Toxic Chemicals Deep at BP Spill Site Raise Warning Flags

(Nov. 4) -- On the surface at least, the Gulf of Mexico appears relatively clean more than six months after the massive BP oil spill, but scientists say they've found toxic materials deep in the ocean at the site of the blowout, and some warn that all the environmental impacts of the gusher won't be known for some time.

In the latest study published this week, researchers report that large quantities of polycyclic aromatic hydrocarbons, or PAHs, were present in the deep sea near the Macondo well head in May, and that the potentially dangerous compounds had likely spread to other areas since those findings.

"Based on our findings, subsurface exposure to PAH resulting from the Deepwater Horizon oil release was likely to be associated with acute toxicity effects in discrete depth layers between 1,000 and 1,400 meters in the region southwest of the wellhead site and extending at least as far as 13 kilometers," researchers from Texas A&M, the University of Southern Mississippi and other institutions wrote in the journal Geophysical Research Letters.

While the most immediate damage from the spill -- as evidenced by tar balls, oiled birds and widespread oil sheen -- may have subsided, it's those persistent pollutants that have some researchers worried -- and stumped.

"PAHs do in general persist, and sometimes for a long time, in marine systems," Doug Rader, chief ocean scientist for the Environmental Defense Fund, told AOL News. "There's still a lot to be known about how exactly long that will be. And there's no reason to think that the tenure of these toxicants will be short."

BP officials were not immediately available to comment on the latest research.

While gulf seafood has been declared safe to eat, much is unknown about how the rest of the region's vast and complex ecosystem may have been affected by the BP spill. Acute damage from the oil spill, particularly to large, photogenic animals like marine mammals, sea turtles and sea birds, wasn't as bad as many environmentalists feared. But the long-term chronic impacts remain hazy and will likely be hard to parse out even in the future, especially in an area that faces pollution not only from oil but from a number of other sources, like fertilizer carried down the Mississippi River.

The deep sea and the sea floor, where the spill originated, may be where much of the contamination lingering from the spill is playing out. And unfortunately, oil on the sea floor or in sediment is not out of play -- it can be consumed by bottom-feeding creatures which are eaten by fish like grouper or snapper. Storms and shrimp nets also could disturb PAH-contaminated sediment and reintroduce the chemicals into the water.

Still, shrimpers and fishermen have been having a good season since they've been let back out on the water, and tests for PAHs, dispersants and other toxic elements have all come back negative. But because the oil may have done the most damage to larval fish and shrimp rather than the adult versions that fishermen are interested in catching, the concern is that later generations of fish and shellfish may come back weaker.

According to the Environmental Protection Agency, PAHs are "highly potent carcinogens that can produce tumors in some organisms at even single doses."

The key to monitoring the situation, Rader said, will be improving the testing models officials have for locating contamination in seafood by modeling ocean currents at various depths to try to predict which areas saw large deposits of oil, and then using that information to help determine how and where they look for chemicals like PAHs. It's no small task -- sea creatures and currents both move -- but finding where persistent pollutants are likely to linger will be crucial to ensuring the continued safety of seafood in the gulf.

"How many of those samples would you need to take to detect a difference? I think the answer would be a lot," Rader said. "BP and certainly the government owe the people of the gulf an investment in both enhanced sampling and monitoring in order to effectively characterize those places where potential problems exist, so that potential management systems can be built."

Right now, consumer confidence in gulf seafood is low, and fishermen have been struggling with comparably low prices as a result. And while the seafood that ends up in the market now is subject to more testing than any other seafood in the world, some hope that even more rigorous examination may help convince consumers that what they're buying is clean.