Frogs pass flame retardants from food to eggs.
Wu, J-P, X-J Luo, Y Zhang, S-H Chen, B-X Mai, Y-T Guan and Z-T Yang. 2009. Residues of polybrominated diphenyl ethers in frogs (Rana limnocharis) from a contaminated site, South China: tissue distribution, biomagnification, and maternal transfer. Environmental Science and Technology 43(14):5212–5217.
A study examining frogs in South China shows for the first time that frogs can pick up PBDE flame retardants from their food, concentrate them in their tissues and organs and deposit higher amounts of them in their eggs, exposing the next generation and potentially affecting frog populations.
The concentrations of PBDEs were greater in the frogs than in their food. The results indicate the fire suppressors may have the potential to biomagnify – increase in concentration with each increasing level of the food chain, as occurs, for example, with the insecticide DDT.
Furthermore, frog moms passed significant amounts of their PBDE body burdens to their eggs. Researchers measured more PBDEs in the eggs (from 10.7 to 125 nanograms per gram wet weight) than in the muscle (0.63 to 11.6 ng/g) and liver (4.57 to 56.2 ng/g) of the frogs. As other studies have linked PBDEs to developmental malformations in amphibians, these new findings suggest that PBDEs could contribute to the global declines in amphibian populations.
PBDEs are compounds used in consumer products to slow and retard fire. Exposure to them is common because many electronics, clothes and other ordinary products contain the flame retardants. In animal studies, PBDEs can interfere with thyroid hormones and so they are considered endocrine disrupting compounds.
Because PBDEs are fat soluble – that is, they tend to be stored in fatty tissues – concentrations tend to build up in animals over time. A number of studies showing the build up of PBDEs in people has led to the ban of some of these compounds in countries around the world.
The researchers measured 18 types of PBDE indicators in insects and the liver, muscle and egg tissue of rice frogs living near an elecronics recycling plant in China.
The levels of the flame retardants increased in each phase as they cycled from the insect prey to the frogs to the eggs. The frogs collected some types of the PBDEs more readily – those with fewer than seven bromine atoms – than other types and tended to accumulate different types of PBDEs than those found in other aquatic animals. In addition, they accumulated the chemicals to a much larger extent – from 1 to more than 25 times greater – than reported in other fresh water animals but at lesser rates than mammals and birds.