New research reveals microplastics are leaking invisible chemicals into our water, a process sped up by sunlight. Discover the unique chemical signatures and the growing risks to aquatic ecosystems.
Microplastics are small fragments of plastic that float in rivers, lakes, and oceans. While they are usually considered as physical waste, recent research reveals that they also release invisible chemicals into the water. These chemicals gradually leak out over time and escape more quickly when the plastic is exposed to sunlight.
Scientists have created the most detailed analysis so far on how this chemical release process works. The chemicals released are known as microplastic-derived dissolved organic matter (MPs DOM). Unlike natural organic material found in rivers and soil, these chemicals originate directly from plastics and act differently in water.
Chemical Cloud
A study published in the journal New Contaminants examined four common types of plastic. Researchers compared the chemicals released from these plastics to the natural organic matter present in rivers. Using advanced lab methods, they found that each plastic releases a unique mix of chemicals, and this mix changes as the plastic breaks down in sunlight.
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The lead researcher explained that microplastics do more than just float as visible waste. They also create an unseen “chemical cloud” in the water, which becomes stronger as the plastic ages and is exposed to environmental factors. Sunlight was found to be the main driver of this process.
Sunlight Makes Plastics Leak Chemicals Faster
To test the effect of light, the researchers placed four types of microplastics in water, both in the dark and under ultraviolet light, for up to four days. The plastics tested included polyethylene and PET, as well as biodegradable options like PLA and PBAT.
In all cases, exposure to light caused a much greater release of chemicals into the water. Biodegradable plastics released the most, likely due to their less stable chemical structures, which break down more easily.
The team also found that the rate of chemical release remained steady over time. This means the process is controlled by changes happening at the surface of the plastic, rather than the amount of chemicals already in the water. Under sunlight, the movement of chemicals from the surface became the main limiting factor.
A Complex and Changing Chemical Mix
A complex and changing chemical mix was found in MPs DOM, consisting of various types of molecules. These included fragments of the plastic, leftover building blocks, and added chemicals used to make plastics flexible or durable. Plastics with more complex structures, such as PET, produced especially complicated chemical mixtures.
As plastics broke down further, the chemicals released became richer in oxygen-containing compounds. This suggests the formation of substances like alcohols and acids. Phthalates, which are commonly used to soften plastics, were also found, as they are only loosely attached to plastic materials.
Interestingly, the chemical patterns of MPs DOM resembled organic material produced by microbes rather than material from land plants and soils. Over time, the balance of different organic substances changed depending on the type of plastic and the amount of sunlight it received.
Why This Matters for the Environment
These hidden chemicals could have significant impacts on aquatic ecosystems. Many of the released molecules are small and can be easily absorbed by microbes. This might affect microbial growth, disturb nutrient cycles, or change how metals and other pollutants behave in water.
Past studies have shown that MPs DOM can produce harmful reactive chemicals, influence by-products in water treatment, and change how pollutants attach to particles. As global plastic production continues to rise, these dissolved chemicals may become a growing environmental concern.
The researchers emphasize that plastic pollution should not be viewed merely as solid waste. As microplastics break down in sunlight, their hidden chemical pollution also increases. Understanding how these chemicals change over time is crucial for assessing their long-term impact on water quality and the health of aquatic ecosystems.
