Uptake of antibiotics from irrigation water by plants

• The capacity of carrot and lettuce to take up antibiotics was investigated.
• Human risk to antibiotics through vegetables irrigated with contaminated water was low.
• Uptake of antibiotics followed a dose–response effect.
• Carrot showed higher average concentration of antibiotics than lettuce samples and was significant.
• Sub-MIC concentrations of antibiotics via vegetables consumed in diet could promote antibiotic resistance.

The capacity of carrot (Daucus corota L.) and lettuce (Lactuca sativa L.), two plants that are usually eaten raw, to uptake tetracycline and amoxicillin (two commonly used antibiotics) from irrigated water was investigated in order to assess the indirect human exposure to antibiotics through consumption of uncooked vegetables. Antibiotics in potted plants that had been irrigated with known concentrations of the antibiotics were extracted using accelerated solvent extraction and analyzed on a liquid chromatograph-tandem mass spectrometer. The plants absorbed the antibiotics from water in all tested concentrations of 0.1–15 mg L−1. Tetracycline was detected in all plant samples, at concentrations ranging from 4.4 to 28.3 ng/g in lettuce and 12.0–36.8 ng g−1 fresh weight in carrots. Amoxicillin showed absorption with concentrations ranging from 13.7 ng g−1 to 45.2 ng g−1 for the plant samples. The mean concentration of amoxicillin (27.1 ng g−1) in all the samples was significantly higher (p = 0.04) than that of tetracycline (20.2 ng g−1) indicating higher uptake of amoxicillin than tetracycline. This suggests that the low antibiotic concentrations found in plants could be important for causing antibiotics resistance when these levels are consumed.