The natural product 2,4,6-tribromoanisole is the predominant polyhalogenated compound in representative Australian passive air samples

Passive air samplers are well-suited for monitoring persistent organic pollutants (POPs) in ambient air. While the presence of POPs had been documented in Australian air, no data existed on structurally similar, halogenated natural products (HNPs), although these were frequently found in marine biota samples from Australia at levels exceeding those of anthropogenic POPs. This study reports quantitative data of the HNP 2,4,6-tribromoanisole (2,4,6-TBA) along with three POPs (polychlorinated biphenyls (PCBs) 153 and 138 as well as hexachlorobenzene (HCB)) in six selected passive air samples from different Australian regions (islands, coastal cities, and inland). For the most abundant HNP, 2,4,6-TBA, time-averaged concentrations for one year were determined at up to 420 pg/m³ (One Tree Island), indicating its predominant natural production in the Great Barrier Reef (GBR). High concentrations of 2,4,6-TBA (17 pg/m³), even in the remote inland sample (~ 800 km from the sea), led to the conclusion that the marine-derived 2,4,6-TBA was transported over long distances in air and can be found ubiquitously in Australian air. Even in the coastal cities of Brisbane and Darwin, 2,4,6-TBA levels were comparable to those of the PCBs. The HNP 2,3,3',4,4',5,5'-heptachloro-1'-methyl-1,2'-bipyrrole (Q1) was also detected in air from two islands. Its presence in air from One Tree Island was in line with expectations, given the high levels in marine mammal samples from the GBR. In direct comparison, the ~15 times higher ratio of Q1/2,4,6-TBA in air from Phillip Island indicated Q1 could be even more abundant in this marine region than in the GBR.