Health risk assessment of emerging organic contaminants from land-applied biosolids: A comparative study between the U.S. and China

Biosolids land application is widely adopted as a sustainable strategy for nutrient recycling. However, the presence of emerging organic contaminants (EOCs) raises challenges to public health. This study conducted a cross-national assessment of six EOCs classes, including polybrominated diphenyl ethers (PBDEs), phthalate esters (PAEs), per- and polyfluoroalkyl substances (PFAS), bisphenol analogues (BPs), polycyclic aromatic hydrocarbons (PAHs), and pharmaceuticals and personal care products (PPCPs), in biosolids collected from the United States (U.S.) and China. Among these, PFAS and PAHs exhibited the highest persistence, reaching up to 1.66 × 10² and 1.03 × 10³ ng/g dw in the U.S. amended soil, and 56.47 and 1.03 × 10³ ng/g dw in Chinese amended soil after 20 years of application, respectively. Risk modeling revealed that PAHs posed low but non-negligible carcinogenic risks (TCR>1.0 × 10^-6) to children in both countries under both one-time and long-term biosolid applications. PFAS posed low non-carcinogenic risks (TNCR: 0.10-0.19) after 5 years, and low carcinogenic risks (TCR: 1.1 × 10^-6-1.5 × 10^-6) to children after 10 years of continuous application in U.S. scenarios. In contrast, PBDEs, PAEs, BPs, and PPCPs presented negligible non-carcinogenic and carcinogenic risks (TNCR<0.1; TCR<1.0 × 10^-6) under all exposure scenarios. These findings underscore the urgency for compound-specific regulation and monitoring, particularly for high-risk EOCs. Integrating risk-based threshold concentrations into biosolids management could enhance the protection for sensitive populations and support safe and sustainable biosolids reuse practices.