PARIS, France - Plastic pollution in the world's oceans has reached "unprecedented levels" over the past 15 years, a new study has found, calling for a legally binding international treaty to stop the harmful waste. Ocean plastic pollution is a persistent problem around the globe -- animals may become entangled in larger pieces of plastic like fishing nets, or ingest microplastics that eventually enter the food chain to be consumed by humans. Research published on Wednesday found that there are an estimated 170 trillion pieces of plastic, mainly microplastics, on the surface of the world's oceans today, much of it discarded since 2005. "Plastic pollution in the wor...Keep on reading: Rise in ocean plastic pollution ‘unprecedented’ since 2005