Your sunscreen is threatening to make pollution even worse

Yahoo

10-07-2025

Slathering on sunscreen on hot days could be having an invisible and, until now, unknown side-effect that is making plastic pollution even worse.
Experts have warned that a chemical found in the product could be "clinging" to plastic in the oceans, preventing it from breaking down more quickly.
As a result sunscreen could be worsening the issue of plastic pollution, which harms the environment, poses threats to wildlife, and can negatively impact human health.
The latest discovery relates to a chemical called ethylhexyl methoxycinnamate (EHMC) and is the first study to investigate such 'co-pollution', where plastics in the sea act as carriers for other chemical contaminants, including ultraviolet (UV) filters from sunscreen.
Ethylhexyl methoxycinnamate, also known as octinoxate, is an oily UV-absorber used in sunscreen as well as moisturisers, lip balms and make-up containing sun protection.
It protects against UVB rays (which cause sunburn) but has limited protection against UVA (which penetrates more deeply into the skin and is responsible for ageing), so it's commonly used in combination with other chemicals.
Sunscreens, like oil, are hydrophobic – meaning that they do not dissolve in water.
This makes them a combined threat as, while it has long been known that they can accumulate on plastics and other surfaces and remain in the environment, now researchers at Stirling University have shown that EHMC could be hindering the development of useful aerobic bacteria that help break down plastic pollutants at an early stage.
The problem with the chemical is that its sun-blocking abilities continue long after it has been slapped on skin at the beach.
To put it simply, the same chemistry that blocks UV rays from human skin then 'protects' the plastic.
The chemical blocks the 'right' sort of bacteria that help plastic to break down more quickly in the oceans, and instead promotes harmful bacteria that then clings to the plastic – preventing it from disintegrating.
Dr Sabine Matallana-Surget, the lead researcher at Stirling University, said: '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.'
But the problem does not end with making plastic last longer.
Plastic waste in the ocean provides a new surface where microbes can grow, forming slimy layers called the plastisphere.
Plastics also absorb other pollutants, including sunscreens washed off human skin that are insoluble in water, and these can then attach to marine plastic surfaces.
Scientists have previously studied the role of the plastisphere, but little is known about how additional chemicals such as EHMC affect the microbes living on the plastic.
The new study shows that when plastics are co-contaminated with EHMC, not only do pollutant-degrading bacteria like Marinomonas decline, but bacteria like Pseudomonas develop more proteins that improve their ability to survive.
Some Pseudomonas strains are also classified as opportunistic pathogens, capable of causing serious infections that can require antibiotic treatment – raising potential public health concerns that the researchers hope will be further investigated.
Dr Matallana-Surget said: '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.'
More than 100,00 marine mammals and a million sea birds are killed each year by plastic pollution, according to the UK Government.
The first decade of this century saw more plastic produced than all the previous plastic put together, with just 9% of that having been recycled, according to Surfers Against Sewage.
Studies estimate that there are now up to 51 trillion pieces of plastic in the oceans, which kill animals and birds either by tangling them in plastic or after the animals ingest plastic.
There are thought to be at least 700 species directly affected by marine debris in the ocean.
By prolonging the life of plastic in the ocean, sunscreen could be directly contributing to this problem.