More than 1.8 million gallons of chemical dispersants have been used in the Gulf of Mexico, making it the largest use of these types of chemicals in U.S. history. However, a Texas Tech University researcher said dispersing the oil could cause more problems than leaving the oil alone.Ron Kendall, director of The Institute of Environmental and Human Health (TIEHH) at Texas Tech University, compared the heavy use of the dispersants to pouring mineral spirits on a puddle of oil on a garage floor. Though the oil is dispersed, it isn’t removed. Instead, it becomes thinner, more easily moved around and harder to mop up. The affected area becomes larger as well.
“The plan to disperse the oil was a risk-benefit scenario,” Kendall said. “The decision was made to keep the oil off the shoreline. That means you’ve got to disperse it at sea. But the dispersants have been used at an unprecedented level at the wellhead and on the surface. What this has done, in my opinion, has created a much more complicated ecotoxicological issue.”
Though a recent news release from Nalco, makers of the dispersants, claims “further federal testing has concluded that the use of the COREXIT dispersant remains a safe, effective and critical tool in mitigating additional damage in the gulf,” Kendall said he believed there were too many variables in play to make such a claim.
The ingredients in Corexit 9500 and 9527 were recently released by the U.S. Environmental Protection Agency, but very little is known about how the dispersants will react in the environment.
“The heavy use of dispersant has created so many forms of the oil now,” he said. “Some of the oil is extremely dispersed in the water column. It appears some of it is in plumes floating in the gulf. Other parts of it have floated to the surface and a ‘chocolate mousse’ has formed. And they’re mixed now with the dispersant. The sea bottom, the water column and the surface are distributed with oil, and then there’s the oil approaching and making landfall on shoreline. We’ve got all kinds of exposure scenarios for many different species of fish and wildlife.”
The good news, he said, was that when Corexit is sprayed from planes on top of the water, it gets exposed to sunlight and oxygen and will eventually break down. The bad news is the dispersant that’s been injected underwater at the wellhead will likely become preserved in deep water where light can’t penetrate and oxygen is depleted.
“Everybody is talking about keeping the oil off the shore, and that was a policy decision that was made,” he said. “Granted, that affects the ecology of shoreline as well as businesses such as fishing and tourism. But that doesn’t necessarily diminish what’s happening offshore and even in deeper waters. Oil dispersed at sea doesn’t mean it’s not going to go somewhere in the future. If a hurricane takes that water and shoves it into the coastline, it could take that oil and put it into all sorts of places that we don’t know where it’s going to go. It’s a serious time.”
Texas Tech researchers recently received their first sample of Corexit 9500 from Nalco. Todd Anderson, an environmental chemist and toxicologist at TIEHH, said his group is studying how pollutants move in the environment and how they get into organisms.
“After quite a bit of struggle, we finally got some Corexit,” he said. “It’s somewhat unprecedented the volume of dispersants being used and the depths at which it’s being applied. There are some unknown questions about the potential interaction of Corexit and the oil. There have been toxicological studies done on the Corexit itself, and numerous toxicology studies done on the effects of oil. But the interaction of those is somewhat of an unknown question.”
Listen to scientist's struggle to acquire samples here.
Corexit breaks oil into smaller droplets, he said. That doesn’t mean the oil is gone – it’s just more widely dispersed in various parts of the gulf ecosystem. But not only that, questions remain as to the Corexit’s impact when it encounters the oil, such as could it enhance certain toxicological aspects of the oil once treated.
“Corexit is pretty fascinating stuff in that it takes a really small amount of the dispersant to have an impact,” Anderson said. “We essentially put a drop of the Corexit into a system of oil and water, and it was pretty fascinating what it did to that little piece of oil. We added more Corexit to see if it enhanced dispersion even more, and it didn’t do that. A relatively small volume impacts or has that dispersant effect. If you go beyond that, it doesn’t enhance it any further. I don’t know what it means toxicologically. That’s what we’re trying to figure out. Chemically, it’s pretty fascinating stuff.”
With the volume of oil spilled somewhere between 94 million and 184 million gallons, this can create a significant exposure scenario for fish and wildlife, he said.
“The dispersant doesn’t dissolve oil, but it breaks it down into smaller droplets that then hopefully make it more amenable to biodegradation,” Anderson said. “But, that could make the oil more available to be taken up by an organism. That’s one of the questions we’re trying to answer. You see these pictures of birds and crabs getting oiled and that tears your heart out. But that’s a physical effect, not a chemical effect. And so, the real interesting chemical questions are the potential interaction of Corexit with crude oil, and what effect does that have on uptake into animals.”
Read about animal research in The New York Times.
The oil from the gulf spill contains fewer polycyclic aromatic hydrocarbons – a class of chemicals in the oil that concerns scientists because of their toxicological impact. But as crews burn off crude oil and gasses, that’s creating more PAHs, he said.
Anderson hopes that Texas Tech scientists will begin to generate data from their findings during the next month. And though a recent attempt to cap the well head appears to have succeeded, Anderson said the story doesn’t end when the oil stops flowing.
“I think certainly from some people’s perspective, it won’t be as sexy a story anymore,” Anderson said. “But the potential long-term impact of that much oil in the gulf is what the scientific community is going to be concerned about. These PAH compounds, their acute toxicity issues are not what we’re really worried about. It’s the chronic exposure – a lifetime type of exposure – to low levels and the impact that has. I think the fiddler crab bioaccumulation studies will give us some idea of the timeframe involved if you have oil there, how long it takes to get taken up into an animal and if the animal gets into clean water how long it takes to get out. It’s not the be-all-end-all study to what impact the oil will have, but it’s a good place to start.”
Read why understanding the mixture is important.
Kendall agreed.
“This whole scenario may play out over months to years to a decade,” he said. “We just don’t know yet. It’s very complex. Not only has this spill been described as the largest spill in U.S. history and the greatest environmental disaster, I would say it’s about the most complex ecotoxicological event that I have dealt with in my career.”
