258 R White increase with a reduction in the size of plastic particles while physical effects, such as the entanglement of seals and other animals in drift plastic, increase with the size and complexity of the debris’ (United Nations Environment Programme 2011, p 25) Fish, seabirds, sea turtles and marine mammals have all been affected by ingestion of plastics A key concern is the biochemical and physiological response of organisms to ingested plastics contaminated with PBTs (Persistent, Bioaccumulative and Toxic chemicals) Not only are there issues associated with the potential impacts of the releases of chemical additives that were part of the plastics’ original formulation, but as plastic breaks down into fragments (plastic particles of small size), it accumulates PBTs that are already present in seawater and sediments Many of these specific pollutants cause chronic effects such as endocrine disruption affecting reproduction, increases in the frequency of genetic mutations (mutagenicity) and a tendency to cause cancer (carcinogeniticy) According to the United Nations Environment Programme (2011, p 28): We know that microplastics are ubiquitous in the ocean, contain a wide range of chemical contaminants, and can be ingested by marine organisms However, the lack of certainly about the possible role of microplastics, as an additional vector for contaminants taken up by organisms, calls for caution and further research Compounding these continuous processes of contamination by plastics are other types of contamination, some of which are systemic (for example, related to agricultural practices), others the outcome of extraordinary events (such as the BP oilrig disaster) For instance, there is evidence that the nitrogen-based fertiliser used in (the increasing) corn production is causing environmental harm in its own right Millions of kilograms/pounds of those nitrates end up in the Gulf of Mexico each year, where it is causing a massive algae bloom This bloom negatively impacts the ecology of the Gulf: ‘When the algae dies it sinks to the bottom, where it absorbs oxygen as it decays In recent years that oxygen depletion has created an aquatic “dead zone” covering about 8,000 square miles in which shrimp, fish, oysters and crabs cannot survive’ (Reliable Plant 2007) The main causes of pollution are human-made and directly linked to existing techniques and processes of production (for example, agriculture, mining, manufacturing), consumption (for example, waste disposal), transportation (for example, internal combustion engine of cars, trucks and buses) and war (for example, use of depleted uranium in armaments) Pollution is