Polybrominated diphenyl ether (PBDE) flame-retardants were recently shown to be present at very high levels in the blood and house dust of Californians, possibly because of a unique Californian law that requires furniture to be flame-resistant. These chemicals are garnering much interest as of late because of their potential toxic health effects on humans. What are PBDEs, and why might they be toxic?
There are 209 different PBDE varieties, also called congeners. They are identical in molecular structure except that the number and/or position of bromine atoms in each congener vary. One of these congeners, pentabrominated diphenyl ether (penta), is a mixture containing congeners with four, five, and six bromine atoms. It was used extensively in polyurethane foam.
The manufacture of penta was banned by the European Union in 2003 and by the U.S. in 2004 because of increasing evidence of the congener’s toxicity in humans and other organisms. However, no import restrictions exist on products containing penta. Other countries can manufacture penta, add it to consumer products and sell those products in America.
Penta and other PBDEs accumulate in fatty tissues in animals of all kinds and can be passed from mother to child via breast milk. Even though penta was banned in the U.S, it is still present in homes, animals, humans and the environment because of its prevalence in furniture bought before the ban; its use in imported furniture and its apparent resistance to degradation. Other PBDE varieties such as octa and deca, used in plastic electronics casings such as for televisions, volatilize out of the plastic and into the air. They are banned in several states because they have been shown to cause liver toxicity, disrupt reproductive systems and cause endocrine disruption.
PBDEs sound like bad actors, but once upon a time they were the good guys. They replaced polychlorinated biphenyl (PCB) flame-retardants, which were banned by the United States Congress in 1976. PCBs, like PBDEs, are incredibly persistent: 30 years after the ban, PCBs are still found ubiquitously in mammals, human blood and umbilical cords, fish, birds, air, soil, lakes, rivers, house dust, sewage and wastewater sludge.
PCBs were used in coolants, insulating plasticizers, paints, cements, electrical wiring PVC coating, electronic components and pesticide extenders as well as in flame-retardants. Some industrial manufacturing areas are extremely contaminated with PCBs, such as the Hudson River, where fishing has been banned since 1976 due to the high levels of PCBs found in the river and fish. PCBs are considered especially deleterious because when burned, they react with oxygen and turn into the very toxic dioxin. PCBs are carcinogenic, decrease bone density in humans, increase behavioral and reflex problems in rats and decrease immune function in mice.
The basic structure of PCBs is similar to that of PBDEs. This is concerning because structurally similar molecules often have similar functions or modes of action in the human body. Both chemicals are also structurally similar to thyroid hormone, and animal studies have shown that PBDEs does in fact alter thyroid homeostasis.
PBDE flame-retardants look similarly to a known, banned toxin. They accumulate in humans and other animals, resist degradation, and exert toxic effects. The question remains, do they reduce the incidence of fire-related deaths?
A 2006 report by J. R. Hall, Jr. for the National Fire Protection Association shows from 1980 to 1999 states not requiring fire-retardants in furniture experienced the same decline in fire-related deaths that California did; flame-retardants have not displayed a measurable effect on the reduction of house fires. Arleme Blum, a Chemist from the University of California, Berkeley who researches extensively about flame-retardants, points out in a 2006 op-ed article for The New York Times, “most fatal furniture fires are caused by cigarettes, which typically smolder for half an hour after being put down.”
Recent legislation at the state level in many states across the nation mandates the manufacture of fire-safe cigarettes, which go out when set down due to “speed bumps” of thickened cigarette paper. Smoking materials such as cigarettes are the primary cause of fire deaths in the United States. If that threat is reduced, what use are toxic chemicals?