More Fat, Less Bone? Flame Retardant May Deliver a One–Two Punch
Authors: Wendee Nicole
Journal: Environmental Health Perspectives (2014)

More Fat, Less Bone?Flame Retardant May Deliver a One-Two Punch Firemaster ® 550 (FM550) was introduced in 2003 as an alternative to the toxic, persistent f lame retardant pentabromodiphenyl ether, for use in mattresses, couches, and other items containing polyurethane foam. 1 FM550 contains a mixture of brominated phthalates and organophosphates.In 2013 a groundbreaking study found that pre-and postnatal exposure to FM550 was associated with increased anxiety, obesity, and early-onset puberty in rats, raising concern over the continued use of these chemicals. 2In this issue of EHP, a team of investigators report further evidence that components of FM550 may act as environmental obesogens, stimulating adipogenesis (fat formation) at the expense of bone health. 3sing computer modeling and receptor binding and activity assays, the authors of the current study found that the phosphate components of FM550 bound to and activated peroxisome proliferator-activated receptor γ, the master regulator of adipogenesis.The brominated components of FM550 did not.Using multipotent mesenchymal stromal cells from rats, they also showed that FM550 and its constituent triphenyl phosphate (TPP) stimulated formation of fat cells. 3hen stem cells differentiate into fat cells, they do so at the expense of bone and cartilage formation. 4In this study, both FM550 and TPP suppressed osteogenesis in bone marrow cultures, with FM550 suppressing activity more than TPP alone. 3The authors hypothesize that environmental obesogens could be contributing to the growing prevalence of osteoporosis worldwide. 5ouse dust contains high levels of organophosphate flame retardants, and their metabolites are ubiquitous in human urine. 6he authors estimated that young children could ingest 120 μg/day TPP from indoor exposure to dust alone. 3The effects shown in this paper occur at significantly higher exposures; thus, at present exposure levels there seems to be a margin of safety," says Jerry Heindel, a health scientist administrator at the National Institute of Environmental Health Sciences, which supported the study in part."However, if exposure increases due to increased use of FM550, the margin of safety could be eroded."According to Barbara Corkey, director of the Obesity Research Center at Boston University School of Medicine, the new study is important to the field "because FM550 is one of thousands of chemicals that have appeared in our environment since the obesity epidemic began.The important question this study raises is how many of the other thousands of compounds that have not been tested [may] also have a small effect on obesity."Corkey was not involved in the research."This is the first study to provide evidence that an organophosphatebased flame retardant could contribute to bone loss," says coauthor Jennifer Schlezinger, an associate professor of environmental health at Boston University School of Public Health.Although the idea that environmental chemicals could be contributing to the obesity epidemic is gaining ground, 4 "few people think about what the consequences of environmental nuclear receptor ligands may be in the bone," Schlezinger says.Other research has found that the anti-diabetes drug rosiglitazone both increases the risk of bone fracture and acts as an obesogen, 7 and tributyltin has been shown to induce adipogenesis and suppress osteogenesis. 8Arsenic and lead also may inhibit bone