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How do sunlight, wind, and seawater turn larger plastic objects into microplastics?
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plastic
Plastic soft-drink bottles are commonly made of polyethylene terephthalate (PET).
Conventional plastics are not biodegradable, meaning they do not break down through the action of microorganisms. Instead, larger plastic objects undergo a process of physical fragmentation into microplastics through environmental weathering.123
This breakdown is driven by several abiotic forces:
- Sunlight: Ultraviolet radiation from sunlight causes the plastic to become brittle, facilitating its eventual fragmentation.24
- Seawater: Exposure to seawater also contributes to the embrittlement of plastic materials.4
- Mechanical Forces: Physical actions, such as wave action and wind abrasion, help break down these weakened, brittle plastic objects into smaller pieces.24
Once these larger items are reduced to fragments less than 5 mm in length, they are classified as secondary microplastics. Because they are not biodegradable, these particles persist in the environment for hundreds of years, accumulating in oceans, soils, and even the atmosphere, where they pose ongoing risks to ecosystems and wildlife.214