Micronutrient and heavy metal concentrations in basil plant cultivated on irradiated and non-irradiated sewage sludge- treated soil and evaluation of human health risk.

Gamma irradiation is regarded as a promising alternative method for sewage sludge (SS) treatment. To evaluate the human health risk and effects of gamma irradiated and non-irradiated SS (SSGI and SSNI, respectively) on micronutrient and heavy metal concentrations in basil (Ocimum basilicum L.) as a test plant, a greenhouse experiment based on completely randomized design was conducted with control (without SS and irradiation) and 15, 30 and 60 g kg of SSNI as well as SSGI (irradiated with doses of 5, 10 and 20 kGy) with three replicates. The results indicated that the concentrations of copper, zinc, iron, nickel, lead, and cadmium in SSGI and SSNI treatments were greater than the limits set by FAO/WHO for vegetables or by European Commission for food. The target hazard quotient (THQ) of all metals except lead in the treatments with >15 g kg SSGI or SSNI and the hazard index (HI) in the control treatment were lower than the threshold value of 1, but the HIs in SSNI and SSGI treatments were greater than the threshold value. Nevertheless, no significant differences existed between most THQs and HIs from dietary intake of basil grown in SSGI as compared with SSNI. It was concluded that the basil cultivated under tested levels of SSGI and SSNI is not permissible for human consumption.