WASHINGTON — Yet another alarm is being raised about the dangers posed by a staple of local cuisine — seafood.

A new federal study says that fish imported from other countries contain potentially hazardous levels of drug residue, which can cause allergic reactions or even cancer in consumers.

About 90 percent of all seafood in the United States comes from overseas, and about half of that comes from fish farms, according to the General Accountability Office. Major suppliers of seafood to the United States include China, Indonesia, Vietnam and Thailand.

To keep the fish alive in congested spaces, some seafood suppliers are treating them with antibiotic and antifungal medicines that are not approved for animal or human use in the U.S., the agency said in a report issued last week.

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“Drug residue in imported seafood is a potential health risk,” said Steve Morris, lead author of the new study. “Folks need to know that. … There are some real concerns about the use of drugs on these farms and the effect it might have on safety.”

The dangers from imported seafood hit home in Hawaii last year when about 300 people contracted hepatitis A after eating scallop sushi from the Philippines. In May, frozen ahi from Indonesia tested positive for hepatitis A. In June, a Big Island-based fish supplier recalled ahi it had imported from the Philippines and Vietnam.

But according to the GAO, unregulated medications administered to fish overseas are another possible health risk.

The potential problems are both immediate and long-term, and include “hypersensitivity reactions, toxicity-related reactions, potential carcinogenic and mutagenic effects, and increasing prevalence of antibiotic-resistant microorganisms,” the U.S. Food and Drug Administration said in 2008.

Some of the unapproved antibiotics in farmed fish — such as ciprofloxacin, erythromycin and tetracyclines — are used in treating human diseases, but they are not considered safe for inadvertent consumption by humans, according to the FDA report.

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The FDA also reported in 2008 that residues of chloramphenicol, nitrofurans, malachite green, gentian (crystal) violet and fluoroquinolones had been repeatedly been found in imported seafood products as well.

The agencies that are supposed to protect American consumers — the FDA and the U.S. Department of Agriculture — aren’t doing enough to prevent tainted seafood from reaching the American market, the GAO said, adding that the agencies cited limited resources as a continuing issue at a time that seafood imports are rising.

Researchers at the GAO found that the FDA was inspecting only about 2 percent of fish processors.

Less than 1 percent of samples taken were also inspected for unsafe drug residues. Of that small amount tested, about 12 percent of shrimp tested positive for drug residues, about 11 percent of tilapia, and about 9 percent of catfish. No drug residues were found in the samples of salmon.

Moreover, the GAO found, of a sample of 74 inspection reports they reviewed, officials from the FDA had visited only one overseas fish farm to see how and where the fish were actually being raised. In that case, the GAO said, the visit occurred only because the farm was located near the processing plant and it was convenient to reach.

Lei Yamasaki, an aquaculture veterinary medical officer for the Hawaii Department of Agriculture, said the GAO report, which she reviewed, underscored a problem that insiders have been aware of for some time.

“The problem has been a known issue for imported seafood,” she said. “Controlling for what they do over there is difficult.”

In contrast, she said, fish farms located in Hawaii are required to meet federal regulations governing the use of pharmaceutical products in producing animals for human consumption.

According to Yamasaki, only a limited number of antibiotics are FDA-approved for use in fish to treat diseases, and can only be used in specific species. They have specified dosages and withdrawal times, and authorization for their use comes from a licensed veterinarian. There are no antibiotics approved in the U.S. for use in shrimp, she said.

Patty Lovera, assistant director of Food & Water Watch, a Washington, D.C.-based consumer advocacy group, echoed Yamasaki’s views, saying that U.S. laws are “tighter on drugs” for animal consumption than foreign countries are.

“They are banned for a reason,” she said. “We don’t want people to have exposure to them. They shouldn’t be used.”

She said that consuming fish treated with antibiotics could make the people who eat them more susceptible to falling victim to drug-resistant bacteria.

“The problem has been a known issue for imported seafood. Controlling for what they do over there is difficult.” — Lei Yamasaki, Hawaii agriculture department

Lovera said that giving the FDA more resources to police the quality of imported fish could help solve the problem, but that the budget impasse in Washington makes that unlikely.

“The budget is a big part of it — and that’s a tortured process this year,” she said.

But the problem isn’t just money, she said, noting that the FDA has a reputation for looser enforcement of food safety than the U.S Department of Agriculture, which recently began inspecting catfish, at the request of the American catfish industry.

“It’s a resource issue and a political will issue at the FDA,” she said.

Hawaii’s Yamasaki said she only eats two kinds of seafood — wild-caught fish from the ocean, and shrimp raised on local fish farms. She said that people can be tempted by the low prices charged for imported seafood, but that “cheaper products” can carry more risks.

“The trend is for people to eat healthy, organic and local,” she said. “People need to be careful.”