A generation ago, environmentalists felt vindicated when a notorious class of flame retardants known as polybrominated diphenyl ethers, or PBDEs, was targeted by state and federal agencies for eventual phase-out. While used by industry to make furniture, upholstery, electrical equipment, electronic devices, textiles, and other household products fire resistant, a growing list of studies had linked these chemicals to significant health problems and highlighted their ubiquity in the environment, with traces of the compounds in everything from breastmilk to household dust. In response, manufacturers agreed to voluntarily phase them out — and to replace them with materials thought to be safer.
Now, however, the replacement flame retardants are raising new concerns — both for their environmental pervasiveness and for suspected health risks of their own. They are known as organophosphate flame retardants, and according to one study published in February, their use has skyrocketed over the past 15 years, leading to human exposure levels that are even higher than they were for PBDEs at their peak.
Researchers have found high levels of organophosphates in air and water samples from around the world, from Lake Michigan to the Arctic. The far-flung signs of contamination — from remote environments to urban centers — are raising new alarm within the scientific community.
“We know everyone is exposed to organophosphate flame retardants,” said Heather Stapleton, a Duke University professor, who has been studying flame retardant chemicals for more than a decade. “We know children have higher exposure than adults, and that exposure is higher than it was for PBDEs.”
In response, researchers are putting renewed emphasis on learning more about the impact these compounds may have on the environment and human health. There are already hints of trouble that some of the substitute flame retardants should be considered suspected carcinogens and that others may negatively affect neurodevelopment and fertility.
A review published last year, for example, suggested that organophosphate flame retardants could in fact pose comparable health risks to the brominated materials that they’ve replaced. Such toxic effects aren’t entirely a surprise as the formula for these phosphorus-based flame retardants is related to that used to create some notably risky organophosphate pesticides, from parathion to chlorpyrifos. And they also reinforce a growing worry that we’ve simply replaced one class of long-lasting and problematic flame retardants with another.
“There’s a little bit of a bait-and-switch going on here with flame retardant chemicals,” said Robin Dodson, research scientist at the Silent Spring Institute, a nonprofit public health research organization. Dodson says she doubts the need for much more study: “We already have enough information to think that these are bad actors and we need to get them out.”
Flame retardant chemicals became as prevalent as they are in part through long-time use in furniture and other products in response to flammability and consumer-protection standards set by the U.S. and other countries at the national level, as well as by individual American states. Experts say that in particular, standards set by the state of California were instrumental early on in driving the use of chemical flame retardants. The state required materials to be tested on an “open-flame standard” meaning that products had to resist burning when exposed to a candle-like flame for 12 seconds — a demand that forced heavy use of retardant materials in everything from pajamas to bedding to furniture.
Four years ago, though, California replaced that with a “smolder standard,” which uses conditions more similar to a cigarette burn — the leading cause of furniture fires. The new test, it turns out, can be passed with a far lower concentration of retardant compounds or, depending on the material, none at all.
There are some signs that use of some organophosphates has decreased since California changed its standard. But furniture is only one product that is now routinely permeated with the retardant compounds. They’re also used in other products to meet flammability standards, such as home insulation and electronics.
“We’ll find them in materials that are not technically required to meet standards,” said Stapleton. But, she adds, information on use is limited, meaning that it’s difficult to get a full picture of how many products use organophosphate retardants — and how many are leaching them into the surrounding environment. The chemicals are also used for purposes other than to reduce fire risk, including as an ingredient in plastic or synthetic rubber, where some organophosphates can improve flexibility in the soles of shoes, for example, or as an additive to floor polishes and paper coatings.
One measure of the chemical seep into the environment, though, is the way flame retardants show up in food products. Researchers in Sweden reported in February that they consistently found a range of organophosphate flame retardants in 12 different food categories, with levels highest in cereals, pastries, sweets and beverages — all among the most heavily processed categories of food, suggesting to the study’s authors that they were a result of contamination that occurred during processing. Such findings are a troubling repeat of similar food contamination by PDBEs found years ago in staples ranging from peanut butter to lunch meat.
“What we suspect is that the environment itself, [meaning where] the food is prepared and processed — including the industrial machinery and equipment, possible presence of dust and plastic tools containing flame retardants — could be a potential source of phosphate flame retardants,” said study author Giulia Poma, a researcher at the University of Antwerp’s Toxicological Center in Belgium.
In the February study that showed increased exposure to organophosphates, Stapleton and colleagues used data from 14 epidemiological studies and biosamples collected from the Northeastern United States, North Carolina, and California between 2002 (just before PBDEs started to be phased out) and 2015. They found metabolite levels of several organophosphates in people’s urine had increased significantly during that time frame — the levels of one such flame retardant was recorded at levels 16.5 times higher in 2015 than in 2002.
Organophosphate levels appear to have rapidly increased at least in part because they are water-soluble and can migrate easily, whereas PBDEs are fat-soluble — which meant they bioaccumulate, or become concentrated, in an individual’s body. In other words, the differing formulas offer a trade-off in type of risks. PBDEs can reach toxic levels more quickly through concentration, while organophosphates have more potential to travel throughout the environment.
Erika Schreder, science director at the advocacy nonprofit Toxic-Free Future, said the main ways organophosphates seem to get out of the products they’re used in, from couches and car seats to electronics and home insulation, are through volatilization, abrasion, and direct transfer to dust — meaning a chemical used in the plastic casing on a TV can directly migrate into the dust that collects on it.
Once they escape the products — and they continue to do so over long periods of time — organophosphates travel far and wide, creating what Dodson calls an infinite reservoir. They’ve been found at high levels, for example, in waterways around the world and in the air from the Great Lakes to the Arctic. In January, researchers reported evidence of organophosphates accumulating in sediment at increasing rates, and estimated that a quarter of the total burden of these chemicals in Lake Michigan is contained in sediment — which may serve as a secondary source of organophosphates released into to the water for years into the future.
Schreder and colleagues have done studies to understand how exactly the chemicals are getting from consumer products into waterways. They found the chemicals present in house dust, at higher levels in household laundry water, and at much higher levels in the effluent at wastewater treatment plants, which then send the materials circulating into the larger water supply.
They would like to know more, however, about where and in what quantities the materials are being used. Manufacturers don’t make that information publicly available, so it’s up to researchers like Stapleton and public health agencies to figure out what people’s exposure levels are, where those exposures are coming from, and what impacts they are having on human health and the environment.
Dodson, of the Silent Spring Institute, points out that manufacturers may not even know themselves. “They buy things to meet certain flammability standards not necessarily knowing what chemicals are used to meet those standards,” she said. “They just need to meet the standard and they can get there however they need to get there.”
The counter to all of the concerns, of course, is that flame retardants, for all their environmental downsides, save people’s lives. In response to queries on the matter, the American Chemistry Council, an industry group, sent a statement from the North American Flame Retardant Alliance, another industry group, regarding the use of organophosphate flame retardants: “Fires and fire deaths have dropped significantly over the past 40 years, due in part to the development of a comprehensive set of fire-safety measures that included flame retardants,” the statement read. “There are different types of flame retardants with very different health and safety profiles.”
While there has been increased debate on how effective the retardant chemicals actually are — a widely-praised Chicago Tribune investigation debunked many of the protective claims, leading some furniture companies to quit their use — they are still favored by many industries as a safety buffer against runaway fires.
The state of California, meanwhile, has found that even under its new requirement, manufacturers are still slipping some retardant compounds into products that claim to be flame-retardant free. Myrto Petreas, environmental chemistry branch chief at the California Department of Toxic Substances Control, said about 30 percent of such products tested did actually contain retardant compounds, including organophosphates. “And probably there are other things that we don’t even know to look for,” she said. “We can never sign a report saying there are no flame retardants. We can say we looked for these, and this is what we found,” she said.
The California legislation, though, is only part of the picture. Stricter flammability standards still exist elsewhere, and the chemical and testing industries have resisted the shift away from open flame toward smolder standards. “I don’t think that debate around chemicals in upholstered furniture is over. I think it is an ongoing debate and we just happen to be shifted toward the smolder standard right now — and it can swing back,” Dodson said. “It could be very easy that we slip back away from smolder standards to open flame standards, and that could have big implications on exposure to these chemicals.”
Experts do note that there are other ways for many products to meet flammability standards without retardant chemicals — such as by using barrier fabrics in furniture. Further, there’s evidence that the compounds may be less necessary in electronics: Flat-screen televisions, for instance, don’t get hot the way older CRT models do. Stapleton would like to see improved flammability testing for television sets that discriminates between the two. For products that do require a level of chemical-based protection, such as some electronics and home insulation, researchers are also looking into improved compounds with fewer health effects or less of a potential to migrate.
Ultimately, that’s the bottom line for Stapleton — finding the best balance of safety, including accounting for environmental health and fire safety at the same time.
“I don’t think any of us that study flame retardants feel that fire safety is not important,” said Stapleton. “We just want to make sure we’re maintaining fire safety in a way that also protects human health.”