A look at how petroleum impacts the seafood chain–and, what would happen to you if you ate an oil-tainted oyster?

“Crude oil has many, many chemicals in it. Most of the chemicals are considered organic, they come from the earth, they are not made by man,” according to Dr. Jim Diaz, head of environmental and occupational health sciences at the Louisiana State University.  And many of them are carcinogenic.

“If an animal ingests petroleum, their tissues, their fat, their lean muscle, their reproductive organs, and their liver could potentially accumulate these chemicals,” says Diaz. Instead of testing for all the potential chemicals associated with oil, scientists will generally test for the presence of a chemical called Benzo[A]pyrene (BAP) as a marker.

“We know that BAP is carcinogenic,” says Diaz, adding that “Anytime you burn, barbeque, blacken [food] or burn fossil fuels,” you release similar chemicals. (Foodies, don’t worry, Diaz still eats blackened shrimp, just not everyday). What’s alarming is when you see these chemicals turn up in raw food.

Research focused on the long term impacts of hydrocarbon contamination in seafood following an oil spill has shown that not all sea life is affected equally.

Mollusks, like oysters, clams, and muscles are affected the most. “They’re filter feeders, so they take in lots of water and eat the little particles, including the viruses and the bacteria and anything else, including dispersed oil,” says Diaz. “They also don’t have good enzyme systems for metabolizing [the oil droplets], so the derivatives of petroleum will accumulate and be found at high levels.”

Going up the food chain, the crustaceans–lobster, crab, shrimp–are the second-most impacted. This group can swim, so they can instinctively move away from the oil–which, according to Diaz, they can smell–but they have a tendency to go back to the same spawning area, even if it’s contaminated.

For fish, the level of bioaccumulation depends on where the fish dwell. Bottom-dwelling fish, like flounder, dover, and sole, tend to be territorial, hesitant to leave their familiar territory so they tend to accumulate higher levels.

True finfish–salmon, tuna, and others, which have been found to have the lowest bioaccumulation (among the typical sea life we consume), will avoid the spill “if they don’t like the smell of the water.”

But finfish, sitting higher up on the seafood chain, are also exposed to oil by ingesting contaminated food items or sediments. Luckily, they have another thing going for them: the ability to process the oil.

As Diaz explains, “These fish have actually–over eons–developed metabolizing systems, so they can actually metabolize and excrete the derivatives of petroleum so they are the safest things to eat.”

The federal government has established levels for what it considers safe for consumption, tailored to each type of fish.

What would happen if you ate seafood with higher levels of oil-derived chemicals? According to Diaz, probably nothing–unless it was over a long period of time. And, as we reported yesterday, oil-tainted fish has a strong smell, making it unpalatable.

Diaz says he remains much more concerned about pregnant women eating seafood with methyl mercury than he is about consumers eating hydrocarbon-tainted seafood.