New research finds that the common fire retardant Firemaster 550 (FM 550) makes both male and female prairie voles less sociable and more anxious. The findings shed new light on how exposure to such chemicals affects the social brain.

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Voles are usually very sociable, but new research shows that exposure to a certain chemical mixture makes them more isolated and anxious.

Our homes contain varieties of questionable substances that researchers have linked with adverse health outcomes.

From cleaning and personal hygiene products to those coating our furniture and floors, numerous potentially harmful chemicals exist in the environments that humans have created.

Among these substances are flame retardants, phthalates, and other chemicals used as preservatives or disinfectants.

Some of the potential health hazards that researchers have linked with such compounds include neurodevelopmental defects, breathing problems, and endocrine dysfunction.

While researchers and public health authorities do not have definitive evidence of a link between, for example, a common class of fire retardants called polybrominated diphenyl ethers (PBDEs) and cancer or diabetes, some studies in rodents have suggested that there may be an association.

Now, new research examines the effect of a common flame retardant mixture on the socioemotional behavior of prairie voles.

Voles are socially monogamous rodents that develop long-lasting bonds with their mates, show highly affiliative behavior, and tend to be aggressive toward strangers.

Manufacturers developed the common flame retardant featured in the study, FM 550, a decade ago to replace PBDEs.

The new research appears in the journal Neurotoxicology and Teratology, and the corresponding author is Heather Patisaul, a professor and Associate Dean for Research at the Department of Biological Sciences at North Carolina State University, in Raleigh.

“There is concern that early life exposure to flame retardants is contributing to neurodevelopmental disorders,” Prof. Patisaul explains.

“We decided to look at the effects of exposure on social and emotional behavior using a prairie vole model. Prairie voles are socially monogamous animals that partner for life and co-parent offspring.”

“They are commonly used in neuroscience studies that address social behavior and so were a good choice for this study,” she says.

For the study, Prof. Patisaul and the team injected pregnant voles with 500, 1000, or 2000 micrograms of FM 550 throughout their pregnancies. After the voles gave birth, the researchers exposed the offspring directly to FM 550 from the day of birth until weaning.

Then, the researchers assessed the voles’ anxiety, memory, and sociability using a variety of standard tests.

“Normally, voles are highly social and prefer to spend time with other animals, particularly their partners,” Prof. Patisaul explains.

However, the voles that had been exposed to FM 550 displayed less social behavior. When females had to choose between spending time with a female stranger or spending time alone, they chose the latter. These effects were dose-respondent.

Similarly, male voles exposed to the retardant also displayed socially avoidant behavior, and they did not show preference for partners.

Furthermore, female voles exposed to FM 550 displayed increased anxiety and reduced interest in exploring new territory, despite the fact that, normally, females are less anxious than males and more exploratory, explains Prof. Patisaul.

“In tests like the open field test,” she goes on, “where they are introduced to an empty, open box, females are more likely than males to explore the middle area, which is considered risky, but exposed females remained in safe areas instead.”

Finally, the researchers took blood tests 4 hours after the last exposure to FM 550.

“FM 550 contains two different types of flame retardant chemicals, brominated [compounds] and organophosphates,” Prof. Patisaul explains.

“We detected the primary brominated flame retardant in both male and female voles, but did not detect many organophosphates, possibly due to their being metabolized more quickly,” she reports.

This is the first study in mammals to show that developmental exposure to these flame retardants affects social behavior, and it supports the hypothesis that developmental exposure to flame retardants can impact the social brain.”

Prof. Heather Patisaul

“Future studies will probe the possible mechanisms by which these effects arise,” concludes the researcher.