Complex sentence: Plastics in oceans typically degrade within a year, but not entirely, and in the process toxic chemicals such as bisphenol A and polystyrene can leach into waters from some plastics.
Split into simpler sentences: Plastics in oceans typically degrade within a year, but not entirely. In the process, toxic chemicals such as bisphenol A and polystyrene can leach into waters from some plastics.