Impacts of BDE209 addition on Pb uptake, subcellular partitioning and gene toxicity in earthworm (Eisenia fetida)

Highlights: • 10 or 100 μg g⁻¹ BDE209 addition caused histological changes in Pb-exposed earthworms' body wall. • Strong histopathological effects with BDE209 addition confirmed the enhanced Pb bioavailability. • The presence of higher levels of BDE209 altered subcellular partitioning of Pb in earthworm. • Co-exposure to Pb and BDE209 declined SOD and CAT gene transcripts synergistically. • BDE209 addition elicited up-regulation of Hsp90 gene expression compared to Pb exposure alone. - Abstract: Lead (Pb) and decabromodiphenyl ether (BDE209) are the mainly co-existed contaminants at e-waste recycling sites. The potential toxicity of Pb (250 μg g⁻¹) to earthworm Eisenia fetida in the presence of BDE209 (1, 10 and 100 μg g⁻¹) was determined during 14-d incubation period. Compared to Pb treatment alone, the co-exposure with 1 μg g⁻¹ BDE209 barely affected Pb uptake, subcellular partitioning and gene expression; however, histopathological changes in earthworms' body wall (epidermal, circular and longitudinal muscles) demonstrated that 10 and 100 μg g⁻¹ BDE209 additions enhanced Pb uptake and altered its subcellular partitioning, indicating that Pb redistributed from fractions E (cell debris) and D (metal-rich granules) to fraction C (cytosols); Additionally, BDE209 supply significantly inhibited (p < 0.05) the induction of SOD (superoxide dismutase) and CAT (catalase) gene expressions (maximum down-regulation 59% for SOD gene at Pb + 100 μg g⁻¹ BDE209 and 89% for CAT gene at Pb + 10 μg g⁻¹ BDE209), while facilitated (p < 0.05) Hsp90 (heat shock protein 90) gene expression with maximum induction rate of 120% after exposure to Pb + 10 μg g⁻¹ BDE209. These findings illustrate the importance of considering environmental BDE209 co-exposure when assessing Pb bioaccumulation and toxicity in multi-contaminated soil ecosystems.