Part C, Chapter 3 - Seabirds as Indicators of Metal and Plastic Pollution

The light weight, robustness, versatility, durability and low cost of plastic materials make them suitable to create a wide range of useful products. Unfortunately, these properties are also the reason why plastics are a serious threat to natural ecosystems throughout the world. Considering the large production, intense consumption and rapid disposal of plastics, they are widespread and ubiquitous in the environment, particularly in oceans. The absolute quantity of plastic that enter the marine environment is poorly described, but it is estimated that around 10% of produced plastics will end up in the oceans. Plastics are made by polymerizing monomers and other substances such as plastic additives, which are chemical compounds like plasticizers (polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs), bisphenol A (BPA), phthalates, among others), which provide the required properties of performance and appearance to a plastic polymer. As they do not break down into their chemical components, plastics will persist in the environment for very long time periods, typically hundreds or thousands of years, and in some cases might not degrade at all. Instead, plastics are exposed to mechanical and chemical weathering processes (e.g., wind, waves, UV light) that break them into smaller pieces over time, leading to the formation of microplastics. In 2008, during the first international research workshop about microplastics' occurrence, effects and fate, microplastics were defined as plastic particles varying from a few μm to 5 mm (5000 μm) in diameter. Currently, microplastics' size classification, especially the upper size limit, is not unanimous, being a source of discussion (e.g., particles smaller than 1 mm). Microplastics form a heterogeneous mix of polymers varying in shape (e.g., pellets, fibres, fragment and films), density, size and additives. There are also manufactured plastics of microscopic size used in some products such as beauty scrubbers and exfoliates, thus entering the ocean from both primary source products and as secondary sources derived from the breakup of larger plastic products. Consequently, plastics are rapidly increasing, ubiquitous marine pollutants, with significant ecological, cultural, aesthetic and economic impacts, and largely ineffective prevention or collection technologies given the scale of the plastic pollution problem.