Background
Since 1974, ITOPF has maintained a database of oil spills from tankers, combined carriers and barges. This covers all ACCIDENTAL spillages. Spills resulting from acts of war are not included.
The database contains information on both the spill itself (amount and type of oil spilt, cause and location) and the vessel involved. For historical reasons, spills are generally categorised by size (<7 tonnes, 7-700 tonnes and >700 tonnes) although the actual amount spilt is also recorded. Information is now held on nearly 10,000 incidents, most of which (84%) fall into the smallest category i.e. <7 tonnes.
Information is gathered from both published sources, such as the shipping press and other specialist publications, and also from vessel owners and their insurers. Not surprisingly, information from published sources generally relates to large spills, often resulting from collisions, groundings, structural damage, fires and explosions, whereas the majority of individual reports relate to small operational spillages. Complete reporting of this latter type of spill is clearly impossible to achieve.
It should be noted that the figures for amount of oil spilt in an incident include all oil lost to the environment, including that which is burnt or remains in a sunken vessel. There is considerable annual variation in both the incidence of oil spills and the amounts of oil lost and so the figures in the following tables, and any averages derived from them should be viewed with caution.
Download a formatted copy of the following information (ITOPF's Oil Tanker Spill Information Pack (1043Kb)) in Adobe Acrobat.
Numbers and Amounts Spilt
The incidence of large spills is relatively low and detailed statistical analysis is rarely possible, consequently emphasis is placed on identifying trends. Thus, it is apparent from the graph below that the number of large spills (>700 tonnes) has decreased significantly during the last thirty-eight years. Data supporting the graph is provided in Table 1; please click the expand button to view. The average number of large spills per year during the 1990s was less than a third of that witnessed during the 1970s. Figures further show that there has been a general decrease in the number of spills over 7 tonnes and that there have been proportionally fewer large spills (> 700 tonnes) than smaller ones.
Figure 1: Numbers of spills over 700 tonnes
Figure 2: Number of medium sized (7-700T) and large (>700T) spills per decade from 1970-2008
Quantities of Oil Spilt
The vast majority of spills are small (i.e. less than 7 tonnes) and data on numbers and amounts is incomplete. However in most years it is probable that they make a relatively small contribution to the total quantity of oil spilled into the marine environment as a result of tanker accidents.
Reliable data on spills 7 tonnes and above is held and the amounts of oil spilt during these incidents have been added to give a series of annual estimates of the total quantity spilled for the years 1970-2008, as provided in the graph below, with supporting data available in Table 2; please click the expand button to view.
Figure 3: Quantities of oil spilt
It is notable that a few very large spills are responsible for a high percentage of the oil spilt. For example, in the ten-year period 1990-1999 there were 358 spills over 7 tonnes, totalling 1,138 thousand tonnes, but 830 thousand tonnes (73%) were spilt in just 10 incidents (just under 3%). The figures for a particular year may therefore be severely distorted by a single large incident. This is clearly illustrated by 1979 (Atlantic Empress - 287,000 tonnes), 1983 (Castillo de Bellver - 252,000 tonnes) and 1991 (ABT Summer - 260,000 tonnes). Approximately 5.65 million tonnes of oil were lost as a result of tanker incidents from 1970 to 2008. However, an analysis of the volume of oil spilt from tankers does demonstrate a significant improvement through the decades as Figure 4 indicates.
Figure 4: Percentage volume of oil spilt per decade
Apart from a fall in the early 1980s during the worldwide economic recession, seaborne oil trade has been growing steadily from 1970 to present (Figure 5) and currently, the tanker industry is responsible for the transport of two thirds of all the oil transported annually. As increased movements would normally signal increased risk, it is encouraging to learn that downward trends in oil spillage continue despite an overall increase in oil trading over the period. This progress is likely the result of the introduction and enforcement of various legal instruments and safety measures through the years, particularly following major incidents.
Figure 5: Seaborne oil trade and number of tanker spills over 7 tonnes, 1970-2008
[Source: Fernresearch, 2007]
Major Oil Spills
Figure 6: Location of Selected Spills (click map to view larger version in PDF format)
The table below gives a brief summary of 20 major oil spills since 1967. A number of these incidents, despite their large size, caused little or no environmental damage as the oil did not impact coastlines, which is why some of the names will be unfamiliar to the general public. The Exxon Valdez is included because it is so well known although it is not the 21st largest spill but rather the 35th.
Table 3: Major Oil Spills Since 1967
| Position | Shipname | Year | Location | Spill Size (tonnes) |
|---|---|---|---|---|
| 1 | Atlantic Empress | 1979 | Off Tobago, West Indies | 287,000 |
| 2 | ABT Summer | 1991 | 700 nautical miles off Angola | 260,000 |
| 3 | Castillo de Bellver | 1983 | Off Saldanha Bay, South Africa | 252,000 |
| 4 | Amoco Cadiz | 1978 | Off Brittany, France | 223,000 |
| 5 | Haven | 1991 | Genoa, Italy | 144,000 |
| 6 | Odyssey | 1988 | 700 nautical miles off Nova Scotia, Canada | 132,000 |
| 7 | Torrey Canyon | 1967 | Scilly Isles, UK | 119,000 |
| 8 | Sea Star | 1972 | Gulf of Oman | 115,000 |
| 9 | Irenes Serenade | 1980 | Navarino Bay, Greece | 100,000 |
| 10 | Urquiola | 1976 | La Coruna, Spain | 100,000 |
| 11 | Hawaiian Patriot | 1977 | 300 nautical miles off Honolulu | 95,000 |
| 12 | Independenta | 1979 | Bosphorus, Turkey | 95,000 |
| 13 | Jakob Maersk | 1975 | Oporto, Portugal | 88,000 |
| 14 | Braer | 1993 | Shetland Islands, UK | 85,000 |
| 15 | Khark 5 | 1989 | 120 nautical miles off Atlantic coast of Morocco | 80,000 |
| 16 | Aegean Sea | 1992 | La Coruna, Spain | 74,000 |
| 17 | Sea Empress | 1996 | Milford Haven, UK | 72,000 |
| 18 | Katina P | 1992 | Off Maputo, Mozambique | 72,000 |
| 19 | Nova | 1985 | Off Kharg Island, Gulf of Iran | 70,000 |
| 20 | Prestige | 2002 | Off Galicia, Spain | 63,000 |
| 35 | Exxon Valdez | 1989 | Prince William Sound, Alaska, USA | 37,000 |
Causes of Spills
Most incidents are the result of a combination of actions and circumstances, all of which contribute in varying degrees to the final outcome. The following analysis explores the incidence of spills of different sizes in terms of the primary event or operation in progress at the time of the spill. These "causes" have been grouped into "Operations" and "Accidents". Spills for which the relevant information is not available or where the cause was not one of those given are listed under "Other/unknown".
It is apparent from the table that:
- most spills from tankers result from routine operations such as loading, discharging and bunkering which normally occur in ports or at oil terminals;
- the majority of these operational spills are small, with some 91% involving quantities of less than 7 tonnes;
- accidental causes such as collisions and groundings generally give rise to much larger spills, with at least 84% of incidents involving quantities in excess of 700 tonnes being attributed to such factors.
Table 4: Incidence of spills by cause, 1974-2008
|
<7 Tonnes |
7-700 Tonnes |
>700 Tonnes |
Total |
OPERATIONS |
|
|
|
|
Loading / Discharging |
2825 |
334 |
30 |
3189 |
Bunkering |
549 |
26 |
0 |
575 |
Other Operations |
1178 |
56 |
1 |
1235 |
|
|
|
|
|
ACCIDENTS |
|
|
|
|
Collisions |
175 |
303 |
99 |
577 |
Groundings |
238 |
226 |
119 |
583 |
Hull Failures |
576 |
90 |
43 |
709 |
Fire & Explosions |
88 |
16 |
30 |
134 |
|
|
|
|
|
Other/Unknown |
2188 |
152 |
26 |
2366 |
|
|
|
|
|
TOTAL |
7817 |
1203 |
348 |
9368 |
Figure 7: Incidence of spills < 7 tonnes by cause,1974-2008
Figure 8: Incidence of spills 7-700 tonnes by cause, 1974-2008
Figure 9: Incidence of spills >700 tonnes by cause, 1974-2008
Further information is available in:
Trends in Oil Spills from Tanker Ships 1995-2004 (2005) [603kb]
by Keisha Huijer
Paper presented at the 28th Arctic and Marine Oilspill Program (AMOP) Technical Seminar, 7-9 June 2005, Calgary, Canada