PBDEs

OVERVIEW

Polybrominated diphenyl ethers (PBDEs) are a group of structurally similar brominated compounds in which 2 to 10 bromine atoms are attached to a diphenyl ether molecule. The general structure of PBDEs is shown below:

STRUCTURE OF PBDES

with n between 1 and 9.
There are 209 possible congeners, although only a fraction of them is found in commercial mixtures. In the United States, there were two main producers of technical mixtures of PBDEs. They were marketed as “penta”, “octa”, and “deca” products. The penta-BDE technical mixture contained tetra-, penta-, and a small amount of hexabrominated BDEs. The octa-BDE technical mixture contained hexa-, hepta-, octa- and nonabrominated homologues. The deca-BDE product contains 97% of decabromodiphenyl ether and small amounts of nonabrominated homologues (Agency for Toxic Substances and Disease Registry). These compounds have been used in a variety of consumer and commercial products and have been added to polymeric materials, both natural and synthetic, to enhance flame-retarding properties.
PBDE concentrations have increased in the environment in the last few decades (Hites, 2004). Also, because penta- and octa- BDE products encountered government regulation in Europe and in some U.S. states, the market seems to be shifting towards non regulated com-pounds. This trend was substantiated by Hoh and Hites, who detected some novel brominated compounds in samples. (Hoh, 2005).
In the lab, PBDEs have been measured in a variety of different matrices, from fish samples (Zhu L.Y. and Hites R.A., Environ. Sci. Technol., 38 (10), 2779 -2784, 2004.) to sediment cores (Zhu L.Y. and Hites R.A., Environ. Sci. Technol., 39 (10), 3488 -3494, 2005.).
Below there are some more details of different studies involving measuremtns of PBDEs.

PBDEs in the Great Lakes atmosphere (IADN samples)

Since the end of 2004, PBDEs measurements have been included in the routine analysis of IADN samples. Preliminary results (see Fig.1) show that the highest concentrations are detected in Chicago and Cleveland. The lowest values are measured in the remote sites of Eagle Harbor and Sleeping Bear Dunes.

plot depicting concentrations of PBDEs at the IADN sites
Figure 1 Boxplots showing the concentration of total PBDEs in pg/m3 at the 5 IADN sites (EH=Eagle Harbor; CH= Chicago; SB=Sleeping Bear Dunes; CL=Cleveland; SP=Sturgeon Point).

When focusing on the three common commercial prodcuts mentioned above, penta- and deca- BDE mxitures are the most abundant ones in terms of concentration, followed by octa-BDE (see Figure 2).

plot showing the profiles of the 3 gropus of PBDEs in the IADN sites
Figure 2 Profiles of PBDEs grouped following commercial mixtures composition at the IADN sites.

PBDEs in cats’ serum

Co-incident with the introduction of polybrominated diphenyl ethers (PBDEs) into household materials nearly 30 years ago, feline hyperthyroidism (FH) has increased dramatically. Risk of developing FH is associated with indoor living and consumption of canned cat food. We hypothesized that increases in FH were, in part, related to increased PBDE exposure, with key routes of exposure being diet and ingestion of house dust. This study was designed to determine whether body burdens of PBDEs in hyperthyroid (HT) cats were greater than that of young or sick non-HT cats. Serum samples and clinical information were collected from 23 cats. Serum and dry and canned cat food were analyzed for PBDEs. A spectrum of BDE congeners was detected in all cats, with BDE-47, 99, 207, and 209 predominating. Mean ± standard error (and median) cumulative PBDE serum concentrations of young, old non-HT, and HT cats were 4.3 ± 1.5 (3.5), 10.5 ± 3.5 (5.9), and 12.7 ± 3.9 (6.2) ng/mL, respectively (see Fig.3).

boxplots with mean concentrations of PBDEs in cats' serum
Fig.3 Boxplots showing the total concentration of PBDEs in the tested cats (HT=hyperthyroid cats; SC=sick controls; YC= young controls).

Due to high variability within each group, no association was detected between HT cats and PBDE levels. Indicative of age- or disease-dependent changes in PBDE metabolism, BDE-47/99 ratios were inversely correlated with age (see Fig.4), and 47/99 and 100/99 ratios in HT cats were significantly lower than those in the other cats.

plot showing the relationship between PBDEs concentration adnd age
Fig. 4 Relationship between PBDEs concentration and age.

Both dry and canned food samples were tested, accounting for a variety of "flavors" such as turkey, beef, chicken and seafood. Interestingly, dry food showed on average higher concentrations than canned food. Among the "flavors" tested, the highest amount of PBDEs was found in the seafood based ones.