Toxicity of microplastics in the marine environment.

Marine litter is one of the most expanding and devastating problems in the marine environment. Among several types of items and origins, microplastics have been drawing attention due to their small particle size (<5 mm), persistence and the potential to be ingested by a high variety of organisms and act as vectors of chemical pollutants. This chapter provides a broad and updated review of the ecotoxicological effects of microplastics on marine biodiversity. Effects of microplastics have been demonstrated from the biochemical to physiological, behavioural and even ecological levels of organization. Most information comes from a range of biomarkers on low levels of organization, such as oxidative stress (lipid peroxidation, DNA damage and the activation of antioxidant enzymes) and immunological responses (phagocytosis activity, signs of inflammation and enzyme/protein response). However, the variety of experimental conditions, including plastic size and shape, polymer type, additives, concentration and period of exposure, and biological model, still does not allow a clear and wide understanding on the effects on the environment and, indeed, humans. This scenario calls for additional and coordinated efforts to improve scientific knowledge on this subject.