Background
ITOPF maintains a database of oil spills from tankers, combined carriers and barges. This contains information on ACCIDENTAL spillages since 1970, except those resulting from acts of war.
The data held includes the type of oil spilt, the spill amount, the cause and location of the incident and the vessel involved. For historical reasons, spills are generally categorised by size,<7 tonnes, 7-700 tonnes and >700 tonnes, (<50 bbls, 50-5,000 bbls, >5,000 bbls) although the actual amount spilt is also recorded. Information is now held on nearly 10,000 incidents, the vast majority of which (82%) 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 difficult to achieve.
It should be noted that the figures for the amount of oil spilt in an incident include all oil lost to the environment, including that which burnt or remained in a sunken vessel. There is considerable annual variation in both the incidence of oil spills and the amounts of oil lost. Consequently, 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 (1296Kb) - 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 table below that the number of large spills (>700 tonnes) has decreased significantly during the last 40 years, such that the average number of major spills for the decade (2000-2009) is about three. Most notably, for the first time since ITOPF began collating tanker spill statistics, the number of major oil spills involving tankers reached zero in 2009.
The average for the 2000s is less than half of the average for the 1990s and just an eighth of the average for the 1970s. The same is true for medium sized spills from tankers (7-700 tonnes) where the average number of spills occurring in the last decade was 14, half of that experienced during the previous decade.
Looking at this downward trend from another perspective, it is notable that the number of large spills in the 1970s is more than a half of all the spills recorded in the 40 years between 1970 and 2009. Furthermore, the average number of large spills per year during the 1990s was less than a third of that witnessed during the 1970s. This downward trend continued during the 2000s during which only 7% of all recorded spills occurred.
Figure 1: Numbers of spills over 700 tonnes
Figure 2: Number of medium sized (7-700T) and large (>700T) spills per decade from 1970-2009
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 due to the inconsistent reporting of smaller incidents worldwide.
Reports on spills of 7 tonnes and above tend to be more reliable and information from these are included in the database to give a series of annual estimates of the total quantity spilled for the years 1970-2009. These amounts are rounded to the nearest thousand where practical.
Figure 3: Quantities of oil spilt
Approximately 5.65 million tonnes of oil were lost as a result of tanker incidents from 1970 to 2009. However, as figure 4 indicates, the volume of oil spilt from tankers does demonstrate a significant improvement through the decades. Consistent with the reduction in the number of oil spills from tankers, the volume of oil spilt also shows a marked reduction. In some cases, the total quantity of oil spilt in the last decade was less than had been spilt previously in a single year. Last year the volume of oil spilt was the lowest in ITOPF’s history of collating statistics on tanker spills.
It is notable that a few very large spills are responsible for a high percentage of the oil spilt. For example, in the 1990s, 360 spills over 7 tonnes were recorded, totalling 1,136,000 tonnes of oil, but 830,000 tonnes (73%) were spilt in just 10 incidents (just under 3% of the number of incidents in that decade). In comparison, in 2000s, 172 spills over 7 tonnes were recorded, totalling 206,000 tonnes of oil, but 93,000 tonnes (45%) were spilt in just 2 incidents (1%). The figures for a particular year may therefore be severely distorted by a single large incident. This is clearly illustrated in 1979 (ATLANTIC EMPRESS - 287,000 tonnes), 1983 (CASTILLO DE BELLVER - 252,000 tonnes) and 1991 (ABT SUMMER - 260,000 tonnes).
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 grown steadily from 1970 to the present (Figure 5). As increased movements would normally signal increased risk, it is encouraging to learn that downward trends in oil spills continue despite an overall increase in oil trading over the period.
Figure 5: Seaborne oil trade and number of tanker spills over 7 tonnes, 1970-2008
[Source: Fernresearch, 2007]
updated figures for 2009 are not available at this time
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, and the map overleaf shows where they occurred. A number of these incidents, despite their large size, caused little or no environmental damage as the oil was spilt some distance offshore and did not impact coastlines. It is for this reason that some of the listed names may be unfamiliar. EXXON VALDEZ is included for comparison although this incident falls someway outside the group.
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 | Nova | 1985 | Off Kharg Island, Gulf of Iran | 70,000 |
| 19 | Katina P | 1992 | Off Maputo, Mozambique | 66,700 |
| 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 90% 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 .
Table 4: Incidence of spills by cause, (<7 tonnes 1974-2009, 7-700 & >700 tonnes 1970-2009)
|
<7 Tonnes |
7-700 Tonnes |
>700 Tonnes |
Total |
OPERATIONS |
|
|
|
|
Loading / Discharging |
3155 |
383 |
36 |
3574 |
Bunkering |
560 |
32 |
0 |
593 |
Other Operations |
1221 |
62 |
5 |
1305 |
|
|
|
|
|
ACCIDENTS |
|
|
|
|
Collisions |
176 |
334 |
129 |
640 |
Groundings |
236 |
265 |
161 |
662 |
Hull Failures |
205 |
57 |
55 |
316 |
| Equipment Failures | 206 |
39 |
4 |
249 |
Fire & Explosions |
87 |
33 |
32 |
152 |
|
|
|
|
|
Other/Unknown |
1983 |
44 |
22 |
2049 |
|
|
|
|
|
TOTAL |
7829 |
1249 |
444 |
9522 |
Figure 7: Incidence of spills < 7 tonnes by cause,1974-2009
Figure 8: Incidence of spills 7-700 tonnes by cause, 1970-2009
Figure 9: Incidence of spills >700 tonnes by cause, 1970-2009
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