the subject of plastic pollution is a global phenomenon that has no-end in sight. plastic pollution is widespread across all entangling oceans due to their buoyant and durable properties that allow for sorption of toxicants to plastic while traveling through the environment. this lead researchers to the conclusion that synthetic polymers are hazardous to marine life and should be declared as a hazardous waste type. there are many transit paths that allow for plastics and pollutions to enter oceans. freshwater waste can enter oceans by rivers; delta or estuary (where rivers meet the ocean). human populations discarding their waste directly into marine waters. through photo-degradation and other forms of weathering processes that aid in plastics fragmentation and dispersal. mass quantities of fragmented plastics - along with pollution are aggregated in subtropical gyres; ocean gyres. plastic accumulation is not limited to ocean gyres; closed bays, gulfs and seas surrounded by densely populated coastlines and watersheds are all susceptible."the pearl river delta is an estuary within the proximity of one of the many ocean gyres that the humpback dolphin inhabits. a tour guide from hong kong dolphinwatch spotted a group of pink dolphins helping a mother support the body of her dead calf above the water in an attempt to revive it. the scene, captured on video and widely shared on facebook, has raised fresh concerns about the dwindling population in a city where dolphin watching is a tourist attraction. "we’re 99 percent certain the calf died from toxins in the mother’s milk, accumulated from polluted seawater," said hong kong dolphinwatch spokeswoman janet walker, who added it was the third such incident reported in april alone. fewer than 2,500 of the mammals survive in the pearl river delta, the body of water between macau and hong kong, with the majority found in chinese waters and the rest in hong kong." (refer to: humans and the environment subsection above)