Science!: Murderous Robots and Pea Aphids

Lauren Admire | 10 May 2010 21:00

What Are We Dumping Onto the Gulf Oil Spill?

On April 20th, an oil drilling rig exploded in the Gulf of Mexico, claiming the lives of 11 workers and causing 1,000 barrels of crude oil a day to seep into the ocean. Although some have claimed the spill is "natural," most agree that it's likely to be the most significant oil-related natural disaster that we've ever seen.

BP is working on several different methods of cleaning the oil spill, including spraying mass amounts of a dispersant called Corexit. This chemical binds to oil droplets, causing them to separate, sink, to eventually be washed away on the current. It's not making the oil "disappear," it's just diluting it. Unfortunately, the chemical BP is using may be just as harmful to the environment as the crude oil is. In fact, The New York Times calls it the "largest and most aggressive experiment with chemical dispersants in the history of the country, and perhaps the world."

Since the spill occurred, about 160,000 gallons of Corexit have been pumped onto the surface of the water, and an additional 6,000 gallons directly at the source of the spill. That is a whole bunch of dispersant - and it won't remain in the Gulf for long. Currents will spread the stuff much further than it was originally sprayed, causing possible long-term, far-spread ramifications that we haven't even began to consider.

It's always a gamble: We have to clean up the oil spill before it drastically affects coastlines and wildlife, but the means we use to do so may cause even farther-reaching side effects.

Perhaps the most startling aspect of the story is that there are cleaner, safer alternatives to Corexit. Though the chemical passed its offshore safety tests, there are some concerning details posted in its Material Safety Data Sheet: "Eye and skin irritant. Repeated or excessive exposure ... may cause injury to red blood cells, kidney or the liver. Harmful by inhalation, in contact with skin and if swallowed." Of course, these are the results of exposure to a concentrated amount, and the risk to the environment in diluted form is billed as moderate to low. However, in Britain, this chemical did not pass on-shore tests, and there's the rub. Further out to sea, using this chemical wouldn't be (as much) of an issue. But with the spill so close to shore, and being carried ever closer, the effects to coastline environments may be severe. Use of the chemical damaged the limpet population in Britain, but what could it do to the Reddish Egret or Brown Pelican population that make their homes on the the Gulf shoreline?

Some of the ingredients of Corexit are listed as proprietary and the details about these ingredients are not shown. Without a complete list of the chemicals involved in the soup, it's hard to determine what sort of effects they will have on the environment. Even more peculiar, reports that there are safer and more effective alternatives that BP could have used:

"Both Corexit and Dispersit were tested by the EPA, and according to those results, Corexit was 54.7 percent effective at breaking down crude oil from the Gulf, and Dispersit was 100 percent effective. Not only did Corexit do a worse job of dispersing oil, but it was three times as lethal to silverfish - used as a benchmark organism in toxicity testing - and more than twice as lethal to shrimp, another benchmark organism and an important part of Gulf fisheries."

The reasoning for using Corexit instead of other, less toxic alternatives is likely an issue of name-brands: Corexit is the go-to dispersant for most oil spills, and stockpiles of it likely make it more accessible than its alternatives. There's been a push to market Dispersit as the next "big thing" when it comes to dispersants, but it's been a hard sell. Just like we're more likely to purchase name brands instead of generic, Corexit is the dispersant that everyone knows - Dispersit is not. The lack of open field testing of the product doesn't help the case, either, though lab results show that it's twice as effective at breaking up oil than Corexit.

The type of dispersant used depends heavily on temperature, salinity and what state the oil is in. Fresh oil is more viscous than weathered oil (present within a few days of an oil spill), which tends to form a mass on the surface of the water. Different types of dispersants are more effective on different types of oil. A study performed by researchers at the National Marine Fisheries Service in Juneau, Alaska, shows that several versions of Corexit are ineffective at dispersing weathered oil, but effective against fresh oil.

Similarly, determining the effect of Corexit on wildlife depends on a host of factors such as exposure conditions, species and life stage. Another study from Exxon showed that crustaceans are more sensitive to concentrations of Corexit 9500 and 9580 than fish. The situation is not black and white: making a choice on dispersant also comes with a choice of which species will be most affected. One thing is clear: If we do nothing, all of them will be harmed.

Source: Discover Magazine


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