Sunlight and colour: the hidden drivers of microfiber pollution in the ocean

A new study by the Chinese Research Academy of Environmental Sciences, published September 2025, proves accelerated degradation of PET textiles under UV exposure in seawater environments. Additionally, it reveals a correlation between the colour of your synthetic clothing and its subsequent microfiber pollution while exposed to (UV) sunlight. 

Under ultraviolet (UV) radiation, widely used polyester (PET) fabrics weaken and fragment in coastal seawater. This is alarming as many clothes reach the ocean at their end of life, polluting shorelines and later circulating through the water. Leading to the formation of micro- and nanoplastic particles and the release of toxic additives and oligomers, which can pose a risk to marine organisms and biodiversity through ingestion.

The findings of the study show that everyday clothing can disintegrate just by being in contact with the environment. 

About the study

The peer-reviewed study (Chen R, Zhao X, Wu X, Wang X, Wang J, et al., Polyethylene terephthalate microfiber release from textiles in coastal seawater ecosystems under sunlight-driven photochemical transformation), investigated the formation of PET (polyethylene terephthalate) microfibers released from textiles when subjected to long-term simulated UV exposure and photoaging in coastal seawater environments. Photoaging is the process of degradation or ageing of a product caused by prolonged exposure to UV radiation.

The researchers focused on coloured synthetic fabrics, particularly PET, which are common in clothing and household textiles. 

The study aimed to understand:

• How UV light drives PET fragmentation in coastal seawater
• Why different dye colours affect the rate of photoaging and whether darker-coloured fibres degrade faster due to stronger UV absorption and reactive oxygen species (ROS) formation

They discovered that long-term exposure to UV can convert PET fabric into thousands of microscopic fragments. After only twelve days of sunlight exposure, 0.1 grams of polyester fabric released between 14,000 and 47,000 microfibers. 

How does PET degrade?

PET (polyethylene terephthalate) microfiber degrades under various natural circumstances. This study by the Chinese Research Academy of Environmental Sciences, focuses on the influence of UV light on breaking down the polymer chains and causing fragmentation into smaller particles. 

Microfibers are thinner than a human hair, and are one of the most common forms of microplastic found in oceans. There is potential that smaller microplastics will be more harmful to marine life and human health, as very small microplastics are capable of accessing cells and tissues.

Colours impact how fast our clothes turn into pollution

The study found that darker coloured textiles degraded faster because their dyes absorbed more sunlight energy and produced higher levels of reactive oxygen species. These highly reactive molecules accelerate the chemical ageing of plastics and cause fibres to weaken and shed.

Purple and green textiles absorbed more UV light and produced higher levels of reactive oxygen species, which accelerated the breakdown of plastic chains.

After 12 days of laboratory sunlight exposure, 0.1 grams of purple fabric released about 47,400 microfiber fragments. Green, yellow, and blue fabrics released fewer particles, at 37,020, 23,250, and 14,400 for each colour. The researchers estimate that this accelerated test represents approximately one year of natural sunlight exposure in coastal waters.

This finding reveals how the fashion industry’s focus on aesthetics, colour, finish, and intensity, has environmental side effects we rarely consider. The very pigments that make clothes visually appealing can speed up their transformation into microplastics once discarded.

Impact on the environment

While the exact scale on which microfiber formation caused by synthetic textiles in aquatic environments is still under research, we know polyester, nylon, and acrylics are a major source of pollution in the ocean. According to the European Environment Agency, about 8% of European microplastics released to oceans are from synthetic textiles — globally, this figure is estimated at 16 – 35%. Between 200,000 and 500,000 tonnes of microplastics from textiles enter the global marine environment each year. Read more on how clothing affects plastic pollution in the oceans.

As opposed to natural fibres that can naturally biodegrade doing less harm to the environment, synthetic fibres degrade into small loose microfibers that are harmful to marine life. They end up in the ecological cycle on land too, especially accumulating up the food chain due to their slender shape and small size. 

Fashion’s role in protecting the oceans

While it was already known that microfibers from textiles are released into the environment by wearing them, washing them and littering them into the environment, this research introduces new dilemmas to the fashion industry, with special attention to clothing’s end-of-life stage. 

Everyone has their own responsibility in limiting the pollution we cause as humans. Both consumers and brands can select the colours and materials of the clothes they buy consciously. To help reduce microplastic pollution, at COSH!, we prefer to choose for more natural materials like hemp, responsibly sourced wool and organic cotton as part of the solution.

In addition, producers can manufacture with an eye for the environmental consequences, for example by suggesting more ecological dyes to the buyer and preventing overproduction. 

Furthermore, policymakers can set certain standards for clothing entering the market and regulate how they should be taken care of throughout their lifecycle. 

It’s clear that every fashion design choice carries an ecological cost, and microfiber pollution isn’t only a material issue, it’s a chemical one. Reducing it requires more than switching fabrics, it demands rethinking the entire textile system, from fibre production to dye chemistry.