About the SA Blog Network



Opinion, arguments & analyses from the editors of Scientific American
Observations HomeAboutContact

EPA dispersant tests show limited toxicity but questions remain

The views expressed are those of the author and are not necessarily those of Scientific American.

Email   PrintPrint

The U.S. Environmental Protection Agency released preliminary data Wednesday from its own toxicity testing for eight dispersants in a bid to corroborate potentially suspect industry-provided results. But questions remain about the safety of these chemicals that can be used to break up oil spills, including COREXIT 9500, which is being employed on a massive scale by BP in the Gulf of Mexico. The agency’s results showed broadly similar impacts on silverside fish (Menidia beryllina) and mysid shrimp (Americamysis bahia) across a range of concentrations. And none of the dispersants showed significant capacity to disrupt the hormonal systems of animals, at least at the cellular level.

"In the tests we performed, all of the dispersants are roughly equal in toxicity and generally less toxic than oil," said EPA Assistant Administrator and chemist Paul Anastas in a press briefing on June 30. "The dispersant constituents are expected to biodegrade in weeks to months, rather than remaining in the ecosystem for years as oil might."

The eight dispersants all fell into the EPA categories of "slightly toxic" or "practically nontoxic." COREXIT 9500 proved slightly toxic to the mysid shrimp and practically nontoxic to the silverside fish. The eight dispersants were chosen because of their initial lower toxicities and widespread availability in large quantities. "Dispersants, like anything, are not without toxicity, nothing is," Anastas added. "The data is telling us that these are not posing the same types of hazard that we’re seeing with the oil," including toxic constituents such as benzene, toluene, xylenes and various polycyclic aromatic hydrocarbons.

The EPA noted that its data closely matched industry provided data—except in two cases where the EPA found lower toxicity than industry. "Given the expected range of inter-laboratory variability, the results of the present study were consistent with test results reported in the [National Contingency Plan] Product Schedule," the EPA wrote in its preliminary report. Anastas added: "We recognize that there can be some inter-laboratory discrepancies or variability. We want to ensure through our own independent testing that we confirm those [industry] results."

The EPA stuck to its own guidelines, employing as a reference toxicant the surfactant sodium dodecyl sulfate, or SDS, but the use of this benchmark compound raised questions for at least one outside toxicologist. "It’s well known in toxicology that it’s just a horrible reference toxicant because it degrades quickly," says toxicologist Carys Mitchelmore of the University of Maryland. "[Toxicologists] haven’t used that for 20 years," preferring copper sulfate or potassium chloride. 

In fact, it remains unclear whether anyone at EPA ever previously checked the industry-submitted data as required, for a variety of reasons. First, when Anastas was asked during the briefing by Scientific American if the agency had checked the industry data, he did not directly answer the question, nor did EPA respond to follow-up questions. Second, the industry-provided data appeared full of potential faults, including, in the case of one dispersant, use of the wrong reference toxicant—a test chemical which ensures consistency of results among various labs, in this case SDS. Third, there is no evidence that the agency had any requirements for acceptable toxicity levels in the industry data. "The magnitude of this event has raised important questions about how these previous, existing regulations [for dispersants in the National Contingency Plan Product Schedule] may need to be reexamined and revisited in ways that ask different questions and even better prepare us in the future," Anastas admitted.

That’s a problem some think should have been resolved a long time ago. "It is ridiculous that we’re in this situation. Thirty years ago with Ixtoc we used dispersants and dispersants have always been controversial," notes Mitchelmore, who co-authored a National Research Council report on dispersants in 2005. "In 2005, we were making the same recommendations that were made in 1989; that’s ridiculous. There’s not too much different in this technology since Ixtoc in 1979."

The EPA must now conduct specific toxicity tests for the Louisiana sweet crude oil that is actually spewing from the Macondo well, both alone and in conjunction with the various dispersants. "Once it’s mixed with oil, that’s where you get the most impact, that’s where you see most of the toxicity," says toxicologist Sergio Alex Villalobos of Nalco, the maker of COREXIT 9500. Anastas suggests that testing will be completed before August, employing a suite of EPA labs as well as National Institutes of Health and contractor labs.

Through June 29, roughly 1.61 million gallons of dispersants—the bulk of it COREXIT 9500—had been applied to the spewing oil, both at the surface and beneath the sea. But the rate of application has slowed since the government ordered BP to slow its use on May 26. "In the month after EPA and the Coast Guard directed BP to ramp down dispersant use, the volume applied dropped nearly 70 percent from peak usage," Anastas said.

Ultimately, the decision to use dispersants was a tradeoff. "With a spill of this size and scope, dispersants are useful in breaking up the oil and preventing its spread, particularly to fragile wetlands," Anastas says. "I know many of you are interested to hear if this testing means EPA will order BP to switch dispersants. We are not making any such recommendation at this time. We have additional testing to do."

For example, more testing will be needed to determine if the breakdown of COREXIT 9500—either into other chemicals or when metabolized by animals—produces toxic products of its own. "In toxicology, it’s quite often not the original compound that’s the toxic entity," Mitchelmore notes.

Image: GULF OF MEXICO – Coast Guard Ens. Adam Mosley, a marine biology under graduate, logs sample data from oiled water in the Gulf of Mexico, May 27, 2010. The samples and field data Mosley collects help environmental scientists determine the effectiveness of dispersants used to break down oil. U.S. Coast Guard photo by Petty Officer 2nd Class Luke Pinneo.

Rights & Permissions

Comments 15 Comments

Add Comment
  1. 1. gunslingor 2:24 pm 07/1/2010

    Okay, now how about the toxicity, not at a cellar level, but to the entire organism? How about long tem effects? What about the toxicity of the dispersent mixed with oil, dispersed throughout the Gulf? What about the toxicity to other life forms, other than the two you decided to test.

    What about reproducive functions.

    I do beleive this stuff is less toxic than oil, but when you mix it with oil the result is undoubtable more toxic than oil.

    Stop burning fossil fuels already, we have no need for the antiquated technology anymore; we have multiple better alternatives, better in everyway.

    Link to this
  2. 2. drafter 2:32 pm 07/1/2010

    The oil companies have been paying the government money, since the Valdez spill, to look into ways of dealing with oil spills, so why are they just now testing this stuff.
    And for "gunslingor" are you a troll? how are you going to put food on your plate without oil unless you’d like to return to the pre-industrial world where everybody was at the whims of nature, including food supplies. The other sources of energy are not yet capable of doing all the things that oil can.

    Link to this
  3. 3. denverjims 3:11 pm 07/1/2010

    gunslinger: You bring up some good questions in your early remarks, but this is "Scientific" American, not "Hightly Opinionated and Biased Toward Green" American (although given the content the last year or so, you – not I – may be right). Anyway:

    1. Where’s the evidence that it is more toxic when mixed w/ oil?

    2. When Boeing rolls out a 767 or Kenworth an 18 wheeler which runs on batteries, I will be more willing to take seriously your last idea. Right now, just sounds un-scientific.

    We all laugh at the folks who "believe" the earth is flat but we are to take seriously those who "believe" we can have a modern society today without oil?

    Link to this
  4. 4. denverjims 3:12 pm 07/1/2010

    gunslinger: You bring up some good questions in your early remarks, but this is "Scientific" American, not "Hightly Opinionated and Biased Toward Green" American (although given the content the last year or so, you – not I – may be right). Anyway:

    1. Where’s the evidence that it is more toxic when mixed w/ oil?

    2. When Boeing rolls out a 767 or Kenworth an 18 wheeler which runs on batteries, I will be more willing to take seriously your last idea. Right now, just sounds un-scientific.

    We all laugh at the folks who "believe" the earth is flat but we are to take seriously those who "believe" we can have a modern society today without oil?

    Link to this
  5. 5. eddiequest 5:35 pm 07/1/2010

    Well – perhaps the way hey said it is a bit naive. BUT… if you are looking for trucks that run on electricity, try this one: Sure the technology is in its infantcy. But, as Ray Kurzweil has told us many times, the exponential power of technology is going to change things VERY quickly, VERY soon. Oil may have gotten us where we are. But I sure as sht don’t want to be living in this crud for too much longer.

    Link to this
  6. 6. H2O SI 9:09 pm 07/1/2010

    There are 100% organic surfactants, or dispersants available however they are being used in other industries other than for the specific oil spill applications which have no long range environmental effects and have been tested and known of since the fifties. The problem which the manufacturers face is that many were small labs which produced small quantities of the product and it was very costly. Over the past two years the methodology has significantly improved and the cost of production has been reduced to become cost effective and comparable in both price and efficacy as the chemical surfactants. Why are these products which have taken years to refine not on the market? It is because they do not have the funds to hire EPA certified labs to conduct the testing to be added to the National Contingency Plan Product Schedule and both the oil companies and the Government have been inundated with literally thousands of products which claim to be able to solve the problem with no scientific backing at all thus the "real" products become awash with skepticism and are buried in piled bureaucracy.

    Link to this
  7. 7. 11:26 pm 07/1/2010

    A Scientific approach was required in the beginning,

    We have spent years developing processes, procedures, and methods of operation to reduce worse case scenarios, and this disaster proves why. This is known as quality control and assurance.

    It was a high risk project to drill an oil well at this depth, and prior too, an assessment performed and contingency plans in place for worst case scenario? The most important aspect of any high risk operation is validating the procedures to prevent worst case scenarios. This is clearly not the case, and if so, why are we discussing the affects of corexit 9500, as being used in the gulf?

    Was there no contingency plan for such a high risk operation?

    Had BP wrote a contingency plan stating, “If oil and gas pressures compromise the well cap, (3) months would be required to drill wells to reduce pressure, and this could result in 200 millions gallons of oil leakage into the gulf, and using 3-4 million gallons of Corexit dispersant”. Would this project have been approved?

    When a project is initiated, engaged and implemented, actions are monitored to reduce risk, and if not, this results in uncontrollable outcomes. If procedures aren’t followed the results are clearly unknown. And thereafter, decisions made without contingency produce more uncontrollable outcomes.

    Can anyone site one study where Corexit 9500 was used to disperse oil, that resulted in minimized cleanup, versus oil floating to surface for cleanup?

    Are we producing more uncontrollable outcomes?

    Link to this
  8. 8. 1:13 am 07/2/2010

    We should all give attention to this disaster; remember lives were lost and more will come, the alternative is to reduce risk. We should be thinking more about our future, because dependency reduces creative thinking. There is a balance between existing energy sources and alternative, and new methods will help reduce unnecessary risk.

    Link to this
  9. 9. frgough 10:57 am 07/2/2010

    The only reason the industry results were "suspect" is because of environmentalists.

    The hilarious thing is, in ten years, you won’t even be able to tell there ever was an oil spill. Ixtoc 1, people. Look it up.

    Because, wait for it… oil is biodegradable.

    Link to this
  10. 10. jerrycam 7:48 pm 07/2/2010

    A comment on the use of dispersants to protect wetlands: In my own observations, I have seen that when oil+dispersants hit the wetlands, the dispersant coats the vegetation as it is moved up and down by ides and waves. This leaves the oil still in the water, forming a typical crude-oil slick. It is likely that using dispersants makes it MORE LIKELY that the oil will damage wetlands, and dispersed oil does not all float and so is not able to be captured by booms.

    Link to this
  11. 11. 9:18 pm 07/2/2010

    What is so Hilarious about oil remaining in the gulf for 10 years?

    Link to this
  12. 12. 10:25 pm 07/2/2010

    I have to say, my favorite comment is by frgough,

    “The hilarious thing is, in ten years, you won’t even be able to tell there ever was an oil spill. Ixtoc 1, people. Look it up.”

    It’s this very attitude why accidents occur, as it’s not important oil would remain in the gulf for ten years, or maybe 20? This is why accidents occur, because someone doesn’t believe one failure lead to another.

    What’s coincident is the attitude above is likely the reason for the accident. How did this accident occur, look it up!

    “The hilarious thing is, in ten years, you won’t even be able to tell there ever was an oil spill. Ixtoc 1, people. Look it up.”

    We need be serious about these accidents and action plans for recovering from worse case scenarios. People, marine life, and eco-systems are part of this equation, and this is not an illusion.

    We need more professionals involved, so potential hazards can be altered if necessary, and reason for the interest in Corexit 9500.

    Link to this
  13. 13. H2O SI 10:29 pm 07/2/2010

    There is a solution to what you are referring to. Using a dispersant or surfactant alone will not reduce the damage caused by the oil which will and has infiltrated the wetlands. A bio-surfactant solution is sprayed on the polluted surfaces to emulsify the oil thus allowing naturally occurring bacteria or "microbes" to metabolize the hydrocarbons into a useful by-product normally found in the environment and metabolized by higher life forms. To speed up the clean up process, the addition of a high concentration of microbes and nutrients would need to be formulated and introduced following the application of the bio-surfactant. Basically, what is being done in the above, is supercharging the natural process which takes place in the wetland and in the ocean. Using petroleum based surfactants and chemicals to clean up the oil spill could create a much larger environmental problem than not using anything. There are formulations developed to do this clean up which are natural and biodegradable, which will have little or no environmental effect.

    Link to this
  14. 14. jerrycam 12:58 am 07/3/2010

    Those "naturally occurring bacteria" referred to are almost all aerobes. They are normally in a position where soluble nutrients like organic nitrogen are limiting. But adding fertilizers (nitrogen & phosphate), whether more bacteria are added or not, will result in a population that is limited by the next lowest nutrient – oxygen. Without supplying more oxygen, these bacteria + fertilizer will give rise to low dissolved oxygen "dead zones" where other marine life may be harmed. The real answer may be to put in microbes that are only anaerobic. That means bacteria are out – but there are Archaea that fit the bill. I have been involved with a company that has tried to get the interest of the US government and BP, with no luck. After contacts have been made they both still deny knowing anything about it. That, plus the string of times the feds in one form or another have acted to slow the cleanup and increase the damage, makes me wonder if this is now being used as a political tool, perhaps to force some new tax on oil and/or energy.

    IMO the reasons for BP’s interest in Corexit can be found in the makeup of their respective boards of directors – they overlap about 50%. Paying Nalco for Corexit is a way of transferring money out of BP North America, and thus out of potential danger from clean-up costs, fines and liability. Its a useful safety strategy should the costs get so great that BP North America goes under.

    Also re: “The hilarious thing is, in ten years, you won’t even be able to tell there ever was an oil spill. Ixtoc 1, people. Look it up.”
    Perhaps you should look it up too – a class 5 hurricane came through the spill area, which is what got rid of the oil. I doubt that anyone (perhaps excepting some really radical environmentalists) want a class 5 running up through New Orleans. Then there is the fact that this spill already is larger than Ixtoc I, and shows no signs of slowing down in the near future.

    Link to this
  15. 15. 2:11 pm 07/13/2010

    Denverjims: could I take a moment of your time.

    When Boeing rolls out a 767 or Ken worth an 18 wheeler which runs on batteries, I will be more willing to take seriously your last idea. Right now, just sounds un-scientific.

    So if thousands of people are sickened by corexit 9500, I will be more willing to take seriously your last ideal.

    Its a balance between alternative resources that reduce UNNECESSARY RISK, so why is risk being taken in the first place? Its due to consumption, and without evaluating alternative solutions. Just use oil based technologies without considering others, just use corexit 9500 without considering others. And why are we using this chemical, because its there and plentiful? Here we go again.

    I worked in the automotive industry for many years, It doesnt require a 3000lb machine to move 600lb of people and cargo? Its called inefficiency, because the vehicle was designed overtime to prevent the heavy engine and systems from being forced into passengers upon frontal impact. You can apply electric vehicle technology in cities to reduce noise and carbon emissions taxi, fuel engines are necessary for more power, longer and continuous range, and greater loads.

    See Denverjim, an alternative was supplied by merely thinking out of the box. Did I miss someone in the last 20 years, do they teach Oil 101 at the universities now?

    Link to this

Add a Comment
You must sign in or register as a member to submit a comment.

More from Scientific American

Email this Article