Despite repeated assurances from federal officials and President Obama, independent scientists and public health experts have serious concerns about the long-term safety of Gulf seafood consumption.

In particular, experts tell Raw Story, contaminants from the massive oil spill and unprecedented use of the dispersants employed to dissolve the spill have the potential to cause cancer and neurological disorders.

In interviews with Raw Story last week, scientists and public health experts expressed concerns over possible long-term risks from eating contaminated Gulf seafood.

Polycyclic aromatic hydrocarbons (PAHs) are cancer-causing chemicals found in crude oil that can accumulate in the food chain, absorbed by fish and shellfish. During the ongoing testing of seafood in the Gulf of Mexico by federal and state authorities, PAHs are of primary concern.

But crude oil also contains heavy metals such as lead, mercury and cadmium that can accumulate in the food chain as well, though at a slower pace than PAHs, and are toxic to the brain and nervous system.

Another potential long-term health concern left in the wake of BP’s catastrophic oil spill is the nearly two million gallons of dispersant unleashed into the Gulf, much of it subsurface, which made both the amount used and its use unprecedented.

In interviews with Raw Story last week, FDA and National Oceanic and Atmospheric Administration officials said that all fish and shellfish in reopened federal and state waters have tested well beneath the level of concern for PAHs.

But what worries some scientists and public health experts is what these tests don’t -- and can’t -- reveal. They feel it’s “premature” for government officials to claim Gulf seafood poses no future health risks.

“Those are the short-term effects,” said Edward Trapido, the Wendell Gauthier Chair of Cancer Epidemiology at the Louisiana State University School of Public Health.

“We don’t know the long-term effects,” he explained. “And we don’t know, particularly related to cancer and particularly related to age and exposure, what the long-term effects will be.”

Trapido testified in June at a House Subcommittee on Energy and Environment hearing on the spill and is heading a research group at LSU that will look at a range of health effects, including psychiatric and behavioral effects, chronic diseases and cancers.

The issue we don’t know at this point, he said, is the extent to which these compounds may bioacccumulate in shellfish or fish and what the half-lives are.

“So you could imagine if a large fish feasted on several hundred small fish and each of those small fish have eaten a certain number of microorganisms which had a little of contaminant, there’s a possibility, certainly, that you could go over the current measurements.”

In interviews with Raw Story last week, NOAA and FDA officials, in general, tended to downplay bioaccumulation of PAHs in Gulf seafood. But in some cases they denied it’s occurring at all, or even that it could occur.

“We have not found it,” FDA spokeswoman Meghan Scott claimed. “Every sample that we have tested for PAHs has come back clean. It has the potential to [bioaccumulate]. But we have not found it, even from samples taken from inside of closure areas.”

Christine Patrick, NOAA spokeswoman for seafood safety, went so far as to tell Raw Story, “The concept that the oil bioaccumulates [in seafood] – that’s not correct. It’s metabolized and excreted.”

Raw Story confirmed, in consultation with independent scientists, that these two statements were, respectively, impossible and inaccurate.

Miriam Rotkin-Ellman, a staff scientist at the Natural Resources Defense Council (NRDC), a leading national environmental group, underscored two things that NOAA, FDA and Gulf state officials have been playing down.

“The monitoring that’s currently being conducted by both NOAA and various different state agencies, and compiled by FDA, show that there is PAH contamination of fish in the Gulf,” she said. “They are detecting various different levels of the various different PAH constituents.”

Ellman, who contributed to last month’s peer-reviewed Journal of the American Medical Association (JAMA) study, which identified a number of issues about the health of Gulf seafood, also noted, “There is a good body of literature showing that seafood can be impacted by these contaminants.”

The JAMA report cites a 2002 study in the peer-reviewed journal Marine Environmental Research on the lasting effects of the Exxon Valdez oil spill, which concluded: "Our data show that 10 years after the spill, nearshore fishes within the original spill zone were still exposed to residual hydrocarbons. All biomarkers [for contaminants] were elevated in fish collected from sites originally oiled, in comparison to fish from unoiled sites.''

Ellman added, “We understand that the different types of seafood – fish vs. crustaceans and bivalves – all have different capacities to retain the contaminants, and that’s important to note. But it’s not the basis on which to make a blanket statement that there’s no risk.”

“So it’s premature,” Trapido cautioned, “to say that it’s safe in the long-term.”

“We can say that it’s safe at this point based on what we know,” he continued. “But as a cancer epidemiologist, which is what I am, I have to maintain an air of skepticism and say, well, we don’t have any data to make a judgment on the long-term cases.”

The startling lack of data on the future health effects from oil spills on humans was a common lament among experts who spoke with Raw Story.

Trapido confirmed that the longest follow-up study that’s ever been done on people exposed to oil spills was just four years, and that was to track mental health only.

Two new areas of scientific research not being accounted for in the current risk assessments could also adversely impact future health, Ellman noted.

She said that studies have shown that early life exposure to the chemical benzo(a)pyrene, one of the most carcinogenic PAHs, increases the risk of cancer later in life. It wouldn’t have the same effect, she clarified, if the exposure came later in life.

“So because children’s bodies are different and they’re developing, exposures that happen early in life can have a more detrimental effect than if they were exposed later on,” said Ellman.

In addition to the cancer risks, Ellman told Raw Story that there’s also a new body of literature that has shown adverse developmental impacts from in utero exposure to PAHs, such as delayed growth, low birth weight and other indicators of impact during fetal development.

NOAA toxicologist John Stein said that he and other scientists within the agency have proposed to continue monitoring the Gulf waters to ensure seafood safety for the next three to five years. But Patrick confirmed that the agency has not made an official commitment to this.

Independent scientists and public health officials who spoke with Raw Story agreed that even if federal and state officials committed to such a time frame, it would still fall short of what's necessary.

They pointed out that due to bioaccumulation in the food chain, it's quite possible contamination levels in Gulf fish and shellfish may actually be higher in three to five years.

"If they were to completely suspend any monitoring prematurely," Ellman warned, "we wouldn't necessarily know whether levels of contaminants in seafood that we're most worried about have gone back down or remain elevated."

Brad Jacobson is a contributing investigative reporter for Raw Story.