Characteristics, fate, and impact of marine plastic debris exposed to sunlight: A review

Highlights: • Plastics exposed to sunlight undergoes visual and physico-chemical modifications. • Exposure medium (air/water) highly affects the photodegradation process. • Fragmentation depends on polymer type, formulation, exposure conditions. • The path and time spent by the plastic in the environment cannot be identified yet. • Plastics risk is associated to organic pollutants and degradation products. The increase of plastic production from the middle of the twentieth century was inevitably followed by an increase in the amount of plastic dumped in the natural environment. There, the plastic debris are exposed to sunlight, temperature, humidity, and physical stress. This can induce photo-oxidative and thermal degradation. This review discusses the mechanism of plastics UV weathering and its characteristics. Comparison of the photodegradation rate and physico-chemical properties are made according to the weathering mode (natural/accelerated) and medium (air/water). Since the photodegradation can lead to plastics fragmentation, this phenomenon is described along with the methodologies used in literature to evaluate the fragmentation. The impact of the photodegraded plastic debris on the marine environment is also presented in term of (i) photodegradation products and stabilizers leakage, (ii) organic pollutants accumulation, transfer, and leakage, and (iii) toxicity on marine organisms.