Lipscomb S, McClelland MM, MacDonald M, et al. Cross-sectional study of social behaviors in preschool children and exposure to flame retardants. Environ Health. 2017;16(1):23.
To assess associations between exposure to flame retardants and differences in social behaviors among children aged 3 to 5 years.
Cross-sectional, observational study
From October 2012 to January 2013, 92 children between the ages of 3 and 5 years were recruited from 28 preschool classrooms in 2 geographic areas of Oregon. Each child was given a silicone passive sampler to wear continuously on their wrists or ankles for 7 days to detect exposure to flame-retardant chemicals. Of the 92 participants, 77 returned the silicone wristbands; of the 77 who returned the wristbands, 5 were excluded due to substantial deviance from protocol (wristband never worn by the child, was lost at school for several days, or went through the laundry) and 3 chose not to answer questions on the sociodemographic questionnaire, leaving a final sample size of 69 children eligible for analysis.
Study Parameters Assessed
The returned wristbands were extracted and analyzed for 41 different flame-retardant compounds using gas chromatography mass spectrophotometry. The children’s parents completed a series of structured questionnaires to capture sociodemographic information (eg, household income, parental education levels, race) and the home learning environment. The questionnaires allowed researchers to control (in statistical analysis) for important psychosocial stressors that negatively affect behavior. The children’s preschool teachers completed the Social Skills Improvement Systems Rating Scale (SISS-RS)—a standardized assessment of social skills and problem behaviors that has strong psychometric properties and measures both normative and clinically relevant variation.
The primary outcome measures were the prevalence of positive social behaviors (cooperation, assertiveness, and self-control) and negative or externalizing social behaviors (hyperactivity, inattention, aggression, and oppositional behavior) among children with varying exposure to brominated diphenyl ethers (BDE) and organophosphate-based flame retardants (OPFR).
Using a HEPA air filter, wet-dusting fabrics and electronics, and having air ducts cleaned regularly to lower household dust contact with flame-retardant sources may decrease the available contaminated dust in the environment.
The concentrations of flame retardants were summed into total BDE and OPFR exposure prior to natural log transformation. Separate generalized additive models were used to evaluate the relationship between 7 subscales of the SISS and total BDE or total OPFR adjusting for age, sex, adverse social experiences, and family context.
All children in the study were exposed to a mixture of flame-retardant compounds. Researchers observed a dose-dependent relationship between total OPFR and 2 subscales where children with higher exposures were rated by their preschool teachers as having less responsible behavior. Additionally, children with higher total BDE exposure were rated by teachers as less assertive.
Is exposure to flame retardants influencing the behavior of children? The evidence is not conclusive. Though the investigators were able to find a statistically significant correlation between less responsible and less assertive behavior and exposure to OPFRs and BDEs, respectively, they failed to demonstrate significant correlation between flame retardant exposure and hyperactivity, aggression, cooperation, self-control, or oppositional behavior. Additional research is needed to examine the possible relationship between OPFR and BDE exposure and negative effects on social behavior.
Because the aim of this study was to focus on current exposure to OPFRs and BDEs, it does not address factors such as maternal toxic exposures during pregnancy and exposure through breast milk, which are known to affect children’s blood levels of toxins at birth and during early developmental stages.1,2
It would be clinically applicable to conduct future studies that address the effect of current exposure to flame-retardant chemicals in the short term. If the exposure is removed, are there significant improvements in responsible and assertive behaviors? A 2008 study by Toms et al found that infants and children ages 0 to 4 years had higher blood concentrations of BDEs than older children, suggesting that these chemicals do not persist in circulation once exposure is reduced.3 For now we can only hypothesize that the chemicals will be eliminated as children age, and we can act to reduce the exposure of young children to these chemicals in the built environment.
The researchers did control for potential confounding factors such as age, gender, and traumatic experiences by using multiple regression analyses, a strength of this study. However, they did not collect data on, nor control for, other factors known to affect social behaviors such as diet,4,5 other health conditions, or history of maternal nutritional deficiency during pregnancy.6
Although using silicone wristbands as passive collection devices is a start for estimating children’s exposure to flame retardants, the researchers acknowledge that this indirect measure of exposure may over- or underestimate true body burden. It is reasonable to assume that the wristbands would not account for additional exposures to ingested OPFRs and BDEs from hand-to-mouth activity, common in children, and may therefore underestimate total exposure in some or all participants. Also, because the pharmacokinetics of differing OPFR and PBD compounds vary,7 the current exposure may not accurately reflect the total body burden and true effect of exposure in the long term. In the future, studies that examine blood levels or urinary metabolites of OPFRs and BDEs may show a greater association between actual body burden of these chemicals and social behaviors.
The results of this study provide good reason to consider methods of reducing exposure to, and assisting elimination of, these chemicals in young children. Sources of exposure to these chemicals include furniture, nursing pillows, carpeting, electronics, strollers, car seats, and vehicles. Some companies have begun offering furniture that is flame-retardant chemical–free. This does not guarantee the elimination of other chemical exposures from components of furniture, though, such as formaldehyde used in particleboard. It has been suggested that used furniture may provide less exposure to these chemicals as it has had time to “off-gas;” however, I could not find any studies on this topic. It is likely that older furniture continues to be a significant source of flame-retardant chemicals as the foam cushions degrade and emit more dust.
Some electronics and furniture companies have committed to eliminating the use of BDEs, but in many cases BDEs have been replaced with OPFRs.8 A more proven option to lower exposure would be to lower exposure to dust particles that are vectors for flame-retardant chemicals.9 For example, using a HEPA air filter, wet-dusting fabrics and electronics, and having air ducts cleaned regularly to lower household dust contact with flame-retardant sources may decrease the available contaminated dust in the environment.
However, the majority of exposure in the study participants and in preschool age children in general may be coming from outside the home. Previous studies have suggested that levels of organophosphate chemicals in public buildings are 4 times higher than levels in most domestic settings.10 Plausible recommendations to reduce exposure in public spaces, such as schools, include ensuring that air ducts are cleaned regularly and other reservoirs of dust are reduced. Aside from increasing regulations regarding the materials allowed in public buildings or avoiding these spaces altogether, there is not much to be done to decrease exposure outside the home, especially at an individual level.
A more practical solution might be to give parents suggestions for what they can do to promote biotransformation and elimination of these compounds in their young children. Animal studies suggest that increased intake of dietary fiber significantly increases the fecal excretion of other lipophilic toxicants such as polychlorinated biphenyl ethers (PCBs) and organophosphate pesticides, with rice bran fiber and spinach being the most effective forms studied.11 It seems reasonable to extrapolate these findings and conclude that dietary fiber could increase the elimination of OPFRs and BDEs as well.
Additionally, clinicians should emphasize the importance of ensuring the child has good nutritional status to support metabolism of these chemicals. Docosahexaenoic acid (DHA) has been shown to cross the blood-brain barrier and protect against oxidative damage of organophosphate pesticides and improve symptoms in disorders like attention deficit hyperactivity disorder (ADHD), which present with symptoms similar to those correlated with exposure in the present study.12,13 It is reasonable to recommend DHA supplementation as both a preventative and a treatment for exposure to OPFRs and BDEs.
Again, we should be reassured, and we should reassure our patients, that research shows that younger children have higher circulating levels of flame-retardant chemicals than older children, suggesting that they may remove these toxins from circulation effectively once exposure is reduced.3