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Movers And Shakers

C&EN Talks With Ronald Tjeerdema

Dispersants are a necessary tool for oil-spill response, the aquatic toxicologist says, and toxicity studies must be done with care

by Jyllian Kemsley
June 3, 2013 | A version of this story appeared in Volume 91, Issue 22


Credit: Evan Tjeerdema
This is a photo of Ronald Tjeerdema.
Credit: Evan Tjeerdema

After the Deepwater Horizon oil rig sank, tens of thousands of barrels of oil spewed daily into the Gulf of Mexico. How to handle the onslaught came down to a choice between two bad options, says Ronald Tjeerdema, a professor of aquatic toxicology at the University of California, Davis. One was to risk coating the beaches and marshes of the northern Gulf Coast with oil and exposing cleanup workers to more of it. The other was to try to keep as much oil as possible in the water, far from the shore.

Oil-spill responders chose to try to keep the oil in the water by using dispersants, and that decision is possibly the most controversial aspect of how they handled the disaster. Dispersants are mixtures of solvents, surfactants, and other compounds that together are designed to break up oil into small droplets. The chemicals had previously been used on surface oil slicks. During the Deepwater spill, responders for the first time injected dispersants into the oil as it came out of the wellhead deep underwater. Criticism of dispersant use has largely centered on the materials’ toxicity.

Those concerns are not entirely unfounded. Chemical dispersants and chemically dispersed oil—as well as oil itself—can be toxic, although the responses of organisms vary. Within one ecosystem there can be thousands of species, “all with different life histories, lifestyles, morphologies, and niches,” Tjeerdema says. “Some might be more susceptible to naturally dispersed oil, while others might be more susceptible to chemically dispersed oil.”

The worries about dispersants must be balanced against the good that dispersants can do, Tjeerdema says. In the case of the Gulf of Mexico, officials and scientists hoped that injecting dispersants at the wellhead on the seafloor would break up the oil, keeping it in the water and making it more accessible to microbes that could digest it. “I think that the public has been having a hard time getting its head around the idea that adding a chemical to the environment can mitigate a problem,” Tjeerdema says.

Tjeerdema, 56, has spent decades studying the effects of oil dispersants on marine organisms. He’s worked with both of the Corexit brands of dispersants used in the Gulf of Mexico, albeit with an eye toward coastal California rather than Gulf ecosystems.

Dispersants are an important tool in the spill-response toolbox, he contends. With the Deepwater spill, “we had a situation where we had a catastrophic amount of oil released into the Gulf,” Tjeerdema says. “The magnitude of spill quickly overwhelmed responders’ abilities to use any other tools. Skimming and burning were not going to suffice.”

Tjeerdema was part of a National Oceanic & Atmospheric Administration spill advisory panel, and he and his 49 fellow panelists had to decide whether or not to recommend dispersant use. They did so unanimously. The decision involved analyzing the costs and benefits of dispersant use to different ecosystems and deciding which would get bigger hits of oil, Tjeerdema notes. He adds that there’s no way to know whether dispersant injection in the Gulf was the right decision, because there’s been no comparable situation in which dispersants were not used.

Going forward, the question remains whether dispersants should be used in a similar future seafloor rupture. More research into the effects of dispersant and chemically dispersed oil on marine organisms could help officials navigate the necessary cost-benefit analyses.

But Tjeerdema is cautious about many of the studies that have appeared recently. Oil’s toxicity when dispersed depends on its specific composition plus additional factors, such as the amount of energy put into mixing and how long the dispersed oil settles. Researchers are not doing the necessary chemical analyses or controlling conditions in a way that ensures studies are reproducible and comparable, making the work “almost unusable,” Tjeerdema says.

More than a decade ago, he and colleagues developed toxicology protocols to address these problems. But he sees researchers now taking shortcuts, such as using open experimental setups that cannot control oil evaporation. He points to lack of understanding and money as key problems in the area. “Quality is expensive,” Tjeerdema says.

Tjeerdema is also concerned about research funded by the Gulf of Mexico Research Initiative (GoMRI), the independent organization charged with distributing millions of dollars from BP to scientists. GoMRI’s focus is on awarding funds to consortia based in Gulf Coast states, and it is not always directing funds to people with experience in oil-spill research, Tjeerdema says. He worries that money will be wasted as inexperienced researchers reinvent the wheel. “It’s not a background that you can pick up easily,” Tjeerdema says. While researchers from elsewhere can be invited to join the consortia, “there are people who’ve been working in this area for decades that are shut out,” Tjeerdema says. Tjeerdema has not participated in any initiative projects. (GoMRI officials respond that their review process is highly selective.)

It would be a shame, Tjeerdema says, if future oil-spill responders hesitated to use oil dispersants because of poor research or fear of public reaction. “Dispersants are useful when used safely and correctly,” he says.



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