Investigation of the incidence of heavy metals contamination in commonly used fertilizers applied to vegetables, fish ponds, and human health risk assessments

Overuse of fertilizers on agricultural lands and fish ponds may result in serious pollution problems, such as heavy metals that can enter the food chain and pose serious health problems. Due to this, the present study investigates the incidence of heavy metals in commonly used fertilizers and its association with heavy metals in vegetables, soil, fish species, and pond water. Samples were collected from different sites (fields and ponds) in district Kohat, where the application of fertilizers was common and control groups (no fertilizers used). Heavy metal analysis was carried out through a spectrophotometer. Results showed higher Cd and Cr concentrations in triple superphosphate (TSP), Cu and Pb in nitrogen, phosphorus, and potassium (NPK), while lower concentrations were found in gypsum. In vegetables (onion, tomato, brinjal, and potato) and associated soil, most of the heavy metals concentrations were significantly higher (P < 0.05) in fertilizer-applied sites than in the control. Also, the Cd concentration in potatoes and Pb level in all vegetables obtained from sites were greater than the WHO/FAO standard limit. In the case of fish species (Hypophthalmichthys molitrix and Cyprinus carpio) muscles and their habitat (water), all the understudy heavy metals were notably higher (P < 0.05) in fertilizer-applied sites (ponds) than the control group. Collectively, in all vegetables and muscles of fish species, the bioaccumulation factor was higher in sites compared to the control. The estimated daily intake (EDI) and target hazard quotient (THQ) values were also higher in fertilizer-applied sites (fields and ponds) than control. The health index (HI) value was > 1 in vegetables (onion, tomato, and potato) and fish muscles collected from different sites compared to the control. Thus, there is the possibility of severe health risks. The use of fertilizers must be carefully monitored in order to ensure that humans and animals are safe from exposure to heavy metals.