R.C. Hunt, who’s raised pigs for 50 years in North Carolina, offers no apologies for a common practice in the U.S. pork industry: mixing feed with a controversial drug that makes the animals grow leaner in the final weeks of their lives.

With the Food and Drug Administration allowing farmers to give the drug, ractopamine, to their pigs since 1999, pork producers say their meat is perfectly safe.

“I believe in the science,” said Hunt, of Wilson, N.C., who produces 125,000 pigs a year and is a former president of the National Pork Producers Council.

But food safety advocates say there’s one big problem: Amid fears that it may be harmful to animals and humans alike, the drug has been banned or restricted in roughly 160 of the world’s 196 countries, including those in the European Union.

The growing anxiety over the safety of U.S. pork and other food products could thwart an expanded trade deal between the two economic superpowers, a top priority for President Barack Obama.

As European and U.S. negotiators met privately in a sixth round of talks in Brussels that ended Friday, critics worried that a pact might result in new trade rules that harm the European food supply.

“We want to have quality food. We don’t want to have food that is produced in ways that are not good for our health,” said Olga Kikou of Brussels, European affairs manager for Compassion in World Farming, an international advocacy organization headquartered in London that focuses on farm animal welfare issues.

Many Europeans have long opposed genetically modified products, but much of the recent uproar has focused on U.S meat. That includes chicken, which in the U.S. is disinfected with chlorine in a commonly used cleaning practice.

In May, German Chancellor Angela Merkel gave assurances that she’d block the imports of any chlorine-washed chicken, or chlorhuhnchen, as it’s known in German. The EU has banned U.S. chickens since 1996, but American chicken producers want the ban lifted as part of a new trade pact.

In June, U.S. Agriculture Secretary Tom Vilsack made a trip to Paris, where he urged Europeans to accept “the common language of science” in trade.

Critics say U.S. officials should put more emphasis on health.

“This is such a great example of how the U.S. is really putting the financial interest of companies ahead of public health,” said Kari Hamerschlag, senior program manager of the food and technology program at the environmental group Friends of the Earth in Berkeley, Calif. “We want to export our really crappy meat-production system to the rest of the world _ and they don’t want it.”

But with the European economy struggling, many trade backers say EU leaders will come under increased pressure from their citizens to change their food rules.

Hunt called Europeans “great people, and they have great opportunities.” But he said they needed imports to satisfy consumer demand for meat.

“I’ve visited farms in the EU. They’re inefficient, they’re antiquated and they’re non-sustainable,” Hunt said. “The EU used to be able to provide all of its pork and beef needs. They can’t do that today… . At some point in time, the people make the decision: If you run short on food, you will have riots in the streets.”

Hunt said he worried that the United States already was “getting behind the food curve” and wouldn’t be able to help feed the growing world population unless farmers adapted: “That’s where I become open to trying scientifically approved technologies.”

Ractopamine, which is fed to 60 percent to 80 percent of all pigs in the U.S., has been linked to more than 160,000 reports of sickened or dead pigs, according to the Center for Food Safety, a nonprofit group that focuses on environmental and health issues.

The drug, part of a class called beta-agonists, increases the pig’s heart rate and relaxes its blood vessels, resulting in leaner muscles for the animal and lower feed and production costs for the producer. It’s manufactured by Elanco, a branch of Eli Lilly, the pharmaceutical giant.

In a May report, the Humane Society Institute for Science and Policy said that a series of studies had shown that pigs fed ractopamine showed increased aggression, more abnormal behavior and difficulty walking.

Hamerschlag said pork producers were on “the absolute wrong side of this issue” and predicted that more Americans will begin pushing for a ban on ractopamine.

“Pork producers would be smart to get out ahead of that,” she said.

Some companies, including Virginia-based Smithfield, are already moving to provide ractopamine-free pork.

Even before a Chinese firm acquired the company last year, Smithfield announced that it had begun converting two of its North Carolina plants _ in Clinton and Tar Heel _ to be free of the additive. China demands that its imported meat be certified as ractopamine-free. When it made the announcement, Smithfield said its move would help the company increase its market share and that it would be well-positioned to provide ractopamine-free meat in the future, domestically and abroad.

Hunt said the fears were unfounded, likening the drug to a vitamin that helps pigs digest their feed. And he said he’d never seen any ill effects.

“We’ve always looked at the ractopamine as kind of a natural product. We’ve been using it for many, many years,” Hunt said.

Currently, though, Hunt said he wasn’t using any ractopamine, because his operation had changed and was now focused on young pigs. The drug is given to pigs during the final weeks of their lives to get them to convert more fat to muscle before they’re slaughtered.

Since negotiations with Europe on a new trade pact began last year, U.S. officials have been taking heat from both sides.

In March, 29 environmental and consumers groups, including the Center for Food Safety, wrote a letter to U.S. Trade Representative Michael Froman saying the U.S. should ban ractopamine “and not export this harmful practice to other parts of the world.”

But with the EU ranking as the world’s second largest pork market, trailing only China, the National Pork Producers Council said the industry “will not accept any outcome other than the elimination of the EU ban on the use of ractopamine.”

Pork producers say the science is clearly on their side, noting that even a United Nations panel that sets global food-safety standards _ the Codex Alimentarius Commission _ voted in 2012 to confirm the safety of ractopamine.

While U.S. trade backers focus on science, Europeans prefer to go with their guts. They even have a name for it: The precautionary principle, which allows government officials to make decisions based on the possibility of risk, not just hard evidence.

Kikou said it was the best way to protect the public.

“You want to be absolutely, absolutely sure, especially in cases of food,” she said. “You know how it is with science: Today we say something and tomorrow you can find some study somewhere that will dispute all the other studies. It just shows two very different perspectives.”

Hunt said opponents in Europe were engaged in “defensive posturing” and were doing everything they could to defend their domestic markets.

“That’s the bottom line,” he said. “I don’t think it has anything to do with food safety.”

The issue is on Congress’ radar, with both of North Carolina’s U.S. senators, Republican Richard Burr and Democrat Kay Hagan, backing ractopamine.

When Russia announced a new zero-tolerance policy toward the drug last year, Burr and Hagan joined a group of 33 senators who denounced the move as “an egregious trade barrier with no scientific merit.”

Breaking into the vast European market could mean big money for North Carolina, which already ranks second in U.S. pork production. North Carolina and top-ranked Iowa account for 45 percent of the nation’s hog inventory, according to the U.S. Agriculture Department.

Hunt, 59, the president and co-owner of Andrews Hunt Farms, which owns 1,000 acres in Franklin, Nash and Wilson counties, said Europeans had a history of targeting any U.S. agricultural innovation.

He said U.S. pork producers were “blessed with the opportunity of feeding lots of people in this world” and they needed to keep up with the latest science and technology.

“I’ve been raising pigs for 50 years, since I was a little boy,” Hunt said. “North Carolina’s my home, and I’m doing everything I can to stay competitive and be productive.”