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 (81%) 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. Unsurprisingly, 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. Whilst we strive to maintain precise records for all spill information, we cannot guarantee the information taken from shipping press and other sources is complete or accurate. Consequently, the figures in the following tables, and any averages derived from them should be viewed with an element of caution.
Download a formatted copy of the following information - ITOPF's Oil Tanker Spill Information Pack (1444Kb) - in Adobe Acrobat.
Numbers and Amounts Spilt
Number of Oil Spills
Following the publication of the previous statistical analysis for 2009, notification was received of an incident involving the sinking of a tanker off Vietnam in 2009 containing more than 700 tonnes of oil. As a consequence, we have revised the figure for 2009 accordingly.
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 Table1 that the number of large spills (>700 tonnes) has decreased significantly during the last 41 years during which records have been kept. The average number of major spills per year for the previous decade (2000-2009) is just over three, approximately eight times less than for the 1970s. Looking at this downward trend from another perspective, 55% of the large spills recorded occurred in the 1970s, and this percentage has decreased each decade to 7% in the 2000s (Figure 1).
A decline can also be observed with medium sized spills (7-700 tonnes) in Table 1. Here, the average number of spills in the 2000s was close to 15, whereas in the 1990s the average number of spills was almost double this number.
For 2010, four large spills were recorded. Whilst this is an increase on the figures for 2008 and 2009, this represents a minor deviation from the average of 3.3 spills per year in the 2000s as a whole (Figure 2 and Table 1). Four medium spills were also recorded in 2010, representing the lowest annual figure recorded for this category. The total of all spills over 7 tonnes for 2010 shows no change against 2009 and is a significant reduction compared to the average for the previous decade.
Figure 1: Major spills as a percentage of those recorded from 1970 to 2010 per decade
Figure 2: Numbers of large spills (over 700 tonnes) from 1970 to 2010
Figure 3: Number of medium sized (7-700T) and large (>700T) spills per decade from 1970-2010
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 is included in the database to give a series of annual estimates of the total quantity spilled for the years 1970-2010. These amounts are rounded to the nearest thousand where practical.
Approximately 5.71 million tonnes of oil were lost as a result of tanker incidents from 1970 to 2010. However, as Figure 4 indicates, the volume of oil spilt from tankers demonstrates 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. For instance, from Table 2 it is interesting to observe that an amount greater than the total quantity of oil spilt between 2000 to 2009 (212,000 tonnes) was spilt in several single years in earlier decades.
The total amount of oil lost to the environment in 2010, whilst more than that of 2008 and 2009, is significantly lower than the average of oil lost in previous decades. Furthermore, at 10,000 tonnes this is the fourth lowest annually recorded figure (Table 2 and Figure 4).
Figure 4: Quantities of oil spilt over 7 tonnes, 1970 to 2010
Figure 5: Spills over 7 tonnes per decade showing the influence of a relatively small number of comparatively large spills on the overall figure
As demonstrated in Figure 5, when looking at the frequency and quantities of spills, it should be noted that a few very large spills are responsible for a high percentage of oil spilt. For example, in more recent decades the following can be seen:
• In the 1990s there were 360 spills over 7 tonnes, resulting in 1,137,000 tonnes of oil lost; 73% of this amount was spilt in just 10 incidents.
• In the 2000s there were 182 spills over 7 tonnes, resulting in 212,000 tonnes of oil lost; 47% of this amount was spilt in just 2 incidents.
The figures for a particular year may therefore be severely distorted by a single large incident. This is clearly illustrated by incidents such as ATLANTIC EMPRESS (1979), 287,000 tonnes spilt; CASTILLO DE BELLVER (1983), 252,000 tonnes spilt and ABT SUMMER (1991), 260,000 tonnes spilt.
Figure 6: Oil spilt per decade from 1970 to 2009 (excluding 2010) as a percentage of the total
Major Oil Spills
Table 3 below gives a brief summary of 20 major oil spills since 1967. The map in Figure 7 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 names listed may be unfamiliar. EXXON VALDEZ is included for comparison although this incident falls someway outside the group.
| 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 |
Table 3: Major oil spills Since 1967
Figure 7: Location of major spills (click map to view larger version in PDF format)
Seaborne Oil Trade
Apart from a fall in the early 1980s during the worldwide economic recession, seaborne oil trade has grown steadily from 1970 (Figure 8). Whilst increased movements might imply increased risk, it is encouraging to observe however that downward trends in oil spills continue despite an overall increase in oil trading over the period.
Figure 8: Seaborne oil trade and number of tanker spills over 7 tonnes, 1970-2010
(crude and oil product)
Causes of Spills
The causes and circumstances of oil spills are varied, but can have a significant effect on the final amount of oil spilt. 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 less than 7 tonnes;
• accidental causes, such as collisions and groundings, generally give rise to much larger spills, with at least 88% of these incidents involving quantities in excess of 700 tonnes.
|
<7 Tonnes |
7-700 Tonnes |
>700 Tonnes |
Total |
OPERATIONS |
|
|
|
|
Loading / Discharging |
3157 |
385 |
37 |
3579 |
Bunkering |
562 |
33 |
1 |
596 |
Other Operations |
1250 |
61 |
15 |
1326 |
|
|
|
|
|
ACCIDENTS |
|
|
|
|
Collisions |
180 |
337 |
132 |
649 |
Groundings |
237 |
269 |
160 |
666 |
Hull Failures |
198 |
57 |
55 |
310 |
| Equipment Failures | 202 |
39 |
4 |
245 |
Fire & Explosions |
84 |
33 |
34 |
151 |
|
|
|
|
|
Other/Unknown |
1975 |
121 |
22 |
2118 |
|
|
|
|
|
TOTAL |
7845 |
1335 |
460 |
9640 |
Table 4: Incidence of spills by cause, (<7 tonnes 1974-2010, 7-700 & >700 tonnes 1970-2010)
Figure 9: Incidence of spills < 7 tonnes by cause,1974-2010
(data before 1974 is not available)
Figure 10: Incidence of spills 7-700 tonnes by cause, 1970-2010
Figure 11: Incidence of spills >700 tonnes by cause, 1970-2010
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