Occurrence and Risk Assessment of Veterinary Antimicrobials in Commercial Organic Fertilizers on Chinese Markets

Commercial organic fertilizers (COFs), as an alternative to chemical fertilizers, have been widely promoted and applied to agricultural soils to improve soil fertility and develop green agriculture. However, the residues of veterinary antimicrobials in COFs could be transferred to agricultural soils and pose ecological risk that should not be ignored. This study quantified the occurrence of fifty-seven veterinary antimicrobials, covering five classes (i.e., twenty-three sulfonamides, nineteen quinolones, seven macrolides, six tetracyclines, and two lincosamides) in ninety-three COFs collected from five provinces in China. Twenty-two veterinary antimicrobials, including eleven quinolones, six sulfonamides, four macrolides, and one lincosamide, were detected in the COFs with total contents up to 3870 ng/g. The contents of individual antimicrobials ranged from 0.66 to 3310 ng/g, and their detection frequencies were between 2% and 49%. The composition and contents of antimicrobials in the COFs varied significantly, depending on their raw materials, production processes, and source regions. Seven antimicrobials, including ciprofloxacin, enrofloxacin, and tilmicosin, could pose low to medium potential ecological risk to soil organisms in the amended soils. The wide occurrence of antimicrobials in COFs and their potential ecological risk indicate the urgent need to establish regulatory limits of antimicrobial residues in COFs to control and prevent antimicrobial pollution in agricultural soils brought by their amendment.