Declining concentrations of chlorinated paraffins in endangered St. Lawrence Estuary belugas (Delphinapterus leucas): response to regulations or a change in diet?

Antoine E. Simond, Peter S. Ross, Jory Cabrol, Véronique Lesage, Stéphane Lair, Million B. Woudneh, Diwen W. Yang, Hui Peng, Katerina Colbourne, Tanya M. Brown

The accumulation of industrial contaminants represent one of the major threats to the endangered St. Lawrence Estuary (SLE) beluga whale population. Elevated concentrations of short-chained chlorinated paraffins (SCCPs) were recently reported in blubber of adult male SLE belugas. SCCPs are complex mixtures of alkanes of varying chain length (10 to 13 carbons) with varying degree of chlorine content (30 to 70% by mass) that have been used in North America primarily as lubricants and coolants in metal working fluids. SCCPs have the potential to biomagnify in marine food webs, and have been found to induce neurotoxic and endocrine disrupting effects in mammals and to potentially alter lipid and amino acid metabolism in belugas. Recent regulations for SCCPs in North America, combined with their replacement by medium- (MCCPs) and long-chained chlorinated paraffins (LCCPs), highlight the importance of tracking this toxic chemical class. The objectives of this study were to evaluate (1) levels and profiles of short-, medium, and long-chained chlorinated paraffins (CPs) in samples obtained from carcasses of adult male, adult female, juvenile, newborn, and fetus belugas, and (2) trends in adult male belugas between 1997 and 2018. SCCPs dominated (64 to 100%) total CP concentrations across all age and sex classes, MCCPs accounted for the remaining proportion of total CPs, and LCCPs were not detected in any sample. Adult male SCCP concentrations from this study were considerably lower (> 2000-fold) than those reported in 2020, likely reflecting a previously erroneous overestimate due to the lack of a suitable analytical method for SCCPs at the time. Both SCCPs and total CPs declined over time in adult males in our study, presumably due in part to the implementation of regulations in 2012. However, there is a need to better understand the possible contribution of a changing diet to contaminant exposure, as stable isotopic ratios of carbon also changed over time.