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Environment Magazine September/October 2008


November-December 2013

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Oil Pollution in the Marine Environment I: Inputs, Big Spills, Small Spills, and Dribbles

The BP Deepwater Horizon Macondo Oil Well spill in the Gulf of Mexico three years ago renewed and reinforced concerns about oil pollution in the marine environment. This article is intended to provide an overview of our knowledge of the inputs of oil in the marine environment, mainly evolving from significant advances as a result of research and assessments of the past 50 years. The title of the article reflects the range of sizes of oil inputs resulting from human activities. There is also a relatively large input of oil that results from natural oil seeps in the marine environment and from everyday activities involving human use of oil.

There have been large accidental oil spills in numerous places around the world for decades. Locations and amounts of several of the largest oil tanker ship spills as published in the database of the International Tanker Owners Pollution Federation LTD (ITOPF)1 are listed in Table 1A. Table 1B shows comparisons of some of the notable largest, near-shore and continental margin oil well spills, and estimates of the oil input to the Gulf as a result of the Iraq conflict. Figure 1 indicates the locations of spills listed in Table 1 and demonstrates that this is a global issue. Several of these tanker spills are less well known because they occurred some distance offshore in deeper waters and none of the spilled oil, or only a small amount of it, reached coastal ecosystems where there were concerns with adverse impacts on these ecosystems or threats to the livelihood and well-being of people using these ecosystems. In a sense, these spills were “safely out to sea” and were “diluted or swallowed up” by the immensity of the ocean. Few of those offshore spills received any significant scientific study. There may have been adverse impacts on the open ocean ecosystems of the spill area for some period of time, such as oiled sea birds, but there may also have been no detectable significant adverse impacts.

Table: Table 1A. Top 20 major oil spills from oil tankers since the Torrey Canyon in 1967, update as of 2012.





Spill Size (tons)




Off Tobago, West Indies





700 nautical miles off Angola





Off Saldanha Bay, South Africa





Off Brittany, France





Genoa, Italy





700 miles off Nova Scotia, Canada





Scilly Isles, UK





Gulf of Oman





Navarino Bay, Greece





La Caruna, Spain





300 nautical miles off Honolulu





Bosphorus, Turkey





Oporto, Portugal





Shetland Islands, UK





120 nautical miles off Atlantic coast of Morocco





La Coruna, Spain





Milford Haven, UK





Off Karg Island, Gulf of Iran





Off Maputo, Mozambique





Off Galacia, Spain





Prince William Sound, Alaska, USA





Taean, Republic of Korea


Source: From the International Tanker Operators Federation LTD. (ITOPF) web site2 ( statistics/statistics/). With permission of the International Tanker Owners Pollution Federation Limited (ITOPF).

Table: Table 1B. Four large major non-tanker oil spills for comparison to Table 1A.

Incident Name



Spill Size, Tons

Kuwait/Gulf War3


Kuwait/ Persian Gulf


BP Deepwater Horizon Macondo Well4


US Waters Gulf of Mexico 60 miles off the State of Louisiana.


IXTOC I Well5,6


Mexican Waters, Bay of Campeche, Gulf of Mexico

Est. 450,000 to 1,400,000

Nowruz Well during the Iraq-Iran war7


Northern Persian Gulf


aThe official estimate of the amount of oil spilled is 4.9 million barrels +/− 10%,8 or a mean of 700,000 tons. (Note that the conversion is barrels x 42 gallons/barrel x 0.0034 tons/gallon = tons8, which is the unit metric tons).

 Figure 1. Map of oil spills listed in Table 1. Modified with locations of four non-tanker spills.

Figure 1. Map of oil spills listed in Table 1. Modified with locations of four non-tanker spills.

Note that the Exxon Valdez oil spill is included in Table 1A and ranks in the ITOPF data base as number 35 in terms of tanker spill size. Because it happened in a coastal area in a relatively pristine environment, it received a lot of media attention and also scientific study. In addition, it was the subject of an intense legal battle over damages. Also included in Table 1A is the spill from the tanker Hebei Spirit off the coast of Taean, Republic of Korea, which ranks 131 in size at 11,000 tons. The spill occurred near one of the Republic of Korea's most popular and beautiful beaches, Maillipo Beach. Also, it was near one of Asia's largest wetland areas, and an area containing sea farms. It was an important spill as far as the people of the area were concerned. This is often the case, even for small oil spills in coastal areas.

For all of these accidents, with the exception of the accidental spills during the Persian Gulf War, the questions were similar: Why can't we prevent such accidents, and once they happen why can we not contain and clean them up quickly? What will happen to the oil? Is this an ecological catastrophe? What will be the biological effects? Also similar for these accidents was the fact that once the large visible oil slicks on the surface disappeared, media attention and initially to a lesser extent, the attention of elected and appointed government officials, shifted elsewhere. In part, this is a manifestation of the lack of dramatic visual scenes of gushing oil and gas and large oil slicks, in part the emergence of other important news issues, and in part the fact that the large widespread environmental catastrophe legitimately feared by some and perhaps hyped by others did not unfold.

The fact that severe, widespread adverse impacts (for example, if, hypothetically 90% of the biota was killed in an entire large area such as the entire Alaskan Coast or for the entire North Sea) did not occur does not mean that there were no adverse impacts. Some accidents involve the loss of human lives or severe injuries. The BP DWH Macondo well accident, first and foremost, involved the loss of lives for 11 people. That in itself is more than enough reason to strive to prevent future accidents. There is a clear indication that settlements for economic and natural resource damage assessment claims related to the BP DWH spill will be at least several billions of dollars once litigation is completed.9

It is important to consider such large spills as objectively as practicable within the context of the inputs of petroleum (oil and gas) to the marine environment.

There have been natural oil and gas seeps in some areas of the oceans for thousands, if not millions, of years. Illustrating this fact, some areas of the world's coasts have indicative names such as Coal Oil Point in Santa Barbara, California, where there are natural oil seeps in the coastal ocean region. Thus, the oft asked question: why the fuss about petroleum inputs to the environment? The answer is akin to that regarding the natural chemicals arsenic, mercury or lead. Human activities mobilize these chemicals and in the case of petroleum, in such a manner that in many locations, the amounts entering the environment can result in higher concentrations than would naturally be present; sometimes this causes adverse effects on people and on marine organisms. Marine mammals and birds can suffer from being coated with oil from contact with slicks not normally present in their home range habitat. If these chemicals are accumulated in seafood, then they can be transmitted to people, and charismatic marine species such as marine mammals and birds via the food web. In the situation with oil spills, depending on the type of oil spilled, people nearby to the spill as it comes ashore, such as fisherman and boaters, and response and cleanup workers can be exposed to unhealthy fumes from the spilled oil.

A review of the scientific literature of the 1910s to 1950s, the early days of accidental oil spills, documents that there have been concerns with oil spills in the marine environment ever since oil has been transported across the seas.1013 During the 1950s and 1960s it became apparent that routine operations of oil tankers resulted in significant inputs of oily tar-like material in the oceans. This material was being captured in nets and fouling coastal areas in some places in the world, including swimming beaches.14 The problem was brought to widespread public attention by the public statements and writings of Thor Heyerdahl reporting on his trans-Atlantic raft voyage.1517

The major source of the floating tar was identified as inputs from ballast water operations. While in transit from ports where they unload their oil cargo to ports where they load on new oil cargo, the cargo tanks were washed out to remove residual oil and oil was replaced with ballast sea water to maintain stability of the ship. The result was oily wastes being discharged into the ocean, and some of this resulted in lumps of tar floating in surface ocean waters. These lumps mainly ranged in size from thumbnail size to fist size. Efforts to assess the extent and severity of floating tar in the oceans were conducted in the late 1960s and early 1970s.1820 These early results catalyzed the formation of an international monitoring program under the auspices of the Intergovernmental Oceanographic Commission and the World Meteorological Organization of UNESCO.21 Nearly simultaneously, member nations of the Intergovernmental Maritime Consultative Organization (now the Intergovernmental Maritime Organization or IMO) negotiated rules and regulations to minimize inputs of ballast tank washings of oil to the ocean by establishing standards for segregated ballast tanks, crude oil washing devices, oily-water separators, pumping and discharge systems, and monitoring devices.22

The Torrey Canyon tanker went aground off England in 1967, and the resulting oil spill of 119,000 tons and the largely unsuccessful attempts to use emulsifiers and dispersants to disperse the oil, aircraft bombing to burn the oil, and other measures, were captured in photos and on TV, and broadcast widely (see Case Histories on the ITOPF web site23). Two years later in 1969 an oil well blew out off the coast of Santa Barbara, California, spilling an estimated 4,700 tons of oil with much news coverage. This happened during a period of much heightened awareness of environmental concerns that led a year later in 1970 to the first Earth Day.24

A generally unheralded smaller oil spill occurred a decade earlier in 1957 when the Tampico Maru ran aground two miles north of Punta Cabras in Baja California, about 90 miles south of the United States-Mexico border. The Tampico Maru was loaded with approximately 7,000 tons of diesel fuel, part of which was lost immediately, and the rest spilled over the next eight to nine months as the vessel broke up. Professor Wheeler North, a marine biologist at the Scripps Institution of Oceanography and later the California Institute of Technology, and his team travelled to the remote location and provided both qualitative observations and quantitative analyses of the effects of the spill on subtidal and intertidal biota over months to a year, and longer in some locations, and then the recovery with a study over a period of 1957 to 1972.25,26 Unfortunately, there were no chemical analyses to compare to the biological analyses of samples from the spill location. However, the biological survey results were pioneering and presaged results of studies of the effects of oil spills during the remainder of the 20th century.

Somewhat unheralded in the public media in the early stages of the spill, the oil barge Florida, went aground in Buzzards Bay on September 16, 1969, off West Falmouth, Massachusetts. There was a relatively small spill of No. 2 Fuel Oil—between 650 and 700 tons. The oil entered coastal ecosystems that were in the “backyard” of several scientists at Woods Hole Oceanographic Institution. Drs. Max Blumer, Howard Sanders, J. Fred Grassle, John Teal, their lab co-workers and graduate student Kathryn Burns brought the latest biological sampling and chemical analysis techniques and knowledge of the composition and geochemistry of oil and biological processes to the study of this small oil spill. They published their results in peer-reviewed scientific literature. Several Woods Hole scientists, the present author included, have published about the fate of this spill.2738 In addition, and of importance, they presented their findings to various public venues and in an article “A Small Oil Spill” in 1971 in Environment.34

Shortly after the barge Florida-West Falmouth spill of No. 2 Fuel Oil, the tanker Arrow grounded on February 4, 1970 in Chedabucto Bay, Nova Scotia, Canada, and subsequently spilled an estimated 1,000 tons of Bunker C oil. The study of the Arrow spill employed some of the same combined chemistry and biology approaches of the West Falmouth oil spill studies.35,36 Back in Buzzards Bay in 1974, the barge Bouchard 65 spilled No. 2 fuel oil, impacting the coast of Bourne, Massachusetts, a few miles from the West Falmouth spill and showed the same or similar environmental fate and effects on intertidal organisms and grasses in an oiled marsh.37,38

The fact that spilled oil in some circumstances could have longer term persistence and effects (two years or perhaps longer after an oil slick disappeared from public view) was a significant stimulus for greater attention to assessing various categories, pathways and amounts of inputs of oil into the sea.

What Is Petroleum? Why the Composition Matters

Petroleum is made of three principal phase components: natural gas, condensate, and crude oil. Natural gas does not condense at standard temperature and pressures when it is brought to the surface from deep sediment reservoirs. It is made up mostly of methane with some contributions of other gaseous chemicals such as ethane, propane and chemicals of similar volatility. Condensate is gaseous in the reservoir but condenses to liquid at standard surface temperature and pressure and is composed of non-gaseous but lower molecular-weight compounds. Crude oil is a complex mixture of hundreds of relatively major component hydrocarbons and thousands of minor component hydrocarbons and related compounds. Crude oil is liquid in the reservoir and liquid at the surface.39

Refining of crude oil is a combination of distillation and “cracking” to yield gasoline, which consists of lower molecular weight hydrocarbons and distillation alone, which yields kerosene (main component of some jet fuels), diesel fuel, heavy gas-oil, lubricating oil, and residuum. Combinations of diesel fuel and heavy gas-oil are used for No. 2 Fuel Oil, which is home heating oil, and heavy gas oil is used for industrial heating purposes. Then there is “bunker fuel oil” which is defined by the viscosity at a given temperature allowing it to be injected through a nozzle into a burner of a ship's power plant. This can be a wide mixture of lower molecular weight kerosene compounds and lubricating oils and residuum from distillation refining. The word “bunker” comes from the time that ships were coal powered and had coal bunkers.

When we ask questions about the fate and effects of an oil spill or other oil inputs, we are asking questions about the fate and effects of a complex mixture of mainly hydrocarbons (chemicals composed of hydrogen and carbon atoms); some smaller amounts of nitrogen, oxygen, and sulfur-containing chemicals; and some even smaller amounts of organic chemicals containing metals such as nickel and vanadium.

The classes of chemicals include: n-alkanes, branched alkanes, cycloalkanes, (the term alkanes is sometimes replaced by the term paraffins and cycloalkanes are sometimes termed cycloparaffins or “naphthenes” in the petroleum industry literature), aromatic and polycyclic aromatic hydrocarbons, and heteroatom compounds where the carbon atom is replaced by a nitrogen, sulfur, or oxygen atom. Furthermore, each of the individual chemicals in petroleum has its specific behavior in the environment. Although it seemed obvious from first principle arguments that the chemical composition of spilled oil or oil from other inputs matters, there is no doubt after 50 years of research that this is true.

Another important point about the chemical composition of oil is that terrestrial and marine organisms biosynthesize hydrocarbons or transform other types of biochemicals into hydrocarbons. These biological compounds are a much simpler mixture of hydrocarbons and are mainly n-alkanes and branched alkanes and also alkenes (alkenes are compounds where the carbon atoms in an alkane-type structure do not have as many hydrogen atoms attached and the carbon-to-carbon bonds are termed unsaturated or alkene bonds). Relatively minor amounts of a few other hydrocarbons are formed when marine organic matter undergoes transformation after deposition and burial in the upper meter or so of organic rich marine sediments, a combined microbial and geochemical process termed early diagenesis. The key differences between biosynthesized hydrocarbons and petroleum hydrocarbons is that the former are a simple mixture without many, if any, aromatic hydrocarbons, and the latter are a very complex mixture of hundreds to thousands of compounds.

What follows is an overview of the current knowledge of oil inputs to the marine environment informed by extensive reviews conducted by groups of experts convened by such authoritative organizations as the U.S. National Research Council,4042 the United Kingdom's Royal Commission43 and the United Nations Joint Group of Experts on the Scientific Aspects of Marine Pollution (GESAMP),44 and literally thousands of peer reviewed papers and reports reviewed in those and other similar reviews.

Inputs of Oil to the Marine Environment

Accidental oil spills garner much public attention as they are an acute input of oil at a specific point in time at a specific place. A recent assessment by ITOPF noted that the annual frequency of oil tanker spills of 700 tons or greater has been decreasing and is projected over the long term to be 0 to 3 per year worldwide (Figure 2).45 Increased regulations, liabilities, increasing insurance costs, and increasing cleanup costs, plus the loss of a valuable cargo and ship are probable causes. Since 2006, ITOPF has been responding to more non-tanker oil spill incidents, such as from “roll-on-roll-off ferries, bulk carriers, general cargo vessels, container carriers, cruise ships and passenger ferries, car carriers, fishing boats, floating storage units, and reefers.”46

 Caption: Figure 2. Number of oil tanker spills greater than 700 MT (y-axis), years (x-axis) .50.

Caption: Figure 2. Number of oil tanker spills greater than 700 MT (y-axis), years (x-axis) .50.

Inputs from oil well accidents are a small part of the total average annual oil input worldwide.47 However, one accident of the size of the IXTOC I spill or the BP DWH Macondo spill (see Table 1B) can dominate average annual inputs in a region or locale for several years or longer.

Caption: A closer shot of the IXTOC I well site with an 800-foot crane ship for scale. Flames in circle about 50 meters across and sometimes 7 meters high.

Caption: A view of the well head site from a distance in the IXTOC I oil spill. Two jack-up oil rigs are in the process of drilling relief wells on either side of the slick with flames and whitish smoke just visible in the distance.

 Caption: A closer shot of the IXTOC I well site with an 800-foot crane ship for scale. Flames in circle about 50 meters across and sometimes 7 meters high.

Caption: A closer shot of the IXTOC I well site with an 800-foot crane ship for scale. Flames in circle about 50 meters across and sometimes 7 meters high.


 Caption: A close up shot of the IXTOC I well site. Flames burn gas that has risen to the surface in a vertical plume from near the ocean bottom (about 40–45 meters) that is bubbling up in a circular vertical plume with oil droplets mixed with water bubbling around the circle of gas flames.

Caption: A close up shot of the IXTOC I well site. Flames burn gas that has risen to the surface in a vertical plume from near the ocean bottom (about 40–45 meters) that is bubbling up in a circular vertical plume with oil droplets mixed with water bubbling around the circle of gas flames.


Accidental inputs of all types account for about 10% or less of the total inputs averaged over several years, and globally. Natural oil seeps and chronic inputs from human activities, such as sloppy uses of oil on land resulting in coastal and river runoff, and atmospheric transport of volatilized hydrocarbons to the ocean, account for more oil entering the ocean than accidental spill inputs as was summarized in the latest 2003 U.S. National Research Council review of the subject48 (Table 2). This NRC review gives the best estimates available to science and yet for some categories, such as natural seeps of oil and inputs from some human uses, there are wide ranges to the estimates. In addition, these estimates are now a decade old. However, it is important to consider these chronic inputs and their fates and effects, in addition to the more visibly spectacular accidental large oil spills, because they can result in accumulation of oil chemicals in portions of ecosystems and also have chronic effects.49

Over the years, since the early assessments by the U.S. National Research Council reports in 1975 there has been a better assessment of inputs from natural seeps in deeper waters. Despite wide ranges of uncertainty, it seems clear that these annual inputs are significant (Table 2). It is important to note that they are not distributed uniformly throughout global marine ecosystems.

The chronic release of oil to the marine environment by discharges related to operations of ships (not tanker ballast operations) is a significant part of the total inputs worldwide (Table 2). Non-tanker vessel operations for ships weighing more than or equal to 100 gross tons result in normal operational discharges of about 270,000 tons worldwide. The sources of such inputs are pumping bilge waters containing oily ballast water and fuel oil sludges overboard. In some countries, such as the United States, these discharges are not allowed in coastal waters. However, elsewhere and in the open ocean these are routine occurrences. Efforts by the International Convention for the Prevention of Pollution from Ships (MARPOL 73/78) to regulate ships greater than 100 gross tons have a goal of reducing these types of inputs; as these regulations are being enforced, they are becoming effective in reducing these types of inputs of oil to the ocean.51

Table: Table 2. Amount of released petroleum worldwide to the ocean (x 103 tons per year) averaged over 1990–1999.

Oil Inputs to the Sea

Best Estimate

Range of Estimates

% of Total Based on Best Estimatea

Natural Seeps




Extraction of Petroleum








Atmospheric deposition




Produced waters




Transportation of Petroleum




Pipeline spills




Tanker vessel spills




Operational Discharges




Coastal Facility Spills




Atmospheric Deposition




Consumption of Petroleum




Land-based (river and runoff)




Recreational Marine Vessel


Worldwide data not available. U.S is 2.2–9.


Spills non-tanker vessels




Operational discharges (vessels > 100GT)




Operational discharges (vessels < 100GT)


Worldwide data not available. U.S. is 0.03–0.3


Atmospheric Deposition




Jettisoned aircraft fuel








aCalculated by this author. Does not equal 100% due to rounding calculations and in estimating subtotals and totals.

Source: Adapted from “Oil in the Sea III: Inputs, Fates, and Effects,” National Academies Press 2004, Washington, DC.

Chronic inputs related to human use of petroleum, especially the land-based inputs to rivers and coastal runoff, are another significant source of oil inputs. Despite the fact that much of the used motor oil from cars and trucks is now recycled in several countries (e.g. the United States and European Union countries) there are considerable amounts of oil chemicals in sewer effluents of cities of these countries discharging to rivers and the coastal ocean.

There has been a recent effort to update the estimates of oil pollution to the marine environment from land-based sources.52 This effort yielded an estimate for North America that was 50% less than the NRC Report.53 However, as with the NRC report, much of the estimates are based on using oil and grease measurements from sewage outfalls and estimating how much of the oil and grease are indeed oil chemicals. Oil and grease often include animal fats and vegetable oils, which are not petroleum hydrocarbons; they are made up of other chemicals such as triglycerides, fatty acids, steroids, and a few biogenic hydrocarbons such as the n-alkanes found in the waxy coating of apples. This has been known for decades.5456 Thus, the problem with this approach is the assumption that a certain proportion of oil and grease are petroleum hydrocarbons and polycyclic aromatic hydrocarbons (PAH) from combustion sources. This is fully recognized by the NRC report and Saito et al., and both call for increased measurement and monitoring of petroleum hydrocarbons in rivers and sewers and land runoff discharging to the ocean.57 Once again, it is important to keep in mind that these best estimates have wide ranges of uncertainty, but they are the best available at present.

UNEP issued a report in 2012 titled “Compendium of Recycling and Destruction Technologies for Waste Oils” to address the growing problem of waste lubricating oil as amounts grow with the increased industrialization and use of autos and trucks in developing and emerging economic countries.58 The report highlights the effectiveness of recycling technologies to produce recycled lubricating oil for cars and autos, and also clean, non-air-polluting ways to use recycled waste oils as fuels for industrial and municipal power plants. In developed countries, collection and recycling of used lubricating oils has become effective (e.g., see Figure 3) for the European Union countries, and more progress is expected for cleaner recycling practices for all countries in the world if the UNEP report recommendations are followed. This should reduce waste oil input to the marine environment in future years.59

Caption: Figure 3. Used oils, collectable oils, and oils actually collected for recycling in EU Countries in tons (y-axis) .61.

Caption: Figure 3. Used oils, collectable oils, and oils actually collected for recycling in EU Countries in tons (y-axis) .61.

Another source of oil to coastal waters, highlighted by the NRC 2003 report, is discharge from the increasingly large numbers of outboard motors and personal water craft such as jet skis. There are insufficient data for a worldwide estimate, but the estimate for the United States was 2,100 to 8,500 tons per year with a best estimate of 5,300 tons. Anyone who has been near an idling two-cylinder outboard motor can observe, on occasion, a rainbow colored oil sheen on the water surface because of oil release. The advent of four-cylinder engines with different combustion and lubrication processes is reducing the oil input from outboard motor sources.60

A category of potential and real input, not included in Table 2 but noted in the NRC report of 2003, is the input from historic ship wrecks, especially those from both tankers and non-tanker vessels sunk during World War II. A few are leaking and causing small oil spills from time to time.62 Following the 2003, NRC report, there has been a 2005 report providing a comprehensive and nicely reasoned assessment for the potential for oil pollution from wrecks.63 The amount of oil available for leakage from a reported 1,583 tank vessels and 6,986 non-tank vessels is between 2.5 million and 20.4 million tons. When each wreck might leak and at what rate is speculative at present but such questions are the source of ongoing investigation and risk assessments by various nations and groups of nations.64 Thus far, it is clear that while some generalities apply to all such spills—such as age of the wreck—risk assessment is site-specific, just as it is with modern individual oil spills.65

Geographic Specific Comparisons of Inputs

One of the several valuable aspects of the 2003 NRC report is the regional estimates of oil inputs for coastal and continental shelf regions of the United States, Canada, and Mexico—roughly equivalent to maritime Exclusive Economic Zones of these countries.65 Data for the Gulf of Mexico region of the United States, including the regions of Texas, Louisiana, Mississippi, Alabama and Florida, suggest that natural seeps contribute 140,000 tons per year.66 This is almost 40% of the input from the BP DWH Macondo spill of 2010 of 401,000 tons. Likewise, the best estimate of inputs from routine operations for transportation and consumption of oil in the region is about 19,000 tons per year, about 10% of the BP DWH Macondo spill.67 It is important to keep in mind the uncertainties of the estimates, but basically ten years of chronic releases of oil to the USA Gulf of Mexico region as a result of human uses of oil, and 2–3 years of natural oil seeps in the same region, amount to the same order of input as the BP DWH Macondo oil spill. Add to this oil inputs from damaged oil production, pipeline, and storage facilities in the region as a result of hurricanes. For example, Hurricane Katrina damage resulted in an estimated 27,000 to 37,000 tons of oil input to the Louisiana coastal region, with estimates of as high as fifty percent being recovered or “evaporated”.6870

The preceding is of interest for comparing inputs. However, each type of input has its own environmental behavior and its own potential or real effects—although some may overlap. Thus, there is no automatic scaling that allows us to predict with any degree of certainty that for an oil input of a given amount, the same percentage of that input will have the same fates or have the same severe, moderate, minimal or no adverse effects.


Accidental oil spills account for a relatively small percentage—no more than 5–10%—of the input of oil to the marine environment. Worldwide, accidental oil spills from tankers of 100 tons or greater have been declining over the long term. There has been, and continues to be, progress in reducing oil discharges from routine oil tanker operations. Advances in scientific surveys and studies of the past two decades document that a significant amount of oil enters the marine environment from natural oil seeps. Chronic inputs from human activities on land account for a significant input from land runoff, river and sewer discharges, and atmospheric transport to the ocean, as has been the situation for several decades. Recycling of waste oils in several developed countries is helping to reduce the chronic oil inputs from land and needs to be adopted by more countries as the use of motor bikes, automobiles, buses, and trucks spreads in emerging economies and developing countries.

The various categories of oil inputs are not distributed uniformly in spatial and temporal frameworks, an important consideration when assessing fates and effects of the inputs. Assessment of some categories of inputs needs wider ranging spatial and temporal measurements and use of chemical analyses specific to petroleum chemicals to reduce the current wide ranges of annual amounts for these inputs.

Despite wide ranges of uncertainty for some categories of inputs, the data and assessments are clear; chronic inputs that are the result of humans personal and collective use of oil must be taken into account to adequately address the impacts of oil on the marine environment.

1. International Tanker Owners Pollution Federation Limited accessed July 1, 2012. statistics/statistics/

2. See note 1 above.

3. N. Tawfiq and D. Olsen, “Saudi Arabia's Response to the 1991 Gulf Oil Spill.” Marine Pollution Bulletin 27 (1993): 333–345.

4. M. McNutt, S. Chu, J. Lubchenco, T. Hunter, G. Dreyfus, S. Murawski and D. Kennedy, “Application of Science and Engineering to Quantify and Control the Deepwater Horizon Oil Spill.” Proceedings of the National Academy of Sciences 109 no. 50 (2012): 20222–20228.

5. National Research Council, Oil in the Sea III: Inputs, Fates, and Effects, National Academies Press (Washington, D.C. 2003).

6. A. Jernelov, “The Threats from Oil Spills: Now, Then, and in the Future.” Ambio (2010) 39: 353–366.

7. See note 6 above.

8. See note 4 above.

9. “BP Gulf Oil Spill Judge Approves $7.8 Billion Settlement” by Jeff Feeley and Margaret Cronin Fisk.

10. P. Galstoff, “Oil Pollution in Coastal Waters.” Proceedings of the North American Wildlife Conference (called by President Franklin D. Roosevelt) 1 (1936): 550–555.

11. A. Nelson-Smith, “A Classified Bibliography of Oil Pollution” Reprinted from “The Biological Effects of Oil Pollution on Littoral Communities.” Supplement to Field Studies Vol. 2 (1968), Field Studies Council, United Kingdom.

12. C. Zobell, “The Occurrence, Effects, and Fate of Oil Polluting the Sea.” International Journal of Air and Water Pollution 7 (1963): 173–198.

13. A. Hawkes, “A Review of the Nature and Extent of Damage Caused by Oil Pollution at sea”. Transactions of the 26th North American Wildlife and Natural Resources Conference (1961): 343–355.

14. See note 1 above.

15. Anon. “Horizon to Horizon” An Environment Staff Report. Environment 13 no.2 (1971):13–21.

16. T. Heyerdahl. “Atlantic Ocean Pollution Observed by Expedition Ra.” Biological Conservation 2, no. 3 (1970):221–222.

17. T. Heyerdahl “Atlantic Ocean Pollution and Biota Observed by the “Ra” Expeditions.” Biological Conservation 3, no. 3 (1971):164–167.

18. M. Horn, J. Teal, and R. Backus, “Petroleum Lumps on the Surface of the Sea.” Science 168 (1970): 245–246.

19. J. Butler, B. Morris, and J. Sass, “Pelagic Tar from Bermuda and the Sargasso Sea”. (St. George, Bermuda, Special Publication No. 10. Bermuda Biological Station for Research (1973).

20. United Nations Environment Programme, Prospects for global ocean pollution monitoring. UNEP Regional Seas Reports and Studies No. 47. (1984).

21. See note 19 above.

22. See note 1 above.

23. Ibid.

24. M. Corwin, “The Oil Spill Heard ‘Round the Country!” Los Angeles Times, 28 January 1989.

25. W. J. North, G. C. Stephens and B. B. North, “Marine Algae and Their Relations to Pollution Problems.” Food and Agriculture Organization (UN) Technical Conference on Marine Pollution, Rome, Italy (1970). Fir:MP/70/R-8, 22 pp.

26. W. J. North, “Position Paper on Effects of Acute Oils Spills”. Background Papers for a Workshop on Inputs, fates, and Effects of Petroleum in the Marine Environment. (1973) National Academy of Sciences, Ocean Studies Board, Washington, D.C.

27. M. Blumer, G. Souza, and J. Sass, “Hydrocarbon Pollution of Edible Shellfish by an Oil Spill.” Marine Biology 5, no. 1070: 195–202.

28. M. Blumer and J. Sass, “Oil Pollution: Persistence and Degradation of Spilled Fuel Oil.” Science 176 (1972): 1120–1122.

29. K. A. Burns, “Hydrocarbon Metabolism in the Intertidal Fiddler crab Uca Pugnax.” Marine Biology 36 (1976): 5–11

30. C. T. Krebs and K. A Burns, “Long-term Effects of an Oil Spill on Populations of the Salt-Marsh Crab Uca Pugnax.” J. Fisheries Research Board of Canada 35, no. 5 (1978):648–649.

31. K. A. Burns and J. M. Teal, “The West Falmouth Oil Spill: Hydrocarbons in the Salt Marsh Ecosystem.” Estuarine and Coastal Marine Science 8 (1979): 349–360.

32. H. L. Sanders, “Florida Oil Spill Impact on Buzzards Bay Benthic Fauna: West Falmouth.” J. Fisheries Research Board of Canada 35, no. 5 (1978): 717–730.

33. H. L. Sanders, J. F. Grassle, G. R. Hampson, L. S. Morse, S. Prince-Gartner, and C. C. Jones. “Anatomy of an Oil Spill: Long Term Effects from the Grounding of the Barge Florida off West Falmouth, Massachusetts.” J. Marine Research 38 (1980): 265–380.

34. M. Blumer, H. L. Sanders, J. F. Grassle, and G. R. Hampson, “A Small Oil Spill” Environment 13, no. 2 (1971): 3–12.

35. P. D. Keizer, T. P. Ahearn, J. Dale, and J. H. Vandermeulen., “Residues of Bunker C oil in Chedabucto Bay, Nova Scotia, 6 years after the Arrow spill”. J. Fisheries Research Board of Canada 35, no. 5 (1978): 528–535.

36. E. S. Gilfillan and J. H. Vandermeulen, “Alterations in Growth and Physiology in Soft Shell Clams, Mya Arenaria, Chronically Oiled with Bunker C from Chedabucto Bay.” J. Fisheries Research Board of Canada 35, no. 5 (1978): 630–642

37. J. M. Teal, K. Burns, J. Farrington, “Analysis of Aromatics Hydrocarbons in Intertidal Sediments Resulting from Two spills of No. @ Fuel Oil in Buzzards Bay, Massachusetts. J. Fisheries Research Board of Canada 35, no. 5 (1978): 510–520

38. G. R. Hampson and E. T. Moul, “No. 2 Fuel Oil Spill in Buzzards Bay, Massachusetts: Immediate Assessment of the Effects on Marine Invertebrates and a 3-Year Study of Growth and Recovery of a Salt Marsh. J. Fisheries Research Board of Canada 35, no. 5 (1978): 731–744

39. J. M. Hunt, Petroleum Geochemistry and Geology (2nd edition), (New York: W. H. Freeman and Company, 1996), 23–57.

40. See note 5 above.

41. National Research Council, Oil in the Sea: Inputs, Fates, and Effects, National Academies Press (Washington, D.C. 1985).

42. National Research Council, Petroleum in the Marine Environment, National Academies Press (Washington, D.C. 1975).

43. Royal Commission on Environmental Pollution. Oil Pollution of the Sea (London, 1981)

44. Joint Group of Experts on the Scientific Aspects of Marine Pollution (GESAMP), IMO/FAO/UNESCO/WMO/WHO/IAEA/UN/UNEP. Impact of Oil and Related Chemicals on the Marine Environment. IMO (London, U.K., 1993).

45. See note 1 above.

46. See note 42 above.

47. See note 5 above.

48. Ibid.

49. Ibid.

50. See note 1 above.

51. See notes 1, 5 above.

52. Saito, M. R. Rosen, L. Roesner and N. Howard, “Improving Estimates of Oil Pollution to the Sea from Land-based Sources” Marine Pollution Bulletin 60: (2010): 990–997.

53. See note 5 above.

54. J. W. Farrington and J. G. Quinn, “Petroleum Hydrocarbons and Fatty Acids in Wastewater Effluents” J. Water Pollution Control Federation 45 (1973): 704–712.

55. R. P. Eaganhouse and I. R. Kaplan, “Extractable Organic Matter in urban Storm Water Runoff: 1. Transport Dynamics and Mass Emission Rates.” Environmental Science and Technology 15 (1981): 310–315.

56. E. J. Hoffman, G. L. Milles, J. S. Latimer, and J. G. Quinn, “Annual Input of Petroleum Hydrocarbons to the Coastal Environment via Urban Runoff.” Canadian Journal of Fisheries and Aquatic Sciences 40, suppl. 2 (1983): 41–53.

57. See notes 4 and 35 above.

58. United Nations Environment Programme, “Compendium of Recycling and Destruction Technologies for Waste Oils.” UNEP Division of Technology, Industry and Economics, International Environmental Technology Centre, Osaka, Japan (2012)170 pp. Accessible through the UNEP IETC website.

59. United Nations Environment Programme, “Compendium of Recycling and Destruction Technologies for Waste Oils.” UNEP Division of Technology, Industry and Economics, International Environmental Technology Centre, Osaka, Japan (2012)170 pp. Accessible through the UNEP IETC website.

60. See note 5 above.

61. Used Oil Refining Study to Address Energy Policy Act of 2005, Section 1838. U.S. Department of Energy, Office of Oil and Natural Gas, Office of Fossil Energy, July 2006. Washington, D.C.

62. See note 5 above.

63. J. Michel, D. S. Etkin, T. Gilbert, R. Urban, J. Waldron, and C. T. Blockridge, “Potentially Polluting Wrecks in Marine Waters”. An Issue Paper Prepared for the 2005 International Oil Spill Conference. 40pps.

64. NOAA. “Risk Assessment for Potentially Polluting Wrecks in U.S. Waters.” March, 2013 Office of National Marine Sanctuaries, Office of Response and Restoration, National Oceanic and Atmospheric Administration, U. S. Department of Commerce, Washington, DC 195 pp.

65. See note 5 above.

66. Ibid.

67. Ibid.

68. “La. Still dealing with Katrina oil spills.” August 19, 2010 1:01 PM. Top News, Latest headlines, World News and U.S. News –

69. Donald W. Davis, “The Aftermath of Hurricanes Katrina and Rita on South Louisiana.

70. C. Pine. Hurricane Katrina and Oil Spills: Impact on Coastal and Ocean Environments. Oceanography 19 (2006): 37–39.

John W. Farrington is Dean Emeritus of Woods Hole Oceanographic Institution where he has conducted research on organic chemicals in the marine environment and been involved in graduate education in the MIT/WHOI Joint Program for the majority of his 42 years in ocean sciences. He has been active at the science-policy interface in the local, national, and international arenas and in “K to gray” education. The author acknowledges helpful discussions over the years with colleagues, postdocs, students and co-workers and financial support for research over four decades from U.S. government agencies and private foundations.

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