA together, it was observed that BPA potentiated the RA signaling pathway more than the normal condition (RA alone), leading to abnormalities in body patterning of critical organs during development,” explains Prof. Takada.
While BPA is already known to be an endocrine-disrupting chemical, its ability to interfere with development through the RA signaling pathway was previously unknown. Notably, BPA alone had no effect, but when combined with RA, it caused a dramatic shift in gene expression and brain structure. Moreover, upon treating the exposed iPSCs with RA receptor blockers, the effects were reduced, which confirms that BPA also acts through the RA receptors and not through estrogenic activity.
Upon exposure to the chemical pair, the zebrafish embryos exhibited various brain abnormalities, such as the rostral shift in brain region markers (e.g., hoxb1a gene), duplication of key neurons (Mauthner cells), and craniofacial malformations. These outcomes might be associated with neurodevelopmental disorders like autism spectrum disorder and attention deficit hyperactivity disorder.
This discovery, while rooted in laboratory models, has immediate relevance. Recently, RA-like activity has been detected in drinking water sources, and BPA continues to be found in food containers, receipts, and household products. With this research, the team hopes to inspire not only stricter environmental health policies but also deeper investigation into chemical-nutrient interactions.
“Our study reveals a causal link between chemical exposure and neurodevelopmental disorders, shedding light on the mechanisms of endocrine disruption. Because RA signaling plays many key roles during development and homeostasis, it may explain the pleiotropic effect of endocrine-disrupting chemicals. Moreover, it emphasizes the potential risk posed by simultaneous exposure to BPA and RA for the safety of fetus and pregnant women,” concludes Prof. Takada.
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Reference
DOI: 10.1289/EHP15574
About Ritsumeikan University, Japan
Ritsumeikan University is one of the most prestigious private universities in Japan. Its main campus is in Kyoto, where inspiring settings await researchers. With an unwavering objective to generate social symbiotic values and emergent talents, it aims to emerge as a next-generation research-intensive university. It will enhance researcher potential by providing support best suited to the needs of young and leading researchers, according to their career stage. Ritsumeikan University also endeavors to build a global research network as a “knowledge node” and disseminate achievements internationally, thereby contributing to the resolution of social/humanistic issues through interdisciplinary research and social implementation.
Website: http://en.ritsumei.ac.jp/
Ritsumeikan University Research Report: https://www.ritsumei.ac.jp/research/radiant/eng/
About Professor Tatsuyuki Takada from Ritsumeikan University, Japan
Dr. Tatsuyuki Takada is a Professor at the College of Pharmaceutical Sciences, Ritsumeikan University, Japan. He earned a Ph.D. from Tohoku University and conducted postdoctoral research at the National Institutes of Health (USA). He has expertise in applied molecular and cellular biology. His research mainly focuses on the mechanism of how chemicals affect development and the conservation of endemic species by investigating cell differentiation signals and their regulation in different biological systems.
Funding information
This study was funded in part by a Grant-in-Aid for Challenging Exploratory Research (17K20049 to T.T.).
Journal
Environmental Health Perspectives
Method of Research
Experimental study
Subject of Research
Animals
Article Title
Effects of Bisphenol A and Retinoic Acid Exposure on Neuron and Brain Formation: A Study in Human Induced Pluripotent Stem Cells and Zebrafish Embryos
