Oil Spills : Liquid petroleum (crude oil and its refined products such as tar, lubricating oil, gasoline, and kerosene) can be released as catastrophic spills from point sources (e.g., from tankers and blowouts) or as chronic discharges typically from nonpoint sources (e.g., from urban runoff or fallout from the atmosphere). Releases of petroleum into the environment occur naturally from seeps as well as from human sources