Risks of veterinary antibiotics contamination in Indian organic farmlands: A reality unfolded

Globally, the widespread use of antibiotics in intensive animal farming has contributed to their increased environmental burden. Notably, data and knowledge on these contaminants in farmlands are lacking in India, despite being a major agricultural producer worldwide. To date, no studies have explored whether antibiotics are an intractable environmental issue in Indian agroecosystems. Specifically, information on the prevalence and spread of common antibiotics in long-term animal manure-laden organic farmlands of India is non-existent. Here, we examined samples of manure, soil and vegetables collected from 24 different organic farmlands in India to assess the presence of residues from 15 typical veterinary antibiotics (VAs). Our findings revealed that nine VAs, including three tetracyclines (TCs), three sulfonamides (SAs), one macrolide (ML), and two quinolones (QNs), were recorded in almost all the manure and soil samples. The residual levels of antibiotics (µg kg^‒1) decreased in the following order: TCs (manure: 22.10‒161.10; soil: 8.30‒61) > SAs (manure: 0.90‒73; soil: 0.20‒48.40) > QNs (manure: nd‒3.60; soil: nd‒1.80) > MLs (manure: nd‒1.50; soil: nd‒0.90). Poultry manure-applied farmlands exhibited the highest antibiotic contamination levels, with total antibiotic concentrations surpassing the ecotoxicological effect trigger value of 100 μg kg⁻¹ set by the Steering Committee of the Veterinary International Committee on Harmonization, highlighting the potential hazard of VAs to the soil ecosystem. The translocation of VAs in vegetables was in the order: leaf > root > fruit, and bioaccumulation of 0.10‒3.90 μg kg⁻¹ was recorded. Notably, the calculated risk quotients of antibiotics in vegetables were ˂1, indicating the negligible risk to human health. Overall, our study unveils a concerning state of VAs pollution in organic farmlands in India that warrants special attention, as it may contribute to the proliferation of antibiotic resistance.