Antibiotic risk assessment in agricultural soil from Tamaulipas, Mexico

Antibiotics are used daily in productive activities, generating waste that enters the environment. In small quantities, these drugs can degrade naturally, but when they accumulate in large quantities, they are considered a pollutant. These pollutants have potentially dangerous effects on aquatic ecosystems, even at low concentrations. However, in many regions the current concentration of antibiotics in soil or water is unknown, making it impossible to assess their potential impact on the environment and public health. Therefore, the objective of this study is to identify the presence and concentration of antibiotics in agricultural soil in Tamaulipas, Mexico, and assess their ecological risk. Fifty agricultural soil samples were analyzed using UPLC-MS to identify nine antibiotics: Ampicillin (AM), Penicillin (P), Gentamicin (G), Streptomycin (STR), Tetracycline (TE), Oxytetracycline (OX), Difloxacin (D), sulfamethoxazole (SMX), and trimethoprim (TR). As part of the results, only seven of the nine antibiotics searched were detected. SMX and TR were not identified in any of the samples. The most frequently detected antibiotics were TE and AM, at 98.0% (49/50), respectively. The antibiotic that showed the highest concentrations was tetracycline between 6.28 and 837.8 μg/kg, while on the contrary, the lowest concentrations were detected in ampicillin between 6.28 to 38 μg/kg. In the ecological risk assessment, a high risk was estimated for TE in 98.0% of the samples and for D in 56.0%. A moderate ecological risk was estimated for AM in 98.0%, G in 66.0%, and OX in 44.0%. These results highlight the need for periodic monitoring of the concentration of these and other widely used antibiotics in the environment, to estimate their potential negative effects.