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A Post-mortem on the Gulf Oil Spill

Oil Spill and its EffectsAccording to a government report, last year’s Deepwater Horizon oil spill killed almost 7,000 animals.

Estimates are the worst man-made disaster in U.S. history dumped from 170 to 210 million gallons* of oil into the Gulf of Mexico.

A few grim statistics:

  • About 8,000 birds were recovered. Over 6,000 were dead, and nearly 4,500 were visibly oiled.
  • Over 1,100 sea turtles were collected; 600 were dead and nearly 500 were visibly oiled.
  • In addition to the turtles, 109 other mammals were recovered, nearly all of them dead.
  • At least two reptiles were recovered, one of them dead.

At the start of this year, there were still over 9,000 clean-up workers in the Gulf, covering nearly 600 miles of oiled shoreline.

According to Admiral Paul Zukunft, the federal coordinator at the spill site, about 9,000 square miles of federal waters are still off-limits to fishing, down from almost 90,000 square miles at the height of the disaster clean-up effort.

* Please note: The 185,000 gallons reported in the dvm360 article is incorrect.

Dr. Becker's Comments:

I have no way of knowing for sure, but the number of dead animals collected seems extremely low given the amount of oil dumped into the Gulf from BP’s Deepwater Horizon broken well pipe.

I’m left wondering how many oiled or dead birds, mammals and reptiles weren’t recovered.

According to the National Wildlife Federation, the Exxon Valdez disaster in 1989, which dumped just under 11 million gallons of oil – a fraction of the Gulf spill – is estimated to have killed up to 250,000 seabirds, nearly 3,000 otters, 300 seals, over 20 orcas, and 250 bald eagles.

A total of 7,000 animals killed in the Gulf seems remarkably low to me.

What Impact Will BP’s ‘Cure’ for the Oil Spill Have on Wildlife?

Another question: what damage is being done to wildlife and the entire Gulf marine environment by the chemical dispersants used to make the oil disappear from the surface of the water?

By November of last year, BP had sprayed over 1 million gallons of chemical dispersants into the Gulf.

These dispersants seem to make surface oil magically disappear. What they actually do is alter the chemical and physical properties of the oil so that it will mix more readily with seawater, making it less obvious on the surface and limiting the oil that washes ashore.

So while the immediate situation for birds and shore-dwelling animals might be improved, it’s reasonable to be concerned that marine life in deeper waters is at risk.

Chemical Dispersants Corexit 9500 and 9527

These Corexit products, manufactured by Nalco Holding Co., are the two used to disperse the oil spilled into the Gulf.

In the early days of the clean-up effort, information on these dispersants was famously hard to come by.

A June 9, 2010 New York Times article titled “Ingredients of Controversial Dispersants Used on Gulf Spill Are Secrets No More” revealed that:

U.S. EPA has quietly released a full list of ingredients in the two controversial dispersants BP PLC is using to combat the Gulf of Mexico oil spill, following weeks of complaints from members of Congress and public health advocates that the dispersant manufacturer had kept its complete formula a secret from the public.

Corexit 9527, an older formula used only during the early days of the clean-up according to Nalco, has been determined by the EPA to be a ‘chronic and acute health hazard.’ The 9527 product contains 2-butoxyethanol, an ingredient identified as the cause of ongoing health problems in Exxon Valdez oil spill cleanup workers. This product also contains propylene glycol.

The Haz-Map sheet comments for 2-butoxyethanol are a bit unsettling:

Severe hemoglobinuria and changes in the lungs, kidneys, and liver are seen in mice after 7-hour lethal concentration studies. Volunteers showed no evidence of adverse effects other than mucous membrane irritation after 8 hour exposures to 200 ppm. No increase in red cell fragility was seen after these brief exposures. [ACGIH] For ethylene glycol ethers, there is limited positive evidence of spontaneous abortions and decreased sperm counts in humans and strong positive evidence of birth defects and testicular damage in animals. [ATSDR Case Studies # 29] Humans are less susceptible than animals to red blood cell hemolysis. [Sullivan, p. 1204] See "Glycol ethers."

Corexit 9500, presumably a less toxic product and the only one Nalco has provided to the Gulf spill effort since late April 2010, contains:

  • Propylene glycol
  • Light petroleum distillates (a chemical refined from crude oil)
  • And a third hazardous ingredient, diocytl sodium sulfosuccinate, which is a detergent and ingredient found in laxatives.

It is this third ingredient that Nalco would not identify until the EPA applied pressure for full disclosure.

A study comparing the 9500 product with the older 9527formula concluded that:

Corexit 9500 represents a reformulation of a long-time industry "standard," Corexit 9527, to allow use on higher viscosity oils and emulsions. The present data suggest that acute aquatic toxicity concerns surrounding the use of this newer dispersant should not be significantly different from those associated with the use of Corexit 9527.

Concern for the Future of Marine Wildlife in the Gulf

There is no way to accurately predict every long term, far-reaching consequence of the Gulf oil spill catastrophe and subsequent clean-up with chemical dispersing agents.

Even though oil is no longer visible on the surface of the water, scientists have located significant amounts on the Gulf floor. And the oil that washed ashore onto wetlands and beaches will have an affect for years to come.

The National Wildlife Federation predicts the following:

  • An unbalanced food web. The oil spill happened during peak breeding season for many species of marine wildlife. The oil could have poisoned egg and larval organisms, potentially wiping them out. Without these generations of organisms, population dips and cascading food web effects will be the result.
  • Decreased fish and wildlife populations. Twenty plus years after the Exxon Valdez oil spill, the herring population has still not recovered.

Another concern is the discovery of dead coral in an area seven miles from the Deepwater Horizon well, at a depth of 4,500 feet, among large plumes of dispersed oil drifting through the ocean.

According to the New York Times:

The discovery of the dead corals offers the strongest evidence so far that oil from the BP well may have harmed marine life in the deep ocean, a concern raised by many biologists soon after the April 20 blowout that caused the spill. At an estimated nearly five million barrels, it was the largest offshore oil spill in the nation’s history.

+ Sources and References