After collecting weathered crude oil from the Gulf of Mexico following the Deepwater Horizon oil spill, researchers at The Institute of Environmental and Human Health (TIEHH) at Texas Tech University have reported that only 8 to 9 percent coverage on the shells of fertilized mallard duck eggs resulted in a 50 percent mortality rate.
However, scientists also reported the amount of time the oil remained at sea and exposed to weather had a significant effect on its toxicity to the fertilized duck eggs, said Phil Smith, an associate professor at TIEHH. They published their findings in Environmental Toxicology and Chemistry, the peer-reviewed flagship journal of Society of Environmental Toxicology and Chemistry (SETAC).
"If you can imagine a duck egg with about 10 percent of its surface area coated with this particular substance we found in the Gulf, you would expect about half of the bird embryos to die, according to our study," Smith said.
Because the timing of the Deepwater Horizon oil spill coincided with nesting periods for large numbers of Gulf Coast birds, Smith said researchers were interested in discovering the toxicity of the crude oil that was floating offshore and coated about 600 miles of beaches and marshlands.
Using a standardized method for examining the oil's toxicity, 160 eggs were treated with varying amounts of crude oil collected off the coast of Alabama about a month after the Deepwater Horizon oil spill.
"These kinds of studies have been conducted for about 40 or 50 years," he said. "It's not a novel or unique method for evaluating the toxicity of any kind of crude oil. What is novel about our approach is we went out to the Gulf and collected crude oil that was available during the spill. This method allowed for a realistic exposure scenario among bird eggs on the Gulf Coast during that time period. In that respect it's somewhat unique."
When compared to the toxicity of fresh crud
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