The document discusses the sources and impacts of oil spills in oceans. It states that over half of the approximately 706 million gallons of waste oil that enters oceans each year comes from land-based sources like cities and farms, while offshore drilling and transportation accidents each account for less than 10%. When oil spills occur, the oil can damage shorelines, fisheries and wildlife by poisoning and smothering organisms and interrupting food chains. Cleanup is difficult and environmental recovery depends on the type of oil and affected habitat.