China is the world's largest producer of farm-raised seafood, exporting billions of dollars worth of shrimp, catfish, tilapia, salmon and other fish. The U.S. imported about $2 billion of seafood products from China in 2007, almost double the volume of four years earlier, according to the U.S. Department of Agriculture.
But industry experts and businesspeople in China say that melamine has been routinely added to fish and animal feed to artificially boost protein readings. And new research suggests that, unlike in cows and pigs, the edible flesh in fish that have been fed melamine contains residues of the nitrogen-rich substance.
Melamine, commonly used in plastics and dishware, can lead to urinary problems such as kidney stones and even renal failure.
Last year, pet foods made with melamine-laced ingredients from China sickened or killed thousands of dogs and cats in the U.S. This year, infant formula tainted with the chemical has been linked to illness in 294,000 small children and six deaths in China, according to China's Ministry of Health.
"China's a big place, and it does a lot of processing, and cheaply too," said Brian Dedmon, purchasing manager for the Fish King distribution plant in Burbank.
Fish King, which supplies hundreds of Southern California restaurants and has a store in Glendale, says it buys processed snow crab meat, squid and other seafood from China to meet market demand and because the price is competitive. Dedmon says the company relies on government inspections, its importers and its own experience to ensure the fish it buys is safe.
"We're definitely concerned about melamine, but by the time the fish gets to us, health issues should've been taken care of by the government agencies and brokers that we go through," he said.
Not on the checklist
But even though some U.S. fish importers are voluntarily testing for melamine, the U.S. Food and Drug Administration, which is responsible for ensuring the safety of imported fish, currently doesn't require seafood products to be screened for melamine. Yet research from its own scientists has raised a warning flag.
Laboratory studies of melamine-fed catfish, trout, tilapia and salmon by the FDA's Animal Drugs Research Center found that fish tissues had melamine concentrations of up to 200 parts per million. That's 80 times the maximum "tolerable" amount set by the FDA for safe consumption.
Other scientists said testing of melamine in farm-raised fish from China should be made mandatory because of the dearth of information about melamine levels in Chinese feed and fish.
"That's the problem; no one has a clue how much concentration and for how long" fish from China have ingested melamine, said Jim Riviere, director of chemical toxicology research at North Carolina State University in Raleigh. "There's an issue of relative human safety," he said. "It would be prudent to screen for melamine."
An FDA representative in Washington wouldn't comment on why Chinese-produced seafood didn't have to be analyzed for melamine when imported to the U.S. Nor were FDA researchers made available to comment on their agency's findings, reported recently in the Journal of Agricultural and Food Chemistry.
Research undertaken by Riviere and others show that melamine in feed consumed by pigs and cows is excreted in the urine or otherwise flushed out, leaving virtually no trace of it in the muscle or meat of the animals. But fish appear to be different,toxicologists say.
Fang Shijun, who has monitored the melamine problem for several years, says he believes that the adulterated products are being supplied only by small operators, which abound in China.
Like those who added melamine to milk and diluted it with water to increase profit, feed businesses can sell more by substituting melamine for real protein sources, especially with the cost of corn and other raw materials having soared in the last couple of years.
"It is impossible to calculate how many of them have done that," said Fang, manager of feed research at Shanghai EFeedLink Information Technology, an agriculture consulting and research firm.