A review of halogenated natural products in Arctic, Subarctic and Nordic ecosystems

Abstract Halogenated natural products (HNPs) are organic compounds containing bromine, chlorine, iodine, and rarely fluorine. HNPs comprise many classes of compounds, ranging in complexity from halocarbons to higher molecular weight compounds, which often contain oxygen and/or nitrogen atoms in addition to halogens. Many HNPs are biosynthesized by marine bacteria, macroalgae, phytoplankton, tunicates, corals, worms, sponges and other invertebrates. This paper reviews HNPs in Arctic, Subarctic and Nordic ecosystems and is based on sections of Chapter 2.16 in the Arctic Monitoring and Assessment Program (AMAP) assessment Chemicals of Emerging Arctic Concern (AMAP, 2017) which deal with the higher molecular weight HNPs. Material is updated and expanded to include more Nordic examples. Much of the chapter is devoted to “bromophenolic” HNPs, viz bromophenols (BPs) and transformation products bromoanisoles (BAs), hydroxylated and methoxylated bromodiphenyl ethers (OH-BDEs, MeO-BDEs) and polybrominated dibenzo- p -dioxins (PBDDs), since these HNPs are most frequently reported. Others discussed are 2,2′-dimethoxy-3,3′,5,5′-tetrabromobiphenyl (2,2′-dimethoxy-BB80), polyhalogenated 1′-methyl-1,2′-bipyrroles (PMBPs), polyhalogenated 1,1′-dimethyl-2,2′-bipyrroles (PDBPs), polyhalogenated N -methylpyrroles (PMPs), polyhalogenated N -methylindoles (PMIs), bromoheptyl- and bromooctyl pyrroles, (1R,2S,4R,5R,1′E)-2-bromo-1-bromomethyl-1,4-dichloro-5-(2′-chloroethenyl)-5-methylcyclohexane (mixed halogenated compound MHC-1), polybrominated hexahydroxanthene derivatives (PBHDs) and polyhalogenated carbazoles (PHCs). Aspects of HNPs covered are physicochemical properties, sources and production, transformation processes, concentrations and trends in the physical environment and biota (marine and freshwater). Toxic properties of some HNPs and a discussion of how climate change might affect HNPs production and distribution are also included. The review concludes with a summary of research needs to better understand the role of HNPs as “chemicals of emerging Arctic concern”.