Guest Post: Use of Corexit in 1978 Oil Spill Delayed Recovery by DECADES

Washington’s Blog

I previously pointed out:

Some experts have also said that the use of Corexit has prolonged by decades the presence of toxic crude oil, because the dispersant sinks the oil beneath the ocean surface, where it cannot be quickly broken down by sun, waves and microbes.

And the head of Lawrence Berkeley National Laboratory’s Ecology Department – Terry Hazen – argues that the use of dispersants can delay recovery of ocean ecosystems by decades:

Hazen has more than 30 years experience studying the effects of oil spills. He says the oil will be damaging enough; toxic dispersants will just make it worse. He points to the 1978 Amoco Cadiz Spill off the coast of Normandy as an example. He says areas where dispersants were used still have not fully recovered, while areas where there was no human intervention are now fine.

As Hazen has noted:

“The untreated coastal areas were fully recovered within five years of the Amoco Cadiz spill,” says Hazen. “As for the treated areas, ecological studies show that 30 years later, those areas still have not recovered.”

Admittedly, chemicals other than Corexit were used in the Amoco Cadiz spill. But the precautionary tale still holds: chemicals should not be applied to oil spills unless scientists are positive that they will provide a net long-term benefit.

Disturbingly, Corexit is apparently still being sprayed in the Gulf. See this, this and this.

I have just learned that Corexit 9500 was actually the dispersant used in the Amoco Cadiz spill. 9500 is the dispersant used in the Gulf (another – even more toxic version – 9527 – has also been applied).

As National Geographic notes in its current issue:

Even in the turbulent, highly oxygenated waters of France’s Breton coast, it took at least seven years after the 1978 Amoco Cadiz spill for local marine species and Brittany’s famed oyster farms to fully recover, according to French biologist Philippe Bodin. An expert on marine copepods, Bodin studied the long-term effects of the spill from the grounded tanker. He believes the impact will be far worse in the generally calmer, lower-oxygen waters of the Gulf, particularly because of the heavy use of the dispersant Corexit 9500. BP has said the chemical is no more toxic than dish-washing liquid, but it was used extensively on the Amoco Cadiz spill, and Bodin found it to be more toxic to marine life than the oil itself. “The massive use of Corexit 9500 in the Gulf is catastrophic for the phytoplankton, zooplankton, and larvae,” he says. “Moreover, currents will drive the dispersant and the oil plumes everywhere in the Gulf.”

For the sake of thoroughness, I should point out that detergents as well as Corexit were apparently applied at the Amoco Cadiz spill site. The detergents might not have helped either.

Still, I find it stunning that Corexit was the dispersant applied in France which scientists say delayed recovery by decades.

Why does Corexit delay recovery of natural ecosystems?

There are a number of reasons (above and beyond the direct toxicity which they may pose to sealife).

Initially, dispersants break oil into tiny droplets, which can be eaten by small critters who think it is food. Bigger critters eat the smaller guys, and then the whole food chain is effected.

In addition, dispersants affect fish so that they absorb more toxic chemicals from the oil, and then are less able to get rid of them from their bodies.

And National Geographic hints at another reason: Dispersants sink the oil, shielding it from the natural processes like sun, waves and microbes which break it down:

[Texas A&M University coral reef expert Wes Tunnell] stood in the clear, waist-deep water of the protected reef lagoon holding what appeared to be a three-inch-thick slab of sandy gray clay. When he broke it in two, it was jet black on the inside, with the texture and smell of an asphalt brownie. Here on the lagoon side, where the reef looked gray and dead, the Ixtoc tar mat was still partially buried in the sediments. But on the ocean side of the reef, where winds and waves and currents were stronger, no oil remained. The lesson for Louisiana and the other Gulf states is clear, Tunnell thinks. Where there is wave energy and oxygen, sunlight and the Gulf’s abundant oil-eating bacteria break it down fairly quickly. When oil falls to the bottom and gets entrained in low-oxygen sediments like those in a lagoon—or in a marsh—it can hang around for decades, degrading the environment.

People might not have understood in 1978 how harmful Corexit was to the ecosystem, but they surely should have known by 2010.

Have we finally learned our lesson … or will Corexit or similar dispersants again be dumped into the ocean the next time there is a major oil spill?

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About George Washington

George Washington is the head writer at Washington’s Blog. A busy professional and former adjunct professor, George’s insatiable curiousity causes him to write on a wide variety of topics, including economics, finance, the environment and politics. For further details, ask Keith Alexander…


  1. Inky

    David J. Peakall, the Nobel prize winner for ecotoxicology, said that the dispersants were worse than the oil spill itself. He did the pioneering work on how DDT can transfer through eggshells, and did a lot of work on shorebirds and petroleum spills. His family said that the only time they’d ever seen him lose his temper was the oil spill that Corexit was first used. He apparently said that if he could get DDT banned, he could flag corexit for the same treatment, but unfortunately passed on before he could present his case against it. This is the man who created the research that “Silent Spring’ was based on, and he said there was nothing more foul than the chemical that was dumped by the millions of gallons into the Gulf. Oh the humanity, as it were.

  2. Poor and Unemployed

    What do you want people? You do not cry for those 34,000 people who die in road accidents in US every year. I do not hear french crying about Amoco Cadiz spill. Why are these so called experts crying about something of which they live off! Yes they live off the grants to scare the people. I have been in the same business for over 40 years and do not believe that we are superior to the nature. Remember – Ashes to Ashes and Dust to Dust. Nature has its way. Oil has been flowing freely before the man knew how to use it. If you believe in evolution – man was a monkey! Would you want to turn the clock back?

    1. Chris

      Frankly, I’d rather live with some monkeys (Bonobos) than the vicious, cruel, and selfish simians called human beings.

    2. Maju

      “I do not hear french crying about Amoco Cadiz spill”.

      No dispersants have been used in any European oil disaster. The effects were bad but not that bad because, in general, solving the problem and not protecting corporations was the main goal.

      Also the dimensions of the Louisiana oil catastrophe have almost no precedents. The only thing worse was the massive spills in the 1st Gulf War (1991) and then you have to go back in time to the 1970s to the Ixtoc disaster in Mexico to find anything similar, specially something similar happening in the sea.

      I’m sure anyhow that the Europeans have “cried” about such disasters when they happened and that, eventually, laws have been approved to make oil traffic safer, etc. But no dispersants were used, as far as I can tell.

      I remember well the Prestige disaster (2002) and the response (after the initial awful maneuvers of the Spanish government trying to send the ship to Portuguese waters) was ok, specially as the fishermen themselves, spontaneously at first, went out to gather the oil offshore, hugely reducing the impact. The government acknowledged their efforts and paid them for that. No dispersants were used and much of the oil was therefore skimmed with some collective effort. It had an impact but nothing like what you see in the US Gulf coast.

      1. Shepton

        Lots of errors here. Dispersants have been used many times in UK spills (yes we are European)with no adverse affects because we use them in the right place – not close to the shore or in shallow water.

        The spill from the Prestige was heavy fuel oil which is not dispersable due to its high viscosity in colder european waters. That spill had a massive impact on the shorelines and though up to 40% of the oil was collcted by fishermen and the european recovery fleet, the rest came ashore and did massive damage.

  3. Lyle

    All this talk assumes poor old mother nature can’t fix things. I have read that natural spillage into the gulf runs about 2 supertankers a year. The gulf waters are also far warmer than the waters off France. This means microbes move much faster than off France. Since there is a good bit of natural spillage some organisms have figured out how to make a living off the oil. So we gave them a feast to end all feasts this year, give them a couple of years and things will recover, it might take 10 years off france and 30 off Prince William sound, since 1 there are no natural seeps in the area, and 2 the water is far colder, so microbial life moves far more slowly.

    I tend to agree with poor and unemployed in that for the last 40 years scientists have been saying how bad things are going to get and that the earth is going to hell in a handbasket in a hurry. I have apocalypse fatigue!! Of course predicting the end of the world is how you get more grants and news coverage.
    The earth and the biosphere will survive and live past the end of the human race, perhaps the downturn in the birth rate world wide will continue until in 2150 the population is down to 3 billion or so.

    1. Levi

      “I have read that natural spillage into the gulf runs about 2 supertankers a year.”

      See — seems to only be a paid link now (a fair number of other pages in google reference the data), but basically the Deepwater Horizon spill rate was roughly equivalent to the entire worldwide seepage (estimates are vague but we’re talking about the same order of magnitude). Can the ecosystem recover? Yes, in the same way as it can recoevr from a volcanic explosion — a large measure of life is destroyed and then gradually repopulates.

      Given enough time, ecosystems can recover from (almost) any damage, but it doesn’t mean it’s not a disaster in the meantime.

  4. ejackson

    Please, enough articles from Washington’s blog about how horrific a disaster the Gulf Oil Spill is. IT’S NOT. Yeah, it’s bad, but shit happens.

    As Lyle said, I’m getting tired of all the fear-mongering. The well is plugged, BP is paying up and it’s OVER. Stop trying to make a mountain out of a molehill. We have more important things than the Gulf Spill at this juncture.

  5. shaepton

    Such nonsense is talked about dispersant. Firstly lets correct some of the errors.

    1 Corexit 9500 had not been formulated in 1987, so it could not have been used. If any dispersant was used then it is likely that it was one of the first generation that was more toxic than those in use today.

    2. It should not be used inshore or in shallow water as the rapid release of the oils toxicity resulting can harm animals that live in the water column.

    3. It does not make oil sink, but it remains in suspension in the top 3 metres or so, which is why we dont use it in shallow water.

    4. To pass the testing regime, the dispersant and dispersed oil mixture must be LESS toxic than the oil itself.

    5. The huge increase of the surface area of the oil does release the oils toxicity quickly, but with sufficient water mixing this rapidly dilutes, leaving the oil very amenable to the oil eating bacteria who have a much bigger surface area to attack.

    6. Finally Net Environmental Benefit Anaylsis (NEBA) shopuld be used prior to the selection of any cleanup technique at sea or on the shoreline to ensure that the technique actually improves the situation and does not cause more damage than the oil itself.

    I am disturbed that eminent scientists are using hearsay to peddle the continuing myths about dispersants.

    So in the right place and against the right oil it is the only

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