WASHINGTON — With the US government close to approving genetically modified salmon for human consumption, a study out Thursday warned that key risks to society could be missed in the rush to the market.

If approved by the Food and Drug Administration, the quick-growing salmon would be the first so-called "Frankenfood" animal approved for consumption by the American public.

But experts said not enough is known about the wider impacts on society of bringing such foods on the market, including a potentially major shift in dietary habits, buying practices and environmental hazards.

The current FDA process involves comparing modified salmon to the regular fish, analyzing the nutritional profile and screening for toxins, said the study by American and Norwegian researchers published in the journal Science.

"A more useful approach would be to evaluate whether society is better off overall with the new product than without it," said Duke University law professor Jonathan Wiener.

In the case of the salmon, which is known to carry omega three fatty acids that are good for the health, the benefits might be positive overall, said economist Martin Smith, also from the North Carolina based university.

"But what is important is that you establish a precedent. More foods like this might come on the market and they might not be ones where there is a public health benefit," he said.

"Making food cheaper is giving people more money to spend on other goods and that is certainly a good thing," he explained.

"But if you make an unhealthy food cheaper then people substitute away from healthier foods and there can be public health consequences and that's a bad thing."

If the FDA gives the salmon the go-ahead it could open the door to a variety of other kinds of genetically engineered animals ranging from tilapia to pigs to cows.

The altered salmon is made by Massachusetts-based AquaBounty which argues that its fish, injected with a gene from the Pacific Chinook salmon, can reach adult size in 16 to 18 months instead of 30 months for normal Atlantic salmon.

An FDA spokeswoman told AFP that the review is "still under way and we don't have any timeline."

Smith said that the team relied on past data about farmed salmon for its research but did not make its own projections about the societal benefits and hazards because they were unsure whether the FDA might make its decision before they could finish.

"It is more important to make the point that such a broad analysis needs to be done," he said.

In September, a group of independent experts also urged US authorities to do more studies before allowing genetically modified salmon on the market, saying that the studies undertaken so far were insufficient to determine with any certainty whether the salmon pose a risk to humans or the environment.

The FDA turned to the committee of independent experts after concluding, based on company data, that the modified fish was safe for human consumption and the environment.

The FDA is not bound to follow the recommendations of its experts group, but generally does so.

Thursday's research in the journal Science was co-authored by Frank Asche of the University of Stavanger, Norway, and Atle Guttormsen of the Norwegian University of Life Sciences.