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Sources of Oil in Water

An oil slick in the wake of a ship at sea

Photo Credit: US Department of Justice

Intentional Oil Dumping Sources

Source: American Academy of Sciences,
Oil in the Sea III, 2003

According to the National Academy of Sciences the majority of the oil in the ocean, about fifty-two percent, is the direct result of human activity. The remaining forty-eight percent comes from natural underwater seeps.

Each year, human activities send between 190 million and 706 million gallons of crude oil or its refined products into the seas.

The single largest source of man-made oil pollution in the oceans is oily waste spilled from ships. Oil illegally dumped from commercial ships accounts for 46% of all the oil entering the world’s oceans from human sources.

Put into perspective, the yearly intentional discharge of oil into the seas through routine shipping operations is equal to eight times the amount released by the Exxon Valdez oil spill.

While oil spills produced by large industrial accidents like the Exxon Valdez, which spilled 11 million gallons of oil in 1989, or British Petroleum’s Deepwater Horizon, which released 210 million gallons of oil in 2010, garner the most media attention, they make up just 18% of the oil released into the water as a result of human activity.

Air pollution from cars and industry accounts for just over 8% of the total input of oil into our oceans from human activity. The hundreds of tons of hydrocarbons that are emitted form particle fallout, which is then swept into the oceans by rainfall.

Runoff from land sources accounts for 21% of oil discharged into the water from human activity. Rain washes oil leaked by cars from roads into storm drains, which empty directly into our waters. Another large source of land runoff pollution comes from the improper disposal of engine oil. An average oil change uses 5 quarts of oil, which can contaminate millions of gallons of fresh water.

According to the EPA, more than half of all Americans change their own oil, but only about one-third of the used oil from do-it-yourself oil changes is collected and recycled.

Industrial activities associated with the extraction of petroleum represent just 6% of oil in the water from human sources.

Learn more about Illegal Dumping by Commercial Ships