Bioaccumulation- and exposure-informed environmental thresholds for antibiotic within a One Health framework

Antibiotics are widely detected in aquatic environments; however, ecological water quality criteria (WQCs) and human health-based limits such as maximum residue limits (MRLs) are derived under separate regulatory frameworks, potentially leaving gaps in achieving integrated One Health protection. Here, we propose a complementary approach that integrates ecological processes, including bioaccumulation and trophic transfer, with food safety-based human exposure limits to evaluate health-protective environmental thresholds. Using trimethoprim as a proof of concept, we illustrate how food safety limits for aquatic products can be translated into organism-level thresholds and further linked to water-phase concentrations using reported bioaccumulation factors. The resulting threshold range is substantially lower than the conventional species sensitivity distribution (SSD)-derived WQC, suggesting that ecotoxicity-based criteria alone may underestimate risks associated with human dietary exposure. Rather than replacing existing WQCs, this framework provides an additional line of evidence for comparing thresholds and identifying the more protective values. By explicitly linking environmental contamination, ecological processes, and human dietary exposure, this approach offers a practical pathway for operationalizing One Health principles in environmental risk management.