In one of the deadliest nightclub fires in American history, 100 people died at a rock concert in Rhode Island nearly a decade ago. But the biggest killer wasn't the flames; it was lethal gases released from burning sound-insulation foam and other plastics.
In a fatal bit of irony, attempts to snuff fires like this catastrophic one could be making some fires even more deadly.
New research suggests that chemicals – brominated and chlorinated flame retardants – that are added to upholstered furniture and other household items to stop the spread of flames increase emissions of two poisonous gases.
"We found that flame retardants have the undesirable effect of increasing the amounts of carbon monoxide and hydrogen cyanide released during combustion," study co-author Anna Stec, a fire specialist at the University of Central Lancashire in the United Kingdom, said in a statement.
These two gases are by far the biggest killer in fires. They are responsible for 60 to 80 percent of fire deaths, according to the National Fire Protection Assn. During the Rhode Island fire, the levels of hydrogen cyanide and carbon monoxide were high enough to kill in less than 90 seconds.
Flame retardants made of brominated or chlorinated chemicals are added to furniture cushions, carpet padding, children's car seats, plastics that encase electronics and other consumer items. Under California standards adopted in the 1970s, foam inside furniture must withstand a 12-second exposure to a small, open flame, and much of the nation’s furniture is manufactured with flame retardants to meet that standard.
However, while the chemicals may be slowing the spread of flames, when fires do occur, they may be more deadly. Few details of the new research from the United Kingdom are available since the findings have not yet been published. But the researchers said in one experiment, nylon containing the flame retardant brominated polystyrene released six times more hydrogen cyanide when set afire than the same material containing a halogen-free flame retardant.
Hydrogen cyanide is 35 times more deadly than carbon monoxide, and during a fire it can kill in as little as one minute, said Todd Shoebridge, a 30-year fire service veteran who is a captain at the Hickory Fire Department in North Carolina. "It's that serious," Shoebridge said.
Both carbon monoxide and hydrogen cyanide are products of incomplete combustion. As a room on fire loses oxygen, combustion becomes less efficient and gases and smoke rapidly increase. Inhaling the toxic air becomes unavoidable for people trapped in a fire.
Brominated and chlorinated flame retardants work by interfering with combustion, which can increase the amount of the gases.
The evidence "leads one to assume that these chemicals could increase fire safety concerns, not decrease them," said Heather Stapleton, an environmental chemist at Duke University who specializes in studying brominated compounds.
The new research focused on brominated polystyrene, a newer flame retardant manufactured by Albemarle Corp. and other companies. It is added to nylon for use in textiles, upholstery and electrical connectors.
These newer compounds were designed to replace older flame retardants, mostly polybrominated diphenyl ethers or PBDEs, which have been banned since 2004 because they were building up in human bodies, including breast milk. PBDEs are still found in furniture manufactured before the bans.
PBDEs and other halogenated flame retardants were already known to produce other toxic chemicals when they burn, including highly toxic dioxins and furans.
Another replacement for PBDEs is called Tris or TDCPP, (1,3-dichloroisopropyl) phosphate. Foam containing this chemical was shown to release high amounts of carbon monoxide and smoke during ignition, according to a 2000 study.
With or without fires, research suggests, flame retardants may have risks. PBDEs and other halogenated flame retardants have come under intense scrutiny in recent years. PBDEs have been linked in some studies of people and animals to impaired neurological development, reduced fertility, early onset of puberty and altered thyroid hormones. Tris also may be toxic to the developing nervous system.
Albemarle Corp., based in Baton Rouge, La., and maker of Saytex 3010G, a brominated polystyrene flame retardant similar to mixtures tested in the new research, did not return requests for comment. Chemtura Corp., another flame retardant manufacturer based in Philadelphia, Penn., also did not return requests.
The companies have maintained that flame retardants play a critical role by allowing longer escape and response times during a fire, thereby saving lives and property.
"It is estimated that escape times can be up to 15 times longer when flame retardants are present, providing increased survival chances," according to a statement from the European Brominated Flame Retardant Industry Panel, which includes Albemarle and Chemtura.
But a document signed by more than 200 scientists from 30 countries disputes that flame retardants have been proven effective. “Brominated and chlorinated flame retardants can increase fire toxicity, but their overall benefit in improving fire safety has not been proven," the 2010 statement says.
The health threats from halogenated flame retardants combined with their persistence in the environment have driven a search for more environmentally friendly alternatives.
"Reducing the use of toxic or untested flame retardant chemicals in consumer products can protect human and animal health and the global environment without compromising fire safety," says a 2010 report by a group of 10 scientists, including Linda Birnbaum, director of the National Institute of Environmental Health Sciences.
In the new research from the United Kingdom, some alternatives were found to create less toxic air than the halogenated flame retardants. Inorganic, or mineral-based, flame retardants had little effect on toxic gases released in a fire.
Each year, about 10,000 people die in fires in industrialized countries. On average in the United States in 2010, someone died in a fire every 169 minutes, according to the National Fire Protection Assn.
Previous research has focused on carbon monoxide and soot from halogenated flame retardants. But lately, hydrogen cyanide and other gases are getting a closer look, said Richard Hull, a chemist at the University of Central Lancashire who presented the new flame retardant research at an American Chemical Society conference in San Diego last week.
"Carbon monoxide is an important toxicant in fire effluents. However, we have seen that it is less important than hydrogen chloride from burning PVC, or hydrogen cyanide from burning nitrogen-containing polymers such as nylon, polyurethane or acrylic, in developed fires," Hull said.
New research has suggested that hydrogen cyanide – so lethal it was used in the Nazi gas chambers – is a bigger cause of fire deaths than previously thought.
In one example, a fire devastated a prison in Buenos Aires, Argentina, in 1990. Thirty-five inmates died as a mattress fire spread through the prison. But flames did not kill the convicts, a post-mortem blood analysis revealed. Hydrogen cyanide did.
"The results indicated that death in the 35 fire victims was probably caused by HCN [hydrogen cyanide], generated during the extensive polyurethane decomposition provoked by a rapid increase of temperature," according to the analysis of the victims in the Argentina fire.
Hydrogen cyanide and carbon monoxide are odorless, colorless chemicals, making them silent killers.
"If there is a fire, it doesn't matter how big or how small," said Shoebridge, who is lead advocate of North Carolina's "Everybody Goes Home" firefighter safety program. "You have the possibility for those gases."