MARIETTA, Ga.—It's Monday night at the Battle & Brew, a gamer hangout in this Atlanta suburb. The crowd is slumping in chairs, ears entombed in headphones, eyes locked on flat-screen monitors and minds lost in tonight’s game of choice: "The Elder Scrolls V: Skyrim."

To help stay alert all night, each man has an open can of "gamer fuel" inches from his keyboard. "I've seen some of these dudes plow through six sodas in six hours," said Brian Smawley, a regular at the gamer bar.

Gamers say they chug their fuel for the sugar and caffeine, but drinkers of Mountain Dew and some other citrus-flavored drinks are also getting a dose of a synthetic chemical called brominated vegetable oil, or BVO.

Patented by chemical companies as a flame retardant, and banned in food throughout Europe and Japan, BVO has been added to sodas for decades in North America. Now some scientists have a renewed interest in this little-known ingredient, found in 10 percent of sodas in the United States.

After a few extreme soda binges—not too far from what many gamers regularly consume—a few patients have needed medical attention for skin lesions, memory loss and nerve disorders, all symptoms of overexposure to bromine. Other studies suggest that BVO could be building up in human tissues, just like other brominated compounds such as flame retardants. In mouse studies, big doses caused reproductive and behavioral problems.

Reports from an industry group helped the U.S. Food and Drug Administration establish in 1977 what it considers a safe limit for BVO in sodas. But some scientists say that limit is based on data that is thin and several decades old, and they insist that the chemical deserves a fresh look.

"Aside from these reports, the scientific data is scarce," said Walter Vetter, a food chemist at Germany's University of Hohenheim and author of a recent, but unpublished, study on BVO in European soda imports.

The next time you grab a Mountain Dew, Squirt, Fanta Orange, Sunkist Pineapple, Gatorade Thirst Quencher Orange, Powerade Strawberry Lemonade or Fresca Original Citrus, take a look at the drink's ingredients. In Mountain Dew, brominated vegetable oil is listed next-to-last, between disodium EDTA and Yellow 5. These are just a sampling of drinks with BVO listed in their ingredients, which is required by the FDA. The most popular sodas – Coca-Cola and Pepsi – do not contain BVO.

You don't have to be a gamer to drink these fruit-flavored sodas. In the United States, 85 percent of kids drink a beverage containing sugar or artificial sweetener at least once per week, according to a study published last month. Sodas are the largest source of calories for teenagers between the ages of 14 to 18, according to a National Cancer Institute study. For adults, soda, energy and sports drinks are the fourth largest source of calories, a federal study found.

Hold a bottle of Mountain Dew to a light. It's cloudy. Brominated vegetable oil creates the cloudy look by keeping the fruity flavor mixed into the drink. Without an emulsifier such as BVO, the flavoring would float to the surface. The FDA limits the use of BVO to 15 parts per million in fruit-flavored beverages.

Brominated vegetable oil, which is derived from soybean or corn, contains bromine atoms, which weigh down the citrus flavoring so it mixes with sugar water, or in the case of flame retardants, slows down chemical reactions that cause a fire.

Brominated flame retardants lately are under intense scrutiny because research has shown that they are building up in people's bodies, including breast milk, around the world. Designed to slow the spread of flames, they are added to polystyrene foam cushions used in upholstered furniture and children's products, as well as plastics used in electronics. Research in animals as well as some human studies have found links to impaired neurological development, reduced fertility, early onset of puberty and altered thyroid hormones.

BVO may not be in use today as a flame retardant in furniture foam, but patents in Europe — granted earlier this year to Dow Global Technologies—and in the United States —granted in 1967 to Koppers Inc.—keep that possibility alive.

"There are some concerns [about BVO] because people are worried that maybe it has the behavior, [and] potential health effects similar to brominated flame retardants," said Heather Stapleton, an environmental chemist at Duke University who specializes in studying brominated compounds.

Soda makers and industry groups say they are not concerned about the safety of brominated vegetable oil, saying their products meet all government standards.

"This is a safe ingredient approved by the FDA, which is used in some citrus-based beverages," said Christopher Gindlesperger of the American Beverage Association, which represents PepsiCo, maker of Mountain Dew. "Importantly, consumers can rest assured that our products are safe and our industry adheres to all government regulations."

Chris Barnes of the Dr. Pepper Snapple Group, makers of Squirt and other drinks that contain BVO, echoed that response.

"All ingredients in Dr. Pepper Snapple Group products meet FDA and other regulator requirements," Barnes said.

Dated data

Some experts are unconvinced, saying that the FDA standards are based on decades-old data.

"Compounds like these that are in widespread use probably should be reexamined periodically with newer technologies to ensure that there aren't effects that would have been missed by prior methods," said Charles Vorhees, a toxicologist at Cincinnati Children’s Hospital Medical Center, who studied BVO's neurological effects in the early 1980s. "I think BVO is the kind of compound that probably warrants some reexamination."

Toxicity testing has changed dramatically in the past few decades. Multiple generations of animals now can be tested for neurodevelopmental, hormonal and reproductive changes that weren't imagined in the 1970s and early 1980s.

"I am no toxicologist, but I think that the toxic evaluation of chemicals has been improved since then," Vetter added.

In 1970, scientists in England found that rats on a six-week diet containing 0.8 percent brominated maize oil had stockpiles of bromine in their fat tissue. The bromine stayed there even after the rats returned to a control diet for two weeks.

Around the same time, a study confirmed that bromine was building up in humans. Researchers measured the serum levels of people in the United Kingdom—where BVO was in use—and in their counterparts in the Netherlands and Germany, where BVO was not used.

"During this time UK citizens had higher bromine serum levels compared to the inhabitants of Germany and the Netherlands," Vetter said. The largest amounts of lipid-bound bromine were found in tissues from children in the UK, according to the study.

The study authors wrote that "it seems highly probable that the intake of brominated vegetable oil is the cause of the tissue bromine residues in children."

Data in rats show that BVO could be toxic. A 1971 study by Canadian researchers found that rats fed a diet containing 0.5 percent brominated oils grew heavy hearts and developed lesions in their heart muscle. In a later study, in 1983, rats fed the same oils had behavioral problems, and those fed 1 percent BVO had trouble conceiving. At 2 percent, they were unable to reproduce.

The diets in that study had "whopping doses" of BVO, about 100-times higher than today's allowable limit, said Vorhees, lead author of the 1983 study.

But two case studies in the past 15 years show that whopping doses also can occur in people—with unhealthy consequences.

Epic binges

On MMO nights at the Battle & Brew, some gamers play 12 straight hours. In these Massively Multiplayer Online games, thousands of players from around the world compete. During these epic battles, a soda every hour is not uncommon. A gamer chugging a 20-ounce bottle of soda every hour will finish 3.5 liters in six hours.

"They're just sitting for 12 hours, just pounding sodas," Smawley said.

Virtually every teen in America plays video games, according to the Pew Research Center. The $110-billion-a-year soft drink industry and the $74-billion-a-year video game industry have noticed. Activision, the makers of "Call of Duty: Modern Warfare 3," the latest edition in this popular video game series, paired with Mountain Dew in a promotion that rewards gamers with bonus points for drinking more Mountain Dew.

In 1997, emergency room doctors at University of California, Davis reported a patient with severe bromine intoxication from drinking two to four liters of orange soda every day. He developed headaches, fatigue, ataxia (loss of muscle coordination) and memory loss.

In a 2003 case reported in Ohio, a 63-year-old man developed ulcers on his swollen hands after drinking eight liters of Red Rudy Squirt every day for several months. The man was diagnosed with bromoderma, a rare skin hypersensitivity to bromine exposure. The patient quit drinking the brominated soft drink and months later recovered.

Reactions this severe may not be a concern in the general population, the study’s doctors said.

"Any normal level of consumption of BVO would not cause any health problems — except the risk of diabetes and obesity from drinking that much sugar water," said Zane Horowitz, medical director of the Oregon Poison Center and author of the 1997 case study.

But in the gamer scene, a normal level of consumption is not normal. Everyone, it seems, knows someone habitually needing a fuel fix, and consuming enough to up his or her risk.

"I've seen hard core guys, after every game they'll just grab another one," said Sean Hyatt, the assistant manager at the Battle & Brew.

And it's not just the "stinkies"—Smawley's derogatory term for the stereotypical gamer slobs—who pound gamer fuel. Vorhees, of the Cincinnati children's hospital, said his son stays up all night when playing a new game with his friends.

"They use Mountain Dew specifically as a beverage to keep them awake—and they hardly eat anything," Vorhees said.

When a person doesn't eat during one of these binges, his or her body is absorbing the entire beverage. It's even worse in kids, Vorhees said, because they have less body mass.

"In kids, the total dosage effect tends to be greater," Vorhees said. "I actually think there are people that get these high exposures."

Banned bromine returns

Based on data from the early studies, the FDA yanked brominated vegetable oil from its Generally Recognized as Safe (GRAS) list for flavor additives in 1970, said Douglas Karas, a spokesman for the FDA. BVO bounced back after studies from an industry group from 1971 to 1974 demonstrated a level of safety.

The Flavor Extract Manufacturers’ Association petitioned the FDA to get BVO back in fruit-flavored beverages, this time as a stabilizer, which is its role today. After evaluating the petition and other data, the FDA in 1977 approved the interim use of BVO at 15 ppm in fruit-flavored beverages, pending the outcome of additional studies.

"This decision was based on the highest No Observed Effect Levels from the existing safety studies and the estimated daily intake," Karas said in an email. "Although there were doses that showed adverse effects in the animal studies, there also were lower doses in which there were no adverse effects observed."

As a condition of interim approval, the industry group submitted additional safety studies to the FDA.

The FDA determined that a two-year feeding study in pigs established a no-effect level of 1,200 ppm. A two-year feeding study in beagle dogs also was conducted. Although there were concerns about quality control with that particular study, Karas said, no cardiovascular effects were observed in the dogs fed BVO at levels as high as 3,600 ppm for two years. After an independent audit of the data to address the quality concerns, the FDA decided to allow BVO in fruit-flavored beverages.

"The findings from these studies supported the safety of BVO in beverages at a level of 15 ppm in fruit-flavored beverages," Karas said. "Its use as a flame retardant does not preclude its use as a food ingredient so long as the food use is safe."

More than 30 years later, brominated vegetable oil's approval status is still listed as interim. Changing the status would be costly and "is not a public health priority for the agency at this time," Karas said.

Michael Jacobson, executive director of the Center for Science in the Public Interest, was involved with the petition to remove BVO from the "safe" list in 1970. He said it's time for the FDA to make a decision, one way or the other.

"Is it harmful at the amounts consumed? Probably not," Jacobson said. "But it would be nice if the FDA did a thorough review of the literature and finalized an approval or a ban."

A safer switch?

BVO has seeped into Europe, mostly forbidden territory for this additive, according to an analysis of imported sodas presented at an international symposium on halogenated persistent organic pollutants in 2010.

"We found products with no label although BVO was present in the soda," said Vetter, lead author of the study.

He said soda makers in North America could easily replace BVO with alternatives such as hydrocolloids – chemicals that are used in many sodas in Europe. Natural hydrocolloids form small droplets on water into which non-water soluble compounds can be stored and stabilized for as long as necessary. They are almost exclusively natural products, Vetter said.

Barnes, of the Dr. Pepper Snapple Group, said that BVO and hydrocolloids "do not provide the same functionality and cannot be substituted for one another."

Vetter disagreed, saying that countries in Europe and elsewhere have used natural hydrocolloids for decades in the soda brands that rely on BVO in North America.

"There are many options to substitute BVO with safe chemicals," Vetter said. "I am not aware of significant disadvantages of BVO over hydrocolloids or vice versa."

With natural alternatives already in use in other countries, why not switch in North America too?

Wim Thielemans, a chemical engineer at the University of Nottingham in the United Kingdom, said since the alternatives are already used in Europe "their performance must be acceptable, if not comparable, to the U.S.-used brominated systems." That means "the main driver for not replacing them may be cost," he said.

"It is a North American problem," Vetter added. "In the E.U., BVO will never be permitted."

This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.