What is the biggest source of ocean pollution?

80% of ocean pollution comes from land. Nonpoint (NPS)source, which is an effect from a runoff, includes many small sources, like septic tanks, cars, trucks, and boats, plus larger sources, such as farms, ranches, and forest areas. Millions of cars drop small amounts of oil each day onto roads and parking lots.

Much of this, too, makes its way to the sea.