A new study by Baylor University environmental health researchers found that zebra fish exposed to several different technical mixtures of polybrominated diphenyl ethers (PBDEs) - a common fire retardant - during early development can cause developmental malformations, changes in behavior and death.
The study will appear in the June issue of the journal Environmental Toxicology and Chemistry and is the first to test multiple PBDE mixtures for changes in behavior, physical malformations and mortality on zebra fish.
PBDEs are found in many common household products from blankets to couches to food wrappers. Lab tests have shown that PBDEs have been found in human breast milk and cord blood. Previous studies have showed children with high levels of PBDEs in their umbilical cord at birth scored lower on tests between one and six years of age. In 2006, the state of California started prohibiting the use of PBDEs.
The family of PBDEs consists of more than 200 possible substances, which are called congeners. Congeners are considered low if they average between 1 to 5 bromine atoms per molecule.
The Baylor researchers tested six PBDE congeners for developmental effects on embryonic zebra fish. Changes in behavior, physical malformations and mortality were recorded daily for seven days.
The results showed:
- Lower brominated congeners were more toxic than higher brominated congeners.
- Embryos were most sensitive to two particular types of PBDE exposures, the two lowest brominated congeners of the six tested. Both induced a curved body axis and eventually death.
- In all, four of the six congeners tested caused developmental malformations, such as a curved body axis and pulmonary edema. Five of the six caused alterations in behaviors, such as decreased swimming rates and increased spontaneous movement in the embryo.
"While most PBDEs have either been banned or phased out throughout the world, it may be more beneficial to identify congeners of concern rather than replacing these compounds with chemicals of unknown biological interactions," said Dr. Erica Bruce, assistant professor of environmental science at Baylor who is an expert in environmental chemicals and their effects on public health. "Alterations in early behavior may potentially be due to disruption of thyroid hormones. Thyroid hormones play a vital role in the development of the cholinergic system and this study gives insight into biological interaction within a few hours of exposure. The observed hyperactivity may be due to overstimulation of the cholinergic system," Bruce said.