Environmental and Health Risk Assessments of Antibiotics and Heavy Metals in Manure in Liuyang City.

With the rapid growth of livestock farming, the use of antibiotics and heavy metals as feed additives has raised environmental and health concerns. This study systematically analyzed the contamination levels of antibiotics and heavy metals in manure samples collected from five farms of varying scales in Liuyang City, Hunan Province. Utilizing 16S rDNA high-throughput sequencing technology, the study also examined the structural and functional characteristics of manure microbial communities. Ecological risk and human health risk assessments were also conducted. Results revealed that antibiotic residues in pig manure were generally higher than those in chicken manure, with significant differences in antibiotic usage across farms of varying scales. Cu and Zn levels exceeded standards in some samples, particularly from small-scale farms. Microbial community structures showed marked differences, with pig manure exhibiting higher microbial diversity. Functional prediction indicated active metabolism, strong environmental adaptability, and robust pollutant degradation capacity. Risk assessments revealed moderate to high ecological and human health risks from certain antibiotics and heavy metals, with significant non-carcinogenic and carcinogenic risks particularly for children. The study emphasizes that rational control of antibiotic and heavy metal use, coupled with enhanced manure management and resource utilization, is crucial for safeguarding ecological security and public health.