CEHN Articles of the Month, July 2015 Issue
In Utero and Childhood Polybrominated Diphenyl Ether Exposures and Body Mass at Age 7 Years: The CHAMACOS Study
Authors: Ayca Erkin-Cakmak, Kim G. Harley, Jonathan Chevrier, Asa Bradman, Katherine Kogut, Karen Huen, and Brenda Eskenazi
Polybromated diphenyl ethers (PBDEs) are flame retardant chemicals added to plastics and foams in consumer products such as furniture to make them difficult to burn. Three major classes of PBDEs (pentaBDEs, octaBDEs, and decaBDEs) have been used in consumer products since the 1970s. While production and import of penta- and octaBDEs were phased out in 2004, both types of chemical classes continue to be emitted from older furniture and products into the environment where they persist for many years, and are commonly found in house dust. PBDEs can accumulate in the human body over time and be transferred from mothers to their children, both pre-natally through the placenta, and post-natally through breastfeeding. Young children may also be exposed from hand-to-mouth behavior if they come into contact with dust that contains PBDEs. PBDEs can disrupt hormone activity, which helps to regulate important bodily processes, including those that affect the maintenance of a healthy weight. Thus researchers have been investigating the link between exposure to PBDEs and obesity. Previous study results on the association of post-natal PBDE exposure with childhood obesity have been mixed, and there have been few-to-no studies investigating pre-natal exposure and childhood obesity.
This study examines the effects of pre- and post-natal exposure to components of a pentaBDE mixture and its association with childhood obesity.
Study subjects were mothers and their children living in the Salinas Valley of California who are participating in a large study that follows the children from in the womb through age 16 (CHAMACOS study). Blood samples were collected from the mothers during pregnancy, and also from their children at 7 years of age, to assess pre-natal and post-natal PBDE levels. The children’s body mass index (BMI) z-scores were calculated to determine outcomes of interest (overweight and obesity).
Higher maternal PBDE levels during pregnancy were associated with higher BMI z-scores in boys, but with lower BMI z-scores for girls, at 7 years of age. However, overall, there were no significant associations between maternal prenatal pentaBDE concentrations and measures of child’s body mass at age 7. Levels of certain types of pentaBDEs as measured in the children (post-natal) were negatively associated with their BMI z-scores.
The relationship between (pre-natal or post-natal) pentaBDE concentration and childhood obesity is likely very complex. While no strong associations were found to support an obesity-causing effect of pre-natal PBDE exposure, significant sex-specific differences were found.
This is one of the first studies to investigate the associations between prenatal exposure to pentaBDEs and child body mass. Findings suggest that associations with pre-natal PBDE exposure may differ between boys and girls. Further studies should be conducted to confirm this observed sex-effect and examine whether this effect is modified by the changes in the hormonal environment through puberty. Future studies should also collect detailed dietary information at each child for follow-up visit.
Despite the complexity involved in determining the relationship between PBDEs and childhood obesity and the remaining research gaps, federal regulatory action has already been enacted based on evidence of adverse neurobehavioral effects of PBDE exposure. The U.S. Environmental Protection Agency (EPA) mandated a phase out of penta- and octaBDEs, and many states have developed their own regulations for PBDEs. In addition, some companies have agreed to voluntarily phase out decaBDEs, which can break down in the environment to the more toxic classes of penta- and octaBDEs over time. Support for green chemistry and the search for safer alternatives to decaPBDEs is needed, and EPA should continue to negotiate for increased voluntary industry phase-outs of these chemicals.