Bilge Dumping at Sea: Why should I care?

Scientific research on the impact of oil pollution on marine life and coastal communities, combined with evidence of frequent bilge dumping, suggests oily bilge could be harming marine ecosystems and coastal economies.

This is the second entry in a multi-part series revealing the significance of bilge dumping globally.

Last year SkyTruth reported 163 accounts of likely bilge dumping across the world, from Brazil, to the Mediterranean, to Southeast Asia and elsewhere. As we described in our recent post,  bilge dumping is the illegal release of untreated oily wastewater from a vessel’s lower hull. This wastewater, or bilge, appears as an oil slick in the ocean, which eventually disperses and can migrate to vulnerable coastlines.  

Because it happens out at sea, bilge dumping traditionally has been an enigmatic source of pollution and challenging to consistently monitor. Although SkyTruth is working to change that, so far the negative effects of bilge dumping are sparsely documented. To explore the potential impacts of frequent bilge dumping worldwide, we can start by considering the contaminants oily bilge waste contains. Oily bilge waste water is the byproduct of operating ocean-going vessels and, according to the Environmental Protection Agency, contains contaminants such as lubricants, grease, and cleaning fluids, as well as harmful or toxic metals such as arsenic, cadmium, chromium, lead, and selenium, some of which are known or probable carcinogens. Other harmful substances in bilge can include organic chemicals such as benzene, chloroform, hexachlorocyclohexane isomers, and naphthalene

The size of tankers and container vessels that dump their waste can help us understand the amount of pollution they are emitting. Commercial marine vessels are some of the largest machines in the world, with some measuring 131 meters (143 yards) in length; comparable to the size of a small skyscraper. The engines in these vessels can be as large as three buses and have up to 333 times more horsepower than the engine of a midsize car. Their large size makes cargo vessels very efficient for transporting goods; but if the waste from these massive engines routinely ends up in the oceans, their environmental impact can be substantial. Even two decades ago, researchers reported that ocean-going vessels generated millions of tons of waste annually. A 2003 report by the nonprofit conservation group Oceana estimated that in European waters alone “illegal dumping and routine operations of vessels account for between 666,000 and over 2.5 million tons of hydrocarbons of marine pollution per year.” That amount is up to 70 times greater than the Exxon Valdez oil spill and is likely even greater today. Over a 20 year span from 1992 to 2012, the amount of ocean-going traffic has grown by 300%, increasing the likelihood of even more vessel pollution. 

A large research collaboration published by The National Academies Press (2003) found that between 1990 and 1999 vessels (in contrast to pipelines or facilities) in US waters produced the largest oil spills. Additionally, this research reports that 12 percent of the total petroleum hydrocarbons found worldwide in the oceans were from “accidental spills and operational discharges of cargo oil occurring during transportation of petroleum products.” This accounted for 160,000 tonnes of oil annually; the equivalent of four Exxon Valdez oil spills every year. 

Exxon Valdez oil spill [photo courtesy ARLIS, Alaska Resources Library & information Services]

Exxon Valdez oil spill [photo courtesy ARLIS, Alaska Resources Library & information Services]

The negative effects of bilge dumping can be seen in the United Arab Emirates. In 2017, one of the emirates, Fujairah experienced three oil spills in just two months. Locals reported that this contributed to a significant decrease in local hotel bookings and left dead fish and black oil on the shores. Last year, nine Brazilian states and 132 beaches were impacted by multiple mysterious incidents of oil washing up onshore. The cause of these incidents still has not been determined, but one possibility is a series of bilge dumping incidents. The impact occurred in multiple biodiverse tourism areas, specifically in Brazil’s oldest national park

SkyTruth also continues to find oil offshore Nigeria, in the Gulf of Guinea. And while this oil is mostly a consequence of energy infrastructure, we suspect this oil stems from bilge dumping as well. Nigeria’s Niger Delta, which drains into the Gulf of Guinea, experiences periodic water contamination from heavy metals due to extensive energy development, so much so that the delta has been called the “oil rivers.” Over a 38 year timespan, 12,000 oil spills were reported in the delta. Communities often use this water untreated for cooking or drinking as well as for local agriculture and fish farming. 

Heavy oil has been sullying the beaches of northeastern Brazil since early September. The cause remains elusive. [Photo courtesy tvBrasil via Creative Commons license]

Recently, an environmental activist and resort director contacted SkyTruth after repeatedly discovering remnants of oil and tar washing up on beaches near Singapore and the Strait of Malacca, one of the world’s busiest shipping lanes. This local activist continues to report regular incidents that they believe may be the result of bilge dumping. 

When oil washes up onshore, our Southeast Asian source states that it sometimes can be small and relatively easy to clean up, but at times, when it’s a bad spill, “it can be barrels full of it, or it can be thick tar balls, sometimes five to six inches across — so large that they look like they came out of a pipe,” he told us. The oil releases a “distinct petroleum smell” and “if it gets in amongst the rocks it can take months to clean out,” he told us. “If it washes up on a beach at high tide, it melts in the sun and is terribly messy to clean up.” Most incidents happen during the northeast monsoon season when the region gets stronger winds; however, outside of this season oil still lingers. “I can almost always walk down a beach and find some,” he told us. 

Video of oil globs from suspected bilge dumping washing up on a beach in Southeast Asia in February 2020. Video by anonymous.

Studies from oil spills suggest that oil at sea disperses over a period of days to weeks, and some of this oil can wash up on coastlines, potentially harming ecosystems and soiling beaches. Vessel bilge dumping incidents typically receive less attention than large oil spills: they are much smaller-scale events, but occur more frequently and potentially can have a significant cumulative effect. The substantial scientific literature analyzing the effects of large-scale historical oil spills — most notably BP’s Deepwater Horizon and the Exxon Valdez — could help shed light on the potential impacts of bilge dumping.

The impact of oil on a community’s natural environment can be very prominent, and it varies. When a slick disintegrates, its components can weather into dense tar balls which pile up on shores, as well form a messy sludge coined chocolate mousse. Well-protected clean-up teams are needed to carefully remove oil from coastal areas.

One unsettling outcome from oil in the water is its effects on marine life — from acute to progressive diseases. After the Deepwater Horizon oil spill, dolphin deaths from lung and adrenal lesions increased, and reproduction decreased, which scientists believe could be linked to exposure to oil. In addition, a multi-state natural resource damage assessment estimates that as many as 102,000 birds were killed or harmed during the Deepwater Horizon spill. Mangroves and coral reefs in Brazil, Panama and Singapore have been harmed by oil in the water. Human health can also be affected. One survey from an oil spill in Pakistan in 2003 found those who lived near the coastline experienced eye, skin, and respiratory health symptoms, asfumes and a mist of oil in the air.” Far worse, years after an oil spill offshore Spain, some cleanup workers of the spill showed signs of genetic mutations in their blood, potential catalysts for more serious disease. 

Lastly, oil spills have triggered social and psychological distress. After the Deepwater Horizon disaster, some impacted individuals were found to have high oil related stress and PTSD related symptoms. This discomfort led to lengthy lawsuits and ongoing political protests by citizens who felt that the energy company responsible, BP, was not taking full responsibility. 

Bilge dumping is unlikely to trigger such large-scale reactions. However, based on what SkyTruth has documented over the past year, we believe that bilge dumping could be the stealthy, less recognized cousin to large oil spills, that cumulatively leads to large amounts of oil in ocean waters and coastlines. Perpetrators often evade prosecution and accountability, leaving communities to bear the impacts and costs. 

Although scientific research on bilge dumping per se is limited, harmful impacts of oil pollution on marine life, human health, and coastal communities are well documented. Given the dozens of likely bilge dumping incidents SkyTruth has revealed over the past year, and the concerns expressed to us by coastal residents, we believe bilge dumping could be a sleeper source of oil pollution in the sea. It’s time to do something about it.