Updated June 14, 2021.
This information was produced in response to discussions with Dr. Asha de Vos, marine biologist and Executive Director of Oceanswell in Sri Lanka.
What happened to the M/V X-Press Pearl?
On May 20, 2021, the cargo ship M/V X-Press Pearl caught fire while anchored off the coast of Sri Lanka, near the capital city of Colombo. According to news reports, the container ship was carrying nitric acid, urea fertiliser, sulphuric acid, ethanol, sodium hydroxide, lubricants and other chemicals, along with 78 metric tons (170,000 pounds) of a material known as plastic nurdles. Many of the shipping containers containing these materials have burned or fallen into the ocean, releasing their contents into the water. At the moment, no one knows how much of which materials were released. But the presence of plastic nurdles on beaches near the ship are visual proof that at least some of that cargo spilled. An unknown portion of the cargo is continuing to wash on shore.
This “nurdling” of the coastline is just part of an ongoing global trend of plastic entering the ocean. Although there are considerable uncertainties about the amount and source of this plastic pollution, the amount of plastic entering the ocean via rivers is estimated to be between 1.15 and 2.41 million metric tons per year. Although the current spill represents just a tiny fraction of the global annual input, the M/V X-Press Pearl spill is unprecedented, its impacts concentrated over a relatively short period of time, in a small volume of ocean, and along short, but growing extent of coastline. One study estimated that Sri Lankans release 3 kilograms of plastic waste per capita each year, making this spill equivalent to the annual output of as many as 26,000 Sri Lankans in almost a single day.
Is there an oil spill originating from M/V X-Press Pearl?
The Marine Pollution Surveillance Program at the National Oceanic and Atmospheric Administration (NOAA) has analyzed satellite images collected June 5-8, and 10 and concluded that there is “possible oil” leaking from the M/V X-Press Pearl. The early images appeared similar to one another, but the June 10 images show a change in the trail of material flowing from the wreck, prompting NOAA to conclude that the trail now contains “possible thicker oil” close to the origination point. The June 10 report estimated the coverage of this material to be 0.67 square kilometers (0.25 square miles), which would equate to 10 to 100 gallons of oil on the surface. Due to cloud cover, the June 13 satellite image of the wreck was unable to capture the full extent of the “possible oil,” but otherwise it was similar to previous images. However, NOAA did not indicate signs of “possible thicker oil” in in the June 13 image.
Satellites are a powerful and useful tool in detecting spills, monitoring and assessing ongoing events, and planning countermeasures. However, false positives do occur (such as those caused by algal blooms) and satellite remote sensing does not provide absolute certainty of the presence of oil, the type of oil, or the amount being released. Standard protocol is to verify by local means (plane, helicopter, boat, or drone) and, if necessary, to collect samples and conduct chemical analysis of the suspected oil to constrain its composition and source. In particular, analysis would be able to tell responders whether a leak was coming from the ship’s cargo hold or fuel tanks, indicating potential for a much larger release, or if the source was from the ship’s machinery and superstructure, indicating a more limited source of lubricating oil or other material.
How much oil is in the M/V X-Press Pearl?
Even though the M/V X-Press Pearl is a cargo ship, and not an oil tanker, there is still a danger of an oil spill, because every ship contains either some type of oil or fuel that is used to run the engines (see below). Various reports have put the amount of fuel in the ship’s tanks at “hundreds of tonnes” to between 278 and 350 metric tonnes. But the exact mix of fuels in the tanks is uncertain.
This is important because different hydrocarbons have different densities, which means an accurate conversion from weight to volume is difficult to make. However, given the range of weights and the range of densities of the different possible fuels, a rough estimate of 80,000 to 100,000 gallons is within reason. But that is what may have been in the tanks at the start of the incident. In the process of the ship sinking, it burned extensively, which may have included some or all of the vessel’s fuel—or the fire may have converted some of the fuel into a heavier, more viscous form. If none of the latter occurred, it is rare that every drop of oil will leak, as there is more than one hold or tank on a ship.
One rule of thumb that may not necessarily remain true here, is 10% of a non-tank ship’s total capacity is most likely to leak in the event of an accident, and it is important to point out that cargo ships (ie, non-tank ships) account for more spills worldwide than oil tankers.
- Congressional Research Service, “Oil Spills: Background and governance” (2017)
- Farrington, JW, “Mixing oil and water,” Oceanus 43:1(2004).
What will happen if oil from the ship leaks into the ocean?
Marine oil spills are often compared to the 1989 Exxon Valdez spill, which sent 11 million gallons (35,000 metric tonnes) of unrefined crude oil into the waters of Alaska’s Prince William Sound. But the people who respond to oil spills often say every spill is different, and the amount of oil that enters the water is only the first of many variables that can separate a long-term environmental disaster from a near-miss.
In the case of the M/V X-Press Pearl, the biggest uncertainty in predicting what will happen if the ship begins leaking is the composition of its fuel. Various reports have said that the ship carries bunker fuel, gas oil, fuel oil, heavy fuel, or marine fuel, among others. Each of these has its own range of characteristics, but in general, ship fuel divides into one of three types: marine gas oil, marine diesel oil, and fuel oil.
Each of these (and all hydrocarbon products) are produced by distilling crude oil into products that are increasingly denser and less volatile with every succeeding step of the distillation process. Marine gas oil is a highly refined hydrocarbon similar to diesel fuel. At the other end of the spectrum is fuel oil (or bunker fuel), which is often considered a byproduct of the distillation process. It is a viscous, almost asphalt-like substance (hence “heavy”) that needs to be mixed with more refined products in order to make it usable. In between these is marine diesel oil, which is closer to a marine gas oil, but includes some “heavy” material.
Despite its black, tarry appearance, fuel oil in the ocean is often much easier to clean than spills of other hydrocarbons. In the ocean, it often forms thick, buoyant mats that are easily identified, and can be contained with floating booms or skimmed off the surface with specialized equipment. If a fuel oil slick reaches shore however, it can be difficult to remove from beaches, rocks, vegetation, or wildlife and may persist for a long time. Its persistence in the environment does not, however, mean that fuel oil is toxic to the animals and ecosystem in which it is trapped.
Marine fuel oil, and the lighter components of marine diesel oil, spread widely and rapidly across the surface of the ocean, forming a characteristic rainbow-hued slick that is less viscous and harder to contain and recover than a fuel oil spill. Moreover, depending on the environmental conditions, these lighter fuels can also mix into the water column and lead to a greater chance of harm to sea life as plants and animals quickly find themselves enveloped in a coat of toxic hydrocarbons. As a result, pound-for-pound and over the short term, diesel fuel is often significantly more damaging to the environment than fuel oil. The only advantage is that lighter hydrocarbons evaporate more quickly and can dissolve into the water column more readily than spills of heavier hydrocarbons.
This threat also includes toxicity to humans, as oil spill response teams are forced to breathe fumes from evaporating hydrocarbons or make physical contact with spilled material during containment and clean-up. Added to this mix of variables is the unprecedented spill of plastic nurdles from the ship. Hydrocarbons in the water can be absorbed by or adhere to the plastic. This provides an additional mechanism for a spill to be transported through the marine ecosystem. It also makes clean-up of the nurdles more difficult because the clumps of oiled pellets that form have to be handled as a toxic substance, rather than the inert, mostly harmless (to humans) material they are when clean.
Weather conditions can also affect the spread and impacts of oil in the ocean. High wind and waves can inhibit the effectiveness of containment and recovery of a spill, but rough seas naturally disperse oil on the sea surface, which is most often thought to be an effective outcome for oil spills.
- Coastal Response Research Center (CRRC)
- ExxonMobil, Oil Spill Response Field Manual, 2014.
- NOAA Office of Response & Restoration
- Oceanography: Special Issue on GoMRI: Deepwater Horizon Oil Spill and Ecosystem Science
- Oceanography: Special Issue on the Gulf of Mexico Research Initiative: Ten Years of Oil Spill and Ecosystem Science (2021).
- Reddy, CR, “Oil in our coastal backyard,” Oceanus, 43:1(2004)
- Sea Grant Programs of the Gulf of Mexico, “Frequently asked questions: Oil edition”.
- Sea Grant Programs of the Gulf of Mexico, “Predicting the movement of oil”.
What are nurdles?
Nurdles are small plastic pellets that are melted down and used in the manufacture of a wide range of end-products. They can be made of any number of plastic polymers and resins; reports about the M/V X-Press Pearl spill indicate that the nurdles released were made of polyethylene (PE). PE is less dense than seawater, which means the nurdles released should float initially. As time passes, exposure to the marine environment may alter their density enough that they sink. This makes nurdles easy to skim off the surface and causes them to aggregate large, visible masses on beaches and elsewhere along the coast.
The presence of nurdles in coastal areas has been recognized as a potential problem since the 1970s, when scientists from the Woods Hole Oceanographic Institution (WHOI) first identified them and studied their composition and potential environmental impacts. Today, high-density polyethylene (HDPE) and low-density polyethylene (LDPE) are two of the most abundant plastics in the ocean.
- Carpenter, EJ and Smith, KL (1972), Plastics on the Sargasso Sea Surface
- Carpenter, EJ, et al. (1972), Polystyrene spherules in coastal waters
- Morét-Ferguson, S, et al. (2010), The size, mass, and composition of plastic debris in the western North Atlantic Ocean
- Nurdle Hunt
- International Pellet Watch
Are nurdles toxic?
The PE in these nurdles is likely to be relatively inert and unlikely to cause direct, immediate toxicity unless they were manufactured with toxic additives. Even if they were not, PE (like other plastics) can adsorb toxic chemicals from the marine environment that could be released when the plastics are ingested by marine organisms or humans. In addition, plastics can break down over time into smaller microplastics and nanoplastics, which may be more likely to be taken up by an organism and cause toxicity. This is not an immediate concern, as this process takes time for environmental conditions to degrade and break down individual pieces. Nurdles can also physically block the feeding or digestive system of animals that consume them, but the size of these pellets would seem to indicate that only small animals would be at risk.
How long will the plastic last in the environment?
This is one of the biggest unknowns about plastic pollution in general. All plastics are different and all behave differently in the ocean. While most people think plastics persist for hundreds or thousands of years, several peer-reviewed studies report that they can break down in the environment over much shorter periods of time. Additional factors affecting the longevity of nurdles include their color and size.
We know that plastics similar to those released in this spill are non-biodegradable.. But it also appears that, when released into the environment, PE can be broken down into smaller and smaller pieces by sunlight and eventually converted to carbon dioxide and removed from the environment. But the timeline of these processes tare highly variable and depend on a number of factors, including the density of the PE, the location and time of year they are released, or the amount of exposure to sunlight they receive.
- Ward, CP & Reddy, CM (2020), We need better data about the environmental persistence of plastic goods
- Ward, CP; Armstrong, CJ; Walsh, AN;Jackson, JJ & Reddy, CM (2019), Sunlight converts polystyrene into carbon dioxide and dissolved organic carbon
How will the nurdles be affected by other chemicals released from the ship?
PE is widely used because it is so durable. In fact, it is used to make containers that hold strong acids such as many of those released in the spill. In addition, most of the chemicals released from the ship quickly became diluted by seawater, further limiting their potential effects on the plastic. PE can, however, begin to break down under exposure to UV light, changing its physical characteristics, including its permeability and imperviousness to other chemicals. Many of the nurdles released from the ship were reportedly burned, which would also affect their physical and chemical properties.
Will the plastic get into seafood?
Plastics the size of nurdles, if consumed by most fish, are likely to pass completely through the intestine and be excreted. However, that means any fish or shellfish that are eaten whole (including their digestive tract) could have nurdles in them.
Will the plastic have an impact on other parts of the coast and ocean?
At this point, it’s difficult to say, as each type of habitat will react differently to the presence of plastics. Deciding whether to remove the nurdles can be as straightforward as shoveling or bulldozing them from beaches into large piles for disposal. But more sensitive parts of the coastline, such as mangroves or coral reefs, will require careful consideration and planning so that clean-up efforts do not cause more damage than the plastic itself.
Can the plastic be cleaned up?
There are many ways to clean up the plastic debris. It will take time and resources, but tools exist to aid in these efforts. The success of clean-up operations will depend on how quickly the nurdles can be contained and collected. While removing every pellet from the environment is unrealistic, cleaning up this local, relatively contained spill will be much easier than trying to clean up plastics in the open ocean that are widely distributed, come from many sources, and are a complex mixture of types and compositions. Still, there are some areas along the coast that will present challenges. Deciding whether to proceed with clean-up or to let nature take its course will need to be made on a case-by-case basis, after careful consideration of all the variables.