Bioaccumulation, Tissue Distribution, and Biotransformation of Photoinitiators in Freshwater Snails: Field Evidence...

Photoinitiators (PIs) are ubiquitous contaminants with endocrine-disrupting effects, yet their bioaccumulation and biotransformation in aquatic organisms remain unclear. This study reports the first multimedia analysis of 24 PIs in a textile-impacted area in eastern China. Apple snails showed the highest PI levels and diversity (∑19PIs 44.5-353 ng/g dw), exceeding those in fish (∑17PIs 18.3-213 ng/g dw), sediment (∑14PIs 4.1-122 ng/g dw), and river water (∑11PIs 11.7-405 ng/L). In snails, several PIs had median bioaccumulation factors (BAFs) > 1000 L/kg and median biota-sediment accumulation factors >1, suggesting accumulation from both aqueous and sediment-associated sources. Viscera were the primary PI sink, with higher burdens than muscle and gonadal tissues. Muscle accumulation was associated with hydrophobicity, showing a parabolic log BAF-log Kow relationship (R2 = 0.97, p < 0.01). Several metabolites were detected in snail tissues, but low metabolite-to-parent ratios (≤9.8%) for confirmed hydroxylated benzophenones indicated limited biotransformation. Three phosphine oxides, benzophenone, and 2-isopropylthioxanthone were identified as priority risk drivers, with risks concentrated in industrial zones. These findings provide field evidence of PI bioaccumulation and biotransformation in freshwater mollusks, informing aquatic ecological risk assessments of PIs.