Over the last decade, at least 20 halogenated organic compounds (HOCs) of unknown origin have been found in animal tissues. Substantial evidence indicates that many of these compounds are naturally produced and not products of either direct or inadvertent industrial synthesis. For example, two methoxylated polybrominated diphenyl ethers (MeO-PBDEs) isolated from a True’s beaked whale were shown to be natural by virtue of their radiocarbon content (Teuten et al., 2005). A similar result was observed for one halogenated dimethyl bipyrrole (DMBP; Tittlemier et al., 1999) obtained from marine mammals and birds in the North Pacific Ocean (Reddy et al., 2004). These natural HOCs have similar physical and chemical properties as industrial HOCs (Tittlemier et al., 2004). Hence, they can be used as models to help understand the cycling and environmental fate of industrial HOCs (Reddy et al., 2004 and Stapleton et al., 2005). Other unknown (and possibly natural) HOCs include methoxylated polychlorinated diphenyl ethers (MeO-PCDEs) (Haglund et al., 1997), dimethoxylated polybrominated biphenyls (diMeO-PBBs) (Marsh et al., 2005), polybrominated dibenzodioxins (Malmvärn et al., 2005), methyl bipyrroles (MBPs) (Vetter et al., 2000 and Teuten et al., 2006a), and halogenated naphthols (Saint-Louis and Pelletier, 2005).
The halogenated naphthols (several of the proposed structures are shown in Fig. 1(a), (c) and (e)) were detected in the livers of dolphins found dead on the coast of eastern Canada and tentatively identified using low resolution gas chromatography–mass spectrometry (GC–MS) (Saint-Louis and Pelletier, 2005). However, the published mass spectra closely resemble halogenated MBPs. The fully chlorinated MBP (known as Q1) has been detected in a wide range of environmental samples, including human breast milk (Vetter et al., 2000). More recently, we have found brominated analogues of Q1 in marine mammals that have stranded in and around the shores of Cape Cod, Massachusetts, USA (Teuten et al., 2006a Teuten, E.L., Pedler, B.E., Hangsterfer, A.N., Reddy, C.M., 2006a. Identification of highly brominated analogues of Q1 in marine mammals. Environmental Pollution, in press, doi:10.1016/j.envpol.2005.10.052.Teuten et al., 2006a). Here, we argue why we believe the halogenated naphthols (Fig. 1(a), (c), and (e)) are more likely brominated analogues of Q1 (Fig. 1(b), (d), and (f)), respectively. This observation expands the geographic range of the halogenated MBPs.