Coexposure to Regulated and Unregulated Organohalogens through Omega-3 Fish Oil Supplements: A Retrospective Screening of Products Purchased in 2014–2017

Omega-3 fish oil supplements are nutraceuticals widely recommended for long-term daily consumption. However, they may also carry bioaccumulative and lipophilic pollutants, and for supplements sold in Latin America the co-occurrence of anthropogenic residues with naturally produced organobromines remains uncharacterized. We therefore determined 23 polychlorinated biphenyls (PCBs), including 11 dioxin-like congeners (dl-PCBs), seven polybrominated diphenyl ethers (PBDEs), eight natural methoxylated PBDEs (MeO-BDEs), and total mercury (HgT) in 47 supplements purchased in Brazil and abroad in 2014–2017 and reassessed exposure retrospectively under the 2022 WHO toxic equivalency factors and the 2026 EFSA tolerable intake for dioxins and dl-PCBs (0.6 pg TEQ kg–1 week–1). MeO-BDEs were quantified in all products and dominated the organobromine burden (median ∑MeO-BDE:∑PBDE ≈ 4), yet no widely adopted health-based guidance value exists for them. On a quantified-only, lower-bound screening basis pending confirmatory analysis, six products exceeded the current tolerable intake for dl-PCBs at the label-recommended dose, four of them by more than 3-fold and the highest by 19-fold. Only the most contaminated product exceeded the value in force at the time of purchase (14 pg TEQ kg–1 week–1). PBDEs and MeO-BDEs covaried at the brand level (Spearman ρ = 0.40), a pattern compatible with a shared marine driver whose origin the data do not resolve. All 15 products bearing contaminant-absence statements contained quantifiable contaminants, although the unrecorded scope of those statements precludes any conclusion about their accuracy. These historical data provide a baseline for coexposure to regulated toxicants and to ubiquitous natural organobromines that still lack toxicological guidance.