The numbers are staggering: as many as 8 million tons of plastic end up in the ocean every year. Exacerbating concerns for ocean life and human health is the perception that plastics last indefinitely in the environment. Different formulations behave differently in the environment, which means different plastics break down in the ocean at different rates. For example, many plastic additives react chemically to light, leading plastics with additives to degrade more quickly in sunlight. These experiments will provide the first realistic, verifiable estimates of the lifetime of plastic goods in the environment—a critical step towards quantifying the risks associated with plastic pollution.