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How Oil REALLY Enters Our Waters
(and What You Can Do About It)

Large oil spills, such as the sinking of the Oil Tanker Prestige off the northwest Spanish coast and the Exxon Valdez spill in Alaska, close beaches, idle the local fishing industry, and cause widespread environmental devastation. Indeed, research conducted since Exxon Valdez shows that oil spills have long-term adverse effects on the marine ecosystem. Although incidents such as these get the most media attention, a 2002 report by the National Academies of Science National Research Council explains that, in fact, most of the petroleum that enters North American waters comes from human activities related to the consumption of oil, not from the ships that transport it.

Since 1975, the Council has released a series of three studies entitled Oil In The Sea. The 2002 report found that approximately 29 million gallons of petroleum enter North American waterways each year as a result of human activities. Nearly 85 percent comes from land-based runoff, polluted rivers, airplanes, and small boats and jet skis, while less than 8 percent comes from tanker or pipeline spills. Oil exploration and extraction contribute 3 percent to that total.

Here is the breakdown of how oil enters North American waters:


Millions of Gallons/Yr





Pipeline/transport spills, and refining/distribution


Two-stroke engines (small boats, jet skis)


Oil and gas exploration




Total petroleum from human activities


Total petroleum from natural processes


The Council hopes that with this report showing the volume of petroleum from slow, chronic sources, more research will be conducted about the impact of this type of pollution on the marine community. Based on existing research, the EPA is working with marine engine manufacturers to phase out the pollution-causing two-stroke engines within the next 10 years. Two-stroke engines are lightweight, inexpensive engines found in jet skis and small outboard motors, as well as dirt bikes and other low-power applications. Their simple design, however, produces pollution by emitting clouds of oily smoke, and by leaking fuel directly into the surrounding water.

The EPA's Dee North stated "The regulations will require that the manufacturers reduce the pollution from their new engines that they sell in the future by over 75 percent. Four-stroke engines are cleaner, quieter, and use about half the fuel. Although the initial cost for the consumer will be higher, improved fuel efficiency should help them recoup a significant amount of their cost over time." EPA regulations will affect only marine manufacturers; boat owners and boat dealers are not responsible for restricting the use or sale of vessels with two-stroke engines.

Recreational boats and jet skis with two-stroke engines are commonly used in coastal waters, which unfortunately are some of the most ecologically sensitive areas. As populations in coastal areas grow, so does the petroleum from human factors. In fact the coastline from Maine to Virginia is the source of more than 50% of the land-based oil contamination along the entire North American coastline. This stretch of land is home to several refineries, and dense populations that use a significant amount of energy.

Recommendations coming from the NAS report include:

  • The Government should research how chronic releases of petroleum affect the marine environment, especially the cumulative effects of multiple types of hydrocarbons present in these releases.

  • The Environmental Protection Agency should continue efforts to phase out two-stroke engines.

  • The U.S. Coast Guard and U.S. Maritime Administration should work with ship owners to expand and enforce shipping standards.

  • Federal agencies should continue to work with state environmental agencies and industry to evaluate the threat posed by aging pipelines and to take steps to minimize the potential for spills.

  • Federal agencies should work with state and local agencies to implement a system for monitoring the input of petroleum to the marine environment from land-based sources via rivers and storm- and water- facilities.

  • Ocean-management agencies should develop more accurate technologies for estimating the amount of oil that seeps into the ocean from geologic formations, to distinguish between the effects of petroleum from human activities from natural processes.

  • Federal agencies work with industry to develop and implement a rapid response system to collect on-site data about spill behavior and impacts.

The NAS report shows the significant impact that we, as individual boaters, have on the quality of our nation's waters. Although the EPA states, "Boat owners are in no way responsible for making modifications to their current engines to meet the standards," there are practices we can follow to help reduce pollution as much as possible. In addition to purchasing cleaner technology engines, EPA suggests boaters do the following:

  • operate only well maintained boats

  • limit full throttle operation

  • eliminate unnecessary idling

  • follow recommended maintenance schedules

  • eliminate spillage when refueling

  • properly measure fuel and oil if required for a particular engine.

Boaters and non-boaters can get involved in other ways as well. Each year, an estimated 200 million gallons of used motor oil is improperly disposed of by being dumped on the ground, tossed in the trash, and poured down storm sewers and drains. Properly disposing of oil would save 1.3 million barrels of oil per day (through recycling), and reduce harmful hydrocarbons and heavy metals in waterways. If you change your own oil, find a local recycling center by clicking here.

The National Academies of Science study was sponsored by the U.S. Minerals Management Service, U.S. Geological Survey, U.S. Department of Energy, U.S. Environmental Protection Agency, National Oceanic and Atmospheric Administration, U.W. Coast Guard, U.S. Navy, American Petroleum Institute, and the National Ocean Industries Association.

For those interested in further research on this important topic, we provide the following resources:

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