Plastic never degrades, and the flow of pollution is as never ending as the flow of water itself. However, the diseases humans can get from it are not as long-lasting. Some of these illnesses are Hepatitis A, cholera, giardia, and staph infection. All of these can last several weeks, and some can lead to death. If people keep throwing trash into the rivers and oceans, they can get these diseases simply because they do not know. Places where the rivers meet the oceans have a lot of pollution, like Ocean Beach, where the river mouth is. Depending on the type of pollution, it can possibly never go away either, or at least take a long time to. Bacteria die off over time, organic pollutants degrade rapidly, things like glass take a long time to degrade, but plastic never degrades, and harmful chemicals can accumulate in fish and bio-accumulate up the food chain, because birds and humans eat the fish.