The Dirt on Shrimp

How our bottom-feeding frenzy may be making us sick.

The weather along Thailand's lush eastern coast changes the minute you leave the beach. A mere 20 or 30 yards inland, the fresh breeze flowing in from the Gulf of Thailand fades amid the thick mangroves, and you enter a dome of oppressive, gagging tropical heat. The view changes, too, from white sand beaches and a few fishing boats bobbing on the expansive blue ocean to acres of murky, rectangular, manmade ponds.

It's here, at a roadside station near the town of Laem Sing, that I watch workers load hundreds of pounds of America's favorite seafood into the backs of sweltering trucks. Some 20 laborers have gathered at the station to sort the still-squirming crustaceans. Load after load of shrimp, treated more like gravel than someone's future appetizer, are dumped from laundry baskets onto a low wooden table slick with pond detritus and dismembered prawns. Women wearing dirty gloves sweat profusely as they flick the Pacific whites into baskets designated for small, medium and large shrimp. Finally, several men, one with a cigarette dangling from his lips, hoist the filled baskets onto the trucks.

The shrimp destined for your kebabs and surf-'n'-turf combos then travel unrefrigerated to their processing plant, which I was told was located several hours away. Shrimp begin to spoil immediately if they aren't adequately chilled, and the few random blocks of ice these shellfish are packed in doesn't fuel much confidence. But this becomes just the first of my worries once I shift my gaze back to the fetid, muddy ponds the shrimp once called home. My guide, fishery scientist Ratana Chuenpagdee, Ph.D., codirector of the coastal development center of Kasetsart University, in Bangkok, explains that the current worldwide enthusiasm for shrimp has turned water farms in many shrimp-exporting nations into health and environmental menaces.

"During the burst of intensive shrimp farming development, they mowed down thousands of acres of mangroves to make these farms. Things are better here, at least environmentally, but in other areas—Vietnam, China, Indonesia—the pollution from sulfurous pond drainage can be tremendous," she says. "And there can be serious problems in the ponds, too, in terms of the health of the shrimp."

Given the filth present at the sorting station, I'm surprised by the uniform landscape around the ponds, which have a stark, industrial beauty to them. Each pond is covered by a canopy of red plastic cords to keep hungry birds away from the crop. Aerators powered by old car engines move water around, sloshing like antebellum riverboats. Gazing into the mire of the pond directly before us, I realize that I could stand here for a week and never see a single shrimp in the shallow, filth-blackened water. But I know the shrimp are there, packed together in the muck at the bottom of what amounts to an underwater feedlot.

As bad as it looks, I have no way of judging their environment. But experts worry that crowded, cruddy conditions make this largely unregulated global industry a potential health nightmare. Not only are the processing and transport systems suspect, but some shrimp farmers use chemicals and pesticides to squeeze as much profit as possible from their farms. In the worst cases, as the hungry shrimp burrow into the chemical-and-excrement-filled mud—every day for four months—they ingest a toxic meal.

And so, perhaps, will you. (Before you read on, learn the 11 secrets the food industry doesn't want you to know.)

Crustacean invasion

Not long ago, shrimp was a seasonal delicacy served fresh at waterfront restaurants or, more likely, packed as tight, rubbery commas into a can. Now they're a seafood staple. In 2008, Americans scarfed up more than 1.7 billion pounds of shrimp—twice what they consumed just 12 years before that, according to the National Oceanic and Atmospheric Administration. That's an average of more than 4 pounds of the little curlicues per person each year.

And who can blame us? Shrimp are sweet and crunchy and tasty, and they go well in most dishes. They line up neatly around the rim of a cocktail glass, and they're perfect when spiced and laid out on the grill or dropped into salads. You can toss them in the air and catch them in your mouth. Not only are shrimp a low-fat source of protein, but they're also high in iron, zinc and niacin.

But our insatiable hunger has had a global ripple effect: Overseas operations that sprang up in response to this feeding frenzy have flooded the market. About 90 percent of what we eat is now imported and sold to grocery stores and restaurants across the United States. A third of this haul comes from Thailand; most of the rest arrives from Indonesia, Ecuador, Vietnam, China and Mexico. "American appetites drive processes half a world away," says biologist Elliott Norse, Ph.D., the president of the Marine Conservation Biology Institute, in Bellevue, Wash. "Shrimp has gone from being an uncommon and expensive commodity to something you can buy year-round at Red Lobster. And this has consequences."

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Toxic gumbo

A handful of countries, especially Thailand, are making valiant efforts to regulate shrimp farming. But the steep decline in prices that has accompanied the high output, along with the parallel decline in income for farmers and laborers, makes the effort a struggle. Farmers have to work to ensure that the majority of their crop makes it onto the ship, so the temptation is huge to deploy whatever chemical weapons they have in their arsenals. "Their mind-set is to squeeze every shrimp from every crop, and then squeeze out as many crops as they can before the pond collapses," Norse says. "They know that the odds of slipping contaminated food past inspections are far better than the odds at the craps table in Vegas. So they use all sorts of exotic chemicals to keep the shrimp alive. And this is what we eat."

Those chemicals include 10 classes of antibiotics and 17 different kinds of pesticides, most of which are banned from use on food in the United States, according to Food & Water Watch, a consumer advocacy group based in Washington, D.C. Two culprits are gentian violet and nitrofurans. Both are potential carcinogens. Find out what other additives are in your favorite foods with this guide.

Shrimp farmers also use disinfectants to clear out viruses, and employ sulfites and other chemicals to prevent blackspot, a harmless but nasty-looking discoloration. Unfortunately, there's a price to be paid for spotless shrimp: A 2009 study published in Chemical Research in Toxicology shows that one of these anti-blackspot agents, 4-hexylresorcinol, is a xenoestrogen, a compound that mimics the female sex hormone estrogen. In humans, xenoestrogens have been implicated in reproductive system abnormalities in men.

Antibiotics represent a different kind of threat: increased resistance among bacteria found in shrimp. In recent years, shrimp from China have tested positive for residues of chloramphenicol, a powerful antibiotic. "Using these drugs in irresponsible or excessive ways can lead to the development, by genetic evolution, of resistant bacteria," says Jonathan Borak, M.D., a clinical professor of environmental health at Yale University's school of public health. "Creating a commercially viable product may be an understandable use, but it can lead to greater risks of antibiotic resistance."

The bacterial menace was highlighted in 2005, when Mississippi State University researchers bought a variety of frozen, ready-to-eat shrimp products that were imported from four different countries. They found 162 different species of bacteria, including E. coli, Salmonella, Staphylococcus and Vibrio. Many had become resistant to one or more antibiotics. "We were surprised to find this many pathogens in ready-to-eat products," says Douglas Marshall, Ph.D., a food scientist and lead author of the study. "Our data suggests that human infection is certainly possible. Outbreaks can and do occur."

Other physicians and public health experts echo this uncertainty, because gauging the precise danger remains a challenge. The long-term, cumulative effect of ingesting these antibiotics and pesticides is still being studied, and there's relatively little inspection going on in U.S. ports—the FDA concedes that barely 2 percent of seafood imports are inspected. Also, there's no consistency in the amount of chemicals any given bite of shrimp might contain. Some experts, in fact, aren't worried at all. "I'd just as happily eat imported shrimp as I would domestic shrimp," says Charles Santerre, Ph.D., a professor of food toxicology at Purdue University. "Shrimp tend to be short-lived, so they accumulate very little antibiotic or pesticide residue."

Shifting tides

Few of the shrimp farmers in Thailand eat their own products, but it isn't because they know something we don't. They simply eat different shrimp, Chuenpagdee says as we explore the fishing community of Bang Chan. In fact, 99 percent of the shrimp farmed in Thailand—mostly Pacific white shrimp—aren't even native to the region. Tiger shrimp are. "This is strictly a cash crop for the locals, who are aiming for export markets," Chuenpagdee says. "It's something other people eat." (Adapting other countries' eating habits can help fight disease and battle bulge—if you follow the world's most powerful eating strategies.)

Chuenpagdee introduces me to the village's leader, Sangobp Bunluea, who chuckles good-naturedly at my attempt to say "hello" in Thai. He's been catching shrimp and fish for decades and represents the divide that his community struggles with. "There's a new split in the village," he says. "My son grows shrimp in farms; I set nets in the wild. But neither of us is doing as well as we used to." Clear-cutting the mangroves years ago destroyed a critical nursery habitat for wild shrimp; this hurt harvesters like Bunluea. His son, the shrimp farmer, is faring no better, Chuenpagdee says, because prices are generally so low.

Later we meet with Samart Sreinkit, a 32-year-old manager with one of Thailand's largest shrimp producers. He works at a corporate experimental farm where he's trying to develop safer, more environmentally friendly, antibiotic- and pesticide-free approaches to shrimp farming. Through Chuenpagdee, he tells me that it's hard to bring in these reforms now, because markets are uncertain and many farmers are quitting the business, leaving their ponds fallow because they can't make enough money.

But the market may yet force that change. "Eighty percent of the pesticide and antibiotic companies in Thailand are out of business now," says Chalor Limsuwan, Ph.D., a shrimp pathologist at Bangkok's Kasetsart University. "Why? You have to satisfy the customers, and the customers don't want residues. So farmers learn to avoid the chemicals." Thailand has been burned by contamination scandals in the past, and the government has instituted a series of "best practices"—and export permits—designed to reduce chemical contamination.

Even if Thailand is able to turn its shrimp industry around, there's a new problem lurking in the background that could stymie its efforts and further endanger consumers in the United States: Shrimp are now being imported into Thailand from Burma, Cambodia and Vietnam—countries that rate far lower than Thailand on the safety and quality scale. The shrimp are purchased at much lower prices than what the Thai farmers are usually paid. They're processed here and sent abroad, labeled as products of Thailand.

Pulling into port

This is an alarming revelation, and though I love shrimp, I leave Thailand distinctly queasy about the idea of eating the little crustaceans. But I want to see the production process through to the end. So back home in San Francisco, I find a bag of frozen Pacific whites—raised, processed and packaged in Thailand.

Pacific white shrimp have little color until they're cooked, but they're still beautiful—long, plump and frozen in a water glaze. Twenty-eight to the 1-pound bag, deheaded and deveined. They're flaccid, of course—as any frozen shrimp is, once it thaws—but still firm enough to hold together on a bamboo spit. And they are delicious barbecued. Not as good as the best Pacific Coast spot prawn I've had, but helped along by a ginger-tamari marinade and a hint of cocktail sauce. My wife and I demolish the bag.

But I find myself squeamish in a way I almost never am with other food. I think of what this shrimp might have ingested and carried around the world from those filthy ponds. It's not that every shrimp dinner emerged from a toxic mud pit. It's that I don't know which ones might have.