Firemaster 550 identified as potential obesogen; linked to weight gain, early puberty, anxiety in rats.

Apr 01, 2013

Patisaul, HB, SC Roberts, N Mabrey, KA McCaffrey, RB Gear, J Braun, SM Belcher and HM Stapleton. 2012. Accumulation and endocrine disrupting effects of the flame retardant mixture Firemaster 550 in rats: An exploratory assessment. Journal of Biochemical and Molecular Toxicology

Synopsis by Craig Butt

Rats exposed to the common flame retardant Firemaster 550 before birth and while nursing gained weight earlier and were obese as adults. Males were 32 percent heavier and females were 22 percent heavier when compared to unexposed adults. The two levels tested represent mid-range and high exposures in people. More studies are needed to understand the health effects of this replacement for the phased-out pentaBDE mixtures.

The flame retardant mixture called Firemaster 550 has been identified as a potential endocrine disruptor in mother rats and their offspring, according to an exploratory study. In particular, the results suggest that Firemaster 550 is an obesogen.[Editor's Note 4/4/2013: "Potential" added to reflect wording of study authors]

The pups born to mothers that ate high doses of the mixture during pregnancy and while nursing were heavier during adolescence and kept the weight on as adults. The animals were 22 to 32 percent heavier as adults when compared to unexposed rats.

Chemicals that are considered obesogens can change fat metabolism and storage, ultimately leading to fat accumulation and weight gain. Some scientists think obesogens are partially to blame for the rising obesity rates in North America and other regions.

Besides being obese, the animals exposed during development were more anxious and the females entered puberty earlier than the unexposed rats.

Firemaster 550 is applied to furniture foam to reduce flammability and is frequently detected in house dust. The mixture is a replacement for polybrominated diphenyl ethers (PBDEs), a large class of once widely-used flame retardants that are banned or being voluntarily phased out of use in the United States, Europe and elsewhere. The long-lived PBDEs can accumulate in the food chain and have known health effects on thyroid hormones and neurodevelopment.

The results have implications for existing flame retardant standards, some of which are being reevaluated in California.

The study is unique because the developing pups were exposed through their mothers. The effects on weight, behavior and puberty were permanent and remained as the pups grew. The study is important because it tested levels similar to what people might be exposed to from highly contaminated house dust.

This is the first study by a group of independent researchers to investigate the toxic effects of Firemaster 550. Two previous studies by industry scientists used very high levels of exposure. They reported the studies as flawed and “spurious” – not real – because effects were seen only at the middle exposure levels and not the highest or lowest.

Firemaster 550 is a chemical flame retardant mixture that is added to furniture foams to meet strict government flammability standards. Recent studies show that, in the United States, chemicals from the Firemaster 550 mixtures are the second most common chemical flame retardant in foams used in baby products and couches. Most U.S. house dust contains low levels of the Firemaster 550 chemicals. It also has been detected in outdoor air, marine mammals and sewage sludge.

The flame retardant is a mixture of several chemicals, including brominated phthalates and triphenyl phosphates. Because it is a mixture, the study's authors are not sure which individual chemical – or combination of chemicals – might be responsible for the toxic effects.

Next to nothing is known about endocrine health effects from reported exposures to Firemaster 550's chemicals.

In this animal study, researchers fed pregnant and nursing rats two doses – 100 and 1,000 micrograms (μg) per day – of the Firemaster 550 commercial mixture. Doses represent high values of what has been measured in house dust. Growth, developmental, behavior and metabolic effects were assessed on the pups and adults. Two main chemicals – TBB and TBPH – and their metabolites were measured. Fat, liver and muscle tissue were examined to see if the chemicals transferred to the developing pups from the mothers. Exposed animals were compared to unexposed counterparts.

Both chemicals and metabolites were measured in the mothers and pups at differing levels and in various tissues. The most significant finding was that TBB at both exposure levels accumulated in the mothers' muscles, liver and brain tissues. Liver enzymes and blood thyroid hormone levels were skewed in the mothers.

Perhaps the most important findings, though, were that the pups of the pregnant and nursing rats exposed to the flame retardant mixture were fatter than unexposed rats. Increased weight gain was observed after 10 days in the males and after 3 weeks – considered adolescence – in the females. At 3 weeks, the males were 59 percent fatter and the females were 31 percent fatter. The increased weight gain persisted into adulthood. At the end of 7 months, an age when rats are considered adults, the males were 32 percent fatter and the females were 22 percent fatter.

In addition, the female babies reached puberty 3 days earlier than those with unexposed mothers. Endocrine-disrupting effects of the flame retardant chemicals or the increased body weight linked to the chemicals could account for the early puberty observed in the study.

“This exploratory study reveals, for the first time, the potential for perinatal FM 550 exposure to have adverse effects indicative of endocrine disruption, at levels much lower than the NOAEL [no effects level] reported by the manufacturer," the authors wrote. [Editor's note 4/4/2013: Study quotations added.]

“Collectively, the data from this exploratory study identify FM 550 as a potential obesogen and contributor to metabolic syndrome," they wrote.

The study results are limited because the heavy animals were observed only at the highest exposure. Also, only three mothers per dosing group were tested, which is small in toxicology testing. The study is considered exploratory and further testing is needed to confirm the results.

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