Reviewed by Lauren HardakerJul 7 2025
According to University of Stirling researchers led by Dr Sabine Matallana-Surget, a chemical typically present in sunscreen may make plastic in the seas even more difficult to break down. The findings were reported in the Journal of Hazardous Materials.
Image credit: Tatevosian Yana/Shutterstock.com
The chemical Ethylhexyl Methoxycinnamate, often known as EHMC, may reduce the decomposition of discarded plastic in the seas and allow biofilm bacteria, which are more resistant to severe environments, to proliferate.
The study is the first to investigate co-pollution, in which plastics in the water serve as carriers for other chemical pollutants, such as ultraviolet (UV) filters from sunscreen.
Dr. Sabine Matallana-Surget, an Associate Professor in the Faculty of Natural Sciences, is now urging policymakers to take immediate action to address what she refers to as the unseen hazard of sunscreen.
These changes matter. By suppressing the aerobic bacteria that help degrade plastic, and selecting those that stabilise or reinforce the biofilm, UV filters would prolong the life of plastics in the ocean – making them more resistant to breakdown by sunlight or microbes. Targeted research and policy interventions are therefore urgently needed to mitigate these compounded ecological threats.
Dr. Sabine Matallana-Surget, Study Research Lead and Associate Professor, Faculty of Natural Sciences, University of Stirling
Impact on the Plastisphere
The plastic waste in the ocean gives a new surface for bacteria to develop, resulting in slimy layers known as the plastisphere. In addition to generating the plastisphere, plastics absorb additional pollutants, such as sunscreens rinsed off human skin that are insoluble in water, which can then bind to marine plastic surfaces.
Sunscreen, like oil, is hydrophobic, which means that it does not dissolve in water. They provide a compounded concern since they may build on plastics and persist in the environment.
Scientists have previously investigated the role of the plastisphere, but little is known about how other chemicals, such as EHMC, impact the microbes that live on the plastic.
This study reveals that when plastics are co-contaminated with EHMC, not only do pollutant-degrading bacteria like Marinomonas fall, but bacteria like Pseudomonas produce more proteins that stabilize biofilms and boost their survival.
Pseudomonas species are noted for their resilience in contaminated settings and capacity to degrade a wide variety of contaminants, including pesticides, heavy metals, and hydrocarbons.
However, certain Pseudomonas strains are categorized as opportunistic pathogens, capable of producing serious infections that may require antibiotic treatment, posing significant public health issues that researchers intend to examine more.
One notable finding of the study was the significantly greater amount of a protein known as outer membrane porin F (OprF) in Pseudomonas exposed to EHMC. This protein is essential for maintaining the formation of biofilms, which allow bacteria to survive in hostile environments.
Researchers also discovered a change toward anaerobic respiration, which allows cells to create energy in the absence of oxygen, indicating a total shift in microbial metabolism within the plastisphere.
According to the study, EHMC could hinder the formation of helpful aerobic bacteria that help break down plastic pollution at an early stage, favoring more stress-tolerant anaerobic biofilm-forming bacteria.
Significant Concerns
Dr. Matallana-Surget added, “The UV-protective properties of EHMC, combined with its suppression of hydrocarbonoclastic bacteria, may indirectly protect plastics from photodegradation and biodegradation, further contributing to their persistence in marine environments.”
“This impact, combined with the enrichment of potentially pathogenic bacteria, raises significant concerns for ecosystem stability and human health, particularly in coastal regions with high rates of tourism, and high levels of plastic pollution,” further added Dr. Matallana-Surget.
Dr. Matallana-Surget led the research in partnership with Dr. Charlotte Lee, who did the primary experimental work, and Dr. Lauren Messer at the University of Stirling, as well as Professor Ruddy Wattiez from the University of Mons in Belgium.
The project, which began with Dr Matallana-Surget’s idea to investigate the rising double pollution issue, has grown out of 15 years of collaboration between the Stirling and Mons teams.
The UKRI Natural Environment Research Council (NERC) and the National Research Foundation Singapore provided funding for this research. It was also sponsored by the European Regional Development Fund and the Walloon Region of Belgium.
It expands on Dr. Matallana-Surget’s prior research, which revealed the critical functions of bacteria found on plastic debris.
Dr. Matallana-Surget also published a study on the impact of the Deepwater Horizon oil disaster on microscopic seawater bacteria, which play an important part in ecosystem functioning.
Journal Reference:
Matallana-Surget, S., et al. (2025) The invisible threats of sunscreen as a plastic co-pollutant: Impact of a common organic UV filter on biofilm formation and metabolic function in the nascent marine plastisphere. Journal of Hazardous Materials. doi.org/10.1016/j.jhazmat.2025.139103.