Out of Sight: BP’s dispersants are toxic — but not as toxic as dispersed oil

Plus the threat the disaster poses to America’s primary coral reef

There has been a lot of confusion about the environmental impact of chemically dispersing oil.  I interviewed one of the country’s foremost authorities on the subject for a piece in Salon, which they headlined “Is BP’s remedy for the spill only making it worse?

I have had a great interest in what we are doing to our oceans since I spent more than two years researching my Ph.D. thesis at the Scripps Institution of Oceanography.  So I’m always delighted to talk to true experts on the subject like Carys Mitchelmore, a professor at the University of Maryland’s Chesapeake Biological Laboratory.  And yes, she brought up global warming without even realizing that is my main focus.

Last Thursday, BP began putting more than 100,000 gallons of chemicals into the Gulf of Mexico to disperse some of the hundreds of thousands — if not millions — of gallons of petroleum its undersea volcano of oil has gushed so far.

Chemically dispersing oil spills “solves the political problem of visible oil but not the environmental problem,” Robert Brulle, a 20-year Coast Guard veteran and an affiliate professor of public health at Drexel University, told me. These dispersants “do not actually reduce the total amount of oil entering the environment,” as a 2005 National Academy of Sciences report on the subject put it.

In short: out of sight, out of mind. But not out of the body of marine life.

Dispersants decrease the amount of oil that directly reaches the shores or the creatures that live on the shores or sea surface. But they increase the exposure to oil by creatures that live in the water or on the sea floor — like, say, shrimp or oysters.

I spoke to Carys Mitchelmore, one of the writers of the toxicity chapter for the NAS report. She explained that dispersants are “a molecule that looks like a snake. The head part likes water and the tail part likes oil.” The dispersant “pulls the oil into the water in the form of tiny droplets.”

And that means subsurface creatures — from oysters to coral to larval eggs — that might never have had significant exposure to the oil are now going to get a double whammy, getting hit by the oil and by the dispersants. Worse, the oil droplets are now in a form that looks like food (e.g., the same size as algae) to filter feeders like oysters, which otherwise may only have been exposed to the far lower levels of dissolved oil components found under a typical oil slick. The droplets can also clog up fish gills.

Mitchelmore noted that “oil contains a whole suite of toxic chemicals, including known carcinogens.” The dispersants can lead to far greater accumulation in living organisms of polycyclic aromatic hydrocarbons (PAHs) — oil-derived toxic compounds that were found in mussels 19 months after one spill in which dispersants were used. After the 1989 Exxon Valdez spill, a study found PAHs had an impact on the developing hearts of both Pacific herring and pink salmon embryos.

The NAS report noted that many traditional lab studies of PAH toxicity use fluorescent lights. But research conducted under conditions equivalent to natural sunlight “indicated toxicity due to PAH increases significantly (from 12 to 50,000 times).” Also, many toxicity studies only look at exposure to PAH over a short period of time, rather than, say, many months. The point is that in the real-world of a massive, chemically dispersed oil spill, toxicity may be thousands of times higher than lab studies suggest.

ProPublica has reported that BP has bought up more than a third of the global supply of dispersants. Nalco Holding Co. has provided its entire inventory of one dispersant, Corexit 9500, to BP and the Coast Guard. Nalco’s chief technology office, Mani Ramesh, has claimed that “Corexit’s active ingredient is an emulsifier also found in ice cream,” and that it is not harmful to marine life.

Mitchelmore, however, has extensively studied the impact of Corexit 9500, and found the chemical to be “pretty toxic to soft corals.” It was “acutely toxic” to corals at low levels, 30 parts per million.  It “affected physiological parameters at levels as low as 10ppm and also low ppm (20ppm) 8 hour exposures lead to reduced growth compared to controls even 32 days after being placed in clean seawater.”

While there hasn’t been much new research since the NAS report, she pointed to a recent Israeli study that looked at six different types of dispersants and found them very toxic to corals. The study recommended that they not be used anywhere near them.  And, of course, the PAH’s are a grave threat to the corals too.

Nonetheless, the dispersant-laced oil spill may soon be entrained in the Loop Current, which is part of the Gulf Stream, sweeping it toward the Florida Keys, home to America’s biggest coral reef.

Mitchelmore is particularly concerned about corals because they are “under siege from multiple sources, including human sewage, metal pollution, and of course they are dealing with issues from global climate change including warming and ocean acidification.”  See for instance, “Nature Geoscience study: Oceans are acidifying 10 times faster today than 55 million years ago when a mass extinction of marine species occurred.”

“We could be getting to the point that puts coral over the edge,” in terms of its long-term survival, she warned.

Corals big

Still, this doesn’t mean she’s against using dispersants. With this disaster, she explained, we have a very tough trade-off. On the one hand, there’s a crucial need to protect the shoreline and sensitive coastal habitats, which will face long-term devastation if oil overwhelms them. A key purpose of the dispersants is to stop the oil from reaching the shore.

On the other hand, dispersants are normally applied on a surface oil slick, but BP is applying them near the sea floor. “This is something new, “Mitchelmore said. “I don’t think this has been done before.” Nobody has any idea what will be the impact of massive exposure to these toxic chemicals on organisms that live on the bottom or feed off the bottom of the ocean.

The effects of this horrendous spill will be with us for many years. Thanks to the dispersants, we may not directly see many of the worst effects, but sensitive marine ecosystems will feel them. Somehow, BP should have to make restitution for that unseen destruction, too.

But, as Professor Brulle has noted, “With a spill of this magnitude and complexity, there is no such thing as an effective response.

What we need to focus on is prevention. That means an end to the voluntary, “trust us,” self-regulation of offshore drilling that BP and Big Oil have insisted upon. And it means that we should reevaluate offshore drilling so close to the coast, which provides very limited benefits (a reduction in the cost of gasoline that comes to pennies a gallon). And it also means we must begin as fast as possible ending our addiction to oil. We need comprehensive energy and climate legislation to shift from the dirty, unsafe fuels of the 19th century to the clean, safe fuels of the 21st century that never run out.

See also Grist and Mother Jones.

Related Post:

17 Responses to Out of Sight: BP’s dispersants are toxic — but not as toxic as dispersed oil

  1. cervantes says:

    You could make the argument that it’s a worthwhile tradeoff to kill benthic organisms in order to spare the primary production of the marshlands and to a lesser extent the coastal surface waters. But if you end up killing coral reefs you lose that argument — you get both ends of the very ugly stick.

    In this situation, I think a bit of a crash course in biological oceanography for the lay readership might be called for, BTW.

  2. Jeff Huggins says:

    “We Won’t Tell You”

    I agree with much of what the post says, and perhaps all. But, I’d like to add a point that involves one particular dimension of the relationship between these issues and “our ways of doing things”.

    Thousands of gallons of dispersants are being put into the ocean by the parties involved in this mess. Yet, when the press and public ask, “What exactly is IN the dispersant?”, the company says, “We won’t tell you.” They say, in effect, that the contents are a proprietary industrial secret, just like the recipes of Coke and Pepsi are secret.

    We saw the same thing a couple weeks ago with “fracing fluids”. Tons of them are injected into the ground, yet the companies won’t say what’s in them. “It’s a secret”, they say.

    “Trust us”, they say.

    “Forget it!”, I say. We (the public) are insane, and should consider ourselves so, if we are going to let people put tens of thousands of gallons of stuff, purposefully, into the ocean or into the ground and tell us “we won’t tell you what’s in this stuff”.

    It’s one thing to have a secret design to make a better computer chip, and another thing to keep your recipe for Coke or Pepsi secret (as long as all of the ingredients are already proven entirely safe), but it’s quite another thing to have chemical compositions whose ingredients are kept secret and then pour those compositions in the tons, or tens of thousands of gallons, into the oceans or into the ground and water system.

    In my view, if companies want to be able to use chemicals in such activities, they need to make the ingredients known, in full. They shouldn’t be able to put tens of thousands of gallons into the oceans without making the full recipe known to all scientific authorities, to the government, and to the public. Period. Many companies compete on bases OTHER THAN SECRETS. Companies don’t have a God-given right to “keep secrets” in such situations, and secrets are not necessary for competition to work. These folks can compete based on cost, service, friendliness, the effectiveness of their products, delivery, and so forth, or they can give coupons, or whatever, but they should not be allowed to put their products into the oceans while keeping the ingredients of those products a secret.

    Dispersants. Fracing fluids. Whatever. NO MORE SECRETS.

    If a government allows this sort of thing to continue, unaddressed, I’ll vote it out of office.



  3. Wit's End says:

    I don’t know why there is such a vocal group that believes the government is secretly deploying chemtrails. There seems to be no problem in this crazy country with releasing huge quantities of chemicals right out in the open.

  4. Andy says:

    The berms and fences being bulldozed and erected along the Gulf’s beaches might keep them clean for tourists, but they’ll also prevent sea turtles from nesting. This area is one of the most important nesting areas in the Gulf. Will the soon to come oil removal efforts on the beaches also crush the eggs of what turtles do make it through to nest? I also don’t believe the amount of dispersant being used is precedented and certainly hasn’t been studied.

  5. Tony says:

    I’ve noticed (hard not to) a consistent theme in these posts about the ongoing disaster in the Gulf. That theme is that “BP is to blame.” I have no quarrel with the idea that BP is the proximate cause, but with whom lies the ultimate responsibility? I would suggest, quite strongly, that we are all responsible, so long as we continue to defend our indefensible addiction to a substance so toxic it literally threatens life on Earth.

    We know, thanks to a growing body of peak oil literature, that the “cheap oil” is running out — supply cannot keep up with demand. And we know, thanks to decades of hard work by climate scientists, that burning oil (cheap or otherwise) is incredibly harmful to the stability of the climate, not to mention the pH of the oceans, etc. etc. And then there’s the obvious and unpardonable dangers associated with the process of extraction. So why do we continue to lust after this dark stuff, this ancient sunlight? We know it can’t sustain us; it now, in fact, is quite clear that its use is actively undermining us (life itself, civilization). The solution is clear: we must wean ourselves from our perilous and precarious addiction, and we must do it NOW. The Transition Towns movement (; is one way forward. Let’s either embrace it, or find other ways that are equally valid. And stop blaming BP for being our dealer.

  6. Wit's End says:

    Tony, your point is well taken however, I think the reason to hold BP financially accountable is not to escape our collective culpability for using their product, but to force the price of oil to accurately reflect the cost to society and the ecosystem. If BP and other producers were to held fully accountable for the real costs such as environmental degradation and cancer, then the price of oil would become extremely high, thus making investment in clean renewable technology more attractive.

    Of course, what will likely happen is that BP will go bankrupt and everything will continue just as usual until we have extracted every drop of fossil fuel, or we destroy much of life on earth, whichever comes first has yet to be determined.

  7. Steve Bloom says:

    Gee, Joe, has this disaster turned you into an environmentalist?

  8. Doug says:

    Tony — very good point. Though while extracting oil at all is the overarching evil, BP was still guilty of saving a few bucks on crucial safeguards (the safety shutoff valve thing, having a full containment team actually on standby, …), with the consequence of human life lost and a local ecological and economic disaster. Whether the field of activity is oil, manufacturing jeans, building bridges, or whatever, companies that knowingly engage in unsafe practices certainly do deserve blame.

  9. Alex Smith says:

    Radio Ecoshock has a 1 hour special with 4 experts on this Gulf gusher.

    In it, Dr. Riki Ott describes the risks of chemical dispersants, which she has studied extensively since the Exxon Valdez spill. Ott is a former fisherwoman and a marine biologist, now reporting from New Orleans.

    Other guests include Richard Heinberg, looking at the big picture, including Peak Oil as a driver for such risky deep water drilling.

    Antonia Juhasz, an oil researcher for Global Currents, tells us about BP’s bad safety record, and their big lobby spending.

    Anita Burke was a VP for Shell International, now with Catalyst Institute. While lamenting the damage, she cautions we should support the efforts of the oil industry to cap the well head. And Burke points to the real villains: you and I, as we drive to the corner store for a plastic bottle of pop.

    The one hour program, 14 megabytes is here:

    Find more, including a partial transcript with links, through the Radio Ecoshock blog at

    Please pass on the link to the Gulf Gusher Special radio show through your web site, blogs, Facebook and Twitter. These expert voices have been warning about major oil accidents for years. They need to be heard now, so we can push harder to get off the fossil fuel economy.

    Alex Smith
    Radio Ecoshock

  10. Anne says:

    It’s my understanding that using dispersants on the surface aids in natural decomposition of the oil, though it is slow, and the “lighter” compounds break down faster than the “heavier” ones. But — sunlight is required, right? So — how will injecting dispersants on the ocean floor solve the problem? I think you’re right Joe, that this is transfer of the problem from one geographic area to another, and that, in this case, from an ecosystems point of view, the damage done will be greater at the floor of the ocean and in the water column, and less oil will make its way to the surface where those pesky satellites taking photographic images can see it. Out of sight maybe, but not out of mind. Good for you for exposing all of this, you are doing Carol Browner’s job without getting her paycheck, ya know?

  11. Fred Teal says:

    TONY, # 4, I AM WITH YOU. Hear! Hear!

  12. Chad says:

    This is a good article, but it misses one key word that would help laymen understand concepts like “dispersant” and “emusifier”.

    The dispersants are SOAP. Yes, SOAP. Soap that is specifically engineered to disperse crude oil. Like most forms of soap, these dispersants are to some degree toxic. You don’t eat the soap in your bathtub for a reason.

    As the article makes clear, there are plenty of trade-offs and unknowns in this business. Dilution and dispersal of the oil will help some creatures, and hurt others. Depending on the situation and specific locality, the balance can tip one way or the other.

    Also, I always think it is important to distinguish between “toxic” and “toxicity”. The latter is really what one should focus on, as its analog nature better reflects reality. “Toxic” implies a binary yes-or-no kind of toxicity, which is often misleading to laymen. To a great extent, the dose DOES make the poison.

  13. prokaryote says:

    The trade off, is the time it takes for breaking up the oil, a few decades at land with help of microbes, vs thousand years all over the ocean. It will travel further, spread and affect more with dispersants.

  14. prokaryote says:

    “The grievous harm from this group of carcinogens has not been addressed adequately by the National Cancer Program,” Leffall and Kripke write. “The Panel urges you most strongly to use the power of your office to remove the carcinogens and other toxins from our food, water, and air that needlessly increase health care costs, cripple our nation’s productivity, and devastate American lives.”

    One of the panel’s central claims is pollutants cause far more cancer than previously appreciated. In an October 2009 review, the Cancer and the Environment committee of the American Cancer Society’s suggested that pollutants cause no more than 5% of all cancers.

    The presidential panel says this greatly underestimates the problem because it does not fully account for synergistic interactions between environmental contaminants, an increasing number and amount of pollutants, and the fact that all avoidable causes of cancer are not known.

  15. Edward says:

    BENZENE is THE cancer causer. Benzene is found in crude oil and coal.

  16. substanti8 says:

    Tony makes a good point about personal responsibility.  I often share the same frustration with American consumers that he seems to express.

    “And stop blaming BP for being our dealer.”

    But if we are to fully accept that analogy (which I do), then we ought to recognize that the dealer bears even more responsibility than the addict.  I think the same is true for oil consumption.  Those with virtually all the political power in this corrupted republic have been quite content to feed our teenage desire for short-term comfort at the expense of the future.

    I recommend this poster of a sea turtle.

  17. Chris Dudley says:

    The advantage I see to using dispersant is exemplified by the mussels mentioned in the article. There is a greater opportunity for the oil to be metabolized if it is spread around widely in bite sized chunks. This presents hard to breakdown components to rotting when the mussel eventually dies and thus eventual breakdown. Collecting oil onshore means longer term toxicity since you end up with a volume where nothing grows so nothing breaks the oil down.

    The down stream coral reef, however, may be a good reason to avoid using dispersant if the reef can’t metabolize even a little oil without facing permanent destruction.

    I continue to think that the high pressure at depth could be used to advantage since the boiling point of water there is higher than the autoignition temperature of the crude oil. Introducing an oxidizer should allow breakdown of the oil before it leaves the vicinity of the spill. It may be more expensive than dispersant, but probably not in the long run.