Microbial-Associated Food Web Trophic Transfer of Heavy Metals Potentiates Health Risks in a Mining-Impacted Subtropical Yuanjiang-Red River Basin

To illustrate the potential health risks to humans posed by heavy metals (HMs) through aquatic food webs magnification, a systematical research was performed at the mining-impacted subtropical river basin, Yuanjiang-Red River Basin. The As and Pb concentrations in multiple fish species exceeded national food safety limits. Meanwhile, Hg and Zn exhibited pronounced trophic biomagnification across the aquatic food web, collectively accounting for 32–84% of total dietary relative risk across the examined fishes. Elevated Hg and Zn levels in human hair samples were spatially consistent with their biomagnification profiles along food webs and hazard quotient indicated non-negligible noncarcinogenic risks from Hg exposure for both adults and children, supporting dietary fish consumption could serve as a plausible exposure pathway of these metals. Microbial profiles revealed both taxonomic and inferred functional compositions were significantly correlated with Hg and Zn levels in dietary organisms and variation in microbial community composition was statistically correlated with HM transfer from water into dietary organisms (path coefficient = 0.333, P = 0.049) according to partial least-squares-structural equation modeling. Therefore, microbial-associated trophic transfer of HMs may constitute an under-recognized health risk to humans in river systems affected by mining activities, even when aqueous HMs comply with national standards.