Dark dyes accelerate plastic fiber release: new insights into ocean microplastic formation

The findings identify photoaging as a key mechanism converting everyday fabrics into marine microplastics, deepening our understanding of microfiber formation and its ecological risks.

Microplastics smaller than 5 millimeters have raised global concern due to their persistence, toxicity, and ability to accumulate across marine food webs. Synthetic microfibers, the dominant form of microplastics in seawater, often come from PET textiles used in clothing, carpets, and curtains. A single laundry cycle can release more than 700,000 fibers, many of which eventually reach coastal waters. Once in the ocean, these fibers undergo physical and chemical weathering—hydrolysis, mechanical abrasion, and particularly photoaging under sunlight. However, how textile color and dye composition influence this degradation and release process has remained an open question. Addressing this knowledge gap is critical for assessing microfiber generation, persistence, and environmental impact.

A study (DOI:10.48130/newcontam-0025-0001) published in New Contaminants on 05 September 2025 by Xiaoli Zhao’s & Xiaowei Wu team, Chinese Research Academy of Environmental Sciences & Nanjing University of Information Science and Technology, reveals how sunlight-driven photoaging of colored PET textiles, particularly those with dark dyes, accelerates microfiber formation and highlights color as a critical but previously overlooked factor in marine microplastic pollution.

In this study, researchers simulated long-term sunlight exposure by subjecting colored PET textiles to ultraviolet (UV) irradiation in coastal seawater, using multiple imaging and spectroscopic methods to monitor degradation. Scanning electron microscopy (SEM) revealed that UV exposure caused progressive structural damage starting from the warp–weft intersections, leading to the detachment of fibers and increased water turbidity after 12 days, while dark controls showed no change. Quantitative analysis indicated that 0.1 g of PET textile released 47,400 (purple), 37,020 (green), 23,250 (yellow), and 14,400 (blue) microfibers, with fragment sizes ranging from 200–2,000 μm and even nanoscale particles (~0.48 μm in purple fibers). Colorimetry showed significant fading, particularly in purple textiles (ΔE ≈ 23.4), and corresponding microfibers (ΔE ≈ 36.1), while ATR-FTIR confirmed that UV aging increased carbonyl index (CI) values—indicative of oxidation—and decreased crystallinity, reflecting molecular chain scission. Purple PET exhibited the highest CI (2.69) and mass loss (38%), suggesting the most severe photoaging. Mechanistic investigations revealed that dye chemistry played a crucial role: UV–vis spectroscopy demonstrated that purple and green dyes absorbed more UV light than blue and yellow dyes, enhancing free radical reactions. Electron paramagnetic resonance (EPR) and nitroblue tetrazolium (NB) assays detected stronger hydroxyl radical (•OH) generation in darker-colored samples, with purple PET producing the highest concentration (6.20 × 10⁻¹⁵ M) and fastest degradation rate (k′ ≈ 8.71 × 10⁻² h⁻¹). These findings demonstrate that textile color significantly influences microfiber release and aging kinetics, with darker dyes accelerating UV-driven oxidation and fragmentation, ultimately intensifying microfiber pollution in coastal marine environments.

The study provides crucial insights into how colored PET fabrics contribute to microfiber pollution, emphasizing that textile dye composition—not just fiber type—plays a decisive role in microfiber formation. These findings can inform future environmental risk assessments and pollution control strategies. By adjusting dye formulations or selecting pigments with lower UV reactivity, textile manufacturers could significantly reduce the generation of microfibers in marine environments. The research also highlights the need for stricter monitoring of synthetic textile degradation and its chemical byproducts in coastal ecosystems.

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References

DOI

10.48130/newcontam-0025-0001

Original Source URL

https://doi.org/10.48130/newcontam-0025-0001

Funding Information

This research was financially supported by the National Natural Science foundation of China (Grant No. 22406091, 41991315, and 41521003), Startup Foundation for Introducing Talent of Nanjing University of Information Science (2024r064), and Natural Science Foundation of Jiangsu Province (BK20240708).

About New Contaminants

New Contaminants is a multidisciplinary platform for communicating advances in fundamental and applied research on emerging contaminants. It is dedicated to serving as an innovative, efficient and professional platform for researchers in the field of new contaminants research around the world to deliver findings from this rapidly expanding field of science.