MUSC News Center
Oil spill study raises 'red flag' about commonly-used compound
Dawn Brazell | News Center | July 2, 2015
|Dr. Demetri Spyropoulos points to a vial of COREXIT, a dispersant used in the Deepwater Horizon oil spill. His team studied the dispersant, oil mixed with dispersant and saline (middle vial) and Deepwater Horizon crude 'source' oil (right).|
That good could come from a devastating oil spill may seem odd.
“We learn from our mistakes, but we’re learning more than we even expected to,” said Demetri Spyropoulos, Ph.D., a researcher and professor at the Medical University of South Carolina and senior author of a study released today in the journal Environmental Health Perspectives, which is published by the National Institute of Environmental Health Sciences.
The study had two “home runs,” he said.
One was that researchers found a commonly-used chemical known as DOSS (dioctyl sodium sulfosuccinate), an ingredient in the dispersant used to clean up the Deepwater Horizon oil spill, is likely an obesogen. An obesogen is a compound that potentially contributes to obesity in people and wildlife. The second major finding was how commonly used this compound is, including in laxatives, some flavored soft and fruit drinks, homogenized milk and many personal care products.
“We were expecting this to be like looking for a needle in a haystack, but instead we were able to zero in on a single component in this complex mix of oil and dispersant,” Spyropoulos said.
Funded by the Gulf of Mexico Research Initiative (GoMRI), scientists were investigating the environmental contamination resulting from the Deepwater Horizon oil spill. The spill began April 20, 2010, in the Gulf of Mexico and was capped 87 days later. An estimated 200 million gallons of oil impacted about 500 miles of the Gulf’s shoreline and about two million gallons of dispersant were used in the cleanup.
A major component of the COREXIT dispersants used to clean up the spill is DOSS. The oil, saline and dispersant mixture is a complicated brew of compounds that scientists were examining to see if any parts of the mixture had biologically active agents that act as endocrine disruptors. The disruptors belong to a class of chemicals that change the body’s hormone systems by mimicking or blocking normal processes.
The study showed DOSS binds to a protein that changes the expression of a suite of genes involved in making new fat cells and other related functions. “One possible effect of that orchestration is to drive stem cells toward fat cells," Spyropoulos said.
“With the obesity epidemic, not only is it about what you eat and how hard you exercise, but that there are chemicals in the environment that might tell your body to behave differently than it normally would, such as make more fat cells or change your metabolism to increase your appetite or slow your metabolism.”
A GRAS (generally recognized as safe) notice on DOSS was submitted to the Food and Drug Administration in 1998, which means manufacturers of food and personal care products can put it into products and not mention that it is in there. Since it’s used in laxatives such as Colace that are prescribed to some pregnant women, and might be in so many commonly-used products, it’s important for researchers to look at its possible impacts on human health, he said.
“We’re at a point where we have put up a red flag, and we can say on a cellular level this likely contributes to fat cell differentiation. We don’t know yet if this compound DOSS will be obesogenic in humans, though, and if so, at what dosages that effect would be achieved and which populations would be most susceptible.”
What researchers can say is that other dispersants may be safer. Collaborating with other GoMRI members who are developing alternative dispersants, MUSC researchers are testing the endocrine activities of the new dispersants. “They sent us an effective two-component dispersant mix. We did the tests we performed on COREXIT and found that it has much lower activity in our tests.”
That’s important because it’s not a matter of if, but when, the next oil spill will occur, he said. “This will help us be better prepared.”
They also are preparing the next generation of scientists who will study how to better protect human health from compounds that act as endocrine disruptors. Another researcher on the study is Alexis Temkin, a marine biomedicine and environmental sciences Ph.D. student at MUSC and a GoMRI Scholar. She, along with Robert Bowers, Ph.D., are first authors on the study. It’s this kind of research that brought Temkin to MUSC and the Hollings Marine Laboratory, which also was involved in the study.
“I knew I wanted to study environmental health on a molecular level and explore the connection between environmental health and public health,” she said. “The Marine Biomedicine Program directed by Lou Guillette was really a perfect fit, and Demetri’s newly funded project studying the long-term health impacts of the DWH oil spill was a great opportunity for me.”
Temkin said their research involved using a cell reporter system to see if certain chemical mixtures interact with proteins involved in cell processes that guide metabolic functions such as fat differentiation. Because cellular processes are microscopic and complex, they engineered the cells to literally light up if a chemical caused that specific change in the cell.
“We then use other experiments like cell differentiation or in vivo model studies to follow up on and further investigate these hits,” she said.
“We were definitely surprised by the results. My original hypothesis was that one or more components of oil could be potential obesogens. When we narrowed it down to a component of COREXIT and then down further to a single chemical, DOSS, I was even more surprised. Investigating the use of DOSS other than its use in COREXIT has been a really eye-opening experience, too, given its broad use as a chemical.”
Temkin said she loves being a GoMRI scholar and that the funding agency places a high value on student work and the collaborative potential between different researchers and projects.
“It’s been a wonderful and supportive environment to pursue a Ph.D.”
It's also fertile ground for future research.
Spyropoulos said they are particularly interested in what happens during fetal exposure. There’s a hypothesis that speculates that what the fetus is exposed to during pregnancy can have a profound impact on its health trajectory throughout life. There is a transfer of some of the compounds that the mother is exposed to that goes to the fetus.
The cells in a fetus begin with pluripotent stem cells that have the potential to differentiate into any cell in the body. “In one model of obesity, there is a mesenchymal stem cell that can produce bone, cartilage, fat and muscle cell types. What our work suggests is that DOSS – if it gets into a mesenchymal stem cell lineage – will affect differentiation that will make it more likely to become a fat cell.”
Spyropoulos said that just because a compound is used at a level lower than what would kill cells in the body doesn’t mean it’s necessarily harmless. The oral laxative used by some pregnant women can be prescribed at up to 1/10th the dosage used in their study, which signifies this is an area that warrants further investigation.
“We need to think more holistically. This chemical helps disperse oil, but is that the only thing it does? This chemical helps a woman who is pregnant with constipation, but what else is it doing? And is it interacting with other chemicals so its impact is stronger?”
More research is needed to study compounds that may alter the behavior of cells and hormonal balances in the body that can contribute to disease, he said. “We now need to take a second look at anything we put on our bodies, in our bodies and in the environment. If some major culprits are identified, that could lead to significant health improvements.”
The study “Effects of Crude Oil/Dispersant Mixture and Dispersant Components on PPARγ Activity in Vitro and in Vivo: Identification of Dioctyl Sodium Sulfosuccinate (DOSS; CAS #577-11-7) as a Probable Obesogen,” is available at this link.
For more information on MUSC’s Marine Biomedicine and Environmental Sciences, visit its website.